clang-15: May produce invalid code when -O1 (or higher) is used with -fzero-call-used-regs=all #57692
Comments
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This was found when building openssh-9.0 (gentoo version: 9.0_p1-r3) with clang-15. After building openssh, utilities such as ssh-keygen started segfaulting as described above. Additionally, |
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CC @isanbard |
…l-used-regs=all Bug: llvm/llvm-project#57692 Bug: https://bugs.gentoo.org/869839 Signed-off-by: Sam James <sam@gentoo.org>
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@efriedma-quic @isanbard Is this something that we should fix before 15.0.1? That window is closing quickly. |
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@tru By the way, OpenSSH uses this by default when the argument is available, unless --without-hardening is passed. So it's not just user-inflicted pain (even if that should work too). |
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It looks like this flag was only added in LLVM 15 via https://reviews.llvm.org/D110869. |
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So this is how the used zeroing sequence looks like: This looks very wrong to me, because it includes a whole bunch of callee-saved registers. In this case |
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I believe the problem is that llvm-project/llvm/lib/CodeGen/PrologEpilogInserter.cpp Lines 1276 to 1279 in 63d1d37 |
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Candidate patch: https://reviews.llvm.org/D133946 |
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@nvinson, @thesamesam, could you test whether this patch fixes OpenSSH? |
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/cherry-pick b430980 |
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/branch llvm/llvm-project-release-prs/issue57692 |
…PR57692) Callee save registers must be preserved, so -fzero-call-used-regs should not be zeroing them. The previous implementation only did not zero callee save registers that were saved&restored inside the function, but we need preserve all of them. Fixes llvm/llvm-project#57692. Differential Revision: https://reviews.llvm.org/D133946 (cherry picked from commit b430980)
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/pull-request llvm/llvm-project-release-prs#159 |
EugeneZelenko
added
llvm:codegen
release:backport
and removed
llvm:optimizations
labels
The issues I originally saw with openssh is that I couldn't log in and the ssh-keygen utility would crash when run. I've rebuilt llvm with the patch and rebuilt openssh. I wasable to log in via ssh after rebuilding and the ssh-keygen utility ran correctly. This patch solves the problems I was seeing with openssh. |
…PR57692) Callee save registers must be preserved, so -fzero-call-used-regs should not be zeroing them. The previous implementation only did not zero callee save registers that were saved&restored inside the function, but we need preserve all of them. Fixes llvm/llvm-project#57692. Differential Revision: https://reviews.llvm.org/D133946 (cherry picked from commit b430980)
…PR57692) Callee save registers must be preserved, so -fzero-call-used-regs should not be zeroing them. The previous implementation only did not zero callee save registers that were saved&restored inside the function, but we need preserve all of them. Fixes llvm/llvm-project#57692. Differential Revision: https://reviews.llvm.org/D133946 (cherry picked from commit b4309800e9dc53a84222a6b57c8615d4a3084988)
…PR57692) Callee save registers must be preserved, so -fzero-call-used-regs should not be zeroing them. The previous implementation only did not zero callee save registers that were saved&restored inside the function, but we need preserve all of them. Fixes llvm/llvm-project#57692. Differential Revision: https://reviews.llvm.org/D133946
This report is copied from https://bugs.gentoo.org/869839
Description:
When building binaries using
-O1(or higher) and the-fzero-call-used-regs=allthe resultant object files may create a broken binary when linked to.Reproducible:
Always
Steps to Reproduce:
get_progname.cget_progname.c:clang -O1 -ggdb -fzero-call-used-regs=all -c get_progname.ctest.ctest.c:clang -O1 -ggdb -fzero-call-used-regs=all -c test.cclang -o test test.o get_progname.o./testActual Results:
./testsegfaults due toargv[0]being incorrectly set toNULLduring executionExpected Results:
./testshould run and exit successfully.Additional Info:
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