/proc/kallsyms is very useful for tracers and other tools that need to
map kernel symbols to addresses.
It would be useful if there were a mapping between kernel symbol and module
name that only changed when the kernel source code is changed. This mapping
should not change simply because a module becomes built into the kernel.
It might also be useful if there were reliable symbol size information to
determine whether an address is within a symbol or outside it, especially
given that there could be huge gaps between symbols.
Fix this by introducing a new config parameter CONFIG_KALLMODSYMS, which
does several things at once (introduced in distinct commits inthis series).
Generate a file "modules_thick.builtin" that maps from the thin archives
that make up built-in modules to their constituent object files. (This
reintroduces the machinery that used to be used to generate
modules.builtin. I am not wedded to this mechanism: if someone can
figure out a mechanism that does not require recursing over the entire
build tree, I'm happy to use it, but I suspect that no such mechanism
exists, since the only place the mapping from object file to module
exists is in the makefiles themselves. Regardless, this is fairly cheap,
adding less than a second to a typical hot-cache build of a large
enterprise kernel. This is true even though it needs to be run
unconditionally whenever the .config changes.)
Generate a linker map ".tmp_vmlinux.map", converting it into
".tmp_vmlinux.ranges", mapping address ranges to object files.
Have scripts/kallsyms read these two new files to map symbol addresses
to built-in-module names and then write a mapping from object file
address to module name to the *.s output file.
The mapping consists of three new symbols:
- kallsyms_module_addresses/kallsyms_module_offsets encodes the
address/offset of each object file (derived from the linker map), in
exactly the same way as kallsyms_addresses/kallsyms_offsets does
for symbols. There is no size: instead, the object files are
assumed to tile the address space. (This is slightly more
space-efficient than using a size). Non-text-section addresses are
skipped: for now, all the users of this interface only need
module/non-module information for instruction pointer addresses, not
absolute-addressed symbols and the like. This restriction can
easily be lifted in future. (For why this isn't called
kallsyms_objfiles, see two entries below.)
- kallsyms_module_names encodes the name of each module in a modified
form of strtab: notably, if an object file appears in *multiple*
modules, all of which are built in, this is encoded via a zero byte,
a one-byte module count, then a series of that many null-terminated
strings. Object files which appear in only one module in such a
multi-module list are redirected to point inside that list, so that
modules which contain some object files shared with other modules
and some object files exclusive to them do not double up the module
name. (There might still be some duplication between multiple
multi-module lists, but this is an extremely marginal size effect,
and resolving it would require an extra layer of lookup tables which
would be even more complex, and incompressible to boot). As a
special case, the table starts with a single zero byte which does
*not* represent the start of a multi-module list.
- kallsyms_modules connects the two, encoding a table associated 1:1
with kallsyms_module_addresses / kallsyms_module_offsets, pointing
at an offset in kallsyms_module_names describing which module (or
modules, for a multi-module list) the code occupying this address
range is part of. If an address range is part of no module (always
built-in) it points at 0 (the null byte at the start of the
kallsyms_module_names list). Entries in this list that would
contain the same value are fused together, along with their
corresponding kallsyms_module_addresses/offsets entries. Due to
this fusion process, and because object files can be split apart into
multiple parts by the linker for hot/cold partitioning and the like,
entries in here do not really correspond to an object file, but more
to some contiguous range of addresses which are guaranteed to belong
to a single built-in module: so it seems best to call the symbols
kallsyms_modules*. (The generator has a data structure that does
correspond more closely to object files, from which kallsyms_modules
is generated, and that does use 'objfiles' terminology.)
Emit a new /proc/kallmodsyms file akin to /proc/kallsyms but with built-in
module names, using a new kallsyms_builtin_module_address() almost identical
to kallsyms_sym_address() to get the address corresponding to a given
.kallsyms_modules index, and a new get_builtin_module_idx quite similar to
get_symbol_pos to determine the index in the .kallsyms_modules array that
relates to a given address. Save a little time by exploiting the fact that
all callers will only ever traverse this list from start to end by allowing
them to pass in the previous index returned from this function as a hint:
thus very few bsearches are actually needed. (In theory this could change
to just walk straight down kallsyms_module_addresses/offsets and not bother
bsearching at all, but doing it this way is hardly any slower and much more
robust.)
The display process is complicated a little by the weird format of the
.kallsyms_module_names table: we have to look for multimodule entries
and print them as space-separated lists of module names.
The resulting /proc/kallmodsyms file looks like this:
ffffffff8b013d20 409 t pt_buffer_setup_aux
ffffffff8b014130 11f T intel_pt_interrupt
ffffffff8b014250 2d T cpu_emergency_stop_pt
ffffffff8b014280 13a t rapl_pmu_event_init [intel_rapl_perf]
ffffffff8b0143c0 bb t rapl_event_update [intel_rapl_perf]
ffffffff8b014480 10 t rapl_pmu_event_read [intel_rapl_perf]
ffffffff8b014490 a3 t rapl_cpu_offline [intel_rapl_perf]
ffffffff8b014540 24 t __rapl_event_show [intel_rapl_perf]
ffffffff8b014570 f2 t rapl_pmu_event_stop [intel_rapl_perf]
This is emitted even if intel_rapl_perf is built into the kernel.
Further down, we see what happens when object files are reused by
multiple modules, all of which are built in to the kernel:
ffffffffa22b3aa0 ab t handle_timestamp [liquidio]
ffffffffa22b3b50 4a t free_netbuf [liquidio]
ffffffffa22b3ba0 8d t liquidio_ptp_settime [liquidio]
ffffffffa22b3c30 b3 t liquidio_ptp_adjfreq [liquidio]
[...]
ffffffffa22b9490 203 t lio_vf_rep_create [liquidio]
ffffffffa22b96a0 16b t lio_vf_rep_destroy [liquidio]
ffffffffa22b9810 1f t lio_vf_rep_modinit [liquidio]
ffffffffa22b9830 1f t lio_vf_rep_modexit [liquidio]
ffffffffa22b9850 d2 t lio_ethtool_get_channels [liquidio] [liquidio_vf]
ffffffffa22b9930 9c t lio_ethtool_get_ringparam [liquidio] [liquidio_vf]
ffffffffa22b99d0 11 t lio_get_msglevel [liquidio] [liquidio_vf]
ffffffffa22b99f0 11 t lio_vf_set_msglevel [liquidio] [liquidio_vf]
ffffffffa22b9a10 2b t lio_get_pauseparam [liquidio] [liquidio_vf]
ffffffffa22b9a40 738 t lio_get_ethtool_stats [liquidio] [liquidio_vf]
ffffffffa22ba180 368 t lio_vf_get_ethtool_stats [liquidio] [liquidio_vf]
ffffffffa22ba4f0 37 t lio_get_regs_len [liquidio] [liquidio_vf]
ffffffffa22ba530 18 t lio_get_priv_flags [liquidio] [liquidio_vf]
ffffffffa22ba550 2e t lio_set_priv_flags [liquidio] [liquidio_vf]
ffffffffa22ba580 69 t lio_set_fecparam [liquidio] [liquidio_vf]
ffffffffa22ba5f0 92 t lio_get_fecparam [liquidio] [liquidio_vf]
[...]
ffffffffa22cbd10 175 t liquidio_set_mac [liquidio_vf]
ffffffffa22cbe90 ab t handle_timestamp [liquidio_vf]
ffffffffa22cbf40 4a t free_netbuf [liquidio_vf]
ffffffffa22cbf90 2b t octnet_link_status_change [liquidio_vf]
ffffffffa22cbfc0 7e t liquidio_vxlan_port_command.constprop.0 [liquidio_vf]
Like /proc/kallsyms, the output is driven by address, so keeps the
curious property of /proc/kallsyms that symbols (like free_netbuf above)
may appear repeatedly with different addresses: but now, unlike in
/proc/kallsyms, we can see that those symbols appear repeatedly because
they are *different symbols* that ultimately belong to different
modules, all of which are built in to the kernel.
Those symbols that come from object files that are genuinely reused and
that appear only once in meory get a /proc/kallmodsyms line with
[multiple] [modules] on it: consumers will have to be ready to handle
such lines.
Also, kernel symbols for built-in modules will probably appear
interspersed with other symbols that are part of different modules and
non-modular always-built-in symbols, which, as usual, have no
square-bracketed module denotation.
As with /proc/kallsyms, non-root usage produces addresses that are
all zero.
I am open to changing the name and/or format of /proc/kallmodsyms, but felt
it best to split it out of /proc/kallsyms to avoid breaking existing
kallsyms parsers. Another possible syntax might be to use {curly brackets}
or something to denote built-in modules: it might be possible to drop
/proc/kallmodsyms and make /proc/kallsyms emit things in this format.
(Equally, now kallmodsyms data uses very little space, the
CONFIG_KALLMODSYMS config option might be something people don't want to
bother with.)
