With recent trunk versions of binutils and gcc, alignment directives are
represented with R_LARCH_ALIGN relocs on LoongArch, which is necessary
for the linker to maintain alignment requirements during its relaxation
passes. And even though the kernel is built with relaxation disabled, so
far a small number of R_LARCH_RELAX marker relocs are still emitted as
part of la.* pseudo instructions in assembly. These two kinds of relocs
do not refer to symbols, which can trip up modpost's section mismatch
checks, because the r_offset of said relocs can be zero or any other
meaningless value, eventually leading to a `from == NULL` condition in
default_mismatch_handler and SIGSEGV.
As the two kinds of relocs are not concerned with symbols, just ignore
them for section mismatch check purposes.
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
The section mismatch check prints a bogus symbol name on some
architectures.
[test code]
#include <linux/init.h>
int __initdata foo;
int get_foo(void) { return foo; }
If you compile it with GCC for riscv or loongarch, modpost will show an
incorrect symbol name:
WARNING: modpost: vmlinux: section mismatch in reference: get_foo+0x8 (section: .text) -> done (section: .init.data)
To get the correct symbol address, the st_value must be added.
This issue has never been noticed since commit 93684d3b80 ("kbuild:
include symbol names in section mismatch warnings") presumably because
st_value becomes zero on most architectures when the referenced symbol
is looked up. It is not true for riscv or loongarch, at least.
With this fix, modpost will show the correct symbol name:
WARNING: modpost: vmlinux: section mismatch in reference: get_foo+0x8 (section: .text) -> foo (section: .init.data)
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
ALL_INIT_TEXT_SECTIONS and ALL_EXIT_TEXT_SECTIONS are only used in
the macro definition of ALL_TEXT_SECTIONS.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
ALL_INIT_SECTIONS is defined as follows:
#define ALL_INIT_SECTIONS INIT_SECTIONS, ALL_XXXINIT_SECTIONS
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Theoretically, we could export conditionally-discarded code sections,
such as .meminit*, if all the users can become modular under a certain
condition. However, that would be difficult to control and such a tricky
case has never occurred.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
These symbol patterns were whitelisted to allow them to reference to
functions with the old __devinit and __devexit annotations.
We stopped doing this a long time ago, for example, commit 6f03979051
("Drivers: scsi: remove __dev* attributes.") remove those annotations
from the scsi drivers.
Keep *_ops, *_probe, and *_console, otherwise they will really cause
section mismatch warnings.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Drivers must not reference .meminit* sections, which are discarded
when CONFIG_MEMORY_HOTPLUG=n.
The reason for whitelisting "*driver" in the section mismatch check
was to allow drivers to reference symbols annotated as __devinit or
__devexit that existed in the past.
Those annotations were removed by the following commits:
- 54b956b903 ("Remove __dev* markings from init.h")
- 92e9e6d1f9 ("modpost.c: Stop checking __dev* section mismatches")
Remove the stale whitelist.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
We have never used __memexit, __memexitdata, or __memexitconst.
These were unneeded.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
The first few lines of section_rel() and section_rela() are the same.
They both retrieve the index of the section to which the relocaton
applies, and skip known-good sections. This common code should be moved
to check_sec_ref().
Avoid ugly casts when computing 'start' and 'stop', and also make the
Elf_Rel and Elf_Rela pointers const.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
We can replace &elf->sechdrs[i] with &sechdrs[i] to slightly shorten
the code because we already have the local variable 'sechdrs'.
However, defining 'sechdr' instead shortens the code further.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
The current TO_NATIVE() has some limitations:
1) You cannot cast the argument.
2) You cannot pass a variable marked as 'const'.
3) Passing an array is a bug, but it is not detected.
Impelement TO_NATIVE() using bswap_*() functions. These are GNU
extensions. If we face portability issues, we can port the code from
include/uapi/linux/swab.h.
With this change, get_rel_type_and_sym() can be simplified by casting
the arguments directly.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Modify modpost to use binary search for converting addresses back
into symbol references. Previously it used linear search.
This change saves a few seconds of wall time for defconfig builds,
but can save several minutes on allyesconfigs.
