2022-05-09 09:26:44

by Masahiro Yamada

Subject: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c

modpost.c is too big, and the half of the code is for section checks.
Split it.

I fixed some style issues in the moved code.

Signed-off-by: Masahiro Yamada <[email protected]>
---

Changes in v4:
- New patch

scripts/mod/Makefile | 2 +-
scripts/mod/modpost.c | 1202 +---------------------------------
scripts/mod/modpost.h | 34 +-
scripts/mod/section-check.c | 1222 +++++++++++++++++++++++++++++++++++
4 files changed, 1240 insertions(+), 1220 deletions(-)
create mode 100644 scripts/mod/section-check.c

diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
index c9e38ad937fd..ca739c6c68a1 100644
--- a/scripts/mod/Makefile
+++ b/scripts/mod/Makefile
@@ -5,7 +5,7 @@ CFLAGS_REMOVE_empty.o += $(CC_FLAGS_LTO)
hostprogs-always-y += modpost mk_elfconfig
always-y += empty.o

-modpost-objs := modpost.o file2alias.o sumversion.o
+modpost-objs := modpost.o section-check.o file2alias.o sumversion.o

devicetable-offsets-file := devicetable-offsets.h

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index a78b75f0eeb0..e7e2c70a98f5 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -31,7 +31,7 @@ static bool external_module;
/* Only warn about unresolved symbols */
static bool warn_unresolved;

-static int sec_mismatch_count;
+int sec_mismatch_count;
static bool sec_mismatch_warn_only = true;
/* ignore missing files */
static bool ignore_missing_files;
@@ -310,8 +310,8 @@ static void add_namespace(struct list_head *head, const char *namespace)
}
}

-static void *sym_get_data_by_offset(const struct elf_info *info,
- unsigned int secindex, unsigned long offset)
+void *sym_get_data_by_offset(const struct elf_info *info,
+ unsigned int secindex, unsigned long offset)
{
Elf_Shdr *sechdr = &info->sechdrs[secindex];

@@ -327,19 +327,17 @@ static void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym)
sym->st_value);
}

-static const char *sech_name(const struct elf_info *info, Elf_Shdr *sechdr)
+const char *sech_name(const struct elf_info *info, Elf_Shdr *sechdr)
{
return sym_get_data_by_offset(info, info->secindex_strings,
sechdr->sh_name);
}

-static const char *sec_name(const struct elf_info *info, int secindex)
+const char *sec_name(const struct elf_info *info, int secindex)
{
return sech_name(info, &info->sechdrs[secindex]);
}

-#define strstarts(str, prefix) (strncmp(str, prefix, strlen(prefix)) == 0)
-
static void sym_update_namespace(const char *symname, const char *namespace)
{
struct symbol *s = find_symbol(symname);
@@ -741,1196 +739,6 @@ static char *get_modinfo(struct elf_info *info, const char *tag)
return get_next_modinfo(info, tag, NULL);
}