The size impact of all of this is minimal: for the case above, the
kallsyms2.S file went from 14107772 to 14137245 bytes, a gain of 29743
bytes, or 0.16%: vmlinux gained 10824 bytes, a gain of .017%, and the
compressed vmlinux only 7552 bytes, a gain of .08%: though the latter
two values are very configuration-dependent, they seem likely to scale
roughly with the kernel they are part of.
The last patch is an RFC to see if the idea is considered to be worth
spending more time optimizing the representation, which adds a new
kallsyms_sizes section that gives the size of each symbol, and uses this
info to report reliable symbol sizes to in-kernel users, and (via a new
column in /proc/kallmodsyms) to out-of-kernel users too. Having reliable
size info lets us identify inter-symbol gaps and sort symbols so that
start/end-marker and overlapping symbols are consistently ordered with
respect to the symbols they overlap. This certainly uses too much space
right now, 200KiB--1MiB: a better representation is certainly needed. One
that springs to mind is making the table sparse (pairs of symbol
index/size), and recording explicit sizes only for those symbols that
are not immediately followed by a subsequent symbol.
Differences from v4, two months ago:
- Fix building of tristate.conf if missing (usually concealed by the
syncconfig being run for other reasons, but not always: the kernel
test robot spotted it).
- Forward-port atop v5.15-rc3.
Differences from v3, a month earlier:
- Fix a kernel test robot warning in get_ksymbol_core (possible
use of uninitialized variable if kallmodsyms was wanted but
kallsyms_module_offsets was not present, which is most unlikely).
Differences from v2, a couple of months before that:
- Split the series up. In particular, the size impact of the table
optimizer is now quantified, and the symbol-size patch is split out and
turned into an RFC patch, with the /proc/kallmodsyms format before that
patch lacking a size column. Some speculation on how to make the symbol
sizes less space-wasteful is added (but not yet implemented).
- Drop a couple of unnecessary #includes, one unnecessarily exported
symbol, and a needless de-staticing.
Differences from v1, a year or so back:
- Move from a straight symbol->module name mapping to a mapping from
address-range to TU to module name list, bringing major space savings
over the previous approach and support for object files used by many
built-in modules at the same time, at the cost of a slightly more complex
approach (unavoidably so, I think, given that we have to merge three data
sources together: the link map in .tmp_vmlinux.ranges, the nm output on
stdin, and the mapping from TU name to module names in
modules_thick.builtin).
We do opportunistic merging of TUs if they cite the same modules and
reuse module names where doing so is simple: see optimize_obj2mod
below. I considered more extensive searches for mergeable entries and
more intricate encodings of the module name list allowing TUs that are
used by overlapping sets of modules to share their names, but such
modules are rare enough (and such overlapping sharings are vanishingly
rare) that it seemed likely to save only a few bytes at the cost of much
more hard-to-test code. This is doubly true now that the tables needed
are only a few kilobytes in length.
Signed-off-by: Nick Alcock <[email protected]>
Signed-off-by: Eugene Loh <[email protected]>
Reviewed-by: Kris Van Hees <[email protected]>
Nick Alcock (7):
kbuild: bring back tristate.conf
kbuild: add modules_thick.builtin
kbuild: generate an address ranges map at vmlinux link time
kallsyms: introduce sections needed to map symbols to built-in modules
kallsyms: optimize .kallsyms_modules*
kallsyms: add /proc/kallmodsyms
kallsyms: add reliable symbol size info
.gitignore | 1 +
Documentation/dontdiff | 1 +
Makefile | 23 +-
include/linux/module.h | 7 +-
init/Kconfig | 8 +
kernel/kallsyms.c | 304 ++++++++++++++---
kernel/module.c | 4 +-
scripts/Kbuild.include | 6 +
scripts/Makefile | 6 +
scripts/Makefile.modbuiltin | 56 ++++
scripts/kallsyms.c | 642 +++++++++++++++++++++++++++++++++++-
scripts/kconfig/confdata.c | 41 ++-
scripts/link-vmlinux.sh | 22 +-
scripts/modules_thick.c | 200 +++++++++++
scripts/modules_thick.h | 48 +++
15 files changed, 1301 insertions(+), 68 deletions(-)
create mode 100644 scripts/Makefile.modbuiltin
create mode 100644 scripts/modules_thick.c
create mode 100644 scripts/modules_thick.h
--
2.33.0.256.gb827f06fa9
This is similar to modules.builtin, and constructed in a similar way to
the way that used to be built before commit
8b41fc4454e36fbfdbb23f940d023d4dece2de29, via tristate.conf inclusion
and recursive concatenation up the tree. Unlike modules.builtin,
modules_thick.builtin givs the names of the object files that make up
modules that are comprised of more than one object file, using a syntax
similar to that of makefiles, e.g.:
crypto/crypto.o: crypto/api.o crypto/cipher.o crypto/compress.o crypto/memneq.o
crypto/crypto_algapi.o: crypto/algapi.o crypto/proc.o crypto/scatterwalk.o
crypto/aead.o:
crypto/geniv.o:
(where the latter two are single-file modules).
An upcoming commit will use this mapping to populate /proc/kallmodsyms.
A parser is included that yields a stram of (module, objfile name[])
mappings: it's a bit baroque, but then parsing text files in C is quite
painful, and I'd rather put the complexity in here than in its callers.
The parser is not built in this commit, nor does it have any callers
yet; nor is any rule added that causes modules_thick.builtin to actually
be constructed. (Again, see a later commit for that.)
I am not wedded to the approach used to construct this file, but I don't
see any other way to do it despite spending a week or so trying to tie
it into Kbuild without using a separate Makefile.modbuiltin: unlike the
names of builtin modules (which are also recorded in the source files
themseves via MODULE_*() macros) the mapping from object file name to
built-in module name is not recorded anywhere but in the makefiles
themselves, so we have to at least reparse them with something to
indicate the builtin-ness of each module (i.e., tristate.conf) if we are
to figure out which modules are built-in and which are not.
Signed-off-by: Nick Alcock <[email protected]>
---
.gitignore | 1 +
Documentation/dontdiff | 1 +
Makefile | 19 +++-
scripts/Kbuild.include | 6 ++
scripts/Makefile.modbuiltin | 56 ++++++++++
scripts/modules_thick.c | 200 ++++++++++++++++++++++++++++++++++++
scripts/modules_thick.h | 48 +++++++++
7 files changed, 330 insertions(+), 1 deletion(-)
create mode 100644 scripts/Makefile.modbuiltin
create mode 100644 scripts/modules_thick.c
create mode 100644 scripts/modules_thick.h
diff --git a/.gitignore b/.gitignore
index 7afd412dadd2..b49cd96f587a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -49,6 +49,7 @@
*.zst
Module.symvers
modules.order
+modules_thick.builtin
#
# Top-level generic files
diff --git a/Documentation/dontdiff b/Documentation/dontdiff
index 910b30a2a7d9..6a78988547d0 100644
--- a/Documentation/dontdiff
+++ b/Documentation/dontdiff
@@ -183,6 +183,7 @@ modules.builtin
modules.builtin.modinfo
modules.nsdeps
modules.order
+modules_thick.builtin
modversions.h*
nconf
nconf-cfg
diff --git a/Makefile b/Makefile
index 77062b44a4b5..880b3e67a47f 100644
--- a/Makefile
+++ b/Makefile
@@ -1507,6 +1507,23 @@ __modinst_pre:
endif # CONFIG_MODULES
+# modules_thick.builtin maps from kernel modules (or rather the object file
+# names they would have had had they not been built in) to their constituent
+# object files: we can use this to determine which modules any given object
+# file is part of. (We cannot eliminate the slight redundancy here without
+# double-expansion.)
+
+modthickbuiltin-files := $(addsuffix /modules_thick.builtin, $(build-dirs))
+
+modules_thick.builtin: $(modthickbuiltin-files)
+ $(Q)$(AWK) '!x[$$0]++' $(addsuffix /$@, $(build-dirs)) > $@
+
+# tristate.conf is not included from this Makefile. Add it as a prerequisite
+# here to make it self-healing in case somebody accidentally removes it.