Before:
$ make LLVM=1 -j128 allyesconfig vmlinux -s KCFLAGS="-Wno-error"
$ time scripts/mod/modpost -M -m -a -N -o vmlinux.symvers vmlinux.o
198.38user 1.27system 3:19.71elapsed
After:
$ make LLVM=1 -j128 allyesconfig vmlinux -s KCFLAGS="-Wno-error"
$ time scripts/mod/modpost -M -m -a -N -o vmlinux.symvers vmlinux.o
11.91user 0.85system 0:12.78elapsed
Signed-off-by: Jack Brennen <jbrennen@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Drivers must not reference functions marked with __exit as these likely
are not available when the code is built-in.
There are few creative offenders uncovered for example in ARCH=amd64
allmodconfig builds. So only trigger the section mismatch warning for
W=1 builds.
The dual rule that drivers must not reference .init.* is implemented
since commit 0db2524523 ("modpost: don't allow *driver to reference
.init.*") which however missed that .exit.* should be handled in the
same way.
Thanks to Masahiro Yamada and Arnd Bergmann who gave valuable hints to
find this improvement.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
* fix reference to exported symbols for parisc64 [Masahiro Yamada]
* Block-TLB (BTLB) support on 32-bit CPUs
* sparse and build-warning fixes
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQS86RI+GtKfB8BJu973ErUQojoPXwUCZQDAAwAKCRD3ErUQojoP
X5wDAP4jxLxuVnUCpV5hUdFoJC5lkRM2LigbWDSfDQGHaycr0QD+NerBYX8Ejo6n
x0zHqqtBBe1fgU0QfRdwHeE7hlOiigI=
=FDci
-----END PGP SIGNATURE-----
Merge tag 'parisc-for-6.6-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux
Pull parisc architecture fixes from Helge Deller:
- fix reference to exported symbols for parisc64 [Masahiro Yamada]
- Block-TLB (BTLB) support on 32-bit CPUs
- sparse and build-warning fixes
* tag 'parisc-for-6.6-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
linux/export: fix reference to exported functions for parisc64
parisc: BTLB: Initialize BTLB tables at CPU startup
parisc: firmware: Simplify calling non-PA20 functions
parisc: BTLB: _edata symbol has to be page aligned for BTLB support
parisc: BTLB: Add BTLB insert and purge firmware function wrappers
parisc: BTLB: Clear possibly existing BTLB entries
parisc: Prepare for Block-TLB support on 32-bit kernel
parisc: shmparam.h: Document aliasing requirements of PA-RISC
parisc: irq: Make irq_stack_union static to avoid sparse warning
parisc: drivers: Fix sparse warning
parisc: iosapic.c: Fix sparse warnings
parisc: ccio-dma: Fix sparse warnings
parisc: sba-iommu: Fix sparse warnigs
parisc: sba: Fix compile warning wrt list of SBA devices
parisc: sba_iommu: Fix build warning if procfs if disabled
John David Anglin reported parisc has been broken since commit
ddb5cdbafa ("kbuild: generate KSYMTAB entries by modpost").
Like ia64, parisc64 uses a function descriptor. The function
references must be prefixed with P%.
Also, symbols prefixed $$ from the library have the symbol type
STT_LOPROC instead of STT_FUNC. They should be handled as functions
too.
Fixes: ddb5cdbafa ("kbuild: generate KSYMTAB entries by modpost")
Reported-by: John David Anglin <dave.anglin@bell.net>
Tested-by: John David Anglin <dave.anglin@bell.net>
Tested-by: Helge Deller <deller@gmx.de>
Closes: https://lore.kernel.org/linux-parisc/1901598a-e11d-f7dd-a5d9-9a69d06e6b6e@bell.net/T/#u
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Helge Deller <deller@gmx.de>
.llvm.call-graph-profile section is added by clang when the kernel is
built with profiles (e.g. -fprofile-sample-use= or -fprofile-use=).
Note that .llvm.call-graph-profile intentionally uses REL relocations
to decrease the object size, for more details see
https://reviews.llvm.org/D104080.
The section contains edge information derived from text sections,
so .llvm.call-graph-profile itself doesn't need more analysis as
the text sections have been analyzed.
This change fixes the kernel build with clang and a sample profile
which currently fails with:
"FATAL: modpost: Please add code to calculate addend for this architecture"
Signed-off-by: Denis Nikitin <denik@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Remove the Elf_Rela variables used in the for-loop in section_rel().
This makes the code consistent; section_rel() only uses Elf_Rel,
section_rela() only uses Elf_Rela.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
MIPS64 little endian target has an odd encoding of r_info.