-/**
- * Test if string s ends in string sub
- * return 0 if match
- **/
-static int strrcmp(const char *s, const char *sub)
-{
- int slen, sublen;
-
- if (!s || !sub)
- return 1;
-
- slen = strlen(s);
- sublen = strlen(sub);
-
- if ((slen == 0) || (sublen == 0))
- return 1;
-
- if (sublen > slen)
- return 1;
-
- return memcmp(s + slen - sublen, sub, sublen);
-}
-
-static const char *sym_name(struct elf_info *elf, Elf_Sym *sym)
-{
- if (sym)
- return elf->strtab + sym->st_name;
- else
- return "(unknown)";
-}
-
-/* The pattern is an array of simple patterns.
- * "foo" will match an exact string equal to "foo"
- * "*foo" will match a string that ends with "foo"
- * "foo*" will match a string that begins with "foo"
- * "*foo*" will match a string that contains "foo"
- */
-static int match(const char *sym, const char * const pat[])
-{
- const char *p;
- while (*pat) {
- const char *endp;
-
- p = *pat++;
- endp = p + strlen(p) - 1;
-
- /* "*foo*" */
- if (*p == '*' && *endp == '*') {
- char *bare = NOFAIL(strndup(p + 1, strlen(p) - 2));
- char *here = strstr(sym, bare);
-
- free(bare);
- if (here != NULL)
- return 1;
- }
- /* "*foo" */
- else if (*p == '*') {
- if (strrcmp(sym, p + 1) == 0)
- return 1;
- }
- /* "foo*" */
- else if (*endp == '*') {
- if (strncmp(sym, p, strlen(p) - 1) == 0)
- return 1;
- }
- /* no wildcards */
- else {
- if (strcmp(p, sym) == 0)
- return 1;
- }
- }
- /* no match */
- return 0;
-}
-
-/* sections that we do not want to do full section mismatch check on */
-static const char *const section_white_list[] =
-{
- ".comment*",
- ".debug*",
- ".cranges", /* sh64 */
- ".zdebug*", /* Compressed debug sections. */
- ".GCC.command.line", /* record-gcc-switches */
- ".mdebug*", /* alpha, score, mips etc. */
- ".pdr", /* alpha, score, mips etc. */
- ".stab*",
- ".note*",
- ".got*",
- ".toc*",
- ".xt.prop", /* xtensa */
- ".xt.lit", /* xtensa */
- ".arcextmap*", /* arc */
- ".gnu.linkonce.arcext*", /* arc : modules */
- ".cmem*", /* EZchip */
- ".fmt_slot*", /* EZchip */
- ".gnu.lto*",
- ".discard.*",
- NULL
-};
-
-/*
- * This is used to find sections missing the SHF_ALLOC flag.
- * The cause of this is often a section specified in assembler
- * without "ax" / "aw".
- */
-static void check_section(const char *modname, struct elf_info *elf,
- Elf_Shdr *sechdr)
-{
- const char *sec = sech_name(elf, sechdr);
-
- if (sechdr->sh_type == SHT_PROGBITS &&
- !(sechdr->sh_flags & SHF_ALLOC) &&
- !match(sec, section_white_list)) {
- warn("%s (%s): unexpected non-allocatable section.\n"
- "Did you forget to use \"ax\"/\"aw\" in a .S file?\n"
- "Note that for example <linux/init.h> contains\n"
- "section definitions for use in .S files.\n\n",
- modname, sec);
- }
-}
-
-
-
-#define ALL_INIT_DATA_SECTIONS \
- ".init.setup", ".init.rodata", ".meminit.rodata", \
- ".init.data", ".meminit.data"
-#define ALL_EXIT_DATA_SECTIONS \
- ".exit.data", ".memexit.data"
-
-#define ALL_INIT_TEXT_SECTIONS \
- ".init.text", ".meminit.text"
-#define ALL_EXIT_TEXT_SECTIONS \
- ".exit.text", ".memexit.text"
-
-#define ALL_PCI_INIT_SECTIONS \
- ".pci_fixup_early", ".pci_fixup_header", ".pci_fixup_final", \
- ".pci_fixup_enable", ".pci_fixup_resume", \
- ".pci_fixup_resume_early", ".pci_fixup_suspend"
-
-#define ALL_XXXINIT_SECTIONS MEM_INIT_SECTIONS
-#define ALL_XXXEXIT_SECTIONS MEM_EXIT_SECTIONS
-
-#define ALL_INIT_SECTIONS INIT_SECTIONS, ALL_XXXINIT_SECTIONS
-#define ALL_EXIT_SECTIONS EXIT_SECTIONS, ALL_XXXEXIT_SECTIONS
-
-#define DATA_SECTIONS ".data", ".data.rel"
-#define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \
- ".kprobes.text", ".cpuidle.text", ".noinstr.text"
-#define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \
- ".fixup", ".entry.text", ".exception.text", ".text.*", \
- ".coldtext", ".softirqentry.text"
-
-#define INIT_SECTIONS ".init.*"
-#define MEM_INIT_SECTIONS ".meminit.*"
-
-#define EXIT_SECTIONS ".exit.*"
-#define MEM_EXIT_SECTIONS ".memexit.*"
-
-#define ALL_TEXT_SECTIONS ALL_INIT_TEXT_SECTIONS, ALL_EXIT_TEXT_SECTIONS, \
- TEXT_SECTIONS, OTHER_TEXT_SECTIONS
-
-/* init data sections */
-static const char *const init_data_sections[] =
- { ALL_INIT_DATA_SECTIONS, NULL };
-
-/* all init sections */
-static const char *const init_sections[] = { ALL_INIT_SECTIONS, NULL };
-
-/* All init and exit sections (code + data) */
-static const char *const init_exit_sections[] =
- {ALL_INIT_SECTIONS, ALL_EXIT_SECTIONS, NULL };
-
-/* all text sections */
-static const char *const text_sections[] = { ALL_TEXT_SECTIONS, NULL };
-
-/* data section */
-static const char *const data_sections[] = { DATA_SECTIONS, NULL };
-
-
-/* symbols in .data that may refer to init/exit sections */
-#define DEFAULT_SYMBOL_WHITE_LIST \
- "*driver", \
- "*_template", /* scsi uses *_template a lot */ \
- "*_timer", /* arm uses ops structures named _timer a lot */ \
- "*_sht", /* scsi also used *_sht to some extent */ \
- "*_ops", \
- "*_probe", \
- "*_probe_one", \
- "*_console"
-
-static const char *const head_sections[] = { ".head.text*", NULL };
-static const char *const linker_symbols[] =
- { "__init_begin", "_sinittext", "_einittext", NULL };
-static const char *const optim_symbols[] = { "*.constprop.*", NULL };
-
-enum mismatch {
- TEXT_TO_ANY_INIT,
- DATA_TO_ANY_INIT,
- TEXT_TO_ANY_EXIT,
- DATA_TO_ANY_EXIT,
- XXXINIT_TO_SOME_INIT,
- XXXEXIT_TO_SOME_EXIT,
- ANY_INIT_TO_ANY_EXIT,
- ANY_EXIT_TO_ANY_INIT,
- EXPORT_TO_INIT_EXIT,
- EXTABLE_TO_NON_TEXT,
-};
-
-/**
- * Describe how to match sections on different criteria:
- *
- * @fromsec: Array of sections to be matched.
- *
- * @bad_tosec: Relocations applied to a section in @fromsec to a section in
- * this array is forbidden (black-list). Can be empty.
- *
- * @good_tosec: Relocations applied to a section in @fromsec must be
- * targeting sections in this array (white-list). Can be empty.
- *
- * @mismatch: Type of mismatch.
- *
- * @symbol_white_list: Do not match a relocation to a symbol in this list
- * even if it is targeting a section in @bad_to_sec.
- *
- * @handler: Specific handler to call when a match is found. If NULL,
- * default_mismatch_handler() will be called.
- *
- */
-struct sectioncheck {
- const char *fromsec[20];
- const char *bad_tosec[20];
- const char *good_tosec[20];
- enum mismatch mismatch;
- const char *symbol_white_list[20];
- void (*handler)(const char *modname, struct elf_info *elf,
- const struct sectioncheck* const mismatch,
- Elf_Rela *r, Elf_Sym *sym, const char *fromsec);
-
-};
-
-static void extable_mismatch_handler(const char *modname, struct elf_info *elf,
- const struct sectioncheck* const mismatch,
- Elf_Rela *r, Elf_Sym *sym,
- const char *fromsec);
-
-static const struct sectioncheck sectioncheck[] = {
-/* Do not reference init/exit code/data from
- * normal code and data
- */
-{
- .fromsec = { TEXT_SECTIONS, NULL },
- .bad_tosec = { ALL_INIT_SECTIONS, NULL },
- .mismatch = TEXT_TO_ANY_INIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-{
- .fromsec = { DATA_SECTIONS, NULL },
- .bad_tosec = { ALL_XXXINIT_SECTIONS, NULL },
- .mismatch = DATA_TO_ANY_INIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-{
- .fromsec = { DATA_SECTIONS, NULL },
- .bad_tosec = { INIT_SECTIONS, NULL },
- .mismatch = DATA_TO_ANY_INIT,
- .symbol_white_list = {
- "*_template", "*_timer", "*_sht", "*_ops",
- "*_probe", "*_probe_one", "*_console", NULL
- },
-},
-{
- .fromsec = { TEXT_SECTIONS, NULL },
- .bad_tosec = { ALL_EXIT_SECTIONS, NULL },
- .mismatch = TEXT_TO_ANY_EXIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-{
- .fromsec = { DATA_SECTIONS, NULL },
- .bad_tosec = { ALL_EXIT_SECTIONS, NULL },
- .mismatch = DATA_TO_ANY_EXIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-/* Do not reference init code/data from meminit code/data */
-{
- .fromsec = { ALL_XXXINIT_SECTIONS, NULL },
- .bad_tosec = { INIT_SECTIONS, NULL },
- .mismatch = XXXINIT_TO_SOME_INIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-/* Do not reference exit code/data from memexit code/data */
-{
- .fromsec = { ALL_XXXEXIT_SECTIONS, NULL },
- .bad_tosec = { EXIT_SECTIONS, NULL },
- .mismatch = XXXEXIT_TO_SOME_EXIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-/* Do not use exit code/data from init code */
-{
- .fromsec = { ALL_INIT_SECTIONS, NULL },
- .bad_tosec = { ALL_EXIT_SECTIONS, NULL },
- .mismatch = ANY_INIT_TO_ANY_EXIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-/* Do not use init code/data from exit code */
-{
- .fromsec = { ALL_EXIT_SECTIONS, NULL },
- .bad_tosec = { ALL_INIT_SECTIONS, NULL },
- .mismatch = ANY_EXIT_TO_ANY_INIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-{
- .fromsec = { ALL_PCI_INIT_SECTIONS, NULL },
- .bad_tosec = { INIT_SECTIONS, NULL },
- .mismatch = ANY_INIT_TO_ANY_EXIT,
- .symbol_white_list = { NULL },
-},
-/* Do not export init/exit functions or data */
-{
- .fromsec = { "__ksymtab*", NULL },
- .bad_tosec = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
- .mismatch = EXPORT_TO_INIT_EXIT,
- .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
-},
-{
- .fromsec = { "__ex_table", NULL },
- /* If you're adding any new black-listed sections in here, consider
- * adding a special 'printer' for them in scripts/check_extable.
- */
- .bad_tosec = { ".altinstr_replacement", NULL },
- .good_tosec = {ALL_TEXT_SECTIONS , NULL},
- .mismatch = EXTABLE_TO_NON_TEXT,
- .handler = extable_mismatch_handler,
-}
-};
-
-static const struct sectioncheck *section_mismatch(
- const char *fromsec, const char *tosec)
-{
- int i;
- int elems = sizeof(sectioncheck) / sizeof(struct sectioncheck);
- const struct sectioncheck *check = &sectioncheck[0];
-
- /*
- * The target section could be the SHT_NUL section when we're
- * handling relocations to un-resolved symbols, trying to match it
- * doesn't make much sense and causes build failures on parisc
- * architectures.
- */
- if (*tosec == '\0')
- return NULL;
-
- for (i = 0; i < elems; i++) {
- if (match(fromsec, check->fromsec)) {
- if (check->bad_tosec[0] && match(tosec, check->bad_tosec))
- return check;
- if (check->good_tosec[0] && !match(tosec, check->good_tosec))
- return check;
- }
- check++;
- }
- return NULL;
-}
-
-/**
- * Whitelist to allow certain references to pass with no warning.
- *
- * Pattern 1:
- * If a module parameter is declared __initdata and permissions=0
- * then this is legal despite the warning generated.
- * We cannot see value of permissions here, so just ignore
- * this pattern.
- * The pattern is identified by:
- * tosec = .init.data
- * fromsec = .data*
- * atsym =__param*
- *
- * Pattern 1a:
- * module_param_call() ops can refer to __init set function if permissions=0
- * The pattern is identified by:
- * tosec = .init.text
- * fromsec = .data*
- * atsym = __param_ops_*
- *
- * Pattern 2:
- * Many drivers utilise a *driver container with references to
- * add, remove, probe functions etc.
- * the pattern is identified by:
- * tosec = init or exit section
- * fromsec = data section
- * atsym = *driver, *_template, *_sht, *_ops, *_probe,
- * *probe_one, *_console, *_timer
- *
- * Pattern 3:
- * Whitelist all references from .head.text to any init section
- *
- * Pattern 4:
- * Some symbols belong to init section but still it is ok to reference
- * these from non-init sections as these symbols don't have any memory
- * allocated for them and symbol address and value are same. So even
- * if init section is freed, its ok to reference those symbols.
- * For ex. symbols marking the init section boundaries.
- * This pattern is identified by
- * refsymname = __init_begin, _sinittext, _einittext
- *
- * Pattern 5:
- * GCC may optimize static inlines when fed constant arg(s) resulting
- * in functions like cpumask_empty() -- generating an associated symbol
- * cpumask_empty.constprop.3 that appears in the audit. If the const that
- * is passed in comes from __init, like say nmi_ipi_mask, we get a
- * meaningless section warning. May need to add isra symbols too...
- * This pattern is identified by
- * tosec = init section
- * fromsec = text section
- * refsymname = *.constprop.*
- *
- * Pattern 6:
- * Hide section mismatch warnings for ELF local symbols. The goal
- * is to eliminate false positive modpost warnings caused by
- * compiler-generated ELF local symbol names such as ".LANCHOR1".
- * Autogenerated symbol names bypass modpost's "Pattern 2"
- * whitelisting, which relies on pattern-matching against symbol
- * names to work. (One situation where gcc can autogenerate ELF
- * local symbols is when "-fsection-anchors" is used.)
- **/
-static int secref_whitelist(const struct sectioncheck *mismatch,
- const char *fromsec, const char *fromsym,
- const char *tosec, const char *tosym)
-{
- /* Check for pattern 1 */
- if (match(tosec, init_data_sections) &&
- match(fromsec, data_sections) &&
- strstarts(fromsym, "__param"))
- return 0;
-
- /* Check for pattern 1a */
- if (strcmp(tosec, ".init.text") == 0 &&
- match(fromsec, data_sections) &&
- strstarts(fromsym, "__param_ops_"))
- return 0;
-
- /* Check for pattern 2 */
- if (match(tosec, init_exit_sections) &&
- match(fromsec, data_sections) &&
- match(fromsym, mismatch->symbol_white_list))
- return 0;
-
- /* Check for pattern 3 */
- if (match(fromsec, head_sections) &&
- match(tosec, init_sections))
- return 0;
-
- /* Check for pattern 4 */
- if (match(tosym, linker_symbols))
- return 0;
-
- /* Check for pattern 5 */
- if (match(fromsec, text_sections) &&
- match(tosec, init_sections) &&
- match(fromsym, optim_symbols))
- return 0;
-
- /* Check for pattern 6 */
- if (strstarts(fromsym, ".L"))
- return 0;
-
- return 1;
-}
-
-static inline int is_arm_mapping_symbol(const char *str)
-{
- return str[0] == '$' && strchr("axtd", str[1])
- && (str[2] == '\0' || str[2] == '.');
-}
-
-/*
- * If there's no name there, ignore it; likewise, ignore it if it's
- * one of the magic symbols emitted used by current ARM tools.
- *
- * Otherwise if find_symbols_between() returns those symbols, they'll
- * fail the whitelist tests and cause lots of false alarms ... fixable
- * only by merging __exit and __init sections into __text, bloating
- * the kernel (which is especially evil on embedded platforms).
- */
-static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
-{
- const char *name = elf->strtab + sym->st_name;
-
- if (!name || !strlen(name))
- return 0;
- return !is_arm_mapping_symbol(name);
-}
-
-/**
- * Find symbol based on relocation record info.
- * In some cases the symbol supplied is a valid symbol so
- * return refsym. If st_name != 0 we assume this is a valid symbol.
- * In other cases the symbol needs to be looked up in the symbol table
- * based on section and address.
- * **/
-static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf64_Sword addr,
- Elf_Sym *relsym)
-{
- Elf_Sym *sym;
- Elf_Sym *near = NULL;
- Elf64_Sword distance = 20;
- Elf64_Sword d;
- unsigned int relsym_secindex;
-
- if (relsym->st_name != 0)
- return relsym;
-
- relsym_secindex = get_secindex(elf, relsym);
- for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
- if (get_secindex(elf, sym) != relsym_secindex)
- continue;
- if (ELF_ST_TYPE(sym->st_info) == STT_SECTION)
- continue;
- if (!is_valid_name(elf, sym))
- continue;
- if (sym->st_value == addr)
- return sym;
- /* Find a symbol nearby - addr are maybe negative */
- d = sym->st_value - addr;
- if (d < 0)
- d = addr - sym->st_value;
- if (d < distance) {
- distance = d;
- near = sym;
- }
- }
- /* We need a close match */
- if (distance < 20)
- return near;
- else
- return NULL;
-}
-
-/*
- * Find symbols before or equal addr and after addr - in the section sec.
- * If we find two symbols with equal offset prefer one with a valid name.
- * The ELF format may have a better way to detect what type of symbol
- * it is, but this works for now.
- **/
-static Elf_Sym *find_elf_symbol2(struct elf_info *elf, Elf_Addr addr,
- const char *sec)
-{
- Elf_Sym *sym;
- Elf_Sym *near = NULL;
- Elf_Addr distance = ~0;
-
- for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
- const char *symsec;
-
- if (is_shndx_special(sym->st_shndx))
- continue;
- symsec = sec_name(elf, get_secindex(elf, sym));
- if (strcmp(symsec, sec) != 0)
- continue;
- if (!is_valid_name(elf, sym))
- continue;
- if (sym->st_value <= addr) {
- if ((addr - sym->st_value) < distance) {
- distance = addr - sym->st_value;
- near = sym;
- } else if ((addr - sym->st_value) == distance) {
- near = sym;
- }
- }
- }
- return near;
-}
-
-/*
- * Convert a section name to the function/data attribute
- * .init.text => __init
- * .memexitconst => __memconst
- * etc.
- *
- * The memory of returned value has been allocated on a heap. The user of this
- * method should free it after usage.
-*/
-static char *sec2annotation(const char *s)
-{
- if (match(s, init_exit_sections)) {
- char *p = NOFAIL(malloc(20));
- char *r = p;
-
- *p++ = '_';
- *p++ = '_';
- if (*s == '.')
- s++;
- while (*s && *s != '.')
- *p++ = *s++;
- *p = '\0';
- if (*s == '.')
- s++;
- if (strstr(s, "rodata") != NULL)
- strcat(p, "const ");
- else if (strstr(s, "data") != NULL)
- strcat(p, "data ");
- else
- strcat(p, " ");
- return r;
- } else {
- return NOFAIL(strdup(""));
- }
-}
-