+$(modthickbuiltin-files): include/config/tristate.conf
+ $(Q)$(MAKE) $(modbuiltin)=$(patsubst %/modules_thick.builtin,%,$@) builtin-file=modules_thick.builtin
+
+
###
# Cleaning is done on three levels.
# make clean Delete most generated files
@@ -1886,7 +1903,7 @@ clean: $(clean-dirs)
-o -name '*.lex.c' -o -name '*.tab.[ch]' \
-o -name '*.asn1.[ch]' \
-o -name '*.symtypes' -o -name 'modules.order' \
- -o -name '.tmp_*.o.*' \
+ -o -name '.tmp_*.o.*' -o -name modules_thick.builtin \
-o -name '*.c.[012]*.*' \
-o -name '*.ll' \
-o -name '*.gcno' \
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index cdec22088423..ef68635831b0 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -74,6 +74,12 @@ endef
# $(Q)$(MAKE) $(build)=dir
build := -f $(srctree)/scripts/Makefile.build obj
+###
+# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.modbuiltin obj=
+# Usage:
+# $(Q)$(MAKE) $(modbuiltin)=dir
+modbuiltin := -f $(srctree)/scripts/Makefile.modbuiltin obj
+
###
# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.dtbinst obj=
# Usage:
diff --git a/scripts/Makefile.modbuiltin b/scripts/Makefile.modbuiltin
new file mode 100644
index 000000000000..a27b692ea795
--- /dev/null
+++ b/scripts/Makefile.modbuiltin
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Generating modules_thick.builtin
+# ==========================================================================
+
+src := $(obj)
+
+PHONY := __modbuiltin
+__modbuiltin:
+
+include include/config/auto.conf
+# tristate.conf sets tristate variables to uppercase 'Y' or 'M'
+# That way, we get the list of built-in modules in obj-Y
+include include/config/tristate.conf
+
+include scripts/Kbuild.include
+
+ifdef building_out_of_srctree
+# Create output directory if not already present
+_dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
+endif
+
+# The filename Kbuild has precedence over Makefile
+kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
+kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
+include $(kbuild-file)
+
+include scripts/Makefile.lib
+
+modthickbuiltin-subdirs := $(patsubst %,%/modules_thick.builtin, $(subdir-ym))
+modthickbuiltin-target := $(obj)/modules_thick.builtin
+
+__modbuiltin: $(obj)/$(builtin-file) $(subdir-ym)
+ @:
+
+$(modthickbuiltin-target): $(subdir-ym) FORCE
+ $(Q) rm -f $@
+ $(Q) $(foreach mod-o, $(filter %.o,$(obj-Y)),\
+ printf "%s:" $(addprefix $(obj)/,$(mod-o)) >> $@; \
+ printf " %s" $(sort $(strip $(addprefix $(obj)/,$($(mod-o:.o=-objs)) \
+ $($(mod-o:.o=-y)) $($(mod-o:.o=-Y))))) >> $@; \
+ printf "\n" >> $@; ) \
+ cat /dev/null $(modthickbuiltin-subdirs) >> $@;
+
+PHONY += FORCE
+
+FORCE:
+
+# Descending
+# ---------------------------------------------------------------------------
+
+PHONY += $(subdir-ym)
+$(subdir-ym):
+ $(Q)$(MAKE) $(modbuiltin)=$@ builtin-file=$(builtin-file)
+
+.PHONY: $(PHONY)
diff --git a/scripts/modules_thick.c b/scripts/modules_thick.c
new file mode 100644
index 000000000000..9a15e99c1330
--- /dev/null
+++ b/scripts/modules_thick.c
@@ -0,0 +1,200 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * A simple modules_thick reader.
+ *
+ * (C) 2014, 2021 Oracle, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "modules_thick.h"
+
+/*
+ * Read a modules_thick.builtin file and translate it into a stream of
+ * name / module-name pairs.
+ */
+
+/*
+ * Construct a modules_thick.builtin iterator.
+ */
+struct modules_thick_iter *
+modules_thick_iter_new(const char *modules_thick_file)
+{
+ struct modules_thick_iter *i;
+
+ i = calloc(1, sizeof(struct modules_thick_iter));
+ if (i == NULL)
+ return NULL;
+
+ i->f = fopen(modules_thick_file, "r");
+
+ if (i->f == NULL) {
+ fprintf(stderr, "Cannot open builtin module file %s: %s\n",
+ modules_thick_file, strerror(errno));
+ return NULL;
+ }
+
+ return i;
+}
+
+/*
+ * Iterate, returning a new null-terminated array of object file names, and a
+ * new dynamically-allocated module name. (The module name passed in is freed.)
+ *
+ * The array of object file names should be freed by the caller: the strings it
+ * points to are owned by the iterator, and should not be freed.
+ */
+
+char ** __attribute__((__nonnull__))
+modules_thick_iter_next(struct modules_thick_iter *i, char **module_name)
+{
+ size_t npaths = 1;
+ char **module_paths;
+ char *last_slash;
+ char *last_dot;
+ char *trailing_linefeed;
+ char *object_name = i->line;
+ char *dash;
+ int composite = 0;
+
+ /*
+ * Read in all module entries, computing the suffixless, pathless name
+ * of the module and building the next arrayful of object file names for
+ * return.
+ *
+ * Modules can consist of multiple files: in this case, the portion
+ * before the colon is the path to the module (as before): the portion
+ * after the colon is a space-separated list of files that should be
+ * considered part of this module. In this case, the portion before the
+ * name is an "object file" that does not actually exist: it is merged
+ * into built-in.a without ever being written out.
+ *
+ * All module names have - translated to _, to match what is done to the
+ * names of the same things when built as modules.
+ */
+
+ /*
+ * Reinvocation of exhausted iterator. Return NULL, once.
+ */
+retry:
+ if (getline(&i->line, &i->line_size, i->f) < 0) {
+ if (ferror(i->f)) {
+ fprintf(stderr, "Error reading from modules_thick file:"
+ " %s\n", strerror(errno));
+ exit(1);
+ }
+ rewind(i->f);
+ return NULL;
+ }
+
+ if (i->line[0] == '\0')
+ goto retry;
+
+ /*
+ * Slice the line in two at the colon, if any. If there is anything
+ * past the ': ', this is a composite module. (We allow for no colon
+ * for robustness, even though one should always be present.)
+ */
+ if (strchr(i->line, ':') != NULL) {
+ char *name_start;
+
+ object_name = strchr(i->line, ':');
+ *object_name = '\0';
+ object_name++;
+ name_start = object_name + strspn(object_name, " \n");
+ if (*name_start != '\0') {
+ composite = 1;
+ object_name = name_start;
+ }
+ }
+
+ /*
+ * Figure out the module name.
+ */
+ last_slash = strrchr(i->line, '/');
+ last_slash = (!last_slash) ? i->line :
+ last_slash + 1;
+ free(*module_name);
+ *module_name = strdup(last_slash);
+ dash = *module_name;
+
+ while (dash != NULL) {
+ dash = strchr(dash, '-');
+ if (dash != NULL)
+ *dash = '_';
+ }
+
+ last_dot = strrchr(*module_name, '.');
+ if (last_dot != NULL)
+ *last_dot = '\0';
+
+ trailing_linefeed = strchr(object_name, '\n');
+ if (trailing_linefeed != NULL)
+ *trailing_linefeed = '\0';
+
+ /*
+ * Multifile separator? Object file names explicitly stated:
+ * slice them up and shuffle them in.
+ *
+ * The array size may be an overestimate if any object file
+ * names start or end with spaces (very unlikely) but cannot be
+ * an underestimate. (Check for it anyway.)
+ */
+ if (composite) {
+ char *one_object;
+
+ for (npaths = 0, one_object = object_name;
+ one_object != NULL;
+ npaths++, one_object = strchr(one_object + 1, ' '));
+ }
+
+ module_paths = malloc((npaths + 1) * sizeof(char *));
+ if (!module_paths) {
+ fprintf(stderr, "%s: out of memory on module %s\n", __func__,
+ *module_name);
+ exit(1);
+ }
+
+ if (composite) {
+ char *one_object;
+ size_t i = 0;
+
+ while ((one_object = strsep(&object_name, " ")) != NULL) {
+ if (i >= npaths) {
+ fprintf(stderr, "%s: num_objs overflow on module "
+ "%s: this is a bug.\n", __func__,
+ *module_name);
+ exit(1);
+ }
+
+ module_paths[i++] = one_object;
+ }
+ } else
+ module_paths[0] = i->line; /* untransformed module name */
+
+ module_paths[npaths] = NULL;
+
+ return module_paths;
+}
+
+/*
+ * Free an iterator. Can be called while iteration is underway, so even
+ * state that is freed at the end of iteration must be freed here too.
+ */
+void
+modules_thick_iter_free(struct modules_thick_iter *i)
+{
+ if (i == NULL)
+ return;
+ fclose(i->f);
+ free(i->line);
+ free(i);
+}
diff --git a/scripts/modules_thick.h b/scripts/modules_thick.h
new file mode 100644
index 000000000000..f5edcaf9550c
--- /dev/null
+++ b/scripts/modules_thick.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * A simple modules_thick reader.
+ *
+ * (C) 2014, 2021 Oracle, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef _LINUX_MODULES_THICK_H
+#define _LINUX_MODULES_THICK_H
+
+#include <stdio.h>
+#include <stddef.h>
+
+/*
+ * modules_thick.builtin iteration state.
+ */
+struct modules_thick_iter {
+ FILE *f;
+ char *line;
+ size_t line_size;
+};
+
+/*
+ * Construct a modules_thick.builtin iterator.
+ */
+struct modules_thick_iter *
+modules_thick_iter_new(const char *modules_thick_file);
+
+/*
+ * Iterate, returning a new null-terminated array of object file names, and a
+ * new dynamically-allocated module name. (The module name passed in is freed.)
+ *
+ * The array of object file names should be freed by the caller: the strings it
+ * points to are owned by the iterator, and should not be freed.