This commit makes the special handling less ugly. It is still ugly,
but #if conditionals will go away, at least.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
All of addend_*_rel() need the Elf_Rela pointer just for calculating
ELF_R_TYPE(r->r_info).
You can do it on the caller to de-duplicate the code.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Now that none of addend_*_rel() returns a meaningful value (the return
value is always 0), change all of them to return the value of r_addend.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Currently, all files with EXPORT_SYMBOL() are rebuilt when CONFIG_MODULES
is flipped due to <linux/export.h> depending on CONFIG_MODULES.
Now that modpost can make a final decision about export symbols,
<linux/export.h> does not need to make EXPORT_SYMBOL() no-op.
Instead, modpost can skip emitting KSYMTAB when CONFIG_MODULES is unset.
This commit will reduce the number of recompilation when CONFIG_MODULES
is toggled.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
- Remove the deprecated rule to build *.dtbo from *.dts
- Refactor section mismatch detection in modpost
- Fix bogus ARM section mismatch detections
- Fix error of 'make gtags' with O= option
- Add Clang's target triple to KBUILD_CPPFLAGS to fix a build error with
the latest LLVM version
- Rebuild the built-in initrd when KBUILD_BUILD_TIMESTAMP is changed
- Ignore more compiler-generated symbols for kallsyms
- Fix 'make local*config' to handle the ${CONFIG_FOO} form in Makefiles
- Enable more kernel-doc warnings with W=2
- Refactor <linux/export.h> by generating KSYMTAB data by modpost
- Deprecate <asm/export.h> and <asm-generic/export.h>
- Remove the EXPORT_DATA_SYMBOL macro
- Move the check for static EXPORT_SYMBOL back to modpost, which makes
the build faster
- Re-implement CONFIG_TRIM_UNUSED_KSYMS with one-pass algorithm
- Warn missing MODULE_DESCRIPTION when building modules with W=1
- Make 'make clean' robust against too long argument error
- Exclude more objects from GCOV to fix CFI failures with GCOV
- Allow 'make modules_install' to install modules.builtin and
modules.builtin.modinfo even when CONFIG_MODULES is disabled
- Include modules.builtin and modules.builtin.modinfo in the linux-image
Debian package even when CONFIG_MODULES is disabled
- Revive "Entering directory" logging for the latest Make version
-----BEGIN PGP SIGNATURE-----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=Rc1z
-----END PGP SIGNATURE-----
Merge tag 'kbuild-v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Remove the deprecated rule to build *.dtbo from *.dts
- Refactor section mismatch detection in modpost
- Fix bogus ARM section mismatch detections
- Fix error of 'make gtags' with O= option
- Add Clang's target triple to KBUILD_CPPFLAGS to fix a build error
with the latest LLVM version
- Rebuild the built-in initrd when KBUILD_BUILD_TIMESTAMP is changed
- Ignore more compiler-generated symbols for kallsyms
- Fix 'make local*config' to handle the ${CONFIG_FOO} form in Makefiles
- Enable more kernel-doc warnings with W=2
- Refactor <linux/export.h> by generating KSYMTAB data by modpost
- Deprecate <asm/export.h> and <asm-generic/export.h>
- Remove the EXPORT_DATA_SYMBOL macro
- Move the check for static EXPORT_SYMBOL back to modpost, which makes
the build faster
- Re-implement CONFIG_TRIM_UNUSED_KSYMS with one-pass algorithm
- Warn missing MODULE_DESCRIPTION when building modules with W=1
- Make 'make clean' robust against too long argument error
- Exclude more objects from GCOV to fix CFI failures with GCOV
- Allow 'make modules_install' to install modules.builtin and
modules.builtin.modinfo even when CONFIG_MODULES is disabled
- Include modules.builtin and modules.builtin.modinfo in the
linux-image Debian package even when CONFIG_MODULES is disabled
- Revive "Entering directory" logging for the latest Make version
* tag 'kbuild-v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (72 commits)
modpost: define more R_ARM_* for old distributions
kbuild: revive "Entering directory" for Make >= 4.4.1
kbuild: set correct abs_srctree and abs_objtree for package builds
scripts/mksysmap: Ignore prefixed KCFI symbols
kbuild: deb-pkg: remove the CONFIG_MODULES check in buildeb
kbuild: builddeb: always make modules_install, to install modules.builtin*
modpost: continue even with unknown relocation type
modpost: factor out Elf_Sym pointer calculation to section_rel()
modpost: factor out inst location calculation to section_rel()
kbuild: Disable GCOV for *.mod.o
kbuild: Fix CFI failures with GCOV
kbuild: make clean rule robust against too long argument error
script: modpost: emit a warning when the description is missing
kbuild: make modules_install copy modules.builtin(.modinfo)
linux/export.h: rename 'sec' argument to 'license'
modpost: show offset from symbol for section mismatch warnings
modpost: merge two similar section mismatch warnings
kbuild: implement CONFIG_TRIM_UNUSED_KSYMS without recursion
modpost: use null string instead of NULL pointer for default namespace
modpost: squash sym_update_namespace() into sym_add_exported()
...
