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[libunwind] [SEH] Implement parsing of aarch64 pdata/xdata (#137949)

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This is needed for forced unwind, for some testcases in
libunwind/libcxxabi.

This adds an aarch64 case for extracting the LanguageHandler and
HandlerData fields from unwind info, in UnwindCursor::getInfoFromSEH,
corresponding to the existing case for x86_64.

This uses the struct IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY_XDATA; this only
became available in WinSDK 10.0.19041.0 and mingw-w64 v11.0 (or a
mingw-w64 git snapshot after April 2023).

(This is only a build-time requirement though; the format for the unwind
data has been fixed since the start of Windows 10 on ARM64, so this
doesn't impose any runtime requirement.)
This commit is contained in:
Martin Storsjö
2025-05-09 11:08:38 +03:00
committed by GitHub
parent 9d5a5424f0
commit 2e436b15d3
1 changed files with 46 additions and 0 deletions
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46
libunwind/src/UnwindCursor.hpp
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@@ -2018,6 +2018,52 @@ bool UnwindCursor<A, R>::getInfoFromSEH(pint_t pc) {
_info.handler = 0;
}
}
#elif defined(_LIBUNWIND_TARGET_AARCH64)
if (unwindEntry->Flag != 0) { // Packed unwind info
_info.end_ip = _info.start_ip + unwindEntry->FunctionLength * 4;
// Only fill in the handler and LSDA if they're stale.
if (pc != getLastPC()) {
// Packed unwind info doesn't have an exception handler.
_info.lsda = 0;
_info.handler = 0;
}
} else {
IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY_XDATA *xdata =
reinterpret_cast<IMAGE_ARM64_RUNTIME_FUNCTION_ENTRY_XDATA *>(
base + unwindEntry->UnwindData);
_info.end_ip = _info.start_ip + xdata->FunctionLength * 4;
// Only fill in the handler and LSDA if they're stale.
if (pc != getLastPC()) {
if (xdata->ExceptionDataPresent) {
uint32_t offset = 1; // The main xdata
uint32_t codeWords = xdata->CodeWords;
uint32_t epilogScopes = xdata->EpilogCount;
if (xdata->EpilogCount == 0 && xdata->CodeWords == 0) {
uint32_t extensionWord = reinterpret_cast<uint32_t *>(xdata)[1];
codeWords = (extensionWord >> 16) & 0xff;
epilogScopes = extensionWord & 0xffff;
offset++;
}
if (!xdata->EpilogInHeader)
offset += epilogScopes;
offset += codeWords;
uint32_t *exceptionHandlerInfo =
reinterpret_cast<uint32_t *>(xdata) + offset;
_dispContext.HandlerData = &exceptionHandlerInfo[1];
_dispContext.LanguageHandler = reinterpret_cast<EXCEPTION_ROUTINE *>(
base + exceptionHandlerInfo[0]);
_info.lsda = reinterpret_cast<unw_word_t>(_dispContext.HandlerData);
if (exceptionHandlerInfo[0])
_info.handler =
reinterpret_cast<unw_word_t>(__libunwind_seh_personality);
else
_info.handler = 0;
} else {
_info.lsda = 0;
_info.handler = 0;
}
}
}
#endif
setLastPC(pc);
return true;