+ */
+
+char ** __attribute__((__nonnull__))
+modules_thick_iter_next(struct modules_thick_iter *i, char **module_name);
+
+void
+modules_thick_iter_free(struct modules_thick_iter *i);
+
+#endif
--
2.33.0.256.gb827f06fa9
This emits a new file, .tmp_vmlinux.ranges, which maps address
range/size pairs in vmlinux to the object files which make them up,
e.g., in part:
0x0000000000000000 0x30 arch/x86/kernel/cpu/common.o
0x0000000000001000 0x1000 arch/x86/events/intel/ds.o
0x0000000000002000 0x4000 arch/x86/kernel/irq_64.o
0x0000000000006000 0x5000 arch/x86/kernel/process.o
0x000000000000b000 0x1000 arch/x86/kernel/cpu/common.o
0x000000000000c000 0x5000 arch/x86/mm/cpu_entry_area.o
0x0000000000011000 0x10 arch/x86/kernel/espfix_64.o
0x0000000000011010 0x2 arch/x86/kernel/cpu/common.o
[...]
In my simple tests this seems to work with clang too, but if I'm not
sure how stable the format of clang's linker mapfiles is: if it turns
out not to work in some versions, the mapfile-massaging awk script added
here might need some adjustment.
Signed-off-by: Nick Alcock <[email protected]>
---
scripts/link-vmlinux.sh | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index d74cee5c4326..a30075c14a25 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -196,7 +196,7 @@ vmlinux_link()
${ld} ${ldflags} -o ${output} \
${wl}--whole-archive ${objs} ${wl}--no-whole-archive \
${wl}--start-group ${libs} ${wl}--end-group \
- $@ ${ldlibs}
+ -Map=.tmp_vmlinux.map $@ ${ldlibs}
}
# generate .BTF typeinfo from DWARF debuginfo
@@ -248,6 +248,19 @@ kallsyms()
{
local kallsymopt;
+ # read the linker map to identify ranges of addresses:
+ # - for each *.o file, report address, size, pathname
+ # - most such lines will have four fields
+ # - but sometimes there is a line break after the first field
+ # - start reading at "Linker script and memory map"
+ # - stop reading at ".brk"
+ ${AWK} '
+ /\.o$/ && start==1 { print $(NF-2), $(NF-1), $NF }
+ /^Linker script and memory map/ { start = 1 }
+ /^\.brk/ { exit(0) }
+ ' .tmp_vmlinux.map | sort > .tmp_vmlinux.ranges
+
+ # get kallsyms options
if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
kallsymopt="${kallsymopt} --all-symbols"
fi
--
2.33.0.256.gb827f06fa9
On Wed, Sep 29, 2021 at 10:51:47PM +0100, Nick Alcock wrote:
> It would be useful if there were a mapping between kernel symbol and module
> name that only changed when the kernel source code is changed. This mapping
> should not change simply because a module becomes built into the kernel.
>
> It might also be useful if there were reliable symbol size information to
> determine whether an address is within a symbol or outside it, especially
> given that there could be huge gaps between symbols.
This is a pretty cool series, but I'm left wondering "for what reason?" :)
Perhaps I missed the specific rationale; there was a lot to run. ;)
It would be useful, sure, but is there something that does, in fact,
need this, or would like this if it were available? Since this provides
a userspace API, what would be consuming that API? For example, when
Syscall User Dispatch was added, it was clear it was for Wine[1].
-Kees
[1] https://lore.kernel.org/lkml/160690190770.3364.5119373826178425644.tip-bot2@tip-bot2/
--
Kees Cook
On Thu, Sep 30, 2021 at 06:19:55PM +0100, Nick Alcock wrote:
> On 30 Sep 2021, Kees Cook said:
> > On Wed, Sep 29, 2021 at 10:51:47PM +0100, Nick Alcock wrote:
> >> It would be useful if there were a mapping between kernel symbol and module
> >> name that only changed when the kernel source code is changed. This mapping
> >> should not change simply because a module becomes built into the kernel.
> >>
> >> It might also be useful if there were reliable symbol size information to
> >> determine whether an address is within a symbol or outside it, especially
> >> given that there could be huge gaps between symbols.
> >> [...]
> > [...]
> > It would be useful, sure, but is there something that does, in fact,
> > need this, or would like this if it were available? Since this provides
> > a userspace API, what would be consuming that API? For example, when
> > Syscall User Dispatch was added, it was clear it was for Wine[1].
>
> We have a long-term consumer in DTrace (e.g.
> <https://github.com/oracle/dtrace-utils/blob/dev/libdtrace/dt_module.c#L1323>).
> (But since we control this consumer we are quite happy to change the
> format of kallmodsyms, integrate it with kallsyms so that kallsyms just
> provides the same information if the file format break were acceptable,
> or whatever you think most sensible. We just want this information
> somehow. :) e.g. the code there doesn't yet handle the
> symbol-in-multiple-modules case: I'll have to add that.)
Ah-ha, excellent. That works for me. :) (If there is a v5, maybe add a
note about DTrace to help show the specific need.)
Thanks!
-Kees
--
Kees Cook
On 30 Sep 2021, Kees Cook said:
> On Wed, Sep 29, 2021 at 10:51:47PM +0100, Nick Alcock wrote:
>> It would be useful if there were a mapping between kernel symbol and module
>> name that only changed when the kernel source code is changed. This mapping
>> should not change simply because a module becomes built into the kernel.
>>
>> It might also be useful if there were reliable symbol size information to
>> determine whether an address is within a symbol or outside it, especially
>> given that there could be huge gaps between symbols.
>
> This is a pretty cool series, but I'm left wondering "for what reason?" :)
> Perhaps I missed the specific rationale; there was a lot to run. ;)
The underlying rationale that the earliest, crude version of this patch
was written for is that DTrace allows symbol and type names to be
module-qualified (e.g. hid`names) and we don't want people's scripts to
break just because they recompile the kernel to make things a module
versus not. But this problem is not DTrace-specific: given that names
are not unique across the kernel when things are built as modules, many
tracing tools that introspect the values of kernel symbols etc might
want to let users qualify names with the modules they apply to, and more
or less none of those are going to want a script that asks for "foo in
the bar module" to suddenly become invalid because the user changed
CONFIG_FOO=m to CONFIG_FOO=y.
Obviously, if they change it to CONFIG_FOO=n, any script that uses names
from FOO is going to break: there's nothing we can do about that. But
not breaking the m/y case seems like a simple quality-of- implementation
issue to make it easier to redistribute scripts to anyone using FOO no
matter what their module/non-module configuration, and a nice easy one
to fix, if only we could easily tell what the module/symbol mapping was.
And with this patch we can (at minimal cost).
(I have also found it to be useful for by-hand stuff, when I can't
remember where the heck some symbol with a non-qualified name is,
usually a file-scope variable: it's faster to grep kallmodsyms than to
do a tags lookup, let alone a grep, if I'm debugging something I know is
loaded into the kernel right now. Which often one is if one is
reproducing the bug... and often the module a symbol is part of is
informative. This is, obviously, crude, but it's still more useful to
have more module names there than fewer if one is doing this sort of
thing.)
(As an aside, this is not all a tracing system needs to do to get this
sort of thing right, particularly where types are concerned: it's still
possible to have conflicting type names across translation units within
a single module. CTF deals with that case perfectly well via child CTF
dicts, and GNU ld splits ambiguously-defined types out so that the user
can say "foo_t in the bar module in wombat.c" in the rare cases where
ambiguity exists.)
> It would be useful, sure, but is there something that does, in fact,
> need this, or would like this if it were available? Since this provides
> a userspace API, what would be consuming that API? For example, when
> Syscall User Dispatch was added, it was clear it was for Wine[1].
We have a long-term consumer in DTrace (e.g.
<https://github.com/oracle/dtrace-utils/blob/dev/libdtrace/dt_module.c#L1323>).
(But since we control this consumer we are quite happy to change the
format of kallmodsyms, integrate it with kallsyms so that kallsyms just
provides the same information if the file format break were acceptable,
or whatever you think most sensible. We just want this information
somehow. :) e.g. the code there doesn't yet handle the
symbol-in-multiple-modules case: I'll have to add that.)
But this feels useful enough to me that I'm hoping that more consumers
will grow. I'm sure SystemTap would find it useful, and I'm hoping
bpftrace etc might as well once that starts to handle modules. They're
all going to need some sort of namespace-qualification and then they're
all going to run into the same script-stability problem as soon as users
try to share scripts at all. We can make that problem largely go away :)
--
NULL && (void)
/proc/kallsyms is very useful for tracers and other tools that need to
map kernel symbols to addresses.
It would be useful if there were a mapping between kernel symbol and module
name that only changed when the kernel source code is changed. This mapping
should not change simply because a module becomes built into the kernel.
It might also be useful if there were reliable symbol size information to
determine whether an address is within a symbol or outside it, especially
given that there could be huge gaps between symbols.
Fix this by introducing a new config parameter CONFIG_KALLMODSYMS, which
does several things at once (introduced in distinct commits inthis series).
