# git rev-parse -q --verify 4356e9f841f7fbb945521cef3577ba394c65f3fc^{commit}
4356e9f841f7fbb945521cef3577ba394c65f3fc
already have revision, skipping fetch
# git checkout -q -f -B kisskb 4356e9f841f7fbb945521cef3577ba394c65f3fc
# git clean -qxdf
# < git log -1
# commit 4356e9f841f7fbb945521cef3577ba394c65f3fc
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Fri Feb 9 12:39:31 2024 -0800
# 
#     work around gcc bugs with 'asm goto' with outputs
#     
#     We've had issues with gcc and 'asm goto' before, and we created a
#     'asm_volatile_goto()' macro for that in the past: see commits
#     3f0116c3238a ("compiler/gcc4: Add quirk for 'asm goto' miscompilation
#     bug") and a9f180345f53 ("compiler/gcc4: Make quirk for
#     asm_volatile_goto() unconditional").
#     
#     Then, much later, we ended up removing the workaround in commit
#     43c249ea0b1e ("compiler-gcc.h: remove ancient workaround for gcc PR
#     58670") because we no longer supported building the kernel with the
#     affected gcc versions, but we left the macro uses around.
#     
#     Now, Sean Christopherson reports a new version of a very similar
#     problem, which is fixed by re-applying that ancient workaround.  But the
#     problem in question is limited to only the 'asm goto with outputs'
#     cases, so instead of re-introducing the old workaround as-is, let's
#     rename and limit the workaround to just that much less common case.
#     
#     It looks like there are at least two separate issues that all hit in
#     this area:
#     
#      (a) some versions of gcc don't mark the asm goto as 'volatile' when it
#          has outputs:
#     
#             https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619
#             https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420
#     
#          which is easy to work around by just adding the 'volatile' by hand.
#     
#      (b) Internal compiler errors:
#     
#             https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422
#     
#          which are worked around by adding the extra empty 'asm' as a
#          barrier, as in the original workaround.
#     
#     but the problem Sean sees may be a third thing since it involves bad
#     code generation (not an ICE) even with the manually added 'volatile'.
#     
#     but the same old workaround works for this case, even if this feels a
#     bit like voodoo programming and may only be hiding the issue.
#     
#     Reported-and-tested-by: Sean Christopherson <seanjc@google.com>
#     Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/
#     Cc: Nick Desaulniers <ndesaulniers@google.com>
#     Cc: Uros Bizjak <ubizjak@gmail.com>
#     Cc: Jakub Jelinek <jakub@redhat.com>
#     Cc: Andrew Pinski <quic_apinski@quicinc.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-12.2.0-nolibc/x86_64-linux/bin/x86_64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-12.2.0-nolibc/x86_64-linux/bin/x86_64-linux-ld --version
# < git log --format=%s --max-count=1 4356e9f841f7fbb945521cef3577ba394c65f3fc
# make -s -j 24 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/x86_64-linux/bin/x86_64-linux-  x86_64_defconfig
# < make -s -j 24 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/x86_64-linux/bin/x86_64-linux-  help
# make -s -j 24 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/x86_64-linux/bin/x86_64-linux-  olddefconfig
# make -s -j 24 ARCH=x86 O=/kisskb/build/linus_x86_64_defconfig_x86_64-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/x86_64-linux/bin/x86_64-linux-  
Completed OK
# rm -rf /kisskb/build/linus_x86_64_defconfig_x86_64-gcc12
# Build took: 0:05:08.596497