Now the only method to configure ELF section's content and size is to assign
a hexadecimal string to the `Content` field. Unfortunately this way is
completely useless when you need to declare a really large section.
To solve this problem this patch adds one more optional field `Size`
to the `RawContentSection` structure. When yaml2obj generates an ELF file
it uses the following algorithm:
1. If both `Content` and `Size` fields are missed create an empty section.
2. If only `Content` field is missed take section length from the `Size`
field and fill the section by zero.
3. If only `Size` field is missed create a section using data from
the `Content` field.
4. If both `Content` and `Size` fields are provided validate that the `Size`
value is not less than size of `Content` data. Than take section length
from the `Size`, fill beginning of the section by `Content` and the rest
by zero.
Examples
--------
* Create a section 0x10000 bytes long filled by zero
Name: .data
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Size: 0x10000
* Create a section 0x10000 bytes long starting from 'CA' 'FE' 'BA' 'BE'
Name: .data
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Content: CAFEBABE
Size: 0x10000
The patch reviewed by Michael Spencer.
llvm-svn: 208995
We already do this for shstrtab, so might as well do it for strtab. This
extracts the string table building code into a separate class. The idea
is to use it for other object formats too.
I mostly wanted to do this for the general principle, but it does save a
little bit on object file size. I tried this on a clang bootstrap and
saved 0.54% on the sum of object file sizes (1.14 MB out of 212 MB for
a release build).
Differential Revision: http://reviews.llvm.org/D3533
llvm-svn: 207670
The patch implements support for both relocation record formats: Elf_Rel
and Elf_Rela. It is possible to define relocation against symbol only.
Relocations against sections will be implemented later. Now yaml2obj
recognizes X86_64, MIPS and Hexagon relocation types.
Example of relocation section specification:
Sections:
- Name: .text
Type: SHT_PROGBITS
Content: "0000000000000000"
AddressAlign: 16
Flags: [SHF_ALLOC]
- Name: .rel.text
Type: SHT_REL
Info: .text
AddressAlign: 4
Relocations:
- Offset: 0x1
Symbol: glob1
Type: R_MIPS_32
- Offset: 0x2
Symbol: glob2
Type: R_MIPS_CALL16
The patch reviewed by Michael Spencer, Sean Silva, Shankar Easwaran.
llvm-svn: 206017
and ContiguousBlobAccumulator classes. Pass ContiguousBlobAccumulator to
the handleSymtabSectionHeader function directly.
No functional changes.
llvm-svn: 205431
Summary:
The FileHeader mapping now accepts an optional Flags sequence that accepts
the EF_<arch>_<flag> constants. When not given, Flags defaults to zero.
Reviewers: atanasyan
Reviewed By: atanasyan
CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D3213
llvm-svn: 205173
The current state of affairs has auxiliary symbols described as a big
bag of bytes. This is less than satisfying, it detracts from the YAML
file as being human readable.
Instead, allow for symbols to optionally contain their auxiliary data.
This allows us to have a much higher level way of describing things like
weak symbols, function definitions and section definitions.
This depends on D3105.
Differential Revision: http://llvm-reviews.chandlerc.com/D3092
llvm-svn: 204214
This compiles with no changes to clang/lld/lldb with MSVC and includes
overloads to various functions which are used by those projects and llvm
which have OwningPtr's as parameters. This should allow out of tree
projects some time to move. There are also no changes to libs/Target,
which should help out of tree targets have time to move, if necessary.
llvm-svn: 203083
* ELFTypes.h contains template magic for defining types based on endianess, size, and alignment.
* ELFFile.h defines the ELFFile class which provides low level ELF specific access.
* ELFObjectFile.h contains ELFObjectFile which uses ELFFile to implement the ObjectFile interface.
llvm-svn: 188022
Although in reality the symbol table in ELF resides in a section, the
standard requires that there be no more than one SHT_SYMTAB. To enforce
this constraint, it is cleaner to group all the symbols under a
top-level `Symbols` key on the object file.
llvm-svn: 184627
The improperly aligned section content in the output was causing
buildbot failures. This should fix them.
Incidentally, this results in a simpler and more robust API for
ContiguousBlobAccumulator.
llvm-svn: 184621
Previously we unconditionally enforced that section references in
symbols in the YAML had a name that was a section name present in the
object, and linked the references to that section. Now, permit empty
section names (already the default, if the `Section` key is not
provided) to indicate SHN_UNDEF.
llvm-svn: 184513
Instead, just have 3 sub-lists, one for each of
{STB_LOCAL,STB_GLOBAL,STB_WEAK}.
This allows us to be a lot more explicit w.r.t. the symbol ordering in
the object file, because if we allowed explicitly setting the STB_*
`Binding` key for the symbol, then we might have ended up having to
shuffle STB_LOCAL symbols to the front of the list, which is likely to
cause confusion and potential for error.
Also, this new approach is simpler ;)
llvm-svn: 184506
After this patch, the ELF file produced by
`yaml2obj-elf-symbol-basic.yaml`, when linked and executed on x86_64
(under SysV ABI, obviously; I tested on Linux), produces a working
executable that goes into an infinite loop!
llvm-svn: 184469
One of the key things that the YAML format abstracts over is the use of
section numbers for referencing sections. Instead, textual section names
are used, which yaml2obj then translates into appropriate section
numbers. (Technically ELF doesn't care about section names (only section
numbers), but since this is a testing tool, readability counts).
This simplifies using section names as symbolic references in various
parts of the code. An upcoming commit will use this to allow symbols to
reference sections.
llvm-svn: 184467
Previously, we would monkeypatch the vector of YAML::Section's in order
to ensure that the SHT_NULL entry is present. Now we just add it
unconditionally.
The proliferation of small numerical adjustments is beginning to
frighten me, but I can't think of a way having a single point of truth
for them without introducing a whole new layer of data structures (i.e.
lots of code and complexity) between the YAML and binary ELF formats.
llvm-svn: 184260
A bug in libObject will cause it to assert() if a symbol table's string
table and the section header string table are the same section, so we
need to ensure that we emit two different string tables (among other
things). The problematic code is the hardcoded usage of ".strtab"
(`dot_strtab_sec`) for looking up symbol names in
ELFObjectFile<ELFT>::getSymbolName.
I discussed this with Michael, and he has some local improvements to the
ELF code in libObject that, among other things, should fix our handling
of this scenario.
llvm-svn: 184161
I was spotting garbage in the output. I'd like to just zero the entire
ELFYAML::Section to be sure, but it contains non-POD types. (I'm also
trying to avoid bloating the ELFYAML::Foo classes with a bunch of
constructor code).
No test, since this is by its very nature unpredictable. I'm pretty sure
that one of the sanitizers would catch it immediately though.
llvm-svn: 184160
Simon Atanasyan