[llvm-bugs] [Bug 43528] New: [CodeGen] Wrong codegen mwait intrinsic + Asan + stack protector

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43528

            Bug ID: 43528
           Summary: [CodeGen] Wrong codegen mwait intrinsic + Asan + stack
                    protector
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: pierregousseau14 at gmail.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

clang version 10.0.0 (https://github.com/llvm/llvm-project.git
17380227e830a7a3fc2adafc2226e4c579b919ef)
Target: x86_64-unknown-linux-gnu
llvm-svn: 373195

This example seems to generate incorrect code, code gen for mwaitx overwrites
ebx.
rbx is set as the stack base pointer.
Stack protector code dereferences rbx and causes a segfault.

"""
static __inline__ void __attribute__((__always_inline__))
_mm_monitorx(void const * __p, unsigned __extensions, unsigned __hints)
{
  __builtin_ia32_monitorx((void *)__p, __extensions, __hints);
}

static __inline__ void __attribute__((__always_inline__))
_mm_mwaitx(unsigned __extensions, unsigned __hints, unsigned __clock)
{
  __builtin_ia32_mwaitx(__extensions, __hints, __clock);
}

int main(int argc, char ** argv) {
  int v;
  v = 0;
  _mm_monitorx(&v, 0, 0);
  _mm_mwaitx(0, 0, 1);
}

"""
clang -fsanitize=address -g -fstack-protector-strong -mmwaitx test.cpp &&
./a.out
==5252==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc
0x0000004ebd15 bp 0x7ffe71535d00 sp 0x7ffe71535c20 T0)
==5252==The signal is caused by a READ memory access.
==5252==Hint: address points to the zero page.

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