[all-commits] [llvm/llvm-project] 610ade: [win/asan] GetInstructionSize: Detect `66 90` two-...

[bernhardu via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 610ade2ed7253593198287aa53a9b05852ef0ede
      https://github.com/llvm/llvm-project/commit/610ade2ed7253593198287aa53a9b05852ef0ede
  Author: bernhardu <bernhardu at mailbox.org>
  Date:   2025-03-21 (Fri, 21 Mar 2025)

  Changed paths:
    M compiler-rt/lib/interception/interception_win.cpp
    M compiler-rt/lib/interception/tests/interception_win_test.cpp

  Log Message:
  -----------
  [win/asan] GetInstructionSize: Detect `66 90` two-byte NOP at 32-bit too. (#132267)

Observed in Wine when trying to intercept `ExitThread`, which forwards
to `ntdll.RtlExitUserThread`.

`gdb` interprets it as `xchg %ax,%ax`.
`llvm-mc` outputs simply `nop`.

```
==Asan-i386-calls-Dynamic-Test.exe==964==interception_win: unhandled instruction at 0x7be27cf0: 66 90 55 89 e5 56 50 8b
```

```
Wine-gdb> bt
#0  0x789a1766 in __interception::GetInstructionSize (address=<optimized out>, rel_offset=<optimized out>) at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/interception/interception_win.cpp:983
#1  0x789ab480 in __sanitizer::SharedPrintfCode(bool, char const*, char*) () at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_printf.cpp:311
#2  0x789a18e7 in __interception::OverrideFunctionWithHotPatch (old_func=2078440688, new_func=2023702608, orig_old_func=warning: (Internal error: pc 0x792f1a2c in read in CU, but not in symtab.)warning: (Error: pc 0x792f1a2c in address map, but not in symtab.)0x792f1a2c) at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/interception/interception_win.cpp:1118
#3  0x789a1f34 in __interception::OverrideFunction (old_func=2078440688, new_func=2023702608, orig_old_func=warning: (Internal error: pc 0x792f1a2c in read in CU, but not in symtab.)warning: (Error: pc 0x792f1a2c in address map, but not in symtab.)0x792f1a2c) at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/interception/interception_win.cpp:1224
#4  0x789a24ce in __interception::OverrideFunction (func_name=0x78a0bc43 <vtable for __asan::AsanThreadContext+1163> "ExitThread", new_func=2023702608, orig_old_func=warning: (Internal error: pc 0x792f1a2c in read in CU, but not in symtab.)warning: (Error: pc 0x792f1a2c in address map, but not in symtab.)0x792f1a2c)    at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/interception/interception_win.cpp:1369
#5  0x789f40ef in __asan::InitializePlatformInterceptors () at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/asan/asan_win.cpp:190
#6  0x789e0c3c in __asan::InitializeAsanInterceptors () at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:802
#7  0x789ee6b5 in __asan::AsanInitInternal () at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/asan/asan_rtl.cpp:442
#8  0x789eefb0 in __asan::AsanInitFromRtl () at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/asan/asan_rtl.cpp:522
#9  __asan::AsanInitializer::AsanInitializer (this=<optimized out>) at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/asan/asan_rtl.cpp:542
#10 __cxx_global_var_init () at C:/llvm-mingw/llvm-mingw/llvm-project/compiler-rt/lib/asan/asan_rtl.cpp:546
...
Wine-gdb> disassemble /r 2078440688,2078440688+20
Dump of assembler code from 0x7be27cf0 to 0x7be27d04:
   0x7be27cf0 <_RtlExitUserThread at 4+0>: 66 90                   xchg   %ax,%ax
...
```



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