On CentOS 7, the following build error occurs.
scripts/mod/modpost.c: In function 'addend_arm_rel':
scripts/mod/modpost.c:1312:7: error: 'R_ARM_MOVW_ABS_NC' undeclared (first use in this function); did you mean 'R_ARM_THM_ABS5'?
case R_ARM_MOVW_ABS_NC:
^~~~~~~~~~~~~~~~~
R_ARM_THM_ABS5
scripts/mod/modpost.c:1312:7: note: each undeclared identifier is reported only once for each function it appears in
scripts/mod/modpost.c:1313:7: error: 'R_ARM_MOVT_ABS' undeclared (first use in this function); did you mean 'R_ARM_THM_ABS5'?
case R_ARM_MOVT_ABS:
^~~~~~~~~~~~~~
R_ARM_THM_ABS5
scripts/mod/modpost.c:1326:7: error: 'R_ARM_THM_MOVW_ABS_NC' undeclared (first use in this function); did you mean 'R_ARM_THM_ABS5'?
case R_ARM_THM_MOVW_ABS_NC:
^~~~~~~~~~~~~~~~~~~~~
R_ARM_THM_ABS5
scripts/mod/modpost.c:1327:7: error: 'R_ARM_THM_MOVT_ABS' undeclared (first use in this function); did you mean 'R_ARM_THM_ABS5'?
case R_ARM_THM_MOVT_ABS:
^~~~~~~~~~~~~~~~~~
R_ARM_THM_ABS5
Fixes: 12ca2c67d7 ("modpost: detect section mismatch for R_ARM_{MOVW_ABS_NC,MOVT_ABS}")
Fixes: cd1824fb7a ("modpost: detect section mismatch for R_ARM_THM_{MOVW_ABS_NC,MOVT_ABS}")
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Currently, unknown relocation types are just skipped.
The value of r_addend is only needed to get the symbol name in case
is_valid_name(elf, sym) returns false.
Even if we do not know how to calculate r_addend, we should continue.
At worst, we will get "(unknown)" as the symbol name, but it is better
than failing to detect section mismatches.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Pass the Elf_Sym pointer to addend_arm_rel() as well as to
check_section_mismatch().
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
All the addend_*_rel() functions calculate the instruction location in
the same way.
Factor out the similar code to the caller. Squash reloc_location() too.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Emit a warning when the mod description is missed and only
when the W=1 is enabled.
Reported-by: Roland Kletzing <devzero@web.de>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=10770
Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Tested-by: Nicolas Schier <n.schier@avm.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Currently, modpost only shows the symbol names and section names, so it
repeats the same message if there are multiple relocations in the same
symbol. It is common the relocation spans across multiple instructions.
It is better to show the offset from the symbol.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
In case of section mismatch, modpost shows slightly different messages.
For extable section mismatch:
"%s(%s+0x%lx): Section mismatch in reference to the %s:%s\n"
For the other cases:
"%s: section mismatch in reference: %s (section: %s) -> %s (section: %s)\n"
They are similar. Merge them.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses
the directory tree to determine which EXPORT_SYMBOL to trim. If an
EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the
second traverse, where some source files are recompiled with their
EXPORT_SYMBOL() tuned into a no-op.
Linus stated negative opinions about this slowness in commits:
- 5cf0fd591f ("Kbuild: disable TRIM_UNUSED_KSYMS option")
- a555bdd0c5 ("Kbuild: enable TRIM_UNUSED_KSYMS again, with some guarding")
We can do this better now. The final data structures of EXPORT_SYMBOL
are generated by the modpost stage, so modpost can selectively emit
KSYMTAB entries that are really used by modules.