-static int is_function(Elf_Sym *sym)
-{
- if (sym)
- return ELF_ST_TYPE(sym->st_info) == STT_FUNC;
- else
- return -1;
-}
-
-static void print_section_list(const char * const list[20])
-{
- const char *const *s = list;
-
- while (*s) {
- fprintf(stderr, "%s", *s);
- s++;
- if (*s)
- fprintf(stderr, ", ");
- }
- fprintf(stderr, "\n");
-}
-
-static inline void get_pretty_name(int is_func, const char** name, const char** name_p)
-{
- switch (is_func) {
- case 0: *name = "variable"; *name_p = ""; break;
- case 1: *name = "function"; *name_p = "()"; break;
- default: *name = "(unknown reference)"; *name_p = ""; break;
- }
-}
-
-/*
- * Print a warning about a section mismatch.
- * Try to find symbols near it so user can find it.
- * Check whitelist before warning - it may be a false positive.
- */
-static void report_sec_mismatch(const char *modname,
- const struct sectioncheck *mismatch,
- const char *fromsec,
- unsigned long long fromaddr,
- const char *fromsym,
- int from_is_func,
- const char *tosec, const char *tosym,
- int to_is_func)
-{
- const char *from, *from_p;
- const char *to, *to_p;
- char *prl_from;
- char *prl_to;
-
- sec_mismatch_count++;
-
- get_pretty_name(from_is_func, &from, &from_p);
- get_pretty_name(to_is_func, &to, &to_p);
-
- warn("%s(%s+0x%llx): Section mismatch in reference from the %s %s%s "
- "to the %s %s:%s%s\n",
- modname, fromsec, fromaddr, from, fromsym, from_p, to, tosec,
- tosym, to_p);
-
- switch (mismatch->mismatch) {
- case TEXT_TO_ANY_INIT:
- prl_from = sec2annotation(fromsec);
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The function %s%s() references\n"
- "the %s %s%s%s.\n"
- "This is often because %s lacks a %s\n"
- "annotation or the annotation of %s is wrong.\n",
- prl_from, fromsym,
- to, prl_to, tosym, to_p,
- fromsym, prl_to, tosym);
- free(prl_from);
- free(prl_to);
- break;
- case DATA_TO_ANY_INIT: {
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The variable %s references\n"
- "the %s %s%s%s\n"
- "If the reference is valid then annotate the\n"
- "variable with __init* or __refdata (see linux/init.h) "
- "or name the variable:\n",
- fromsym, to, prl_to, tosym, to_p);
- print_section_list(mismatch->symbol_white_list);
- free(prl_to);
- break;
- }
- case TEXT_TO_ANY_EXIT:
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The function %s() references a %s in an exit section.\n"
- "Often the %s %s%s has valid usage outside the exit section\n"
- "and the fix is to remove the %sannotation of %s.\n",
- fromsym, to, to, tosym, to_p, prl_to, tosym);
- free(prl_to);
- break;
- case DATA_TO_ANY_EXIT: {
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The variable %s references\n"
- "the %s %s%s%s\n"
- "If the reference is valid then annotate the\n"
- "variable with __exit* (see linux/init.h) or "
- "name the variable:\n",
- fromsym, to, prl_to, tosym, to_p);
- print_section_list(mismatch->symbol_white_list);
- free(prl_to);
- break;
- }
- case XXXINIT_TO_SOME_INIT:
- case XXXEXIT_TO_SOME_EXIT:
- prl_from = sec2annotation(fromsec);
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The %s %s%s%s references\n"
- "a %s %s%s%s.\n"
- "If %s is only used by %s then\n"
- "annotate %s with a matching annotation.\n",
- from, prl_from, fromsym, from_p,
- to, prl_to, tosym, to_p,
- tosym, fromsym, tosym);
- free(prl_from);
- free(prl_to);
- break;
- case ANY_INIT_TO_ANY_EXIT:
- prl_from = sec2annotation(fromsec);
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The %s %s%s%s references\n"
- "a %s %s%s%s.\n"
- "This is often seen when error handling "
- "in the init function\n"
- "uses functionality in the exit path.\n"
- "The fix is often to remove the %sannotation of\n"
- "%s%s so it may be used outside an exit section.\n",
- from, prl_from, fromsym, from_p,
- to, prl_to, tosym, to_p,
- prl_to, tosym, to_p);
- free(prl_from);
- free(prl_to);
- break;
- case ANY_EXIT_TO_ANY_INIT:
- prl_from = sec2annotation(fromsec);
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The %s %s%s%s references\n"
- "a %s %s%s%s.\n"
- "This is often seen when error handling "
- "in the exit function\n"
- "uses functionality in the init path.\n"
- "The fix is often to remove the %sannotation of\n"
- "%s%s so it may be used outside an init section.\n",
- from, prl_from, fromsym, from_p,
- to, prl_to, tosym, to_p,
- prl_to, tosym, to_p);
- free(prl_from);
- free(prl_to);
- break;
- case EXPORT_TO_INIT_EXIT:
- prl_to = sec2annotation(tosec);
- fprintf(stderr,
- "The symbol %s is exported and annotated %s\n"
- "Fix this by removing the %sannotation of %s "
- "or drop the export.\n",
- tosym, prl_to, prl_to, tosym);
- free(prl_to);
- break;
- case EXTABLE_TO_NON_TEXT:
- fatal("There's a special handler for this mismatch type, "
- "we should never get here.");
- break;
- }
- fprintf(stderr, "\n");
-}
-
-static void default_mismatch_handler(const char *modname, struct elf_info *elf,
- const struct sectioncheck* const mismatch,
- Elf_Rela *r, Elf_Sym *sym, const char *fromsec)
-{
- const char *tosec;
- Elf_Sym *to;
- Elf_Sym *from;
- const char *tosym;
- const char *fromsym;
-
- from = find_elf_symbol2(elf, r->r_offset, fromsec);
- fromsym = sym_name(elf, from);
-
- if (strstarts(fromsym, "reference___initcall"))
- return;
-
- tosec = sec_name(elf, get_secindex(elf, sym));
- to = find_elf_symbol(elf, r->r_addend, sym);
- tosym = sym_name(elf, to);
-
- /* check whitelist - we may ignore it */
- if (secref_whitelist(mismatch,
- fromsec, fromsym, tosec, tosym)) {
- report_sec_mismatch(modname, mismatch,
- fromsec, r->r_offset, fromsym,
- is_function(from), tosec, tosym,
- is_function(to));
- }
-}
-
-static int is_executable_section(struct elf_info* elf, unsigned int section_index)
-{
- if (section_index > elf->num_sections)
- fatal("section_index is outside elf->num_sections!\n");
-
- return ((elf->sechdrs[section_index].sh_flags & SHF_EXECINSTR) == SHF_EXECINSTR);
-}
-
-/*
- * We rely on a gross hack in section_rel[a]() calling find_extable_entry_size()
- * to know the sizeof(struct exception_table_entry) for the target architecture.
- */
-static unsigned int extable_entry_size = 0;
-static void find_extable_entry_size(const char* const sec, const Elf_Rela* r)
-{
- /*
- * If we're currently checking the second relocation within __ex_table,
- * that relocation offset tells us the offsetof(struct
- * exception_table_entry, fixup) which is equal to sizeof(struct
- * exception_table_entry) divided by two. We use that to our advantage
- * since there's no portable way to get that size as every architecture
- * seems to go with different sized types. Not pretty but better than
- * hard-coding the size for every architecture..
- */
- if (!extable_entry_size)
- extable_entry_size = r->r_offset * 2;
-}
-
-static inline bool is_extable_fault_address(Elf_Rela *r)
-{
- /*
- * extable_entry_size is only discovered after we've handled the
- * _second_ relocation in __ex_table, so only abort when we're not
- * handling the first reloc and extable_entry_size is zero.
- */
- if (r->r_offset && extable_entry_size == 0)
- fatal("extable_entry size hasn't been discovered!\n");
-
- return ((r->r_offset == 0) ||
- (r->r_offset % extable_entry_size == 0));
-}
-
-#define is_second_extable_reloc(Start, Cur, Sec) \
- (((Cur) == (Start) + 1) && (strcmp("__ex_table", (Sec)) == 0))
-
-static void report_extable_warnings(const char* modname, struct elf_info* elf,
- const struct sectioncheck* const mismatch,
- Elf_Rela* r, Elf_Sym* sym,
- const char* fromsec, const char* tosec)
-{
- Elf_Sym* fromsym = find_elf_symbol2(elf, r->r_offset, fromsec);
- const char* fromsym_name = sym_name(elf, fromsym);
- Elf_Sym* tosym = find_elf_symbol(elf, r->r_addend, sym);
- const char* tosym_name = sym_name(elf, tosym);
- const char* from_pretty_name;
- const char* from_pretty_name_p;
- const char* to_pretty_name;
- const char* to_pretty_name_p;
-
- get_pretty_name(is_function(fromsym),
- &from_pretty_name, &from_pretty_name_p);
- get_pretty_name(is_function(tosym),
- &to_pretty_name, &to_pretty_name_p);
-
- warn("%s(%s+0x%lx): Section mismatch in reference"
- " from the %s %s%s to the %s %s:%s%s\n",
- modname, fromsec, (long)r->r_offset, from_pretty_name,
- fromsym_name, from_pretty_name_p,
- to_pretty_name, tosec, tosym_name, to_pretty_name_p);
-
- if (!match(tosec, mismatch->bad_tosec) &&
- is_executable_section(elf, get_secindex(elf, sym)))
- fprintf(stderr,
- "The relocation at %s+0x%lx references\n"
- "section \"%s\" which is not in the list of\n"
- "authorized sections. If you're adding a new section\n"
- "and/or if this reference is valid, add \"%s\" to the\n"
- "list of authorized sections to jump to on fault.\n"
- "This can be achieved by adding \"%s\" to \n"
- "OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.\n",
- fromsec, (long)r->r_offset, tosec, tosec, tosec);
-}
-
-static void extable_mismatch_handler(const char* modname, struct elf_info *elf,
- const struct sectioncheck* const mismatch,
- Elf_Rela* r, Elf_Sym* sym,
- const char *fromsec)
-{
- const char* tosec = sec_name(elf, get_secindex(elf, sym));
-
- sec_mismatch_count++;
-
- report_extable_warnings(modname, elf, mismatch, r, sym, fromsec, tosec);
-
- if (match(tosec, mismatch->bad_tosec))
- fatal("The relocation at %s+0x%lx references\n"
- "section \"%s\" which is black-listed.\n"
- "Something is seriously wrong and should be fixed.\n"
- "You might get more information about where this is\n"
- "coming from by using scripts/check_extable.sh %s\n",
- fromsec, (long)r->r_offset, tosec, modname);
- else if (!is_executable_section(elf, get_secindex(elf, sym))) {
- if (is_extable_fault_address(r))
- fatal("The relocation at %s+0x%lx references\n"
- "section \"%s\" which is not executable, IOW\n"
- "it is not possible for the kernel to fault\n"
- "at that address. Something is seriously wrong\n"
- "and should be fixed.\n",
- fromsec, (long)r->r_offset, tosec);
- else
- fatal("The relocation at %s+0x%lx references\n"
- "section \"%s\" which is not executable, IOW\n"
- "the kernel will fault if it ever tries to\n"
- "jump to it. Something is seriously wrong\n"
- "and should be fixed.\n",
- fromsec, (long)r->r_offset, tosec);
- }
-}
-
-static void check_section_mismatch(const char *modname, struct elf_info *elf,
- Elf_Rela *r, Elf_Sym *sym, const char *fromsec)
-{
- const char *tosec = sec_name(elf, get_secindex(elf, sym));
- const struct sectioncheck *mismatch = section_mismatch(fromsec, tosec);
-
- if (mismatch) {
- if (mismatch->handler)
- mismatch->handler(modname, elf, mismatch,
- r, sym, fromsec);
- else
- default_mismatch_handler(modname, elf, mismatch,
- r, sym, fromsec);
- }
-}
-
-static unsigned int *reloc_location(struct elf_info *elf,
- Elf_Shdr *sechdr, Elf_Rela *r)
-{
- return sym_get_data_by_offset(elf, sechdr->sh_info, r->r_offset);
-}
-
-static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
-{
- unsigned int r_typ = ELF_R_TYPE(r->r_info);
- unsigned int *location = reloc_location(elf, sechdr, r);
-
- switch (r_typ) {
- case R_386_32:
- r->r_addend = TO_NATIVE(*location);
- break;
- case R_386_PC32:
- r->r_addend = TO_NATIVE(*location) + 4;
- /* For CONFIG_RELOCATABLE=y */
- if (elf->hdr->e_type == ET_EXEC)
- r->r_addend += r->r_offset;
- break;
- }
- return 0;
-}
-
-#ifndef R_ARM_CALL
-#define R_ARM_CALL 28
-#endif
-#ifndef R_ARM_JUMP24
-#define R_ARM_JUMP24 29
-#endif
-
-#ifndef R_ARM_THM_CALL
-#define R_ARM_THM_CALL 10
-#endif
-#ifndef R_ARM_THM_JUMP24
-#define R_ARM_THM_JUMP24 30
-#endif
-#ifndef R_ARM_THM_JUMP19
-#define R_ARM_THM_JUMP19 51
-#endif
-
-static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
-{
- unsigned int r_typ = ELF_R_TYPE(r->r_info);
-
- switch (r_typ) {
- case R_ARM_ABS32:
- /* From ARM ABI: (S + A) | T */
- r->r_addend = (int)(long)
- (elf->symtab_start + ELF_R_SYM(r->r_info));
- break;
- case R_ARM_PC24:
- case R_ARM_CALL:
- case R_ARM_JUMP24:
- case R_ARM_THM_CALL:
- case R_ARM_THM_JUMP24:
- case R_ARM_THM_JUMP19:
- /* From ARM ABI: ((S + A) | T) - P */
- r->r_addend = (int)(long)(elf->hdr +
- sechdr->sh_offset +
- (r->r_offset - sechdr->sh_addr));
- break;
- default:
- return 1;
- }
- return 0;
-}
-
-static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
-{
- unsigned int r_typ = ELF_R_TYPE(r->r_info);
- unsigned int *location = reloc_location(elf, sechdr, r);
- unsigned int inst;
-
- if (r_typ == R_MIPS_HI16)
- return 1; /* skip this */
- inst = TO_NATIVE(*location);
- switch (r_typ) {
- case R_MIPS_LO16:
- r->r_addend = inst & 0xffff;
- break;
- case R_MIPS_26:
- r->r_addend = (inst & 0x03ffffff) << 2;
- break;
- case R_MIPS_32:
- r->r_addend = inst;
- break;
- }
- return 0;
-}
-
-#ifndef EM_RISCV
-#define EM_RISCV 243
-#endif
-
-#ifndef R_RISCV_SUB32
-#define R_RISCV_SUB32 39
-#endif
-
-static void section_rela(const char *modname, struct elf_info *elf,
- Elf_Shdr *sechdr)
-{
- Elf_Sym *sym;
- Elf_Rela *rela;
- Elf_Rela r;
- unsigned int r_sym;
- const char *fromsec;
-
- Elf_Rela *start = (void *)elf->hdr + sechdr->sh_offset;
- Elf_Rela *stop = (void *)start + sechdr->sh_size;
-
- fromsec = sech_name(elf, sechdr);
- fromsec += strlen(".rela");
- /* if from section (name) is know good then skip it */
- if (match(fromsec, section_white_list))
- return;
-
- for (rela = start; rela < stop; rela++) {
- r.r_offset = TO_NATIVE(rela->r_offset);
-#if KERNEL_ELFCLASS == ELFCLASS64
- if (elf->hdr->e_machine == EM_MIPS) {
- unsigned int r_typ;
- r_sym = ELF64_MIPS_R_SYM(rela->r_info);
- r_sym = TO_NATIVE(r_sym);
- r_typ = ELF64_MIPS_R_TYPE(rela->r_info);
- r.r_info = ELF64_R_INFO(r_sym, r_typ);
- } else {
- r.r_info = TO_NATIVE(rela->r_info);
- r_sym = ELF_R_SYM(r.r_info);
- }
-#else
- r.r_info = TO_NATIVE(rela->r_info);
- r_sym = ELF_R_SYM(r.r_info);
-#endif
- r.r_addend = TO_NATIVE(rela->r_addend);
- switch (elf->hdr->e_machine) {
- case EM_RISCV:
- if (!strcmp("__ex_table", fromsec) &&
- ELF_R_TYPE(r.r_info) == R_RISCV_SUB32)
- continue;
- break;
- }
- sym = elf->symtab_start + r_sym;
- /* Skip special sections */
- if (is_shndx_special(sym->st_shndx))
- continue;
- if (is_second_extable_reloc(start, rela, fromsec))
- find_extable_entry_size(fromsec, &r);
- check_section_mismatch(modname, elf, &r, sym, fromsec);
- }
-}
-
-static void section_rel(const char *modname, struct elf_info *elf,
- Elf_Shdr *sechdr)
-{
- Elf_Sym *sym;
- Elf_Rel *rel;
- Elf_Rela r;
- unsigned int r_sym;
- const char *fromsec;
-
- Elf_Rel *start = (void *)elf->hdr + sechdr->sh_offset;
- Elf_Rel *stop = (void *)start + sechdr->sh_size;
-
- fromsec = sech_name(elf, sechdr);
- fromsec += strlen(".rel");
- /* if from section (name) is know good then skip it */
- if (match(fromsec, section_white_list))
- return;
-
- for (rel = start; rel < stop; rel++) {
- r.r_offset = TO_NATIVE(rel->r_offset);
-#if KERNEL_ELFCLASS == ELFCLASS64
- if (elf->hdr->e_machine == EM_MIPS) {
- unsigned int r_typ;
- r_sym = ELF64_MIPS_R_SYM(rel->r_info);
- r_sym = TO_NATIVE(r_sym);
- r_typ = ELF64_MIPS_R_TYPE(rel->r_info);
- r.r_info = ELF64_R_INFO(r_sym, r_typ);
- } else {
- r.r_info = TO_NATIVE(rel->r_info);
- r_sym = ELF_R_SYM(r.r_info);
- }
-#else
- r.r_info = TO_NATIVE(rel->r_info);
- r_sym = ELF_R_SYM(r.r_info);
-#endif
- r.r_addend = 0;
- switch (elf->hdr->e_machine) {
- case EM_386:
- if (addend_386_rel(elf, sechdr, &r))
- continue;
- break;
- case EM_ARM:
- if (addend_arm_rel(elf, sechdr, &r))
- continue;
- break;
- case EM_MIPS:
- if (addend_mips_rel(elf, sechdr, &r))
- continue;
- break;
- }
- sym = elf->symtab_start + r_sym;
- /* Skip special sections */
- if (is_shndx_special(sym->st_shndx))
- continue;
- if (is_second_extable_reloc(start, rel, fromsec))
- find_extable_entry_size(fromsec, &r);
- check_section_mismatch(modname, elf, &r, sym, fromsec);
- }
-}
-
-/**
- * A module includes a number of sections that are discarded
- * either when loaded or when used as built-in.
- * For loaded modules all functions marked __init and all data
- * marked __initdata will be discarded when the module has been initialized.
- * Likewise for modules used built-in the sections marked __exit
- * are discarded because __exit marked function are supposed to be called
- * only when a module is unloaded which never happens for built-in modules.
- * The check_sec_ref() function traverses all relocation records
- * to find all references to a section that reference a section that will
- * be discarded and warns about it.
- **/
-static void check_sec_ref(struct module *mod, const char *modname,
- struct elf_info *elf)
-{
- int i;
- Elf_Shdr *sechdrs = elf->sechdrs;
-
- /* Walk through all sections */
- for (i = 0; i < elf->num_sections; i++) {
- check_section(modname, elf, &elf->sechdrs[i]);
- /* We want to process only relocation sections and not .init */
- if (sechdrs[i].sh_type == SHT_RELA)
- section_rela(modname, elf, &elf->sechdrs[i]);
- else if (sechdrs[i].sh_type == SHT_REL)
- section_rel(modname, elf, &elf->sechdrs[i]);
- }
-}
-
static char *remove_dot(char *s)
{
size_t n = strcspn(s, ".");
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index d9daeff07b83..ffa4512e992f 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -52,28 +52,6 @@
#define ELF_R_TYPE ELF64_R_TYPE
#endif

