forked from OSchip/llvm-project
[llvm-readelf/obj] - Stop printing wrong addresses for arm32 unwind info for non-relocatable objects.
This is the first patch for https://bugs.llvm.org/show_bug.cgi?id=47581. Currently -u does not compute function addresses correctly and dumps broken addresses for non-relocatable objects. ARM spec says: "An index table entry consists of 2 words. The first word contains a prel31 offset (see Relocations) to the start of a function, with bit 31 clear." ... "The relocated 31 bits form a place-relative signed offset to the referenced entity. For brevity, this document will refer to the results of these relocations as "prel31 offsets"." (https://developer.arm.com/documentation/ihi0038/c/?lang=en#index-table-entries) (https://developer.arm.com/documentation/ihi0038/c/?lang=en#relocations) Currently we use an address of the SHT_ARM_EXIDX section instead of an address of an entry in computations. As a result we compute an offset that is not really "place-relative", but section relative, what is wrong. The patch fixes this issue. Differential revision: https://reviews.llvm.org/D88076
This commit is contained in:
Georgii Rymar
parent
5bddaf6dbf
commit
bb0597067d
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@ -0,0 +1,94 @@
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## Check that we dump the unwind information for a non-relocatable input properly.
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## Check that we correctly decode function addresses and that we are able to
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## locate corresponding STT_FUNC symbols and dump function names properly.
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# RUN: yaml2obj %s -o %t
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# RUN: llvm-readobj -u %t | FileCheck --check-prefix=UNWIND %s
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# RUN: llvm-readelf -u %t | FileCheck --check-prefix=UNWIND %s
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# UNWIND: UnwindInformation {
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# UNWIND-NEXT: UnwindIndexTable {
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# UNWIND-NEXT: SectionIndex: 2
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# UNWIND-NEXT: SectionName: .ARM.exidx
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# UNWIND-NEXT: SectionOffset: 0x34
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# UNWIND-NEXT: Entries [
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# UNWIND-NEXT: Entry {
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# UNWIND-NEXT: FunctionAddress: 0x230
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# UNWIND-NEXT: FunctionName: func1
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# UNWIND-NEXT: Model: Compact (Inline)
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# UNWIND-NEXT: PersonalityIndex: 0
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# UNWIND-NEXT: Opcodes [
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# UNWIND-NEXT: 0xB0 ; finish
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# UNWIND-NEXT: 0xB0 ; finish
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# UNWIND-NEXT: 0xB0 ; finish
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# UNWIND-NEXT: ]
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# UNWIND-NEXT: }
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# UNWIND-NEXT: Entry {
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# UNWIND-NEXT: FunctionAddress: 0x234
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# UNWIND-NEXT: FunctionName: func2
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# UNWIND-NEXT: Model: Compact (Inline)
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# UNWIND-NEXT: PersonalityIndex: 0
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# UNWIND-NEXT: Opcodes [
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# UNWIND-NEXT: 0x9B ; vsp = r11
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# UNWIND-NEXT: 0x84 0x80 ; pop {fp, lr}
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# UNWIND-NEXT: ]
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# UNWIND-NEXT: }
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# UNWIND-NEXT: Entry {
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# UNWIND-NEXT: FunctionAddress: 0x248
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# UNWIND-NEXT: FunctionName: func3
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# UNWIND-NEXT: Model: Compact (Inline)
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# UNWIND-NEXT: PersonalityIndex: 0
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# UNWIND-NEXT: Opcodes [
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# UNWIND-NEXT: 0xB0 ; finish
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# UNWIND-NEXT: 0xB0 ; finish
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# UNWIND-NEXT: 0xB0 ; finish
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# UNWIND-NEXT: ]
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# UNWIND-NEXT: }
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# UNWIND-NEXT: Entry {
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# UNWIND-NEXT: FunctionAddress: 0x24C
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# UNWIND-NEXT: Model: CantUnwind
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# UNWIND-NEXT: }
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# UNWIND-NEXT: ]
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# UNWIND-NEXT: }
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# UNWIND-NEXT: }
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--- !ELF
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FileHeader:
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Class: ELFCLASS32
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Data: ELFDATA2LSB
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Type: ET_DYN
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Machine: EM_ARM
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Sections:
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- Name: .text
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Type: SHT_PROGBITS
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Address: 0x230
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- Name: .ARM.exidx
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Type: SHT_ARM_EXIDX
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Address: 0x24C
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ContentArray: [
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## Entry 1. Address of .ARM.exidx (0x24C) + entry offset (0) + 0x7fffffe4 == 0x230 (func1).
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0xE4, 0xFF, 0xFF, 0x7F, ## Word(0) = 0x7fffffe4 (31 bit).
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0xB0, 0xB0, 0xB0, 0x80, ## Word(1): arbitrary opcodes.
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## Entry 2. Address of .ARM.exidx (0x24C) + entry offset (8) + 0x7fffffe0 == 0x234 (func2).
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0xE0, 0xFF, 0xFF, 0x7F, ## Word(0) = 0x7fffffe0 (31 bit).
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0x80, 0x84, 0x9B, 0x80, ## Word(1): arbitrary opcodes.
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## Entry 3. Address of .ARM.exidx (0x24C) + entry offset (16) + 0x7fffffec == 0x248 (func2).
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0xEC, 0xFF, 0xFF, 0x7F, ## Word(0) = 0x7fffffec (31 bit).
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0xB0, 0xB0, 0xB0, 0x80, ## Word(1): arbitrary opcodes.
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## Entry 4. Address of .ARM.exidx (0x24C) + entry offset (24) + 0x7fffffe8 == 0x24C.