Commit f73edc8951 ("kbuild: unify two modpost invocations") is another
ground-work to do this in a one-pass algorithm. With the list of modules,
modpost sets sym->used if it is used by a module. modpost emits KSYMTAB
only for symbols with sym->used==true.
BTW, Nicolas explained why the trimming was implemented with recursion:
https://lore.kernel.org/all/2o2rpn97-79nq-p7s2-nq5-8p83391473r@syhkavp.arg/
Actually, we never achieved that level of optimization where the chain
reaction of trimming comes into play because:
- CONFIG_LTO_CLANG cannot remove any unused symbols
- CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is enabled only for vmlinux,
but not modules
If deeper trimming is required, we need to revisit this, but I guess
that is unlikely to happen.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
The default namespace is the null string, "".
When set, the null string "" is converted to NULL:
s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL;
When printed, the NULL pointer is get back to the null string:
sym->namespace ?: ""
This saves 1 byte memory allocated for "", but loses the readability.
In kernel-space, we strive to save memory, but modpost is a userspace
tool used to build the kernel. On modern systems, such small piece of
memory is not a big deal.
Handle the namespace string as is.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Pass a set of the name, license, and namespace to sym_add_exported().
sym_update_namespace() is unneeded.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Commit 31cb50b559 ("kbuild: check static EXPORT_SYMBOL* by script
instead of modpost") moved the static EXPORT_SYMBOL* check from the
mostpost to a shell script because I thought it must be checked per
compilation unit to avoid false negatives.
I came up with an idea to do this in modpost, against combined ELF
files. The relocation entries in ELF will find the correct exported
symbol even if there exist symbols with the same name in different
compilation units.
Again, the same sample code.
Makefile:
obj-y += foo1.o foo2.o
foo1.c:
#include <linux/export.h>
static void foo(void) {}
EXPORT_SYMBOL(foo);
foo2.c:
void foo(void) {}
Then, modpost can catch it correctly.
MODPOST Module.symvers
ERROR: modpost: vmlinux: local symbol 'foo' was exported
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Commit 7b4537199a ("kbuild: link symbol CRCs at final link, removing
CONFIG_MODULE_REL_CRCS") made modpost output CRCs in the same way
whether the EXPORT_SYMBOL() is placed in *.c or *.S.
For further cleanups, this commit applies a similar approach to the
entire data structure of EXPORT_SYMBOL().
The EXPORT_SYMBOL() compilation is split into two stages.
When a source file is compiled, EXPORT_SYMBOL() will be converted into
a dummy symbol in the .export_symbol section.
For example,
EXPORT_SYMBOL(foo);
EXPORT_SYMBOL_NS_GPL(bar, BAR_NAMESPACE);
will be encoded into the following assembly code:
.section ".export_symbol","a"
__export_symbol_foo:
.asciz "" /* license */
.asciz "" /* name space */
.balign 8
.quad foo /* symbol reference */
.previous
.section ".export_symbol","a"
__export_symbol_bar:
.asciz "GPL" /* license */
.asciz "BAR_NAMESPACE" /* name space */
.balign 8
.quad bar /* symbol reference */
.previous
They are mere markers to tell modpost the name, license, and namespace
of the symbols. They will be dropped from the final vmlinux and modules
because the *(.export_symbol) will go into /DISCARD/ in the linker script.
Then, modpost extracts all the information about EXPORT_SYMBOL() from the
.export_symbol section, and generates the final C code:
KSYMTAB_FUNC(foo, "", "");
KSYMTAB_FUNC(bar, "_gpl", "BAR_NAMESPACE");
KSYMTAB_FUNC() (or KSYMTAB_DATA() if it is data) is expanded to struct
kernel_symbol that will be linked to the vmlinux or a module.
With this change, EXPORT_SYMBOL() works in the same way for *.c and *.S
files, providing the following benefits.
[1] Deprecate EXPORT_DATA_SYMBOL()
In the old days, EXPORT_SYMBOL() was only available in C files. To export
a symbol in *.S, EXPORT_SYMBOL() was placed in a separate *.c file.
arch/arm/kernel/armksyms.c is one example written in the classic manner.