-/* The 64-bit MIPS ELF ABI uses an unusual reloc format. */
-typedef struct
-{
- Elf32_Word r_sym; /* Symbol index */
- unsigned char r_ssym; /* Special symbol for 2nd relocation */
- unsigned char r_type3; /* 3rd relocation type */
- unsigned char r_type2; /* 2nd relocation type */
- unsigned char r_type1; /* 1st relocation type */
-} _Elf64_Mips_R_Info;
-
-typedef union
-{
- Elf64_Xword r_info_number;
- _Elf64_Mips_R_Info r_info_fields;
-} _Elf64_Mips_R_Info_union;
-
-#define ELF64_MIPS_R_SYM(i) \
- ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_sym)
-
-#define ELF64_MIPS_R_TYPE(i) \
- ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_type1)
-
#if KERNEL_ELFDATA != HOST_ELFDATA

static inline void __endian(const void *src, void *dest, unsigned int size)
@@ -96,6 +74,7 @@ static inline void __endian(const void *src, void *dest, unsigned int size)

#endif

+#define strstarts(str, prefix) (strncmp(str, prefix, strlen(prefix)) == 0)
#define NOFAIL(ptr) do_nofail((ptr), #ptr)
void *do_nofail(void *ptr, const char *expr);

@@ -173,6 +152,10 @@ static inline unsigned int get_secindex(const struct elf_info *info,
return info->symtab_shndx_start[sym - info->symtab_start];
}

+/* section-check.c */
+void check_sec_ref(struct module *mod, const char *modname,
+ struct elf_info *elf);
+
/* file2alias.c */
void handle_moddevtable(struct module *mod, struct elf_info *info,
Elf_Sym *sym, const char *symname);
@@ -182,6 +165,13 @@ void add_moddevtable(struct buffer *buf, struct module *mod);
void get_src_version(const char *modname, char sum[], unsigned sumlen);

/* from modpost.c */
+extern int sec_mismatch_count;
+
+void *sym_get_data_by_offset(const struct elf_info *info,
+ unsigned int secindex, unsigned long offset);
+const char *sech_name(const struct elf_info *info, Elf_Shdr *sechdr);
+const char *sec_name(const struct elf_info *info, int secindex);
+
char *read_text_file(const char *filename);
char *get_line(char **stringp);