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0xE8, 0xFF, 0xFF, 0x7F, ## Word(0) = 0x7fffffe8 (31 bit).
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0x01, 0x00, 0x00, 0x00 ## Word(1) == EXIDX_CANTUNWIND
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]
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Symbols:
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- Name: func1
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Type: STT_FUNC
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Section: .text
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Value: 0x230
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- Name: func2
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Type: STT_FUNC
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Section: .text
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Value: 0x234
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- Name: func3
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Type: STT_FUNC
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Section: .text
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Value: 0x248
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@ -341,7 +341,8 @@ class PrinterContext {
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return Location + Place;
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}
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ErrorOr<StringRef> FunctionAtAddress(unsigned Section, uint64_t Address) const;
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ErrorOr<StringRef> FunctionAtAddress(uint64_t Address,
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Optional<unsigned> SectionIndex) const;
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const Elf_Shdr *FindExceptionTable(unsigned IndexTableIndex,
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off_t IndexTableOffset) const;
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@ -363,8 +364,8 @@ const size_t PrinterContext<ET>::IndexTableEntrySize = 8;
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template <typename ET>
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ErrorOr<StringRef>
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PrinterContext<ET>::FunctionAtAddress(unsigned Section,
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uint64_t Address) const {
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PrinterContext<ET>::FunctionAtAddress(uint64_t Address,
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Optional<unsigned> SectionIndex) const {
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if (!Symtab)
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return inconvertibleErrorCode();
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auto StrTableOrErr = ELF.getStringTableForSymtab(*Symtab);
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@ -372,9 +373,11 @@ PrinterContext<ET>::FunctionAtAddress(unsigned Section,
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reportError(StrTableOrErr.takeError(), FileName);
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StringRef StrTable = *StrTableOrErr;
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for (const Elf_Sym &Sym : unwrapOrError(FileName, ELF.symbols(Symtab)))
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if (Sym.st_shndx == Section && Sym.st_value == Address &&
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Sym.getType() == ELF::STT_FUNC) {
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for (const Elf_Sym &Sym : unwrapOrError(FileName, ELF.symbols(Symtab))) {
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if (SectionIndex && *SectionIndex != Sym.st_shndx)
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continue;
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if (Sym.st_value == Address && Sym.getType() == ELF::STT_FUNC) {
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auto NameOrErr = Sym.getName(StrTable);
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if (!NameOrErr) {
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// TODO: Actually report errors helpfully.
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@ -383,6 +386,8 @@ PrinterContext<ET>::FunctionAtAddress(unsigned Section,
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}
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return *NameOrErr;
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}
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}
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return inconvertibleErrorCode();
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}
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@ -485,7 +490,8 @@ void PrinterContext<ET>::PrintExceptionTable(const Elf_Shdr *IT,
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uint64_t Address = PREL31(Word, EHT->sh_addr);
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SW.printHex("PersonalityRoutineAddress", Address);
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if (ErrorOr<StringRef> Name = FunctionAtAddress(EHT->sh_link, Address))
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if (ErrorOr<StringRef> Name =
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FunctionAtAddress(Address, (unsigned)EHT->sh_link))
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SW.printString("PersonalityRoutineName", *Name);
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}
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}
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@ -518,6 +524,7 @@ void PrinterContext<ET>::PrintIndexTable(unsigned SectionIndex,
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const support::ulittle32_t *Data =
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reinterpret_cast<const support::ulittle32_t *>(Contents->data());
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const unsigned Entries = IT->sh_size / IndexTableEntrySize;
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const bool IsRelocatable = ELF.getHeader().e_type == ELF::ET_REL;
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ListScope E(SW, "Entries");
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for (unsigned Entry = 0; Entry < Entries; ++Entry) {
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@ -533,9 +540,31 @@ void PrinterContext<ET>::PrintIndexTable(unsigned SectionIndex,
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continue;
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}
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const uint64_t Offset = PREL31(Word0, IT->sh_addr);
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SW.printHex("FunctionAddress", Offset);
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if (ErrorOr<StringRef> Name = FunctionAtAddress(IT->sh_link, Offset))
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// FIXME: For a relocatable object ideally we might want to:
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// 1) Find a relocation for the offset of Word0.
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// 2) Verify this relocation is of an expected type (R_ARM_PREL31) and
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// verify the symbol index.
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// 3) Resolve the relocation using it's symbol value, addend etc.
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// Currently the code assumes that Word0 contains an addend of a
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// R_ARM_PREL31 REL relocation that references a section symbol. RELA
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// relocations are not supported and it works because addresses of sections
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// are nulls in relocatable objects.
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//
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// For a non-relocatable object, Word0 contains a place-relative signed
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// offset to the referenced entity.
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const uint64_t Address =
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IsRelocatable
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? PREL31(Word0, IT->sh_addr)
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: PREL31(Word0, IT->sh_addr + Entry * IndexTableEntrySize);
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SW.printHex("FunctionAddress", Address);
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// In a relocatable output we might have many .ARM.exidx sections linked to
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// their code sections via the sh_link field. For a non-relocatable ELF file
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// the sh_link field is not reliable, because we have one .ARM.exidx section
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// normally, but might have many code sections.
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Optional<unsigned> SecIndex =
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IsRelocatable ? Optional<unsigned>(IT->sh_link) : None;
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if (ErrorOr<StringRef> Name = FunctionAtAddress(Address, SecIndex))
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SW.printString("FunctionName", *Name);
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if (Word1 == EXIDX_CANTUNWIND) {
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