2023-06-05 16:22:47

by Josh Poimboeuf

Subject: [PATCH v2 1/2] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions

If the code specified UNWIND_HINT_UNDEFINED, skip the "undefined stack
state" warning due to a stack operation. Just ignore the stack op and
continue to propagate the undefined state.

Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/check.c | 12 ++++++++++++
tools/objtool/include/objtool/cfi.h | 1 +
2 files changed, 13 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4b869de7e827..b11c25a715ac 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -33,6 +33,7 @@ static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
static struct cfi_init_state initial_func_cfi;
static struct cfi_state init_cfi;
static struct cfi_state func_cfi;
+static struct cfi_state force_undefined_cfi;

struct instruction *find_insn(struct objtool_file *file,
struct section *sec, unsigned long offset)
@@ -2240,6 +2241,11 @@ static int read_unwind_hints(struct objtool_file *file)

insn->hint = true;

+ if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
+ insn->cfi = &force_undefined_cfi;
+ continue;
+ }
+
if (hint->type == UNWIND_HINT_TYPE_SAVE) {
insn->hint = false;
insn->save = true;
@@ -2793,6 +2799,10 @@ static int update_cfi_state(struct instruction *insn,
struct cfi_reg *cfa = &cfi->cfa;
struct cfi_reg *regs = cfi->regs;

+ /* ignore UNWIND_HINT_UNDEFINED regions */
+ if (cfi->force_undefined)
+ return 0;
+
/* stack operations don't make sense with an undefined CFA */
if (cfa->base == CFI_UNDEFINED) {
if (insn_func(insn)) {
@@ -4607,6 +4617,8 @@ int check(struct objtool_file *file)
init_cfi_state(&init_cfi);
init_cfi_state(&func_cfi);
set_func_state(&func_cfi);
+ init_cfi_state(&force_undefined_cfi);
+ force_undefined_cfi.force_undefined = true;

if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
goto out;
diff --git a/tools/objtool/include/objtool/cfi.h b/tools/objtool/include/objtool/cfi.h
index b1258e79a1b7..c8a6bec4f6b9 100644
--- a/tools/objtool/include/objtool/cfi.h
+++ b/tools/objtool/include/objtool/cfi.h
@@ -36,6 +36,7 @@ struct cfi_state {
bool drap;
bool signal;
bool end;
+ bool force_undefined;
};

#endif /* _OBJTOOL_CFI_H */
--
2.40.1

2023-06-09 07:58:53

by tip-bot2 for Alexey Makhalov

Subject: [tip: objtool/core] objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions

The following commit has been merged into the objtool/core branch of tip:

Commit-ID: 1e4b619185e83e54aca617cf5070c64a88fe936b
Gitweb: https://git.kernel.org/tip/1e4b619185e83e54aca617cf5070c64a88fe936b
Author: Josh Poimboeuf <[email protected]>
AuthorDate: Mon, 05 Jun 2023 09:12:21 -07:00
Committer: Josh Poimboeuf <[email protected]>
CommitterDate: Wed, 07 Jun 2023 10:03:11 -07:00

objtool: Allow stack operations in UNWIND_HINT_UNDEFINED regions

If the code specified UNWIND_HINT_UNDEFINED, skip the "undefined stack
state" warning due to a stack operation. Just ignore the stack op and
continue to propagate the undefined state.

Link: https://lore.kernel.org/r/820c5b433f17c84e8761fb7465a8d319d706b1cf.1685981486.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/check.c | 12 ++++++++++++
tools/objtool/include/objtool/cfi.h | 1 +
2 files changed, 13 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4b869de..b11c25a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -33,6 +33,7 @@ static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
static struct cfi_init_state initial_func_cfi;
static struct cfi_state init_cfi;
static struct cfi_state func_cfi;
+static struct cfi_state force_undefined_cfi;

struct instruction *find_insn(struct objtool_file *file,
struct section *sec, unsigned long offset)
@@ -2240,6 +2241,11 @@ static int read_unwind_hints(struct objtool_file *file)

insn->hint = true;

+ if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
+ insn->cfi = &force_undefined_cfi;
+ continue;
+ }
+
if (hint->type == UNWIND_HINT_TYPE_SAVE) {
insn->hint = false;
insn->save = true;
@@ -2793,6 +2799,10 @@ static int update_cfi_state(struct instruction *insn,
struct cfi_reg *cfa = &cfi->cfa;
struct cfi_reg *regs = cfi->regs;

+ /* ignore UNWIND_HINT_UNDEFINED regions */
+ if (cfi->force_undefined)
+ return 0;
+
/* stack operations don't make sense with an undefined CFA */
if (cfa->base == CFI_UNDEFINED) {
if (insn_func(insn)) {
@@ -4607,6 +4617,8 @@ int check(struct objtool_file *file)
init_cfi_state(&init_cfi);
init_cfi_state(&func_cfi);
set_func_state(&func_cfi);
+ init_cfi_state(&force_undefined_cfi);
+ force_undefined_cfi.force_undefined = true;

if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
goto out;
diff --git a/tools/objtool/include/objtool/cfi.h b/tools/objtool/include/objtool/cfi.h
index b1258e7..c8a6bec 100644
--- a/tools/objtool/include/objtool/cfi.h
+++ b/tools/objtool/include/objtool/cfi.h
@@ -36,6 +36,7 @@ struct cfi_state {
bool drap;
bool signal;
bool end;
+ bool force_undefined;
};

#endif /* _OBJTOOL_CFI_H */