Generate a file "modules_thick.builtin" that maps from the thin archives
that make up built-in modules to their constituent object files. (This
reintroduces the machinery that used to be used to generate
modules.builtin. I am not wedded to this mechanism: if someone can
figure out a mechanism that does not require recursing over the entire
build tree, I'm happy to use it, but I suspect that no such mechanism
exists, since the only place the mapping from object file to module
exists is in the makefiles themselves. Regardless, this is fairly cheap,
adding less than a second to a typical hot-cache build of a large
enterprise kernel. This is true even though it needs to be run
unconditionally whenever the .config changes.)
Generate a linker map ".tmp_vmlinux.map", converting it into
".tmp_vmlinux.ranges", mapping address ranges to object files.
Have scripts/kallsyms read these two new files to map symbol addresses
to built-in-module names and then write a mapping from object file
address to module name to the *.s output file.
The mapping consists of three new symbols:
- kallsyms_module_addresses/kallsyms_module_offsets encodes the
address/offset of each object file (derived from the linker map), in
exactly the same way as kallsyms_addresses/kallsyms_offsets does
for symbols. There is no size: instead, the object files are
assumed to tile the address space. (This is slightly more
space-efficient than using a size). Non-text-section addresses are
skipped: for now, all the users of this interface only need
module/non-module information for instruction pointer addresses, not
absolute-addressed symbols and the like. This restriction can
easily be lifted in future. (For why this isn't called
kallsyms_objfiles, see two entries below.)
- kallsyms_module_names encodes the name of each module in a modified
form of strtab: notably, if an object file appears in *multiple*
modules, all of which are built in, this is encoded via a zero byte,
a one-byte module count, then a series of that many null-terminated
strings. Object files which appear in only one module in such a
multi-module list are redirected to point inside that list, so that
modules which contain some object files shared with other modules
and some object files exclusive to them do not double up the module
name. (There might still be some duplication between multiple
multi-module lists, but this is an extremely marginal size effect,
and resolving it would require an extra layer of lookup tables which
would be even more complex, and incompressible to boot). As a
special case, the table starts with a single zero byte which does
*not* represent the start of a multi-module list.
- kallsyms_modules connects the two, encoding a table associated 1:1
with kallsyms_module_addresses / kallsyms_module_offsets, pointing
at an offset in kallsyms_module_names describing which module (or
modules, for a multi-module list) the code occupying this address
range is part of. If an address range is part of no module (always
built-in) it points at 0 (the null byte at the start of the
kallsyms_module_names list). Entries in this list that would
contain the same value are fused together, along with their
corresponding kallsyms_module_addresses/offsets entries. Due to
this fusion process, and because object files can be split apart into
multiple parts by the linker for hot/cold partitioning and the like,
entries in here do not really correspond to an object file, but more
to some contiguous range of addresses which are guaranteed to belong
to a single built-in module: so it seems best to call the symbols
kallsyms_modules*. (The generator has a data structure that does
correspond more closely to object files, from which kallsyms_modules
is generated, and that does use 'objfiles' terminology.)
Emit a new /proc/kallmodsyms file akin to /proc/kallsyms but with built-in
module names, using a new kallsyms_builtin_module_address() almost identical
to kallsyms_sym_address() to get the address corresponding to a given
.kallsyms_modules index, and a new get_builtin_module_idx quite similar to
get_symbol_pos to determine the index in the .kallsyms_modules array that
relates to a given address. Save a little time by exploiting the fact that
all callers will only ever traverse this list from start to end by allowing
them to pass in the previous index returned from this function as a hint:
thus very few bsearches are actually needed. (In theory this could change
to just walk straight down kallsyms_module_addresses/offsets and not bother
bsearching at all, but doing it this way is hardly any slower and much more
robust.)
The display process is complicated a little by the weird format of the
.kallsyms_module_names table: we have to look for multimodule entries
and print them as space-separated lists of module names.
The resulting /proc/kallmodsyms file looks like this:
ffffffff8b013d20 409 t pt_buffer_setup_aux
ffffffff8b014130 11f T intel_pt_interrupt
ffffffff8b014250 2d T cpu_emergency_stop_pt
ffffffff8b014280 13a t rapl_pmu_event_init [intel_rapl_perf]
ffffffff8b0143c0 bb t rapl_event_update [intel_rapl_perf]
ffffffff8b014480 10 t rapl_pmu_event_read [intel_rapl_perf]
ffffffff8b014490 a3 t rapl_cpu_offline [intel_rapl_perf]
ffffffff8b014540 24 t __rapl_event_show [intel_rapl_perf]
ffffffff8b014570 f2 t rapl_pmu_event_stop [intel_rapl_perf]
This is emitted even if intel_rapl_perf is built into the kernel.
Further down, we see what happens when object files are reused by
multiple modules, all of which are built in to the kernel:
ffffffffa22b3aa0 ab t handle_timestamp [liquidio]
ffffffffa22b3b50 4a t free_netbuf [liquidio]
ffffffffa22b3ba0 8d t liquidio_ptp_settime [liquidio]
ffffffffa22b3c30 b3 t liquidio_ptp_adjfreq [liquidio]
[...]
ffffffffa22b9490 203 t lio_vf_rep_create [liquidio]
ffffffffa22b96a0 16b t lio_vf_rep_destroy [liquidio]
ffffffffa22b9810 1f t lio_vf_rep_modinit [liquidio]
ffffffffa22b9830 1f t lio_vf_rep_modexit [liquidio]
ffffffffa22b9850 d2 t lio_ethtool_get_channels [liquidio] [liquidio_vf]
ffffffffa22b9930 9c t lio_ethtool_get_ringparam [liquidio] [liquidio_vf]
ffffffffa22b99d0 11 t lio_get_msglevel [liquidio] [liquidio_vf]
ffffffffa22b99f0 11 t lio_vf_set_msglevel [liquidio] [liquidio_vf]
ffffffffa22b9a10 2b t lio_get_pauseparam [liquidio] [liquidio_vf]
ffffffffa22b9a40 738 t lio_get_ethtool_stats [liquidio] [liquidio_vf]
ffffffffa22ba180 368 t lio_vf_get_ethtool_stats [liquidio] [liquidio_vf]
ffffffffa22ba4f0 37 t lio_get_regs_len [liquidio] [liquidio_vf]
ffffffffa22ba530 18 t lio_get_priv_flags [liquidio] [liquidio_vf]
ffffffffa22ba550 2e t lio_set_priv_flags [liquidio] [liquidio_vf]
ffffffffa22ba580 69 t lio_set_fecparam [liquidio] [liquidio_vf]
ffffffffa22ba5f0 92 t lio_get_fecparam [liquidio] [liquidio_vf]
[...]
ffffffffa22cbd10 175 t liquidio_set_mac [liquidio_vf]
ffffffffa22cbe90 ab t handle_timestamp [liquidio_vf]
ffffffffa22cbf40 4a t free_netbuf [liquidio_vf]
ffffffffa22cbf90 2b t octnet_link_status_change [liquidio_vf]
ffffffffa22cbfc0 7e t liquidio_vxlan_port_command.constprop.0 [liquidio_vf]
Like /proc/kallsyms, the output is driven by address, so keeps the
curious property of /proc/kallsyms that symbols (like free_netbuf above)
may appear repeatedly with different addresses: but now, unlike in
/proc/kallsyms, we can see that those symbols appear repeatedly because
they are *different symbols* that ultimately belong to different
modules, all of which are built in to the kernel.
Those symbols that come from object files that are genuinely reused and
that appear only once in meory get a /proc/kallmodsyms line with
[multiple] [modules] on it: consumers will have to be ready to handle
such lines.
Also, kernel symbols for built-in modules will probably appear
interspersed with other symbols that are part of different modules and
non-modular always-built-in symbols, which, as usual, have no
square-bracketed module denotation.
As with /proc/kallsyms, non-root usage produces addresses that are
all zero.
I am open to changing the name and/or format of /proc/kallmodsyms, but felt
it best to split it out of /proc/kallsyms to avoid breaking existing
kallsyms parsers. Another possible syntax might be to use {curly brackets}
or something to denote built-in modules: it might be possible to drop
/proc/kallmodsyms and make /proc/kallsyms emit things in this format.
(Equally, now kallmodsyms data uses very little space, the
CONFIG_KALLMODSYMS config option might be something people don't want to
bother with.)
The size impact of all of this is minimal: for the case above, the
kallsyms2.S file went from 14107772 to 14137245 bytes, a gain of 29743
bytes, or 0.16%: vmlinux gained 10824 bytes, a gain of .017%, and the
compressed vmlinux only 7552 bytes, a gain of .08%: though the latter
two values are very configuration-dependent, they seem likely to scale
roughly with the kernel they are part of.
The last patch is an RFC to see if the idea is considered to be worth
spending more time optimizing the representation, which adds a new
kallsyms_sizes section that gives the size of each symbol, and uses this
info to report reliable symbol sizes to in-kernel users, and (via a new
column in /proc/kallmodsyms) to out-of-kernel users too. Having reliable
size info lets us identify inter-symbol gaps and sort symbols so that
start/end-marker and overlapping symbols are consistently ordered with
respect to the symbols they overlap. This certainly uses too much space
right now, 200KiB--1MiB: a better representation is certainly needed. One
that springs to mind is making the table sparse (pairs of symbol
index/size), and recording explicit sizes only for those symbols that
are not immediately followed by a subsequent symbol.