Commit 22823ab419 ("EXPORT_SYMBOL() for asm") removed this limitation.
Since then, EXPORT_SYMBOL() can be placed close to the symbol definition
in *.S files. It was a nice improvement.
However, as that commit mentioned, you need to use EXPORT_DATA_SYMBOL()
for data objects on some architectures.
In the new approach, modpost checks symbol's type (STT_FUNC or not),
and outputs KSYMTAB_FUNC() or KSYMTAB_DATA() accordingly.
There are only two users of EXPORT_DATA_SYMBOL:
EXPORT_DATA_SYMBOL_GPL(empty_zero_page) (arch/ia64/kernel/head.S)
EXPORT_DATA_SYMBOL(ia64_ivt) (arch/ia64/kernel/ivt.S)
They are transformed as follows and output into .vmlinux.export.c
KSYMTAB_DATA(empty_zero_page, "_gpl", "");
KSYMTAB_DATA(ia64_ivt, "", "");
The other EXPORT_SYMBOL users in ia64 assembly are output as
KSYMTAB_FUNC().
EXPORT_DATA_SYMBOL() is now deprecated.
[2] merge <linux/export.h> and <asm-generic/export.h>
There are two similar header implementations:
include/linux/export.h for .c files
include/asm-generic/export.h for .S files
Ideally, the functionality should be consistent between them, but they
tend to diverge.
Commit 8651ec01da ("module: add support for symbol namespaces.") did
not support the namespace for *.S files.
This commit shifts the essential implementation part to C, which supports
EXPORT_SYMBOL_NS() for *.S files.
<asm/export.h> and <asm-generic/export.h> will remain as a wrapper of
<linux/export.h> for a while.
They will be removed after #include <asm/export.h> directives are all
replaced with #include <linux/export.h>.
[3] Implement CONFIG_TRIM_UNUSED_KSYMS in one-pass algorithm (by a later commit)
When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses
the directory tree to determine which EXPORT_SYMBOL to trim. If an
EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the
second traverse, where some source files are recompiled with their
EXPORT_SYMBOL() tuned into a no-op.
We can do this better now; modpost can selectively emit KSYMTAB entries
that are really used by modules.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Commits ffb1b4a410 ("x86/unwind/orc: Add 'signal' field to ORC
metadata") and fb799447ae ("x86,objtool: Split UNWIND_HINT_EMPTY in
two") changed the ORC format. Although ORC is internal to the kernel,
it's the only way for external tools to get reliable kernel stack traces
on x86-64. In particular, the drgn debugger [1] uses ORC for stack
unwinding, and these format changes broke it [2]. As the drgn
maintainer, I don't care how often or how much the kernel changes the
ORC format as long as I have a way to detect the change.
It suffices to store a version identifier in the vmlinux and kernel
module ELF files (to use when parsing ORC sections from ELF), and in
kernel memory (to use when parsing ORC from a core dump+symbol table).
Rather than hard-coding a version number that needs to be manually
bumped, Peterz suggested hashing the definitions from orc_types.h. If
there is a format change that isn't caught by this, the hashing script
can be updated.
This patch adds an .orc_header allocated ELF section containing the
20-byte hash to vmlinux and kernel modules, along with the corresponding
__start_orc_header and __stop_orc_header symbols in vmlinux.
1: https://github.com/osandov/drgn
2: https://github.com/osandov/drgn/issues/303
Fixes: ffb1b4a410 ("x86/unwind/orc: Add 'signal' field to ORC metadata")
Fixes: fb799447ae ("x86,objtool: Split UNWIND_HINT_EMPTY in two")
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lkml.kernel.org/r/aef9c8dc43915b886a8c48509a12ec1b006ca1ca.1686690801.git.osandov@osandov.com
The > comparison should be >= to prevent an out of bounds array
access.
Fixes: 52dc0595d5 ("modpost: handle relocations mismatch in __ex_table.")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
"No build warning" is a strong requirement these days, so you must fix
all issues before enabling a new warning flag.
We often add a new warning to W=1 first so that the kbuild test robot
blocks new breakages.
This commit allows modpost to show extra warnings only when W=1
(or KBUILD_EXTRA_WARN=1) is given.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
For ARM, modpost fails to detect some types of section mismatches.
[test code]
.section .init.data,"aw"
bar:
.long 0
.section .data,"aw"
.globl foo
foo:
.long bar - .