diff --git a/scripts/mod/section-check.c b/scripts/mod/section-check.c
new file mode 100644
index 000000000000..0412658751a1
--- /dev/null
+++ b/scripts/mod/section-check.c
@@ -0,0 +1,1222 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "modpost.h"
+
+/* The 64-bit MIPS ELF ABI uses an unusual reloc format. */
+typedef struct {
+ Elf32_Word r_sym; /* Symbol index */
+ unsigned char r_ssym; /* Special symbol for 2nd relocation */
+ unsigned char r_type3; /* 3rd relocation type */
+ unsigned char r_type2; /* 2nd relocation type */
+ unsigned char r_type1; /* 1st relocation type */
+} _Elf64_Mips_R_Info;
+
+typedef union {
+ Elf64_Xword r_info_number;
+ _Elf64_Mips_R_Info r_info_fields;
+} _Elf64_Mips_R_Info_union;
+
+#define ELF64_MIPS_R_SYM(i) \
+ ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_sym)
+
+#define ELF64_MIPS_R_TYPE(i) \
+ ((__extension__ (_Elf64_Mips_R_Info_union)(i)).r_info_fields.r_type1)
+
+/* Test if string s ends in string sub. Return 0 if match. */
+static int strrcmp(const char *s, const char *sub)
+{
+ int slen, sublen;
+
+ if (!s || !sub)
+ return 1;
+
+ slen = strlen(s);
+ sublen = strlen(sub);
+
+ if ((slen == 0) || (sublen == 0))
+ return 1;
+
+ if (sublen > slen)
+ return 1;
+
+ return memcmp(s + slen - sublen, sub, sublen);
+}
+
+static const char *sym_name(struct elf_info *elf, Elf_Sym *sym)
+{
+ if (sym)
+ return elf->strtab + sym->st_name;
+ else
+ return "(unknown)";
+}
+
+/*
+ * The pattern is an array of simple patterns.
+ * "foo" will match an exact string equal to "foo"
+ * "*foo" will match a string that ends with "foo"
+ * "foo*" will match a string that begins with "foo"
+ * "*foo*" will match a string that contains "foo"
+ */
+static int match(const char *sym, const char * const pat[])
+{
+ const char *p;
+
+ while (*pat) {
+ const char *endp;
+
+ p = *pat++;
+ endp = p + strlen(p) - 1;
+
+ /* "*foo*" */
+ if (*p == '*' && *endp == '*') {
+ char *bare = NOFAIL(strndup(p + 1, strlen(p) - 2));
+ char *here = strstr(sym, bare);
+
+ free(bare);
+ if (here != NULL)
+ return 1;
+ }
+ /* "*foo" */
+ else if (*p == '*') {
+ if (strrcmp(sym, p + 1) == 0)
+ return 1;
+ }
+ /* "foo*" */
+ else if (*endp == '*') {
+ if (strncmp(sym, p, strlen(p) - 1) == 0)
+ return 1;
+ }
+ /* no wildcards */
+ else {
+ if (strcmp(p, sym) == 0)
+ return 1;
+ }
+ }
+ /* no match */
+ return 0;
+}
+
+/* sections that we do not want to do full section mismatch check on */
+static const char *const section_white_list[] = {
+ ".comment*",
+ ".debug*",
+ ".cranges", /* sh64 */
+ ".zdebug*", /* Compressed debug sections. */
+ ".GCC.command.line", /* record-gcc-switches */
+ ".mdebug*", /* alpha, score, mips etc. */
+ ".pdr", /* alpha, score, mips etc. */
+ ".stab*",
+ ".note*",
+ ".got*",
+ ".toc*",
+ ".xt.prop", /* xtensa */
+ ".xt.lit", /* xtensa */
+ ".arcextmap*", /* arc */
+ ".gnu.linkonce.arcext*", /* arc : modules */
+ ".cmem*", /* EZchip */
+ ".fmt_slot*", /* EZchip */
+ ".gnu.lto*",
+ ".discard.*",
+ NULL
+};
+
+/*
+ * This is used to find sections missing the SHF_ALLOC flag.
+ * The cause of this is often a section specified in assembler
+ * without "ax" / "aw".
+ */
+static void check_section(const char *modname, struct elf_info *elf,
+ Elf_Shdr *sechdr)
+{
+ const char *sec = sech_name(elf, sechdr);
+
+ if (sechdr->sh_type == SHT_PROGBITS &&
+ !(sechdr->sh_flags & SHF_ALLOC) &&
+ !match(sec, section_white_list)) {
+ warn("%s (%s): unexpected non-allocatable section.\n"
+ "Did you forget to use \"ax\"/\"aw\" in a .S file?\n"
+ "Note that for example <linux/init.h> contains\n"
+ "section definitions for use in .S files.\n\n",
+ modname, sec);
+ }
+}
+
+#define ALL_INIT_DATA_SECTIONS \
+ ".init.setup", ".init.rodata", ".meminit.rodata", \
+ ".init.data", ".meminit.data"
+#define ALL_EXIT_DATA_SECTIONS \
+ ".exit.data", ".memexit.data"
+
+#define ALL_INIT_TEXT_SECTIONS \
+ ".init.text", ".meminit.text"
+#define ALL_EXIT_TEXT_SECTIONS \
+ ".exit.text", ".memexit.text"
+
+#define ALL_PCI_INIT_SECTIONS \
+ ".pci_fixup_early", ".pci_fixup_header", ".pci_fixup_final", \
+ ".pci_fixup_enable", ".pci_fixup_resume", \
+ ".pci_fixup_resume_early", ".pci_fixup_suspend"
+
+#define ALL_XXXINIT_SECTIONS MEM_INIT_SECTIONS
+#define ALL_XXXEXIT_SECTIONS MEM_EXIT_SECTIONS
+
+#define ALL_INIT_SECTIONS INIT_SECTIONS, ALL_XXXINIT_SECTIONS
+#define ALL_EXIT_SECTIONS EXIT_SECTIONS, ALL_XXXEXIT_SECTIONS
+
+#define DATA_SECTIONS ".data", ".data.rel"
+#define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \
+ ".kprobes.text", ".cpuidle.text", ".noinstr.text"
+#define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \
+ ".fixup", ".entry.text", ".exception.text", ".text.*", \
+ ".coldtext", ".softirqentry.text"
+
+#define INIT_SECTIONS ".init.*"
+#define MEM_INIT_SECTIONS ".meminit.*"
+
+#define EXIT_SECTIONS ".exit.*"
+#define MEM_EXIT_SECTIONS ".memexit.*"
+
+#define ALL_TEXT_SECTIONS ALL_INIT_TEXT_SECTIONS, ALL_EXIT_TEXT_SECTIONS, \
+ TEXT_SECTIONS, OTHER_TEXT_SECTIONS
+
+/* init data sections */
+static const char *const init_data_sections[] = {
+ ALL_INIT_DATA_SECTIONS, NULL
+};
+
+/* all init sections */
+static const char *const init_sections[] = {
+ ALL_INIT_SECTIONS, NULL
+};
+
+/* All init and exit sections (code + data) */
+static const char *const init_exit_sections[] = {
+ ALL_INIT_SECTIONS, ALL_EXIT_SECTIONS, NULL
+};
+
+/* all text sections */
+static const char *const text_sections[] = {
+ ALL_TEXT_SECTIONS, NULL
+};
+
+/* data section */
+static const char *const data_sections[] = {
+ DATA_SECTIONS, NULL
+};
+
+/* symbols in .data that may refer to init/exit sections */
+#define DEFAULT_SYMBOL_WHITE_LIST \
+ "*driver", \
+ "*_template", /* scsi uses *_template a lot */ \
+ "*_timer", /* arm uses ops structures named _timer a lot */ \
+ "*_sht", /* scsi also used *_sht to some extent */ \
+ "*_ops", \
+ "*_probe", \
+ "*_probe_one", \
+ "*_console"
+
+static const char *const head_sections[] = {
+ ".head.text*", NULL
+};
+static const char *const linker_symbols[] = {
+ "__init_begin", "_sinittext", "_einittext", NULL
+};
+static const char *const optim_symbols[] = {
+ "*.constprop.*", NULL
+};
+
+enum mismatch {
+ TEXT_TO_ANY_INIT,
+ DATA_TO_ANY_INIT,
+ TEXT_TO_ANY_EXIT,
+ DATA_TO_ANY_EXIT,
+ XXXINIT_TO_SOME_INIT,
+ XXXEXIT_TO_SOME_EXIT,
+ ANY_INIT_TO_ANY_EXIT,
+ ANY_EXIT_TO_ANY_INIT,
+ EXPORT_TO_INIT_EXIT,
+ EXTABLE_TO_NON_TEXT,
+};
+
+/*
+ * Describe how to match sections on different criteria:
+ *
+ * @fromsec: Array of sections to be matched.
+ *
+ * @bad_tosec: Relocations applied to a section in @fromsec to a section in
+ * this array is forbidden (black-list). Can be empty.
+ *
+ * @good_tosec: Relocations applied to a section in @fromsec must be
+ * targeting sections in this array (white-list). Can be empty.
+ *
+ * @mismatch: Type of mismatch.
+ *
+ * @symbol_white_list: Do not match a relocation to a symbol in this list
+ * even if it is targeting a section in @bad_to_sec.
+ *
+ * @handler: Specific handler to call when a match is found. If NULL,
+ * default_mismatch_handler() will be called.
+ */
+struct sectioncheck {
+ const char *fromsec[20];
+ const char *bad_tosec[20];
+ const char *good_tosec[20];
+ enum mismatch mismatch;
+ const char *symbol_white_list[20];
+ void (*handler)(const char *modname, struct elf_info *elf,
+ const struct sectioncheck *mismatch,
+ Elf_Rela *r, Elf_Sym *sym, const char *fromsec);
+};
+
+static void extable_mismatch_handler(const char *modname, struct elf_info *elf,
+ const struct sectioncheck *mismatch,
+ Elf_Rela *r, Elf_Sym *sym,
+ const char *fromsec);
+
+static const struct sectioncheck sectioncheck[] = {
+ /* Do not reference init/exit code/data from normal code and data */
+ {
+ .fromsec = { TEXT_SECTIONS, NULL },
+ .bad_tosec = { ALL_INIT_SECTIONS, NULL },
+ .mismatch = TEXT_TO_ANY_INIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ {
+ .fromsec = { DATA_SECTIONS, NULL },
+ .bad_tosec = { ALL_XXXINIT_SECTIONS, NULL },
+ .mismatch = DATA_TO_ANY_INIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ {
+ .fromsec = { DATA_SECTIONS, NULL },
+ .bad_tosec = { INIT_SECTIONS, NULL },
+ .mismatch = DATA_TO_ANY_INIT,
+ .symbol_white_list = {
+ "*_template", "*_timer", "*_sht", "*_ops",
+ "*_probe", "*_probe_one", "*_console", NULL
+ },
+ },
+ {
+ .fromsec = { TEXT_SECTIONS, NULL },
+ .bad_tosec = { ALL_EXIT_SECTIONS, NULL },
+ .mismatch = TEXT_TO_ANY_EXIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ {
+ .fromsec = { DATA_SECTIONS, NULL },
+ .bad_tosec = { ALL_EXIT_SECTIONS, NULL },
+ .mismatch = DATA_TO_ANY_EXIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ /* Do not reference init code/data from meminit code/data */
+ {
+ .fromsec = { ALL_XXXINIT_SECTIONS, NULL },
+ .bad_tosec = { INIT_SECTIONS, NULL },
+ .mismatch = XXXINIT_TO_SOME_INIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ /* Do not reference exit code/data from memexit code/data */
+ {
+ .fromsec = { ALL_XXXEXIT_SECTIONS, NULL },
+ .bad_tosec = { EXIT_SECTIONS, NULL },
+ .mismatch = XXXEXIT_TO_SOME_EXIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ /* Do not use exit code/data from init code */
+ {
+ .fromsec = { ALL_INIT_SECTIONS, NULL },
+ .bad_tosec = { ALL_EXIT_SECTIONS, NULL },
+ .mismatch = ANY_INIT_TO_ANY_EXIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ /* Do not use init code/data from exit code */
+ {
+ .fromsec = { ALL_EXIT_SECTIONS, NULL },
+ .bad_tosec = { ALL_INIT_SECTIONS, NULL },
+ .mismatch = ANY_EXIT_TO_ANY_INIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ {
+ .fromsec = { ALL_PCI_INIT_SECTIONS, NULL },
+ .bad_tosec = { INIT_SECTIONS, NULL },
+ .mismatch = ANY_INIT_TO_ANY_EXIT,
+ .symbol_white_list = { NULL },
+ },
+ /* Do not export init/exit functions or data */
+ {
+ .fromsec = { "__ksymtab*", NULL },
+ .bad_tosec = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
+ .mismatch = EXPORT_TO_INIT_EXIT,
+ .symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },
+ },
+ {
+ .fromsec = { "__ex_table", NULL },
+ /*
+ * If you're adding any new black-listed sections in here,
+ * consider adding a special 'printer' for them in
+ * scripts/check_extable.
+ */
+ .bad_tosec = { ".altinstr_replacement", NULL },
+ .good_tosec = {ALL_TEXT_SECTIONS, NULL},
+ .mismatch = EXTABLE_TO_NON_TEXT,
+ .handler = extable_mismatch_handler,
+ }
+};
+
+static const struct sectioncheck *section_mismatch(const char *fromsec,
+ const char *tosec)
+{
+ int i;
+ int elems = sizeof(sectioncheck) / sizeof(struct sectioncheck);
+ const struct sectioncheck *check = &sectioncheck[0];
+
+ /*
+ * The target section could be the SHT_NUL section when we're
+ * handling relocations to un-resolved symbols, trying to match it
+ * doesn't make much sense and causes build failures on parisc
+ * architectures.
+ */
+ if (*tosec == '\0')
+ return NULL;
+
+ for (i = 0; i < elems; i++) {
+ if (match(fromsec, check->fromsec)) {
+ if (check->bad_tosec[0] && match(tosec, check->bad_tosec))
+ return check;
+ if (check->good_tosec[0] && !match(tosec, check->good_tosec))
+ return check;
+ }
+ check++;
+ }
+ return NULL;
+}
+
+/*
+ * Whitelist to allow certain references to pass with no warning.
+ *
+ * Pattern 1:
+ * If a module parameter is declared __initdata and permissions=0
+ * then this is legal despite the warning generated.
+ * We cannot see value of permissions here, so just ignore
+ * this pattern.
+ * The pattern is identified by:
+ * tosec = .init.data
+ * fromsec = .data*
+ * atsym =__param*
+ *
+ * Pattern 1a:
+ * module_param_call() ops can refer to __init set function if permissions=0
+ * The pattern is identified by:
+ * tosec = .init.text
+ * fromsec = .data*
+ * atsym = __param_ops_*
