fc4494dffa
https://reviews.llvm.org/rGd656ae28095726830f9beb8dbd4d69f5144ef821
introduced a additional checks before calling noreturn functions in
response to this security paper related to Catch Handler Oriented
Programming (CHOP):
https://download.vusec.net/papers/chop_ndss23.pdf
See also:
https://bugs.chromium.org/p/llvm/issues/detail?id=30
This causes stack canaries to be inserted in C code which was
unexpected; we noticed certain Linux kernel trees stopped booting after
this (in functions trying to initialize the stack canary itself).
https://github.com/ClangBuiltLinux/linux/issues/1815
There is no point checking the stack canary like this when exceptions
are disabled (-fno-exceptions or function is marked noexcept) or for C
code. The GCC patch for this issue does something similar:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=a25982ada523689c8745d7fb4b1b93c8f5dab2e7
Android measured a 2% regression in RSS as a result of d656ae2809 and
undid it globally:
https://android-review.googlesource.com/c/platform/build/soong/+/2524336
Reviewed By: xiangzhangllvm
Differential Revision: https://reviews.llvm.org/D147975
26 lines
830 B
LLVM
26 lines
830 B
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc -mtriple=x86_64-pc-linux-gnu -o - < %s | FileCheck %s
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; Make sure the stack protect not infinitly check __stack_chk_fail.
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define dso_local void @__stack_chk_fail() local_unnamed_addr #0 {
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; CHECK-LABEL: __stack_chk_fail:
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; CHECK: # %bb.0: # %entry
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; CHECK-NEXT: pushq %rax
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; CHECK-NEXT: movq %fs:40, %rax
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; CHECK-NEXT: movq %rax, (%rsp)
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; CHECK-NEXT: movq %fs:40, %rax
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; CHECK-NEXT: cmpq (%rsp), %rax
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; CHECK-NEXT: jne .LBB0_2
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; CHECK-NEXT: # %bb.1: # %SP_return
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; CHECK-NEXT: callq foo@PLT
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; CHECK-NEXT: .LBB0_2: # %CallStackCheckFailBlk
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; CHECK-NEXT: callq __stack_chk_fail
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entry:
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tail call void @foo() noreturn
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unreachable
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}
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declare void @foo() noreturn
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attributes #0 = { noreturn nounwind sspreq }
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