It is apparently a bad reference, but modpost does not report anything.
The test code above produces the following relocations.
Relocation section '.rel.data' at offset 0xe8 contains 1 entry:
Offset Info Type Sym.Value Sym. Name
00000000 00000403 R_ARM_REL32 00000000 .init.data
Currently, R_ARM_REL32 is just skipped.
Handle it like R_ARM_ABS32.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
addend_arm_rel() processes R_ARM_THM_CALL, R_ARM_THM_JUMP24,
R_ARM_THM_JUMP19 in a wrong way.
Here, test code.
[test code for R_ARM_THM_JUMP24]
.section .init.text,"ax"
bar:
bx lr
.section .text,"ax"
.globl foo
foo:
b bar
[test code for R_ARM_THM_CALL]
.section .init.text,"ax"
bar:
bx lr
.section .text,"ax"
.globl foo
foo:
push {lr}
bl bar
pop {pc}
If you compile it with CONFIG_THUMB2_KERNEL=y, modpost will show the
symbol name, (unknown).
WARNING: modpost: vmlinux.o: section mismatch in reference: foo (section: .text) -> (unknown) (section: .init.text)
(You need to use GNU linker instead of LLD to reproduce it.)
Fix the code to make modpost show the correct symbol name. I checked
arch/arm/kernel/module.c to learn the encoding of R_ARM_THM_CALL and
R_ARM_THM_JUMP24. The module does not support R_ARM_THM_JUMP19, but
I checked its encoding in ARM ARM.
The '+4' is the compensation for pc-relative instruction. It is
documented in "ELF for the Arm Architecture" [1].
"If the relocation is pc-relative then compensation for the PC bias
(the PC value is 8 bytes ahead of the executing instruction in Arm
state and 4 bytes in Thumb state) must be encoded in the relocation
by the object producer."
[1]: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst
Fixes: c9698e5cd6 ("ARM: 7964/1: Detect section mismatches in thumb relocations")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
When CONFIG_THUMB2_KERNEL is enabled, modpost fails to detect some
types of section mismatches.
[test code]
#include <linux/init.h>
int __initdata foo;
int get_foo(void) { return foo; }
It is apparently a bad reference, but modpost does not report anything.
The test code above produces the following relocations.
Relocation section '.rel.text' at offset 0x1e8 contains 2 entries:
Offset Info Type Sym.Value Sym. Name
00000000 0000052f R_ARM_THM_MOVW_AB 00000000 .LANCHOR0
00000004 00000530 R_ARM_THM_MOVT_AB 00000000 .LANCHOR0
Currently, R_ARM_THM_MOVW_ABS_NC and R_ARM_THM_MOVT_ABS are just skipped.
Add code to handle them. I checked arch/arm/kernel/module.c to learn
how the offset is encoded in the instruction.
One more thing to note for Thumb instructions - the st_value is an odd
value, so you need to mask the bit 0 to get the offset. Otherwise, you
will get an off-by-one error in the nearest symbol look-up.
It is documented in "ELF for the ARM Architecture" [1]:
In addition to the normal rules for symbol values the following rules
shall also apply to symbols of type STT_FUNC:
* If the symbol addresses an Arm instruction, its value is the
address of the instruction (in a relocatable object, the offset
of the instruction from the start of the section containing it).
* If the symbol addresses a Thumb instruction, its value is the
address of the instruction with bit zero set (in a relocatable
object, the section offset with bit zero set).
* For the purposes of relocation the value used shall be the address
of the instruction (st_value & ~1).
[1]: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
find_fromsym() and find_tosym() are similar - both of them iterate
in the .symtab section and return the nearest symbol.
The difference between them is that find_tosym() allows a negative
distance, but the distance must be less than 20.
Factor out the common part into find_nearest_sym().
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
For ARM defconfig (i.e. multi_v7_defconfig), modpost fails to detect
some types of section mismatches.
[test code]
#include <linux/init.h>
int __initdata foo;
int get_foo(void) { return foo; }
It is apparently a bad reference, but modpost does not report anything.
The test code above produces the following relocations.
Relocation section '.rel.text' at offset 0x200 contains 2 entries:
Offset Info Type Sym.Value Sym. Name
00000000 0000062b R_ARM_MOVW_ABS_NC 00000000 .LANCHOR0
00000004 0000062c R_ARM_MOVT_ABS 00000000 .LANCHOR0
Currently, R_ARM_MOVW_ABS_NC and R_ARM_MOVT_ABS are just skipped.