+ *
+ * Pattern 2:
+ * Many drivers utilise a *driver container with references to
+ * add, remove, probe functions etc.
+ * the pattern is identified by:
+ * tosec = init or exit section
+ * fromsec = data section
+ * atsym = *driver, *_template, *_sht, *_ops, *_probe,
+ * *probe_one, *_console, *_timer
+ *
+ * Pattern 3:
+ * Whitelist all references from .head.text to any init section
+ *
+ * Pattern 4:
+ * Some symbols belong to init section but still it is ok to reference
+ * these from non-init sections as these symbols don't have any memory
+ * allocated for them and symbol address and value are same. So even
+ * if init section is freed, its ok to reference those symbols.
+ * For ex. symbols marking the init section boundaries.
+ * This pattern is identified by
+ * refsymname = __init_begin, _sinittext, _einittext
+ *
+ * Pattern 5:
+ * GCC may optimize static inlines when fed constant arg(s) resulting
+ * in functions like cpumask_empty() -- generating an associated symbol
+ * cpumask_empty.constprop.3 that appears in the audit. If the const that
+ * is passed in comes from __init, like say nmi_ipi_mask, we get a
+ * meaningless section warning. May need to add isra symbols too...
+ * This pattern is identified by
+ * tosec = init section
+ * fromsec = text section
+ * refsymname = *.constprop.*
+ *
+ * Pattern 6:
+ * Hide section mismatch warnings for ELF local symbols. The goal
+ * is to eliminate false positive modpost warnings caused by
+ * compiler-generated ELF local symbol names such as ".LANCHOR1".
+ * Autogenerated symbol names bypass modpost's "Pattern 2"
+ * whitelisting, which relies on pattern-matching against symbol
+ * names to work. (One situation where gcc can autogenerate ELF
+ * local symbols is when "-fsection-anchors" is used.)
+ */
+static int secref_whitelist(const struct sectioncheck *mismatch,
+ const char *fromsec, const char *fromsym,
+ const char *tosec, const char *tosym)
+{
+ /* Check for pattern 1 */
+ if (match(tosec, init_data_sections) &&
+ match(fromsec, data_sections) &&
+ strstarts(fromsym, "__param"))
+ return 0;
+
+ /* Check for pattern 1a */
+ if (strcmp(tosec, ".init.text") == 0 &&
+ match(fromsec, data_sections) &&
+ strstarts(fromsym, "__param_ops_"))
+ return 0;
+
+ /* Check for pattern 2 */
+ if (match(tosec, init_exit_sections) &&
+ match(fromsec, data_sections) &&
+ match(fromsym, mismatch->symbol_white_list))
+ return 0;
+
+ /* Check for pattern 3 */
+ if (match(fromsec, head_sections) &&
+ match(tosec, init_sections))
+ return 0;
+
+ /* Check for pattern 4 */
+ if (match(tosym, linker_symbols))
+ return 0;
+
+ /* Check for pattern 5 */
+ if (match(fromsec, text_sections) &&
+ match(tosec, init_sections) &&
+ match(fromsym, optim_symbols))
+ return 0;
+
+ /* Check for pattern 6 */
+ if (strstarts(fromsym, ".L"))
+ return 0;
+
+ return 1;
+}
+
+static inline int is_arm_mapping_symbol(const char *str)
+{
+ return str[0] == '$' && strchr("axtd", str[1])
+ && (str[2] == '\0' || str[2] == '.');
+}
+
+/*
+ * If there's no name there, ignore it; likewise, ignore it if it's
+ * one of the magic symbols emitted used by current ARM tools.
+ *
+ * Otherwise if find_symbols_between() returns those symbols, they'll
+ * fail the whitelist tests and cause lots of false alarms ... fixable
+ * only by merging __exit and __init sections into __text, bloating
+ * the kernel (which is especially evil on embedded platforms).
+ */
+static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
+{
+ const char *name = elf->strtab + sym->st_name;
+
+ if (!name || !strlen(name))
+ return 0;
+ return !is_arm_mapping_symbol(name);
+}
+
+/*
+ * Find symbol based on relocation record info.
+ * In some cases the symbol supplied is a valid symbol so
+ * return refsym. If st_name != 0 we assume this is a valid symbol.
+ * In other cases the symbol needs to be looked up in the symbol table
+ * based on section and address.
+ */
+static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf64_Sword addr,
+ Elf_Sym *relsym)
+{
+ Elf_Sym *sym;
+ Elf_Sym *near = NULL;
+ Elf64_Sword distance = 20;
+ Elf64_Sword d;
+ unsigned int relsym_secindex;
+
+ if (relsym->st_name != 0)
+ return relsym;
+
+ relsym_secindex = get_secindex(elf, relsym);
+ for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
+ if (get_secindex(elf, sym) != relsym_secindex)
+ continue;
+ if (ELF_ST_TYPE(sym->st_info) == STT_SECTION)
+ continue;
+ if (!is_valid_name(elf, sym))
+ continue;
+ if (sym->st_value == addr)
+ return sym;
+ /* Find a symbol nearby - addr are maybe negative */
+ d = sym->st_value - addr;
+ if (d < 0)
+ d = addr - sym->st_value;
+ if (d < distance) {
+ distance = d;
+ near = sym;
+ }
+ }
+ /* We need a close match */
+ if (distance < 20)
+ return near;
+ else
+ return NULL;
+}
+
+/*
+ * Find symbols before or equal addr and after addr - in the section sec.
+ * If we find two symbols with equal offset prefer one with a valid name.
+ * The ELF format may have a better way to detect what type of symbol
+ * it is, but this works for now.
+ */
+static Elf_Sym *find_elf_symbol2(struct elf_info *elf, Elf_Addr addr,
+ const char *sec)
+{
+ Elf_Sym *sym;
+ Elf_Sym *near = NULL;
+ Elf_Addr distance = ~0;
+
+ for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
+ const char *symsec;
+
+ if (is_shndx_special(sym->st_shndx))
+ continue;
+ symsec = sec_name(elf, get_secindex(elf, sym));
+ if (strcmp(symsec, sec) != 0)
+ continue;
+ if (!is_valid_name(elf, sym))
+ continue;
+ if (sym->st_value <= addr) {
+ if ((addr - sym->st_value) < distance) {
+ distance = addr - sym->st_value;
+ near = sym;
+ } else if ((addr - sym->st_value) == distance) {
+ near = sym;
+ }
+ }
+ }
+ return near;
+}
+
+/*
+ * Convert a section name to the function/data attribute
+ * .init.text => __init
+ * .memexitconst => __memconst
+ * etc.
+ *
+ * The memory of returned value has been allocated on a heap. The user of this
+ * method should free it after usage.
+ */
+static char *sec2annotation(const char *s)
+{
+ if (match(s, init_exit_sections)) {
+ char *p = NOFAIL(malloc(20));
+ char *r = p;
+
+ *p++ = '_';
+ *p++ = '_';
+ if (*s == '.')
+ s++;
+ while (*s && *s != '.')
+ *p++ = *s++;
+ *p = '\0';
+ if (*s == '.')
+ s++;
+ if (strstr(s, "rodata") != NULL)
+ strcat(p, "const ");
+ else if (strstr(s, "data") != NULL)
+ strcat(p, "data ");
+ else
+ strcat(p, " ");
+ return r;
+ } else {
+ return NOFAIL(strdup(""));
+ }
+}
+
+static int is_function(Elf_Sym *sym)
+{
+ if (sym)
+ return ELF_ST_TYPE(sym->st_info) == STT_FUNC;
+ else
+ return -1;
+}
+
+static void print_section_list(const char * const list[20])
+{
+ const char *const *s = list;
+
+ while (*s) {
+ fprintf(stderr, "%s", *s);
+ s++;
+ if (*s)
+ fprintf(stderr, ", ");
+ }
+ fprintf(stderr, "\n");
+}
+
+static inline void get_pretty_name(int is_func, const char **name,
+ const char **name_p)
+{
+ switch (is_func) {
+ case 0:
+ *name = "variable";
+ *name_p = "";
+ break;
+ case 1:
+ *name = "function";
+ *name_p = "()";
+ break;
+ default:
+ *name = "(unknown reference)";
+ *name_p = "";
+ break;
+ }
+}
+
+/*
+ * Print a warning about a section mismatch.
+ * Try to find symbols near it so user can find it.
+ * Check whitelist before warning - it may be a false positive.
+ */
+static void report_sec_mismatch(const char *modname,
+ const struct sectioncheck *mismatch,
+ const char *fromsec,
+ unsigned long long fromaddr,
+ const char *fromsym,
+ int from_is_func,
+ const char *tosec, const char *tosym,
+ int to_is_func)
+{
+ const char *from, *from_p;
+ const char *to, *to_p;
+ char *prl_from;
+ char *prl_to;
+
+ sec_mismatch_count++;
+
+ get_pretty_name(from_is_func, &from, &from_p);
+ get_pretty_name(to_is_func, &to, &to_p);
+
+ warn("%s(%s+0x%llx): Section mismatch in reference from the %s %s%s to the %s %s:%s%s\n",
+ modname, fromsec, fromaddr, from, fromsym, from_p, to, tosec,
+ tosym, to_p);
+
+ switch (mismatch->mismatch) {
+ case TEXT_TO_ANY_INIT:
+ prl_from = sec2annotation(fromsec);
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The function %s%s() references\n"
+ "the %s %s%s%s.\n"
+ "This is often because %s lacks a %s\n"
+ "annotation or the annotation of %s is wrong.\n",
+ prl_from, fromsym,
+ to, prl_to, tosym, to_p,
+ fromsym, prl_to, tosym);
+ free(prl_from);
+ free(prl_to);
+ break;
+ case DATA_TO_ANY_INIT: {
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The variable %s references\n"
+ "the %s %s%s%s\n"
+ "If the reference is valid then annotate the\n"
+ "variable with __init* or __refdata (see linux/init.h) or name the variable:\n",
+ fromsym, to, prl_to, tosym, to_p);
+ print_section_list(mismatch->symbol_white_list);
+ free(prl_to);
+ break;
+ }
+ case TEXT_TO_ANY_EXIT:
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The function %s() references a %s in an exit section.\n"
+ "Often the %s %s%s has valid usage outside the exit section\n"
+ "and the fix is to remove the %sannotation of %s.\n",
+ fromsym, to, to, tosym, to_p, prl_to, tosym);
+ free(prl_to);
+ break;
+ case DATA_TO_ANY_EXIT: {
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The variable %s references\n"
+ "the %s %s%s%s\n"
+ "If the reference is valid then annotate the\n"
+ "variable with __exit* (see linux/init.h) or name the variable:\n",
+ fromsym, to, prl_to, tosym, to_p);
+ print_section_list(mismatch->symbol_white_list);
+ free(prl_to);
+ break;
+ }
+ case XXXINIT_TO_SOME_INIT:
+ case XXXEXIT_TO_SOME_EXIT:
+ prl_from = sec2annotation(fromsec);
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The %s %s%s%s references\n"
+ "a %s %s%s%s.\n"
+ "If %s is only used by %s then\n"
+ "annotate %s with a matching annotation.\n",
+ from, prl_from, fromsym, from_p,
+ to, prl_to, tosym, to_p,
+ tosym, fromsym, tosym);
+ free(prl_from);
+ free(prl_to);
+ break;
+ case ANY_INIT_TO_ANY_EXIT:
+ prl_from = sec2annotation(fromsec);
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The %s %s%s%s references\n"
+ "a %s %s%s%s.\n"
+ "This is often seen when error handling in the init function\n"
+ "uses functionality in the exit path.\n"
+ "The fix is often to remove the %sannotation of\n"
+ "%s%s so it may be used outside an exit section.\n",
+ from, prl_from, fromsym, from_p,
+ to, prl_to, tosym, to_p,
+ prl_to, tosym, to_p);
+ free(prl_from);
+ free(prl_to);
+ break;
+ case ANY_EXIT_TO_ANY_INIT:
+ prl_from = sec2annotation(fromsec);
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The %s %s%s%s references\n"
+ "a %s %s%s%s.\n"
+ "This is often seen when error handling in the exit function\n"
+ "uses functionality in the init path.\n"
+ "The fix is often to remove the %sannotation of\n"
+ "%s%s so it may be used outside an init section.\n",
+ from, prl_from, fromsym, from_p,
+ to, prl_to, tosym, to_p,
+ prl_to, tosym, to_p);
+ free(prl_from);
+ free(prl_to);
+ break;
+ case EXPORT_TO_INIT_EXIT:
+ prl_to = sec2annotation(tosec);
+ fprintf(stderr,
+ "The symbol %s is exported and annotated %s\n"
+ "Fix this by removing the %sannotation of %s or drop the export.\n",
+ tosym, prl_to, prl_to, tosym);
+ free(prl_to);
+ break;
+ case EXTABLE_TO_NON_TEXT:
+ fatal("There's a special handler for this mismatch type, we should never get here.");
+ break;
+ }
+ fprintf(stderr, "\n");
+}
+
+static void default_mismatch_handler(const char *modname, struct elf_info *elf,
+ const struct sectioncheck *mismatch,
+ Elf_Rela *r, Elf_Sym *sym, const char *fromsec)
+{
+ const char *tosec;
+ Elf_Sym *to;
+ Elf_Sym *from;
+ const char *tosym;
+ const char *fromsym;
+
+ from = find_elf_symbol2(elf, r->r_offset, fromsec);
+ fromsym = sym_name(elf, from);
+
+ if (strstarts(fromsym, "reference___initcall"))
+ return;
