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SubjectRe: [next] [clang] x86_64-linux-gnu-ld: mm/mremap.o: in function `move_pgt_entry': mremap.c:(.text+0x763): undefined reference to `__compiletime_assert_342'
On Thu, 17 Jun 2021 at 17:41, Naresh Kamboju <naresh.kamboju@linaro.org> wrote:
>
> Linux next 20210617 tag following x86_64 builds failed with clang-10
> and clang-11.
> Regressions found on x86_64:
>
> - build/clang-11-tinyconfig
> - build/clang-11-allnoconfig
> - build/clang-10-tinyconfig
> - build/clang-10-allnoconfig
> - build/clang-11-x86_64_defconfig
> - build/clang-10-defconfig
>
> We are running git bisect to identify the bad commit.
>
> Build log:
> ------------
> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool:
> eb_relocate_parse_slow()+0x466: stack state mismatch: cfa1=4+120
> cfa2=-1+0
> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool:
> eb_copy_relocations()+0x1e0: stack state mismatch: cfa1=4+104
> cfa2=-1+0
> x86_64-linux-gnu-ld: mm/mremap.o: in function `move_pgt_entry':
> mremap.c:(.text+0x763): undefined reference to `__compiletime_assert_342'

The git bisect pointed out the first bad commit.

The first bad commit:
commit 928cf6adc7d60c96eca760c05c1000cda061604e
Author: Stephen Boyd <swboyd@chromium.org>
Date: Thu Jun 17 15:21:35 2021 +1000
module: add printk formats to add module build ID to stacktraces

Let's make kernel stacktraces easier to identify by including the build
ID[1] of a module if the stacktrace is printing a symbol from a module.
This makes it simpler for developers to locate a kernel module's full
debuginfo for a particular stacktrace. Combined with
scripts/decode_stracktrace.sh, a developer can download the matching
debuginfo from a debuginfod[2] server and find the exact file and line
number for the functions plus offsets in a stacktrace that match the
module. This is especially useful for pstore crash debugging where the
kernel crashes are recorded in something like console-ramoops and the
recovery kernel/modules are different or the debuginfo doesn't exist on
the device due to space concerns (the debuginfo can be too large for space
limited devices).

Originally, I put this on the %pS format, but that was quickly rejected
given that %pS is used in other places such as ftrace where build IDs
aren't meaningful. There was some discussions on the list to put every
module build ID into the "Modules linked in:" section of the stacktrace
message but that quickly becomes very hard to read once you have more than
three or four modules linked in. It also provides too much information
when we don't expect each module to be traversed in a stacktrace. Having
the build ID for modules that aren't important just makes things messy.
Splitting it to multiple lines for each module quickly explodes the number
of lines printed in an oops too, possibly wrapping the warning off the
console. And finally, trying to stash away each module used in a
callstack to provide the ID of each symbol printed is cumbersome and would
require changes to each architecture to stash away modules and return
their build IDs once unwinding has completed.

Instead, we opt for the simpler approach of introducing new printk formats
'%pS[R]b' for "pointer symbolic backtrace with module build ID" and '%pBb'
for "pointer backtrace with module build ID" and then updating the few
places in the architecture layer where the stacktrace is printed to use
this new format.

Before:

Call trace:
lkdtm_WARNING+0x28/0x30 [lkdtm]
direct_entry+0x16c/0x1b4 [lkdtm]
full_proxy_write+0x74/0xa4
vfs_write+0xec/0x2e8

After:

Call trace:
lkdtm_WARNING+0x28/0x30 [lkdtm 6c2215028606bda50de823490723dc4bc5bf46f9]
direct_entry+0x16c/0x1b4 [lkdtm 6c2215028606bda50de823490723dc4bc5bf46f9]
full_proxy_write+0x74/0xa4
vfs_write+0xec/0x2e8

Link: https://lkml.kernel.org/r/20210511003845.2429846-6-swboyd@chromium.org
Link: https://fedoraproject.org/wiki/Releases/FeatureBuildId [1]
Link: https://sourceware.org/elfutils/Debuginfod.html [2]
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Evan Green <evgreen@chromium.org>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Documentation/core-api/printk-formats.rst | 11 ++++
include/linux/kallsyms.h | 20 +++++-
include/linux/module.h | 8 ++-
kernel/kallsyms.c | 101 ++++++++++++++++++++++++------
kernel/module.c | 31 ++++++++-
lib/vsprintf.c | 8 ++-
6 files changed, 154 insertions(+), 25 deletions(-)
Previous HEAD position was b2dcc0267277 dump_stack: add vmlinux build
ID to stack traces
HEAD is now at 7d9c6b8147bd Add linux-next specific files for 20210617



> make[1]: *** [/builds/linux/Makefile:1252: vmlinux] Error 1
> make[1]: Target '__all' not remade because of errors.
> make: *** [Makefile:222: __sub-make] Error 2
> make: Target '__all' not remade because of errors.
> make --silent --keep-going --jobs=8
> O=/home/tuxbuild/.cache/tuxmake/builds/current ARCH=x86_64
> CROSS_COMPILE=x86_64-linux-gnu- 'HOSTCC=sccache clang' 'CC=sccache
> clang' headers_install
> INSTALL_HDR_PATH=/home/tuxbuild/.cache/tuxmake/builds/current/install_hdr/
> tar caf /home/tuxbuild/.cache/tuxmake/builds/current/headers.tar.xz -C
> /home/tuxbuild/.cache/tuxmake/builds/current/install_hdr .
>
> ref:
> https://builds.tuxbuild.com/1u4ZKFTh12vrYBVf8b1xGpaFOrE/
>
> # TuxMake is a command line tool and Python library that provides
> # portable and repeatable Linux kernel builds across a variety of
> # architectures, toolchains, kernel configurations, and make targets.
> #
> # TuxMake supports the concept of runtimes.
> # See https://docs.tuxmake.org/runtimes/, for that to work it requires
> # that you install podman or docker on your system.
> #
> # To install tuxmake on your system globally:
> # sudo pip3 install -U tuxmake
> #
> # See https://docs.tuxmake.org/ for complete documentation.
>
> tuxmake --runtime podman --target-arch x86_64 --toolchain clang-11
> --kconfig x86_64_defconfig
>
> ref:
> https://builds.tuxbuild.com/1u4ZKFTh12vrYBVf8b1xGpaFOrE/
>
> build info:
> git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
> git_sha: 7d9c6b8147bdd76d7eb2cf6f74f84c6918ae0939
> git_short_log: 7d9c6b8147bd (\Add linux-next specific files for 20210617\)
> kconfig: x86_64_defconfig
> kernel_image:
> kernel_version: 5.13.0-rc6
> toolchain: clang-11

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>

> --
> Linaro LKFT
> https://lkft.linaro.org

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