Differences from v4, two months ago:
- Fix building of tristate.conf if missing (usually concealed by the
syncconfig being run for other reasons, but not always: the kernel
test robot spotted it).
- Forward-port atop v5.15-rc3.
Differences from v3, a month earlier:
- Fix a kernel test robot warning in get_ksymbol_core (possible
use of uninitialized variable if kallmodsyms was wanted but
kallsyms_module_offsets was not present, which is most unlikely).
Differences from v2, a couple of months before that:
- Split the series up. In particular, the size impact of the table
optimizer is now quantified, and the symbol-size patch is split out and
turned into an RFC patch, with the /proc/kallmodsyms format before that
patch lacking a size column. Some speculation on how to make the symbol
sizes less space-wasteful is added (but not yet implemented).
- Drop a couple of unnecessary #includes, one unnecessarily exported
symbol, and a needless de-staticing.
Differences from v1, a year or so back:
- Move from a straight symbol->module name mapping to a mapping from
address-range to TU to module name list, bringing major space savings
over the previous approach and support for object files used by many
built-in modules at the same time, at the cost of a slightly more complex
approach (unavoidably so, I think, given that we have to merge three data
sources together: the link map in .tmp_vmlinux.ranges, the nm output on
stdin, and the mapping from TU name to module names in
modules_thick.builtin).
We do opportunistic merging of TUs if they cite the same modules and
reuse module names where doing so is simple: see optimize_obj2mod
below. I considered more extensive searches for mergeable entries and
more intricate encodings of the module name list allowing TUs that are
used by overlapping sets of modules to share their names, but such
modules are rare enough (and such overlapping sharings are vanishingly
rare) that it seemed likely to save only a few bytes at the cost of much
more hard-to-test code. This is doubly true now that the tables needed
are only a few kilobytes in length.
Signed-off-by: Nick Alcock <[email protected]>
Signed-off-by: Eugene Loh <[email protected]>
Reviewed-by: Kris Van Hees <[email protected]>
Nick Alcock (7):
kbuild: bring back tristate.conf
kbuild: add modules_thick.builtin
kbuild: generate an address ranges map at vmlinux link time
kallsyms: introduce sections needed to map symbols to built-in modules
kallsyms: optimize .kallsyms_modules*
kallsyms: add /proc/kallmodsyms
kallsyms: add reliable symbol size info
.gitignore | 1 +
Documentation/dontdiff | 1 +
Makefile | 23 +-
include/linux/module.h | 7 +-
init/Kconfig | 8 +
kernel/kallsyms.c | 304 ++++++++++++++---
kernel/module.c | 4 +-
scripts/Kbuild.include | 6 +
scripts/Makefile | 6 +
scripts/Makefile.modbuiltin | 56 ++++
scripts/kallsyms.c | 642 +++++++++++++++++++++++++++++++++++-
scripts/kconfig/confdata.c | 41 ++-
scripts/link-vmlinux.sh | 22 +-
scripts/modules_thick.c | 200 +++++++++++
scripts/modules_thick.h | 48 +++
15 files changed, 1301 insertions(+), 68 deletions(-)
create mode 100644 scripts/Makefile.modbuiltin
create mode 100644 scripts/modules_thick.c
create mode 100644 scripts/modules_thick.h
--
2.33.0.256.gb827f06fa9
Use the tables added in the previous commits to introduce a new
/proc/kallmodsyms, in which [module names] are also given for things
that *could* have been modular had they not been built in to the kernel.
So symbols that are part of, say, ext4 are reported as [ext4] even if
ext4 happens to be buiilt in to the kernel in this configuration.
Symbols that are part of multiple modules at the same time are shown
with [multiple] [module names]: consumers will have to be ready to
handle such lines. Also, kernel symbols for built-in modules will be
sorted by size, as usual for the core kernel, so will probably appear
interspersed with other symbols that are part of different modules and
non-modular always-built-in symbols, which, as usual, have no
square-bracketed module denotation. This differs from /proc/kallsyms,
where all symbols associated with a module will always appear in a group
(and randomly ordered).
The result looks like this:
ffffffff8b013d20 t pt_buffer_setup_aux
ffffffff8b014130 T intel_pt_interrupt
ffffffff8b014250 T cpu_emergency_stop_pt
ffffffff8b014280 t rapl_pmu_event_init [intel_rapl_perf]
ffffffff8b0143c0 t rapl_event_update [intel_rapl_perf]
ffffffff8b014480 t rapl_pmu_event_read [intel_rapl_perf]
ffffffff8b014490 t rapl_cpu_offline [intel_rapl_perf]
ffffffff8b014540 t __rapl_event_show [intel_rapl_perf]
ffffffff8b014570 t rapl_pmu_event_stop [intel_rapl_perf]
This is emitted even if intel_rapl_perf is built into the kernel (but,
obviously, not if it's not in the .config at all, or is in a module that
is not loaded).
Further down, we see what happens when object files are reused by
multiple modules, all of which are built in to the kernel:
ffffffffa22b3aa0 t handle_timestamp [liquidio]
ffffffffa22b3b50 t free_netbuf [liquidio]
ffffffffa22b3ba0 t liquidio_ptp_settime [liquidio]
ffffffffa22b3c30 t liquidio_ptp_adjfreq [liquidio]
[...]
ffffffffa22b9490 t lio_vf_rep_create [liquidio]
ffffffffa22b96a0 t lio_vf_rep_destroy [liquidio]
ffffffffa22b9810 t lio_vf_rep_modinit [liquidio]
ffffffffa22b9830 t lio_vf_rep_modexit [liquidio]
ffffffffa22b9850 t lio_ethtool_get_channels [liquidio] [liquidio_vf]
ffffffffa22b9930 t lio_ethtool_get_ringparam [liquidio] [liquidio_vf]
ffffffffa22b99d0 t lio_get_msglevel [liquidio] [liquidio_vf]
ffffffffa22b99f0 t lio_vf_set_msglevel [liquidio] [liquidio_vf]
ffffffffa22b9a10 t lio_get_pauseparam [liquidio] [liquidio_vf]
ffffffffa22b9a40 t lio_get_ethtool_stats [liquidio] [liquidio_vf]
ffffffffa22ba180 t lio_vf_get_ethtool_stats [liquidio] [liquidio_vf]
ffffffffa22ba4f0 t lio_get_regs_len [liquidio] [liquidio_vf]
ffffffffa22ba530 t lio_get_priv_flags [liquidio] [liquidio_vf]
ffffffffa22ba550 t lio_set_priv_flags [liquidio] [liquidio_vf]
ffffffffa22ba580 t lio_set_fecparam [liquidio] [liquidio_vf]
ffffffffa22ba5f0 t lio_get_fecparam [liquidio] [liquidio_vf]
[...]
ffffffffa22cbd10 t liquidio_set_mac [liquidio_vf]
ffffffffa22cbe90 t handle_timestamp [liquidio_vf]
ffffffffa22cbf40 t free_netbuf [liquidio_vf]
ffffffffa22cbf90 t octnet_link_status_change [liquidio_vf]
ffffffffa22cbfc0 t liquidio_vxlan_port_command.constprop.0 [liquidio_vf]
Like /proc/kallsyms, the output is driven by address, so keeps the
curious property of /proc/kallsyms that symbols (like free_netbuf above)
may appear repeatedly with different addresses: but now, unlike in
/proc/kallsyms, we can see that those symbols appear repeatedly because
they are *different symbols* that ultimately belong to different
modules, all of which are built in to the kernel.
As with /proc/kallsyms, non-root usage produces addresses that are
all zero.
I am not wedded to the name or format of /proc/kallmodsyms, but felt it
best to split it out of /proc/kallsyms to avoid breaking existing
kallsyms parsers. Another possible syntax might be to use {curly
brackets} or something to denote built-in modules: it might be possible
to drop /proc/kallmodsyms and make /proc/kallsyms emit things in this
format. (Equally, now kallmodsyms data uses very little space, the
CONFIG_KALLMODSYMS config option might be something people don't want to
bother with.)
Internally, this uses a new kallsyms_builtin_module_address() almost
identical to kallsyms_sym_address() to get the address corresponding to
a given .kallsyms_modules index, and a new get_builtin_module_idx quite
similar to get_symbol_pos to determine the index in the
.kallsyms_modules array that relates to a given address. Save a little
time by exploiting the fact that all callers will only ever traverse
this list from start to end by allowing them to pass in the previous
index returned from this function as a hint: thus very few bsearches are
actually needed. (In theory this could change to just walk straight
down kallsyms_module_addresses/offsets and not bother bsearching at all,
but doing it this way is hardly any slower and much more robust.)
The display process is complicated a little by the weird format of the
.kallsyms_module_names table: we have to look for multimodule entries
and print them as space-separated lists of module names.
