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[llvm-readobj] - Fix the invalid dumping of the dynamic sections without terminating DT_NULL entry. 

This is https://bugs.llvm.org/show_bug.cgi?id=40861,

Previously llvm-readobj would print the DT_NULL sometimes
for the dynamic section that has no terminator entry.

The logic of printDynamicTable was a bit overcomplicated.
I rewrote it slightly to fix the issue and commented.

Differential revision: https://reviews.llvm.org/D58716

llvm-svn: 355073
This commit is contained in:
George Rimar 2019-02-28 08:15:59 +00:00
parent 6c57395fb4
commit 7b4fce12b3
2 changed files with 91 additions and 19 deletions
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78
llvm/test/tools/llvm-readobj/elf-dynamic-table-dtnull.s Normal file
View File

@ -0,0 +1,78 @@
# Check we are able to dump the dynamic section without a DT_NULL entry correctly.
# RUN: yaml2obj -docnum=1 %s -o %t.o
# RUN: llvm-readobj --dynamic-table %t.o | FileCheck %s --check-prefix=NONULL
# RUN: llvm-readelf --dynamic-table %t.o | FileCheck %s --check-prefix=NONULL
# NONULL: DynamicSection [ (1 entries)
# NONULL-NEXT: Tag Type Name/Value
# NONULL-NEXT: 0x0000000000000015 DEBUG 0x0
# NONULL-NEXT: ]
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_EXEC
Machine: EM_X86_64
Sections:
- Name: .dynamic
Type: SHT_DYNAMIC
Address: 0x0000000000001010
AddressAlign: 0x0000000000000010
EntSize: 0x0000000000000010
Entries:
- Tag: DT_DEBUG
Value: 0x0000000000000000
ProgramHeaders:
- Type: PT_LOAD
VAddr: 0x1000
Sections:
- Section: .dynamic
- Type: PT_DYNAMIC
VAddr: 0x1010
Sections:
- Section: .dynamic
# Sometimes .dynamic section content length can be greater than the
# length of its entries. In this case, we should not try to dump anything
# past the DT_NULL entry, which works as a terminator.
# RUN: yaml2obj -docnum=2 %s -o %t.o
# RUN: llvm-readobj --dynamic-table %t.o | FileCheck %s --check-prefix=LONG
# RUN: llvm-readelf --dynamic-table %t.o | FileCheck %s --check-prefix=LONG
# LONG: DynamicSection [ (2 entries)
# LONG-NEXT: Tag Type Name/Value
# LONG-NEXT: 0x0000000000000015 DEBUG 0x0
# LONG-NEXT: 0x0000000000000000 NULL 0x0
# LONG-NEXT: ]
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_EXEC
Machine: EM_X86_64
Sections:
- Name: .dynamic
Type: SHT_DYNAMIC
Address: 0x0000000000001010
AddressAlign: 0x0000000000000010
EntSize: 0x0000000000000010
Entries:
- Tag: DT_DEBUG
Value: 0x0000000000000000
- Tag: DT_NULL
Value: 0x0000000000000000
- Tag: DT_NULL
Value: 0x0000000000000000
ProgramHeaders:
- Type: PT_LOAD
VAddr: 0x1000
Sections:
- Section: .dynamic
- Type: PT_DYNAMIC
VAddr: 0x1010
Sections:
- Section: .dynamic

32
llvm/tools/llvm-readobj/ELFDumper.cpp
View File

@ -1914,35 +1914,29 @@ template <> void ELFDumper<ELF32LE>::printUnwindInfo() {
template<class ELFT>
void ELFDumper<ELFT>::printDynamicTable() {
auto I = dynamic_table().begin();
auto E = dynamic_table().end();
// A valid .dynamic section contains an array of entries terminated with
// a DT_NULL entry. However, sometimes the section content may continue
// past the DT_NULL entry, so to dump the section correctly, we first find
// the end of the entries by iterating over them.
size_t Size = 0;
Elf_Dyn_Range DynTableEntries = dynamic_table();
for (; Size < DynTableEntries.size();)
if (DynTableEntries[Size++].getTag() == DT_NULL)
break;
if (I == E)
return;
--E;
while (I != E && E->getTag() == ELF::DT_NULL)
--E;
if (E->getTag() != ELF::DT_NULL)
++E;
++E;
ptrdiff_t Total = std::distance(I, E);
if (Total == 0)
if (!Size)
return;
raw_ostream &OS = W.getOStream();
W.startLine() << "DynamicSection [ (" << Total << " entries)\n";
W.startLine() << "DynamicSection [ (" << Size << " entries)\n";
bool Is64 = ELFT::Is64Bits;
W.startLine()
<< " Tag" << (Is64 ? " " : " ") << "Type"
<< " " << "Name/Value\n";
while (I != E) {
const Elf_Dyn &Entry = *I;
for (size_t I = 0; I < Size; ++I) {
const Elf_Dyn &Entry = DynTableEntries[I];
uintX_t Tag = Entry.getTag();
++I;
W.startLine() << " " << format_hex(Tag, Is64 ? 18 : 10, opts::Output != opts::GNU) << " "
<< format("%-21s", getTypeString(ObjF->getELFFile()->getHeader()->e_machine, Tag));
printValue(Tag, Entry.getVal());