Created for Wine's memset by clang or mingw-gcc,
the latter places it quite at the start of the function:
```
0x00006ffffb67e210 <memset+0>: 0f b6 d2 movzbl %dl,%edx
0x00006ffffb67e213 <memset+3>: 48 b8 01 01 01 01 01 01 01 01 movabs $0x101010101010101,%rax
```
`3200 uint64_t v = 0x101010101010101ull * (unsigned char)c;`
290fd532ee/dlls/msvcrt/string.c (L3200)
Fixes:
```
[6113/7139] Building CXX object projects\compiler-rt\lib\interception\CMakeFiles\RTInterception.x86_64.dir\interception_win.cpp.obj
C:\git\llvm-project\compiler-rt\lib\interception\interception_win.cpp(746,5): warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
746 | case 0xB841: // 41 B8 XX XX XX XX : mov r8d, XX XX XX XX
| ^
C:\git\llvm-project\compiler-rt\lib\interception\interception_win.cpp(746,5): note: insert 'FALLTHROUGH;' to silence this warning
746 | case 0xB841: // 41 B8 XX XX XX XX : mov r8d, XX XX XX XX
| ^
| FALLTHROUGH;
C:\git\llvm-project\compiler-rt\lib\interception\interception_win.cpp(746,5): note: insert 'break;' to avoid fall-through
746 | case 0xB841: // 41 B8 XX XX XX XX : mov r8d, XX XX XX XX
| ^
| break;
1 warning generated.
```
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@4+0>: 66 90 xchg %ax,%ax
...
```
When ntdll was added to the list of of "interesting DLLs" list (in
d58230b9dc), the intention was not to
intercept the "mini CRT" functions it exports. OverrideFunction would
only intercept the *first* function it found when searching the list of
DLLs, and ntdll was put last in that list.
However, after 42cdfbcf3e,
OverrideFunction intercepts *all* matching functions in those DLLs. As
a side-effect, the runtime would now intercept functions like memset
etc. also in ntdll.
This causes a problem when ntdll-internal functions like
RtlDispatchException call the intercepted memset, which tries to
inspect uncommitted shadow memory, raising an exception, and getting
stuck in that loop until the stack overflows.
Since we never intended to intercept ntdll's memset etc., the simplest
fix seems to be to actively ignore ntdll when intercepting those
functions.
Fixes#114793
warning: format specifies type 'void *' but the argument has type 'uptr'
(aka 'unsigned long long') [-Wformat] (observed at x86_64, in
AllocateTrampolineRegion)
warning: format specifies type 'char *' but the argument has type
'RVAPtr<char>' [-Wformat] (observed at x86_64, in
InternalGetProcAddress)
It appears already some lines above with this comment:
"Cannot overwrite control-instruction. Return 0 to indicate failure.".
Replacing just the comment in the first appearance.
Found after creating the test in #113085.
There may not always be available virtual memory at higher addresses
than the target function. Therefore, search also lower addresses while
ensuring that we stay within the accessible memory range.
Additionally, add more ReportError calls to make the reasons for
interception failure more clear.
The instruction is present in some library in the 24H2 update for
Windows 11:
==8508==interception_win: unhandled instruction at 0x7ff83e193a40: 44 0f
b6 1a 4c 8b d2 48
This could be generalized, but getting all the ModR/M byte combinations
right is tricky. Many other classes of instructions handled in this file
could use some generalization too.
MSVC can sometimes generate instructions in function prologues that asan
previously didn't know the size of. This teaches asan those sizes. This isn't
super useful for using ASAN with non-msvc compilers, but it does stand alone.
From https://reviews.llvm.org/D151008
Since we may copy code (see CopyInstructions) to the trampoline which
could reference data inside the original module, we really want the
trampoline to be within 2 GB of not just the original function, but
within anything that function may have rip-relative accesses to, i.e.
within 2 GB of that function's whole module.
This fixes interception failures like the following scenario:
1. Intercept `CreateProcess` in kernel32.dll, allocating a trampoline
region right after
2. Start intercepting `memcpy` in the main executable, which is loaded
at a lower address than kernel32.dll, but still within 2 GB of the
trampoline region so we keep using it.
3. Try to copy instructions from `memcpy` to the trampoline. Turns out
one instruction references data that is more than 2GB away from the
trampoline, so it can't be relocated.
4. The process exits due to a CHECK failure
(Full story at https://crbug.com/341936875#comment45 and following.)