+
+ tosec = sec_name(elf, get_secindex(elf, sym));
+ to = find_elf_symbol(elf, r->r_addend, sym);
+ tosym = sym_name(elf, to);
+
+ /* check whitelist - we may ignore it */
+ if (secref_whitelist(mismatch,
+ fromsec, fromsym, tosec, tosym)) {
+ report_sec_mismatch(modname, mismatch,
+ fromsec, r->r_offset, fromsym,
+ is_function(from), tosec, tosym,
+ is_function(to));
+ }
+}
+
+static int is_executable_section(struct elf_info *elf, unsigned int section_index)
+{
+ if (section_index > elf->num_sections)
+ fatal("section_index is outside elf->num_sections!\n");
+
+ return ((elf->sechdrs[section_index].sh_flags & SHF_EXECINSTR) == SHF_EXECINSTR);
+}
+
+/*
+ * We rely on a gross hack in section_rel[a]() calling find_extable_entry_size()
+ * to know the sizeof(struct exception_table_entry) for the target architecture.
+ */
+static unsigned int extable_entry_size;
+static void find_extable_entry_size(const char *sec, const Elf_Rela *r)
+{
+ /*
+ * If we're currently checking the second relocation within __ex_table,
+ * that relocation offset tells us the offsetof(struct
+ * exception_table_entry, fixup) which is equal to sizeof(struct
+ * exception_table_entry) divided by two. We use that to our advantage
+ * since there's no portable way to get that size as every architecture
+ * seems to go with different sized types. Not pretty but better than
+ * hard-coding the size for every architecture..
+ */
+ if (!extable_entry_size)
+ extable_entry_size = r->r_offset * 2;
+}
+
+static inline bool is_extable_fault_address(Elf_Rela *r)
+{
+ /*
+ * extable_entry_size is only discovered after we've handled the
+ * _second_ relocation in __ex_table, so only abort when we're not
+ * handling the first reloc and extable_entry_size is zero.
+ */
+ if (r->r_offset && extable_entry_size == 0)
+ fatal("extable_entry size hasn't been discovered!\n");
+
+ return ((r->r_offset == 0) ||
+ (r->r_offset % extable_entry_size == 0));
+}
+
+#define is_second_extable_reloc(Start, Cur, Sec) \
+ (((Cur) == (Start) + 1) && (strcmp("__ex_table", (Sec)) == 0))
+
+static void report_extable_warnings(const char *modname, struct elf_info *elf,
+ const struct sectioncheck *mismatch,
+ Elf_Rela *r, Elf_Sym *sym,
+ const char *fromsec, const char *tosec)
+{
+ Elf_Sym *fromsym = find_elf_symbol2(elf, r->r_offset, fromsec);
+ const char *fromsym_name = sym_name(elf, fromsym);
+ Elf_Sym *tosym = find_elf_symbol(elf, r->r_addend, sym);
+ const char *tosym_name = sym_name(elf, tosym);
+ const char *from_pretty_name;
+ const char *from_pretty_name_p;
+ const char *to_pretty_name;
+ const char *to_pretty_name_p;
+
+ get_pretty_name(is_function(fromsym),
+ &from_pretty_name, &from_pretty_name_p);
+ get_pretty_name(is_function(tosym),
+ &to_pretty_name, &to_pretty_name_p);
+
+ warn("%s(%s+0x%lx): Section mismatch in reference from the %s %s%s to the %s %s:%s%s\n",
+ modname, fromsec, (long)r->r_offset, from_pretty_name,
+ fromsym_name, from_pretty_name_p,
+ to_pretty_name, tosec, tosym_name, to_pretty_name_p);
+
+ if (!match(tosec, mismatch->bad_tosec) &&
+ is_executable_section(elf, get_secindex(elf, sym)))
+ fprintf(stderr,
+ "The relocation at %s+0x%lx references\n"
+ "section \"%s\" which is not in the list of\n"
+ "authorized sections. If you're adding a new section\n"
+ "and/or if this reference is valid, add \"%s\" to the\n"
+ "list of authorized sections to jump to on fault.\n"
+ "This can be achieved by adding \"%s\" to\n"
+ "OTHER_TEXT_SECTIONS in scripts/mod/modpost.c.\n",
+ fromsec, (long)r->r_offset, tosec, tosec, tosec);
+}
+
+static void extable_mismatch_handler(const char *modname, struct elf_info *elf,
+ const struct sectioncheck *mismatch,
+ Elf_Rela *r, Elf_Sym *sym, const char *fromsec)
+{
+ const char *tosec = sec_name(elf, get_secindex(elf, sym));
+
+ sec_mismatch_count++;
+
+ report_extable_warnings(modname, elf, mismatch, r, sym, fromsec, tosec);
+
+ if (match(tosec, mismatch->bad_tosec))
+ fatal("The relocation at %s+0x%lx references\n"
+ "section \"%s\" which is black-listed.\n"
+ "Something is seriously wrong and should be fixed.\n"
+ "You might get more information about where this is\n"
+ "coming from by using scripts/check_extable.sh %s\n",
+ fromsec, (long)r->r_offset, tosec, modname);
+ else if (!is_executable_section(elf, get_secindex(elf, sym))) {
+ if (is_extable_fault_address(r))
+ fatal("The relocation at %s+0x%lx references\n"
+ "section \"%s\" which is not executable, IOW\n"
+ "it is not possible for the kernel to fault\n"
+ "at that address. Something is seriously wrong\n"
+ "and should be fixed.\n",
+ fromsec, (long)r->r_offset, tosec);
+ else
+ fatal("The relocation at %s+0x%lx references\n"
+ "section \"%s\" which is not executable, IOW\n"
+ "the kernel will fault if it ever tries to\n"
+ "jump to it. Something is seriously wrong\n"
+ "and should be fixed.\n",
+ fromsec, (long)r->r_offset, tosec);
+ }
+}
+
+static void check_section_mismatch(const char *modname, struct elf_info *elf,
+ Elf_Rela *r, Elf_Sym *sym, const char *fromsec)
+{
+ const char *tosec = sec_name(elf, get_secindex(elf, sym));
+ const struct sectioncheck *mismatch = section_mismatch(fromsec, tosec);
+
+ if (mismatch) {
+ if (mismatch->handler)
+ mismatch->handler(modname, elf, mismatch,
+ r, sym, fromsec);
+ else
+ default_mismatch_handler(modname, elf, mismatch,
+ r, sym, fromsec);
+ }
+}
+
+static unsigned int *reloc_location(struct elf_info *elf,
+ Elf_Shdr *sechdr, Elf_Rela *r)
+{
+ return sym_get_data_by_offset(elf, sechdr->sh_info, r->r_offset);
+}
+
+static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
+{
+ unsigned int r_typ = ELF_R_TYPE(r->r_info);
+ unsigned int *location = reloc_location(elf, sechdr, r);
+
+ switch (r_typ) {
+ case R_386_32:
+ r->r_addend = TO_NATIVE(*location);
+ break;
+ case R_386_PC32:
+ r->r_addend = TO_NATIVE(*location) + 4;
+ /* For CONFIG_RELOCATABLE=y */
+ if (elf->hdr->e_type == ET_EXEC)
+ r->r_addend += r->r_offset;
+ break;
+ }
+ return 0;
+}
+
+#ifndef R_ARM_CALL
+#define R_ARM_CALL 28
+#endif
+#ifndef R_ARM_JUMP24
+#define R_ARM_JUMP24 29
+#endif
+
+#ifndef R_ARM_THM_CALL
+#define R_ARM_THM_CALL 10
+#endif
+#ifndef R_ARM_THM_JUMP24
+#define R_ARM_THM_JUMP24 30
+#endif
+#ifndef R_ARM_THM_JUMP19
+#define R_ARM_THM_JUMP19 51
+#endif
+
+static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
+{
+ unsigned int r_typ = ELF_R_TYPE(r->r_info);
+
+ switch (r_typ) {
+ case R_ARM_ABS32:
+ /* From ARM ABI: (S + A) | T */
+ r->r_addend = (int)(long)
+ (elf->symtab_start + ELF_R_SYM(r->r_info));
+ break;
+ case R_ARM_PC24:
+ case R_ARM_CALL:
+ case R_ARM_JUMP24:
+ case R_ARM_THM_CALL:
+ case R_ARM_THM_JUMP24:
+ case R_ARM_THM_JUMP19:
+ /* From ARM ABI: ((S + A) | T) - P */
+ r->r_addend = (int)(long)(elf->hdr +
+ sechdr->sh_offset +
+ (r->r_offset - sechdr->sh_addr));
+ break;
+ default:
+ return 1;
+ }
+ return 0;
+}
+
+static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
+{
+ unsigned int r_typ = ELF_R_TYPE(r->r_info);
+ unsigned int *location = reloc_location(elf, sechdr, r);
+ unsigned int inst;
+
+ if (r_typ == R_MIPS_HI16)
+ return 1; /* skip this */
+ inst = TO_NATIVE(*location);
+ switch (r_typ) {
+ case R_MIPS_LO16:
+ r->r_addend = inst & 0xffff;
+ break;
+ case R_MIPS_26:
+ r->r_addend = (inst & 0x03ffffff) << 2;
+ break;
+ case R_MIPS_32:
+ r->r_addend = inst;
+ break;
+ }
+ return 0;
+}
+
+#ifndef EM_RISCV
+#define EM_RISCV 243
+#endif
+
+#ifndef R_RISCV_SUB32
+#define R_RISCV_SUB32 39
+#endif
+
+static void section_rela(const char *modname, struct elf_info *elf,
+ Elf_Shdr *sechdr)
+{
+ Elf_Sym *sym;
+ Elf_Rela *rela;
+ Elf_Rela r;
+ unsigned int r_sym;
+ const char *fromsec;
+
+ Elf_Rela *start = (void *)elf->hdr + sechdr->sh_offset;
+ Elf_Rela *stop = (void *)start + sechdr->sh_size;
+
+ fromsec = sech_name(elf, sechdr);
+ fromsec += strlen(".rela");
+ /* if from section (name) is know good then skip it */
+ if (match(fromsec, section_white_list))
+ return;
+
+ for (rela = start; rela < stop; rela++) {
+ r.r_offset = TO_NATIVE(rela->r_offset);
+#if KERNEL_ELFCLASS == ELFCLASS64
+ if (elf->hdr->e_machine == EM_MIPS) {
+ unsigned int r_typ;
+
+ r_sym = ELF64_MIPS_R_SYM(rela->r_info);
+ r_sym = TO_NATIVE(r_sym);
+ r_typ = ELF64_MIPS_R_TYPE(rela->r_info);
+ r.r_info = ELF64_R_INFO(r_sym, r_typ);
+ } else {
+ r.r_info = TO_NATIVE(rela->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+ }
+#else
+ r.r_info = TO_NATIVE(rela->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+#endif
+ r.r_addend = TO_NATIVE(rela->r_addend);
+ switch (elf->hdr->e_machine) {
+ case EM_RISCV:
+ if (!strcmp("__ex_table", fromsec) &&
+ ELF_R_TYPE(r.r_info) == R_RISCV_SUB32)
+ continue;
+ break;
+ }
+ sym = elf->symtab_start + r_sym;
+ /* Skip special sections */
+ if (is_shndx_special(sym->st_shndx))
+ continue;
+ if (is_second_extable_reloc(start, rela, fromsec))
+ find_extable_entry_size(fromsec, &r);
+ check_section_mismatch(modname, elf, &r, sym, fromsec);
+ }
+}
+
+static void section_rel(const char *modname, struct elf_info *elf,
+ Elf_Shdr *sechdr)
+{
+ Elf_Sym *sym;
+ Elf_Rel *rel;
+ Elf_Rela r;
+ unsigned int r_sym;
+ const char *fromsec;
+
+ Elf_Rel *start = (void *)elf->hdr + sechdr->sh_offset;
+ Elf_Rel *stop = (void *)start + sechdr->sh_size;
+
+ fromsec = sech_name(elf, sechdr);
+ fromsec += strlen(".rel");
+ /* if from section (name) is know good then skip it */
+ if (match(fromsec, section_white_list))
+ return;
+
+ for (rel = start; rel < stop; rel++) {
+ r.r_offset = TO_NATIVE(rel->r_offset);
+#if KERNEL_ELFCLASS == ELFCLASS64
+ if (elf->hdr->e_machine == EM_MIPS) {
+ unsigned int r_typ;
+
+ r_sym = ELF64_MIPS_R_SYM(rel->r_info);
+ r_sym = TO_NATIVE(r_sym);
+ r_typ = ELF64_MIPS_R_TYPE(rel->r_info);
+ r.r_info = ELF64_R_INFO(r_sym, r_typ);
+ } else {
+ r.r_info = TO_NATIVE(rel->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+ }
+#else
+ r.r_info = TO_NATIVE(rel->r_info);
+ r_sym = ELF_R_SYM(r.r_info);
+#endif
+ r.r_addend = 0;
+ switch (elf->hdr->e_machine) {
+ case EM_386:
+ if (addend_386_rel(elf, sechdr, &r))
+ continue;
+ break;
+ case EM_ARM:
+ if (addend_arm_rel(elf, sechdr, &r))
+ continue;
+ break;
+ case EM_MIPS:
+ if (addend_mips_rel(elf, sechdr, &r))
+ continue;
+ break;
+ }
+ sym = elf->symtab_start + r_sym;
+ /* Skip special sections */
+ if (is_shndx_special(sym->st_shndx))
+ continue;
+ if (is_second_extable_reloc(start, rel, fromsec))
+ find_extable_entry_size(fromsec, &r);
+ check_section_mismatch(modname, elf, &r, sym, fromsec);
+ }
+}
+
+/*
+ * A module includes a number of sections that are discarded
+ * either when loaded or when used as built-in.
+ * For loaded modules all functions marked __init and all data
+ * marked __initdata will be discarded when the module has been initialized.
+ * Likewise for modules used built-in the sections marked __exit
+ * are discarded because __exit marked function are supposed to be called
+ * only when a module is unloaded which never happens for built-in modules.
+ * The check_sec_ref() function traverses all relocation records
+ * to find all references to a section that reference a section that will
+ * be discarded and warns about it.
+ */
+void check_sec_ref(struct module *mod, const char *modname,
+ struct elf_info *elf)
+{
+ int i;
+ Elf_Shdr *sechdrs = elf->sechdrs;
+
+ /* Walk through all sections */
+ for (i = 0; i < elf->num_sections; i++) {
+ check_section(modname, elf, &elf->sechdrs[i]);
+ /* We want to process only relocation sections and not .init */
+ if (sechdrs[i].sh_type == SHT_RELA)
+ section_rela(modname, elf, &elf->sechdrs[i]);
+ else if (sechdrs[i].sh_type == SHT_REL)
+ section_rel(modname, elf, &elf->sechdrs[i]);
+ }
+}
--
2.32.0

