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[yaml2obj] Simplify p_filesz/p_memsz computing 

This fixes a bug as well. When "FileSize:" (p_filesz) is specified and
different from the actual value, the following code probably should not
use PHeader.p_filesz:

  if (SHeader->sh_offset == PHeader.p_offset + PHeader.p_filesz)
    PHeader.p_memsz += SHeader->sh_size;

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D67256

llvm-svn: 371420
This commit is contained in:
Fangrui Song 2019-09-09 16:45:17 +00:00
parent 2b7089949e
commit c28f3e6e2c
2 changed files with 39 additions and 28 deletions
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42
llvm/lib/ObjectYAML/ELFEmitter.cpp
View File

@ -627,35 +627,23 @@ void ELFState<ELFT>::setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
PHeader.p_offset = std::min(PHeader.p_offset, SHeader->sh_offset);
}
// Find the maximum offset of the end of a section in order to set p_filesz,
// if not set explicitly.
if (YamlPhdr.FileSize) {
PHeader.p_filesz = *YamlPhdr.FileSize;
} else {
PHeader.p_filesz = 0;
for (Elf_Shdr *SHeader : Sections) {
uint64_t EndOfSection;
if (SHeader->sh_type == llvm::ELF::SHT_NOBITS)
EndOfSection = SHeader->sh_offset;
else
EndOfSection = SHeader->sh_offset + SHeader->sh_size;
uint64_t EndOfSegment = PHeader.p_offset + PHeader.p_filesz;
EndOfSegment = std::max(EndOfSegment, EndOfSection);
PHeader.p_filesz = EndOfSegment - PHeader.p_offset;
}
// Find the maximum offset of the end of a section in order to set p_filesz
// and p_memsz. When setting p_filesz, trailing SHT_NOBITS sections are not
// counted.
uint64_t FileOffset = PHeader.p_offset, MemOffset = PHeader.p_offset;
for (Elf_Shdr *SHeader : Sections) {
uint64_t End = SHeader->sh_offset + SHeader->sh_size;
MemOffset = std::max(MemOffset, End);
if (SHeader->sh_type != llvm::ELF::SHT_NOBITS)
FileOffset = std::max(FileOffset, End);
}
// If not set explicitly, find the memory size by adding the size of
// sections at the end of the segment. These should be empty (size of zero)
// and NOBITS sections.
if (YamlPhdr.MemSize) {
PHeader.p_memsz = *YamlPhdr.MemSize;
} else {
PHeader.p_memsz = PHeader.p_filesz;
for (Elf_Shdr *SHeader : Sections)
if (SHeader->sh_offset == PHeader.p_offset + PHeader.p_filesz)
PHeader.p_memsz += SHeader->sh_size;
}
// Set the file size and the memory size if not set explicitly.
PHeader.p_filesz = YamlPhdr.FileSize ? uint64_t(*YamlPhdr.FileSize)
: FileOffset - PHeader.p_offset;
PHeader.p_memsz = YamlPhdr.MemSize ? uint64_t(*YamlPhdr.MemSize)
: MemOffset - PHeader.p_offset;
// Set the alignment of the segment to be the same as the maximum alignment
// of the sections with the same offset so that by default the segment

25
llvm/test/tools/yaml2obj/program-header-size-offset.yaml
View File

@ -11,7 +11,7 @@
# CHECK: Offset: 0x2000
# CHECK: FileSize: 6
# CHECK: MemSize: 6
# CHECK: MemSize: 4
# CHECK: Offset: 0x2000
# CHECK: FileSize: 4
@ -28,6 +28,10 @@
# CHECK: Offset: 0x3000
# CHECK: FileSize: 3
# CHECK: MemSize: 2
# CHECK: Offset: 0x2004
# CHECK: FileSize: 4
# CHECK: MemSize: 6
# CHECK: ]
!ELF
@ -40,14 +44,26 @@ Sections:
- Name: .text
Type: SHT_PROGBITS
Size: 4
ShOffset: 0x1000
AddressAlign: 0x1000
- Name: .rodata
Type: SHT_PROGBITS
Size: 4
ShOffset: 0x2000
AddressAlign: 0x1000
- Name: .data
Type: SHT_PROGBITS
ShOffset: 0x2004
Size: 4
- Name: .nobits1
Type: SHT_NOBITS
ShOffset: 0x2008
Size: 1
- Name: .nobits2
Type: SHT_NOBITS
# Intentionally set to 0x2009 though the previous section is SHT_NOBITS.
ShOffset: 0x2009
Size: 1
ProgramHeaders:
# Program header with no sections.
- Type: 0x6abcdef0 # arbitrary type
@ -83,3 +99,10 @@ ProgramHeaders:
MemSize: 2
Sections:
- Section: .data
# Program header with 2 SHT_NOBITS sections.
- Type: 0x6abcdef0
Offset: 0x2004
Sections:
- Section: .data
- Section: .nobits1
- Section: .nobits2