Signed-off-by: Nick Alcock <[email protected]>
---
kernel/kallsyms.c | 242 +++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 227 insertions(+), 15 deletions(-)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 0ba87982d017..38109bb02bef 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -48,8 +48,18 @@ __section(".rodata") __attribute__((weak));
extern const unsigned long kallsyms_relative_base
__section(".rodata") __attribute__((weak));
+extern const unsigned long kallsyms_num_modules
+__section(".rodata") __attribute__((weak));
+
+extern const unsigned long kallsyms_module_names_len
+__section(".rodata") __attribute__((weak));
+
extern const char kallsyms_token_table[] __weak;
extern const u16 kallsyms_token_index[] __weak;
+extern const unsigned long kallsyms_module_addresses[] __weak;
+extern const int kallsyms_module_offsets[] __weak;
+extern const u32 kallsyms_modules[] __weak;
+extern const char kallsyms_module_names[] __weak;
extern const unsigned int kallsyms_markers[] __weak;
@@ -185,6 +195,25 @@ static inline bool cleanup_symbol_name(char *s)
static inline bool cleanup_symbol_name(char *s) { return false; }
#endif
+#ifdef CONFIG_KALLMODSYMS
+static unsigned long kallsyms_builtin_module_address(int idx)
+{
+ if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
+ return kallsyms_module_addresses[idx];
+
+ /* values are unsigned offsets if --absolute-percpu is not in effect */
+ if (!IS_ENABLED(CONFIG_KALLSYMS_ABSOLUTE_PERCPU))
+ return kallsyms_relative_base + (u32)kallsyms_module_offsets[idx];
+
+ /* ...otherwise, positive offsets are absolute values */
+ if (kallsyms_module_offsets[idx] >= 0)
+ return kallsyms_module_offsets[idx];
+
+ /* ...and negative offsets are relative to kallsyms_relative_base - 1 */
+ return kallsyms_relative_base - 1 - kallsyms_module_offsets[idx];
+}
+#endif
+
/* Lookup the address for this symbol. Returns 0 if not found. */
unsigned long kallsyms_lookup_name(const char *name)
{
@@ -288,6 +317,54 @@ static unsigned long get_symbol_pos(unsigned long addr,
return low;
}
+/*
+ * The caller passes in an address, and we return an index to the corresponding
+ * builtin module index in .kallsyms_modules, or (unsigned long) -1 if none
+ * match.
+ *
+ * The hint_idx, if set, is a hint as to the possible return value, to handle
+ * the common case in which consecutive runs of addresses relate to the same
+ * index.
+ */
+#ifdef CONFIG_KALLMODSYMS
+static unsigned long get_builtin_module_idx(unsigned long addr, unsigned long hint_idx)
+{
+ unsigned long low, high, mid;
+
+ if (!IS_ENABLED(CONFIG_KALLSYMS_BASE_RELATIVE))
+ BUG_ON(!kallsyms_module_addresses);
+ else
+ BUG_ON(!kallsyms_module_offsets);
+
+ /*
+ * Do a binary search on the sorted kallsyms_modules array. The last
+ * entry in this array indicates the end of the text section, not an
+ * object file.
+ */
+ low = 0;
+ high = kallsyms_num_modules - 1;
+
+ if (hint_idx > low && hint_idx < (high - 1) &&
+ addr >= kallsyms_builtin_module_address(hint_idx) &&
+ addr < kallsyms_builtin_module_address(hint_idx + 1))
+ return hint_idx;
+
+ if (addr >= kallsyms_builtin_module_address(low)
+ && addr < kallsyms_builtin_module_address(high)) {
+ while (high - low > 1) {
+ mid = low + (high - low) / 2;
+ if (kallsyms_builtin_module_address(mid) <= addr)
+ low = mid;
+ else
+ high = mid;
+ }
+ return low;
+ }
+
+ return (unsigned long) -1;
+}
+#endif
+
/*
* Lookup an address but don't bother to find any names.
*/
@@ -559,6 +636,8 @@ struct kallsym_iter {
char type;
char name[KSYM_NAME_LEN];
char module_name[MODULE_NAME_LEN];
+ const char *builtin_module_names;
+ unsigned long hint_builtin_module_idx;
int exported;
int show_value;
};
@@ -589,6 +668,8 @@ static int get_ksymbol_mod(struct kallsym_iter *iter)
&iter->value, &iter->type,
iter->name, iter->module_name,
&iter->exported);
+ iter->builtin_module_names = NULL;
+
if (ret < 0) {
iter->pos_mod_end = iter->pos;
return 0;
@@ -608,6 +689,8 @@ static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter)
&iter->value, &iter->type,
iter->name, iter->module_name,
&iter->exported);
+ iter->builtin_module_names = NULL;
+
if (ret < 0) {
iter->pos_ftrace_mod_end = iter->pos;
return 0;
@@ -622,6 +705,7 @@ static int get_ksymbol_bpf(struct kallsym_iter *iter)
strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN);
iter->exported = 0;
+ iter->builtin_module_names = NULL;
ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end,
&iter->value, &iter->type,
iter->name);
@@ -642,23 +726,53 @@ static int get_ksymbol_kprobe(struct kallsym_iter *iter)
{
strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN);
iter->exported = 0;
+ iter->builtin_module_names = NULL;
return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end,
&iter->value, &iter->type,
iter->name) < 0 ? 0 : 1;
}
/* Returns space to next name. */
-static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
+static unsigned long get_ksymbol_core(struct kallsym_iter *iter, int kallmodsyms)
{
unsigned off = iter->nameoff;
- iter->module_name[0] = '\0';
+ iter->exported = 0;
iter->value = kallsyms_sym_address(iter->pos);
iter->type = kallsyms_get_symbol_type(off);
+ iter->module_name[0] = '\0';
+ iter->builtin_module_names = NULL;
+
off = kallsyms_expand_symbol(off, iter->name, ARRAY_SIZE(iter->name));
+#ifdef CONFIG_KALLMODSYMS
+ if (kallmodsyms) {
+ unsigned long mod_idx = (unsigned long) -1;
+
+ if (kallsyms_module_offsets)
+ mod_idx =
+ get_builtin_module_idx(iter->value,
+ iter->hint_builtin_module_idx);
+ /*
+ * This is a built-in module iff the tables of built-in modules
+ * (address->module name mappings) and module names are known,
+ * and if the address was found there, and if the corresponding
+ * module index is nonzero. All other cases mean off the end of
+ * the binary or in a non-modular range in between one or more
+ * modules. (Also guard against a corrupt kallsyms_objfiles
+ * array pointing off the end of kallsyms_modules.)
+ */
+ if (kallsyms_modules != NULL && kallsyms_module_names != NULL &&
+ mod_idx != (unsigned long) -1 &&
+ kallsyms_modules[mod_idx] != 0 &&
+ kallsyms_modules[mod_idx] < kallsyms_module_names_len)
+ iter->builtin_module_names =
+ &kallsyms_module_names[kallsyms_modules[mod_idx]];
+ iter->hint_builtin_module_idx = mod_idx;
+ }
+#endif
return off - iter->nameoff;
}
@@ -704,7 +818,7 @@ static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
}
/* Returns false if pos at or past end of file. */
-static int update_iter(struct kallsym_iter *iter, loff_t pos)
+static int update_iter(struct kallsym_iter *iter, loff_t pos, int kallmodsyms)
{
/* Module symbols can be accessed randomly. */
if (pos >= kallsyms_num_syms)
@@ -714,7 +828,7 @@ static int update_iter(struct kallsym_iter *iter, loff_t pos)
if (pos != iter->pos)
reset_iter(iter, pos);
- iter->nameoff += get_ksymbol_core(iter);
+ iter->nameoff += get_ksymbol_core(iter, kallmodsyms);
iter->pos++;
return 1;
@@ -724,14 +838,14 @@ static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
(*pos)++;
- if (!update_iter(m->private, *pos))
+ if (!update_iter(m->private, *pos, 0))
return NULL;
return p;
}
static void *s_start(struct seq_file *m, loff_t *pos)
{
- if (!update_iter(m->private, *pos))
+ if (!update_iter(m->private, *pos, 0))
return NULL;
return m->private;
}
@@ -740,7 +854,7 @@ static void s_stop(struct seq_file *m, void *p)
{
}
-static int s_show(struct seq_file *m, void *p)
+static int s_show_internal(struct seq_file *m, void *p, int kallmodsyms)
{
void *value;
struct kallsym_iter *iter = m->private;
@@ -751,23 +865,67 @@ static int s_show(struct seq_file *m, void *p)
value = iter->show_value ? (void *)iter->value : NULL;
- if (iter->module_name[0]) {
+ /*
+ * Real module, or built-in module and /proc/kallsyms being shown.
+ */
+ if (iter->module_name[0] != '\0' ||
+ (iter->builtin_module_names != NULL && kallmodsyms != 0)) {
char type;
/*
- * Label it "global" if it is exported,
- * "local" if not exported.
+ * Label it "global" if it is exported, "local" if not exported.