2022-05-09 17:25:17

by Nick Desaulniers

Subject: Re: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c

On Sun, May 8, 2022 at 12:10 PM Masahiro Yamada <[email protected]> wrote:
>
> modpost.c is too big, and the half of the code is for section checks.
> Split it.
>
> I fixed some style issues in the moved code.

It would be helpful for review if the split and restyle were distinct
patches. Otherwise I can't tell what has changed.

This does lose the ability to use git blame to get more context on
some of the oddities in modpost (which I have found useful in the
past). I don't feel strongly though.

>
> Signed-off-by: Masahiro Yamada <[email protected]>
> ---
>
> Changes in v4:
> - New patch
>
> scripts/mod/Makefile | 2 +-
> scripts/mod/modpost.c | 1202 +---------------------------------
> scripts/mod/modpost.h | 34 +-
> scripts/mod/section-check.c | 1222 +++++++++++++++++++++++++++++++++++
> 4 files changed, 1240 insertions(+), 1220 deletions(-)
> create mode 100644 scripts/mod/section-check.c
>
> diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
> index c9e38ad937fd..ca739c6c68a1 100644
> --- a/scripts/mod/Makefile
> +++ b/scripts/mod/Makefile
> @@ -5,7 +5,7 @@ CFLAGS_REMOVE_empty.o += $(CC_FLAGS_LTO)
> hostprogs-always-y += modpost mk_elfconfig
> always-y += empty.o
>
> -modpost-objs := modpost.o file2alias.o sumversion.o
> +modpost-objs := modpost.o section-check.o file2alias.o sumversion.o
>
> devicetable-offsets-file := devicetable-offsets.h
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index a78b75f0eeb0..e7e2c70a98f5 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -31,7 +31,7 @@ static bool external_module;
> /* Only warn about unresolved symbols */
> static bool warn_unresolved;
>
> -static int sec_mismatch_count;
> +int sec_mismatch_count;

^ this should go in modpost.h if it is to be used in two translation
units, rather than forward declaring it in section-check.c. You did
this for the functions.
--
Thanks,
~Nick Desaulniers

2022-05-10 14:50:11

by Masahiro Yamada

Subject: Re: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c

On Tue, May 10, 2022 at 2:20 AM Nick Desaulniers
<[email protected]> wrote:
>
> On Sun, May 8, 2022 at 12:10 PM Masahiro Yamada <[email protected]> wrote:
> >
> > modpost.c is too big, and the half of the code is for section checks.
> > Split it.
> >
> > I fixed some style issues in the moved code.
>
> It would be helpful for review if the split and restyle were distinct
> patches. Otherwise I can't tell what has changed.
>
> This does lose the ability to use git blame to get more context on
> some of the oddities in modpost (which I have found useful in the
> past). I don't feel strongly though.


OK, I will just move the code in v5.





> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index a78b75f0eeb0..e7e2c70a98f5 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -31,7 +31,7 @@ static bool external_module;
> > /* Only warn about unresolved symbols */
> > static bool warn_unresolved;
> >
> > -static int sec_mismatch_count;
> > +int sec_mismatch_count;
>
> ^ this should go in modpost.h if it is to be used in two translation
> units, rather than forward declaring it in section-check.c. You did
> this for the functions.


Sorry, I do not understand.


In modpost.h, I put the declaration:

extern int sec_mismatch_count;

If I moved it to the header without 'extern'
I would get multiple definitions.







--
Best Regards
Masahiro Yamada

2022-05-11 23:19:23

by Masahiro Yamada

Subject: Re: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c

On Thu, May 12, 2022 at 3:48 AM Nick Desaulniers
<[email protected]> wrote:
>
> On Mon, May 9, 2022 at 11:57 PM Masahiro Yamada <[email protected]> wrote:
> >
> > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > > > index a78b75f0eeb0..e7e2c70a98f5 100644
> > > > --- a/scripts/mod/modpost.c
> > > > +++ b/scripts/mod/modpost.c
> > > > @@ -31,7 +31,7 @@ static bool external_module;
> > > > /* Only warn about unresolved symbols */
> > > > static bool warn_unresolved;
> > > >
> > > > -static int sec_mismatch_count;
> > > > +int sec_mismatch_count;
> > >
> > > ^ this should go in modpost.h if it is to be used in two translation
> > > units, rather than forward declaring it in section-check.c. You did
> > > this for the functions.
> >
> >
> > Sorry, I do not understand.
> >
> >
> > In modpost.h, I put the declaration:
> >
> > extern int sec_mismatch_count;
> >
> > If I moved it to the header without 'extern'
> > I would get multiple definitions.
>
> Yeah, you need to _declare_ it w/ extern in the header, then _define_
> it in one source file.
>
> That way, if the type ever changes, the sources will agree on type in
> all source files. You will get a redefinition error if the definition
> changes the type of the variable since the last declaration.
>
> What you're doing is forward declaring, which works, and is a common
> pattern for (bloated) C++, but is less type safe than sharing a single
> common declaration between multiple source files via a single common
> shared header. (Sorry I didn't respond before you sent v5)

Sorry, I still do not understand your suggestion.


Could you provide me with a code diff
showing how to do this better?



--
Best Regards
Masahiro Yamada

2022-05-12 11:15:29

by Nick Desaulniers

Subject: Re: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c

On Mon, May 9, 2022 at 11:57 PM Masahiro Yamada <[email protected]> wrote:
>
> > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > > index a78b75f0eeb0..e7e2c70a98f5 100644
> > > --- a/scripts/mod/modpost.c
> > > +++ b/scripts/mod/modpost.c
> > > @@ -31,7 +31,7 @@ static bool external_module;
> > > /* Only warn about unresolved symbols */
> > > static bool warn_unresolved;
> > >
> > > -static int sec_mismatch_count;
> > > +int sec_mismatch_count;
> >
> > ^ this should go in modpost.h if it is to be used in two translation
> > units, rather than forward declaring it in section-check.c. You did
> > this for the functions.
>
>
> Sorry, I do not understand.
>
>
> In modpost.h, I put the declaration:
>
> extern int sec_mismatch_count;
>
> If I moved it to the header without 'extern'
> I would get multiple definitions.

Yeah, you need to _declare_ it w/ extern in the header, then _define_
it in one source file.

That way, if the type ever changes, the sources will agree on type in
all source files. You will get a redefinition error if the definition
changes the type of the variable since the last declaration.

What you're doing is forward declaring, which works, and is a common
pattern for (bloated) C++, but is less type safe than sharing a single
common declaration between multiple source files via a single common
shared header. (Sorry I didn't respond before you sent v5)
--
Thanks,
~Nick Desaulniers

2022-05-14 01:12:41

by Nick Desaulniers

Subject: Re: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c

On Wed, May 11, 2022 at 12:51 PM Jeff Johnson <[email protected]> wrote:
>
> On 5/11/2022 12:27 PM, Masahiro Yamada wrote:
> > On Thu, May 12, 2022 at 3:48 AM Nick Desaulniers
> > <[email protected]> wrote:
> >>
> >> On Mon, May 9, 2022 at 11:57 PM Masahiro Yamada <[email protected]> wrote:
> >>>
> >>>>> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> >>>>> index a78b75f0eeb0..e7e2c70a98f5 100644
> >>>>> --- a/scripts/mod/modpost.c
> >>>>> +++ b/scripts/mod/modpost.c
> >>>>> @@ -31,7 +31,7 @@ static bool external_module;
> >>>>> /* Only warn about unresolved symbols */
> >>>>> static bool warn_unresolved;
> >>>>>
> >>>>> -static int sec_mismatch_count;
> >>>>> +int sec_mismatch_count;
> >>>>
> >>>> ^ this should go in modpost.h if it is to be used in two translation
> >>>> units, rather than forward declaring it in section-check.c. You did
> >>>> this for the functions.
> >>>
> >>>
> >>> Sorry, I do not understand.
> >>>
> >>>
> >>> In modpost.h, I put the declaration:
> >>>
> >>> extern int sec_mismatch_count;
> >>>
> >>> If I moved it to the header without 'extern'
> >>> I would get multiple definitions.
> >>
> >> Yeah, you need to _declare_ it w/ extern in the header, then _define_
> >> it in one source file.
> >>
> >> That way, if the type ever changes, the sources will agree on type in
> >> all source files. You will get a redefinition error if the definition
> >> changes the type of the variable since the last declaration.
> >>
> >> What you're doing is forward declaring, which works, and is a common
> >> pattern for (bloated) C++, but is less type safe than sharing a single
> >> common declaration between multiple source files via a single common
> >> shared header. (Sorry I didn't respond before you sent v5)
> >
> > Sorry, I still do not understand your suggestion.
> >
> >
> > Could you provide me with a code diff
> > showing how to do this better?
>
> I think you are doing exactly what he's asking for:
> declare it with extern in the header (modpost.h change)
> define it in one source file (modpost.c change)
>

Oh! Indeed, sorry, I'm getting lost here in the review. Sorry for the
noise then.
--
Thanks,
~Nick Desaulniers

2022-05-14 02:01:37

by Jeff Johnson

Subject: Re: [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c

On 5/11/2022 12:27 PM, Masahiro Yamada wrote:
> On Thu, May 12, 2022 at 3:48 AM Nick Desaulniers
> <[email protected]> wrote:
>>
>> On Mon, May 9, 2022 at 11:57 PM Masahiro Yamada <[email protected]> wrote:
>>>
>>>>> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
>>>>> index a78b75f0eeb0..e7e2c70a98f5 100644
>>>>> --- a/scripts/mod/modpost.c
>>>>> +++ b/scripts/mod/modpost.c
>>>>> @@ -31,7 +31,7 @@ static bool external_module;
>>>>> /* Only warn about unresolved symbols */
>>>>> static bool warn_unresolved;
>>>>>
>>>>> -static int sec_mismatch_count;
>>>>> +int sec_mismatch_count;
>>>>
>>>> ^ this should go in modpost.h if it is to be used in two translation
>>>> units, rather than forward declaring it in section-check.c. You did
>>>> this for the functions.
>>>
>>>
>>> Sorry, I do not understand.
>>>
>>>
>>> In modpost.h, I put the declaration:
>>>
>>> extern int sec_mismatch_count;
>>>
>>> If I moved it to the header without 'extern'
>>> I would get multiple definitions.
>>
>> Yeah, you need to _declare_ it w/ extern in the header, then _define_
>> it in one source file.
>>
>> That way, if the type ever changes, the sources will agree on type in
>> all source files. You will get a redefinition error if the definition
>> changes the type of the variable since the last declaration.
>>
>> What you're doing is forward declaring, which works, and is a common
>> pattern for (bloated) C++, but is less type safe than sharing a single
>> common declaration between multiple source files via a single common
>> shared header. (Sorry I didn't respond before you sent v5)
>
> Sorry, I still do not understand your suggestion.
>
>
> Could you provide me with a code diff
> showing how to do this better?

I think you are doing exactly what he's asking for:
declare it with extern in the header (modpost.h change)
define it in one source file (modpost.c change)