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[BOLT] Fix invalid abbrev error when reading debug_info section with readelf 

Summary:
This fixes a bug which causes the debug_info and debug_loc sections to be unreadable by readelf/objdump.

Basically, we're using 12 bytes of a ULEB128 value to fill in space, but readelf can't read more than 9 bytes of ULEB128. Thus, we replace that value with a string of 'a' instead.

(cherry picked from FBD18097728)
This commit is contained in:
Xin-Xin Wang 2019-10-23 15:19:49 -07:00 committed by Maksim Panchenko
parent 28f91871b3
commit 8e2d3f7c30
1 changed files with 26 additions and 5 deletions
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31
bolt/src/DWARFRewriter.cpp
View File

@ -613,15 +613,28 @@ void DWARFRewriter::updateGdbIndexSection() {
void
DWARFRewriter::convertToRanges(const DWARFAbbreviationDeclaration *Abbrev) {
dwarf::Form HighPCForm = Abbrev->findAttribute(dwarf::DW_AT_high_pc)->Form;
std::lock_guard<std::mutex> Lock(AbbrevPatcherMutex);
AbbrevPatcher->addAttributePatch(Abbrev,
dwarf::DW_AT_low_pc,
dwarf::DW_AT_ranges,
dwarf::DW_FORM_sec_offset);
AbbrevPatcher->addAttributePatch(Abbrev,
dwarf::DW_AT_high_pc,
dwarf::DW_AT_low_pc,
dwarf::DW_FORM_udata);
if (HighPCForm == dwarf::DW_FORM_addr ||
HighPCForm == dwarf::DW_FORM_data8) {
// LowPC must have 12 bytes, use indirect
AbbrevPatcher->addAttributePatch(Abbrev,
dwarf::DW_AT_high_pc,
dwarf::DW_AT_low_pc,
dwarf::DW_FORM_indirect);
} else if (HighPCForm == dwarf::DW_FORM_data4) {
// LowPC must have 8 bytes, use addr
AbbrevPatcher->addAttributePatch(Abbrev,
dwarf::DW_AT_high_pc,
dwarf::DW_AT_low_pc,
dwarf::DW_FORM_addr);
} else {
llvm_unreachable("unexpected form");
}
}
void DWARFRewriter::convertToRanges(DWARFDie DIE,
@ -712,6 +725,7 @@ void DWARFRewriter::convertToRanges(DWARFDie DIE,
DIE, LowPCOffset, HighPCOffset, LowPCFormValue, HighPCFormValue);
unsigned LowPCSize = 0;
assert(DIE.getDwarfUnit()->getAddressByteSize() == 8);
if (HighPCFormValue.getForm() == dwarf::DW_FORM_addr ||
HighPCFormValue.getForm() == dwarf::DW_FORM_data8) {
LowPCSize = 12;
@ -723,6 +737,13 @@ void DWARFRewriter::convertToRanges(DWARFDie DIE,
std::lock_guard<std::mutex> Lock(DebugInfoPatcherMutex);
DebugInfoPatcher->addLE32Patch(LowPCOffset, RangesSectionOffset);
DebugInfoPatcher->addUDataPatch(LowPCOffset + 4, 0, LowPCSize);
if (LowPCSize == 12) {
// Write an indirect 0 value for DW_AT_low_pc so that we can fill
// 12 bytes of space (see T56239836 for more details)
DebugInfoPatcher->addUDataPatch(LowPCOffset + 4, dwarf::DW_FORM_addr, 4);
DebugInfoPatcher->addLE64Patch(LowPCOffset + 8, 0);
} else {
DebugInfoPatcher->addLE64Patch(LowPCOffset + 4, 0);
}
}