Add code to handle them. I checked arch/arm/kernel/module.c to learn
how the offset is encoded in the instruction.
The referenced symbol in relocation might be a local anchor.
If is_valid_name() returns false, let's search for a better symbol name.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
addend_arm_rel() processes R_ARM_PC24, R_ARM_CALL, R_ARM_JUMP24 in a
wrong way.
Here, test code.
[test code for R_ARM_JUMP24]
.section .init.text,"ax"
bar:
bx lr
.section .text,"ax"
.globl foo
foo:
b bar
[test code for R_ARM_CALL]
.section .init.text,"ax"
bar:
bx lr
.section .text,"ax"
.globl foo
foo:
push {lr}
bl bar
pop {pc}
If you compile it with ARM multi_v7_defconfig, modpost will show the
symbol name, (unknown).
WARNING: modpost: vmlinux.o: section mismatch in reference: foo (section: .text) -> (unknown) (section: .init.text)
(You need to use GNU linker instead of LLD to reproduce it.)
Fix the code to make modpost show the correct symbol name.
I imported (with adjustment) sign_extend32() from include/linux/bitops.h.
The '+8' is the compensation for pc-relative instruction. It is
documented in "ELF for the Arm Architecture" [1].
"If the relocation is pc-relative then compensation for the PC bias
(the PC value is 8 bytes ahead of the executing instruction in Arm
state and 4 bytes in Thumb state) must be encoded in the relocation
by the object producer."
[1]: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst
Fixes: 56a974fa2d ("kbuild: make better section mismatch reports on arm")
Fixes: 6e2e340b59 ("ARM: 7324/1: modpost: Fix section warnings for ARM for many compilers")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
addend_arm_rel() processes R_ARM_ABS32 in a wrong way.
Here, test code.
[test code 1]
#include <linux/init.h>
int __initdata foo;
int get_foo(void) { return foo; }
If you compile it with ARM versatile_defconfig, modpost will show the
symbol name, (unknown).
WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> (unknown) (section: .init.data)
(You need to use GNU linker instead of LLD to reproduce it.)
If you compile it for other architectures, modpost will show the correct
symbol name.
WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data)
For R_ARM_ABS32, addend_arm_rel() sets r->r_addend to a wrong value.
I just mimicked the code in arch/arm/kernel/module.c.
However, there is more difficulty for ARM.
Here, test code.
[test code 2]
#include <linux/init.h>
int __initdata foo;
int get_foo(void) { return foo; }
int __initdata bar;
int get_bar(void) { return bar; }
With this commit applied, modpost will show the following messages
for ARM versatile_defconfig:
WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data)
WARNING: modpost: vmlinux.o: section mismatch in reference: get_bar (section: .text) -> foo (section: .init.data)
The reference from 'get_bar' to 'foo' seems wrong.
I have no solution for this because it is true in assembly level.
In the following output, relocation at 0x1c is no longer associated
with 'bar'. The two relocation entries point to the same symbol, and
the offset to 'bar' is encoded in the instruction 'r0, [r3, #4]'.
Disassembly of section .text:
00000000 <get_foo>:
0: e59f3004 ldr r3, [pc, #4] @ c <get_foo+0xc>
4: e5930000 ldr r0, [r3]
8: e12fff1e bx lr
c: 00000000 .word 0x00000000
00000010 <get_bar>:
10: e59f3004 ldr r3, [pc, #4] @ 1c <get_bar+0xc>
14: e5930004 ldr r0, [r3, #4]
18: e12fff1e bx lr
1c: 00000000 .word 0x00000000
Relocation section '.rel.text' at offset 0x244 contains 2 entries:
Offset Info Type Sym.Value Sym. Name
0000000c 00000c02 R_ARM_ABS32 00000000 .init.data
0000001c 00000c02 R_ARM_ABS32 00000000 .init.data
When find_elf_symbol() gets into a situation where relsym->st_name is
zero, there is no guarantee to get the symbol name as written in C.
I am keeping the current logic because it is useful in many architectures,
but the symbol name is not always correct depending on the optimization.
I left some comments in find_tosym().
Fixes: 56a974fa2d ("kbuild: make better section mismatch reports on arm")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
