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[llvm-readobj] Display sections that do not belong to a segment in the section-mapping 

Summary:
The following patch adds the "None" line to the section to segment mapping dump.
That line lists the sections that do not belong to any segment.
I realize that this change differs from GNU readelf which does not display the latter information.

I'd rather not add this "feature" under a command line option.  I think that might introduce confusion, since users would have to
make an additional decision as to if they want to see all of the section-to-segment map or just a subset of it.

Another option is to only print the "None" line if the `--section-mapping` option is passed; however,
that might also introduce some confusion, because the section-to-segment map would be different between`--program-headers`
and the `--section-mapping` output.  While the difference is just the "None" line, it seems that if we choose to display
the segment-to-section mapping, then we should always display the whole map including the sections
that do not belong to segments.

```
Section to Segment mapping:
  Segment Sections...
   00
   01     .interp
   02     .interp .note.ABI-tag .gnu.hash
   03     .init_array .fini_array .dynamic
   04     .dynamic
   05     .note.ABI-tag
   06     .eh_frame_hdr
   07
   08     .init_array .fini_array .dynamic .got
   None   .comment .symtab .strtab .shstrtab <--- THIS LINE
```

Reviewers: grimar, rupprecht, jhenderson, espindola

Reviewed By: rupprecht

Subscribers: khemant, emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D57700

llvm-svn: 353217
This commit is contained in:
Matt Davis 2019-02-05 21:01:01 +00:00
parent 315056692d
commit 0d0e9c08a4
3 changed files with 19 additions and 2 deletions
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2
lld/test/ELF/linkerscript/segment-none.s
View File

@ -23,7 +23,7 @@
# CHECK: Section to Segment mapping:
# CHECK-NEXT: Segment Sections...
# CHECK-NOT: .foo
# CHECK: None {{.*}}.foo
# DEFINED: Section to Segment mapping:
# DEFINED-NEXT: Segment Sections...

2
llvm/test/tools/llvm-readobj/gnu-phdrs.test
View File

@ -59,6 +59,7 @@ ELF32-NEXT: 06 .tdata .tbss
ELF32-NEXT: 07 .eh_frame_hdr
ELF32-NEXT: 08
ELF32-NEXT: 09 .tdata .ctors .dtors .jcr .dynamic .got
ELF32-NEXT: None .comment .shstrtab .symtab .strtab
ELF64-PHDRS: Elf file type is EXEC (Executable file)
ELF64-PHDRS-NEXT: Entry point 0x400610
@ -90,6 +91,7 @@ ELF64-MAPPING-NEXT: 06 .tdata .tbss
ELF64-MAPPING-NEXT: 07 .eh_frame_hdr
ELF64-MAPPING-NEXT: 08
ELF64-MAPPING-NEXT: 09 .tdata .init_array .fini_array .jcr .dynamic .got
ELF64-MAPPING-NEXT: None .comment .shstrtab .symtab .strtab
ELF64-ONEMAPPING: Section to Segment mapping:
ELF64-ONEMAPPING-NOT: Section to Segment mapping:

17
llvm/tools/llvm-readobj/ELFDumper.cpp
View File

@ -19,6 +19,7 @@
#include "llvm-readobj.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
@ -3316,6 +3317,7 @@ void GNUStyle<ELFT>::printProgramHeaders(const ELFO *Obj) {
template <class ELFT>
void GNUStyle<ELFT>::printSectionMapping(const ELFO *Obj) {
OS << "\n Section to Segment mapping:\n Segment Sections...\n";
DenseSet<const Elf_Shdr *> BelongsToSegment;
int Phnum = 0;
for (const Elf_Phdr &Phdr : unwrapOrError(Obj->program_headers())) {
std::string Sections;
@ -3330,12 +3332,25 @@ void GNUStyle<ELFT>::printSectionMapping(const ELFO *Obj) {
Phdr.p_type != ELF::PT_TLS;
if (!TbssInNonTLS && checkTLSSections(Phdr, Sec) &&
checkoffsets(Phdr, Sec) && checkVMA(Phdr, Sec) &&
checkPTDynamic(Phdr, Sec) && (Sec.sh_type != ELF::SHT_NULL))
checkPTDynamic(Phdr, Sec) && (Sec.sh_type != ELF::SHT_NULL)) {
Sections += unwrapOrError(Obj->getSectionName(&Sec)).str() + " ";
BelongsToSegment.insert(&Sec);
}
}
OS << Sections << "\n";
OS.flush();
}
// Display sections that do not belong to a segment.
std::string Sections;
for (const Elf_Shdr &Sec : unwrapOrError(Obj->sections())) {
if (BelongsToSegment.find(&Sec) == BelongsToSegment.end())
Sections += unwrapOrError(Obj->getSectionName(&Sec)).str() + ' ';
}
if (!Sections.empty()) {
OS << " None " << Sections << '\n';
OS.flush();
}
}
template <class ELFT>