*/
type = iter->exported ? toupper(iter->type) :
tolower(iter->type);
- seq_printf(m, "%px %c %s\t[%s]\n", value,
- type, iter->name, iter->module_name);
+#ifdef CONFIG_KALLMODSYMS
+ if (kallmodsyms) {
+ /*
+ * /proc/kallmodsyms, built as a module.
+ */
+ if (iter->builtin_module_names == NULL)
+ seq_printf(m, "%px %c %s\t[%s]\n", value,
+ type, iter->name,
+ iter->module_name);
+ /*
+ * /proc/kallmodsyms, single-module symbol.
+ */
+ else if (*iter->builtin_module_names != '\0')
+ seq_printf(m, "%px %c %s\t[%s]\n", value,
+ type, iter->name,
+ iter->builtin_module_names);
+ /*
+ * /proc/kallmodsyms, multimodule symbol. Formatted
+ * as \0MODULE_COUNTmodule-1\0module-2\0, where
+ * MODULE_COUNT is a single byte, 2 or higher.
+ */
+ else {
+ size_t i = *(char *)(iter->builtin_module_names + 1);
+ const char *walk = iter->builtin_module_names + 2;
+
+ seq_printf(m, "%px %c %s\t[%s]", value,
+ type, iter->name, walk);
+
+ while (--i > 0) {
+ walk += strlen(walk) + 1;
+ seq_printf (m, " [%s]", walk);
+ }
+ seq_printf(m, "\n");
+ }
+ } else /* !kallmodsyms */
+#endif /* CONFIG_KALLMODSYMS */
+ seq_printf(m, "%px %c %s\t[%s]\n", value,
+ type, iter->name, iter->module_name);
} else
seq_printf(m, "%px %c %s\n", value,
iter->type, iter->name);
return 0;
}
+static int s_show(struct seq_file *m, void *p)
+{
+ return s_show_internal(m, p, 0);
+}
+
static const struct seq_operations kallsyms_op = {
.start = s_start,
.next = s_next,
@@ -775,6 +933,35 @@ static const struct seq_operations kallsyms_op = {
.show = s_show
};
+#ifdef CONFIG_KALLMODSYMS
+static int s_mod_show(struct seq_file *m, void *p)
+{
+ return s_show_internal(m, p, 1);
+}
+static void *s_mod_next(struct seq_file *m, void *p, loff_t *pos)
+{
+ (*pos)++;
+
+ if (!update_iter(m->private, *pos, 1))
+ return NULL;
+ return p;
+}
+
+static void *s_mod_start(struct seq_file *m, loff_t *pos)
+{
+ if (!update_iter(m->private, *pos, 1))
+ return NULL;
+ return m->private;
+}
+
+static const struct seq_operations kallmodsyms_op = {
+ .start = s_mod_start,
+ .next = s_mod_next,
+ .stop = s_stop,
+ .show = s_mod_show
+};
+#endif
+
static inline int kallsyms_for_perf(void)
{
#ifdef CONFIG_PERF_EVENTS
@@ -810,7 +997,8 @@ bool kallsyms_show_value(const struct cred *cred)
}
}
-static int kallsyms_open(struct inode *inode, struct file *file)
+static int kallsyms_open_internal(struct inode *inode, struct file *file,
+ const struct seq_operations *ops)
{
/*
* We keep iterator in m->private, since normal case is to
@@ -818,7 +1006,7 @@ static int kallsyms_open(struct inode *inode, struct file *file)
* using get_symbol_offset for every symbol.
*/
struct kallsym_iter *iter;
- iter = __seq_open_private(file, &kallsyms_op, sizeof(*iter));
+ iter = __seq_open_private(file, ops, sizeof(*iter));
if (!iter)
return -ENOMEM;
reset_iter(iter, 0);
@@ -831,6 +1019,18 @@ static int kallsyms_open(struct inode *inode, struct file *file)
return 0;
}
+static int kallsyms_open(struct inode *inode, struct file *file)
+{
+ return kallsyms_open_internal(inode, file, &kallsyms_op);
+}
+
+#ifdef CONFIG_KALLMODSYMS
+static int kallmodsyms_open(struct inode *inode, struct file *file)
+{
+ return kallsyms_open_internal(inode, file, &kallmodsyms_op);
+}
+#endif
+
#ifdef CONFIG_KGDB_KDB
const char *kdb_walk_kallsyms(loff_t *pos)
{
@@ -841,7 +1041,7 @@ const char *kdb_walk_kallsyms(loff_t *pos)
reset_iter(&kdb_walk_kallsyms_iter, 0);
}
while (1) {
- if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
+ if (!update_iter(&kdb_walk_kallsyms_iter, *pos, 0))
return NULL;
++*pos;
/* Some debugging symbols have no name. Ignore them. */
@@ -858,9 +1058,21 @@ static const struct proc_ops kallsyms_proc_ops = {
.proc_release = seq_release_private,
};
+#ifdef CONFIG_KALLMODSYMS
+static const struct proc_ops kallmodsyms_proc_ops = {
+ .proc_open = kallmodsyms_open,
+ .proc_read = seq_read,
+ .proc_lseek = seq_lseek,
+ .proc_release = seq_release_private,
+};
+#endif
+
static int __init kallsyms_init(void)
{
proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops);
+#ifdef CONFIG_KALLMODSYMS
+ proc_create("kallmodsyms", 0444, NULL, &kallmodsyms_proc_ops);
+#endif
return 0;
}
device_initcall(kallsyms_init);
--
2.33.0.256.gb827f06fa9
Hi Nick,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on linux/master]
[also build test WARNING on linus/master v5.15-rc7]
[cannot apply to jeyu/modules-next masahiroy/kconfig next-20211027]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Nick-Alcock/kbuild-bring-back-tristate-conf/20211028-024948
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2f111a6fd5b5297b4e92f53798ca086f7c7d33a4
config: hexagon-randconfig-r041-20211027 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 5db7568a6a1fcb408eb8988abdaff2a225a8eb72)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/3e2ed787d495a82851cad4d99a369524140966ae
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Nick-Alcock/kbuild-bring-back-tristate-conf/20211028-024948
git checkout 3e2ed787d495a82851cad4d99a369524140966ae
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=hexagon
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email protected]>
All warnings (new ones prefixed by >>):
kernel/kallsyms.c:645:12: warning: no previous prototype for function 'arch_get_kallsym' [-Wmissing-prototypes]
int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
^
kernel/kallsyms.c:645:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value,
^
static
kernel/kallsyms.c:1054:30: warning: unused variable 'kallsyms_proc_ops' [-Wunused-const-variable]
static const struct proc_ops kallsyms_proc_ops = {
^
>> kernel/kallsyms.c:1062:30: warning: unused variable 'kallmodsyms_proc_ops' [-Wunused-const-variable]
static const struct proc_ops kallmodsyms_proc_ops = {
^
3 warnings generated.
vim +/kallmodsyms_proc_ops +1062 kernel/kallsyms.c
1060
1061 #ifdef CONFIG_KALLMODSYMS
> 1062 static const struct proc_ops kallmodsyms_proc_ops = {
1063 .proc_open = kallmodsyms_open,
1064 .proc_read = seq_read,
1065 .proc_lseek = seq_lseek,
1066 .proc_release = seq_release_private,
1067 };
1068 #endif
1069
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]
For reference, and to be maximally pedantic:
On 28 Oct 2021, kernel test robot said:
> Hi Nick,
>
> Thank you for the patch! Perhaps something to improve:
Nope! This is a (very small) flaw in the !CONFIG_PROC_FS case in
include/linux/proc_fs.h. (I don't think one can seriously call it a
*bug*, as such.)
It's not a problem in this patch.
> config: hexagon-randconfig-r041-20211027 (attached as .config)
This config includes:
# CONFIG_PROC_FS is not set
> All warnings (new ones prefixed by >>):
[unrelated warnings snipped]
> static
> kernel/kallsyms.c:1054:30: warning: unused variable 'kallsyms_proc_ops' [-Wunused-const-variable]
> static const struct proc_ops kallsyms_proc_ops = {
> ^
This warning already existed (and doubtless countless others just like
it all over the tree in this configuration). This is because
proc_create(), in the !CONFIG_PROC_FS case, is a #define that just does
nothing: so the compiler can see that none of its args are used, and
will complain about those that have no other references. The proc_ops is
almost certainly going to be one such.
The new warning is just the same:
>>> kernel/kallsyms.c:1062:30: warning: unused variable 'kallmodsyms_proc_ops' [-Wunused-const-variable]
> static const struct proc_ops kallmodsyms_proc_ops = {
> ^
> 3 warnings generated.
The kallmodsyms_proc_ops is obviously doing the same thing as
kallsyms_proc_ops (because it has to), so it gets the same warning.
Short of wrapping every single declaration of a proc_ops structure, and
every call to proc_create, in #ifdef CONFIG_PROC_FS (which is obviously
gross and exactly the thing the macro in proc_fs.h is intended to
avoid), there is no way of fixing this warning on its own: it must be
fixed in proc_fs.h. (Perhaps by making a bunch of those macros into
functions with __attribute__((__unused__)) attached to appropriate
args.)
--
NULL && (void)