1
0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2025-02-01 05:01:59 +01:00

863 Commits

Author SHA1 Message Date
George Rimar
21610566c8 Recommit r368812 "[llvm/Object] - Convert SectionRef::getName() to return Expected<>"
Changes: no changes. A fix for the clang code will be landed right on top.

Original commit message:

SectionRef::getName() returns std::error_code now.
Returning Expected<> instead has multiple benefits.

For example, it forces user to check the error returned.
Also Expected<> may keep a valuable string error message,
what is more useful than having a error code.
(Object\invalid.test was updated to show the new messages printed.)

This patch makes a change for all users to switch to Expected<> version.

Note: in a few places the error returned was ignored before my changes.
In such places I left them ignored. My intention was to convert the interface
used, and not to improve and/or the existent users in this patch.
(Though I think this is good idea for a follow-ups to revisit such places
and either remove consumeError calls or comment each of them to clarify why
it is OK to have them).

Differential revision: https://reviews.llvm.org/D66089

llvm-svn: 368826
2019-08-14 11:10:11 +00:00
George Rimar
f64562dc67 Revert r368812 "[llvm/Object] - Convert SectionRef::getName() to return Expected<>"
It broke clang BB: http://lab.llvm.org:8011/builders/clang-x86_64-debian-fast/builds/16455

llvm-svn: 368813
2019-08-14 08:56:55 +00:00
George Rimar
3a9b0e354d [llvm/Object] - Convert SectionRef::getName() to return Expected<>
SectionRef::getName() returns std::error_code now.
Returning Expected<> instead has multiple benefits.

For example, it forces user to check the error returned.
Also Expected<> may keep a valuable string error message,
what is more useful than having a error code.
(Object\invalid.test was updated to show the new messages printed.)

This patch makes a change for all users to switch to Expected<> version.

Note: in a few places the error returned was ignored before my changes.
In such places I left them ignored. My intention was to convert the interface
used, and not to improve and/or the existent users in this patch.
(Though I think this is good idea for a follow-ups to revisit such places
and either remove consumeError calls or comment each of them to clarify why
it is OK to have them).

Differential revision: https://reviews.llvm.org/D66089

llvm-svn: 368812
2019-08-14 08:46:54 +00:00
Alex Langford
88fae211c4 [NFCI] Explicitly provide user-defined constructor for SectionRef
I am changing this to work around an issue that is being hit when
building with clang 3.8. Specifically, clang 3.8 requires that we have a user
defined default constructor for SectionRef for the default initialization of a
const SectionRef.

llvm-svn: 368758
2019-08-13 22:16:18 +00:00
Jordan Rupprecht
3abe0b3ab9 [llvm-readelf] Implement note parsing for NT_FILE and unknown descriptors
Summary:
This patch implements two note parsers; one for NT_FILE coredumps, e.g.:

```
  CORE                  0x00000080      NT_FILE (mapped files)
    Page size: 4096
                 Start                 End         Page Offset
    0x0000000000001000  0x0000000000002000  0x0000000000003000
        /path/to/a.out
    0x0000000000004000  0x0000000000005000  0x0000000000006000
        /path/to/libc.so
    0x0000000000007000  0x0000000000008000  0x0000000000009000
        [stack]
```

(A more realistic example can be tested locally by creating a crashing program and running `llvm-readelf -n core`)

And also implements a raw hex dump for unknown descriptor data for unhandled descriptor types.

Reviewers: MaskRay, jhenderson, grimar, alexshap

Reviewed By: MaskRay, grimar

Subscribers: emaste, llvm-commits, labath

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65832

llvm-svn: 368698
2019-08-13 14:38:45 +00:00
George Rimar
cb83c675d9 [llvm-readobj] - Remove 'error(Error EC)' helper.
We do not need it. I replaced it with
reportError(StringRef Input, Error Err).

Differential revision: https://reviews.llvm.org/D66011

llvm-svn: 368677
2019-08-13 12:07:41 +00:00
Jordan Rupprecht
0d351d4f7c [llvm-readobj] Downgrade 'PT_DYNAMIC segment offset + size exceeds the size of the file' from an error to a warning
Summary: This allows llvm-readobj to print other useful information for truncated files instead of giving up.

Reviewers: jhenderson, grimar, MaskRay

Reviewed By: jhenderson, grimar, MaskRay

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66036

llvm-svn: 368576
2019-08-12 14:05:37 +00:00
James Henderson
14a24c9e03 [llvm-readelf]Print filename for multiple inputs and fix formatting regression
This patch addresses two closely related bugs:
https://bugs.llvm.org/show_bug.cgi?id=42930 and
https://bugs.llvm.org/show_bug.cgi?id=42931.

GNU readelf prints the file name for every input unless there is only
one input and that input is not an archive. This patch adds the printing
for multiple inputs. A previous change did it for archives, but
introduced a regression with GNU compatibility for single-output
formatting, resulting in a spurious initial blank line. This is fixed in
this patch too.

Reviewed by: grimar, MaskRay

Differential Revision: https://reviews.llvm.org/D65953

llvm-svn: 368435
2019-08-09 12:30:08 +00:00
George Rimar
8921d6b9ca [llvm-readobj] - Remove error(llvm::Expected<T> &&E)
This is a bit strange method. It works like a unwrapOrError,
but named error. It does not report an Input name.
I removed it.

Differential revision: https://reviews.llvm.org/D66000

llvm-svn: 368430
2019-08-09 11:03:21 +00:00
George Rimar
da9ac1c3d1 [llvm-readobj] - Remove deprecated unwrapOrError(Expected<T> EO).
This patch changes the code to use a modern unwrapOrError(StringRef Input, Expected<T> EO)
version that contains the input source name and removes the deprecated version.

Differential revision: https://reviews.llvm.org/D65946

llvm-svn: 368428
2019-08-09 10:53:12 +00:00
George Rimar
738b777bed [llvm-readobj] - Remove unwrapOrError(ErrorOr<T> EO) helper.
It is outdated. Using of Expected<> is preferred, also it does
not provide a way to report a file name.

I updated the code to use the modern version of unwrapOrError instead.

Differential revision: https://reviews.llvm.org/D65951

llvm-svn: 368410
2019-08-09 08:29:26 +00:00
George Rimar
644ccd71c4 [llvm-readobj/libObject] - Introduce a custom warning handler for ELFFile<ELFT> methods.
Currently, we have a code duplication in llvm-readobj which was introduced in D63266.
The duplication was introduced to allow llvm-readobj to dump the partially
broken object. Methods in ELFFile<ELFT> perform a strict validation of the inputs,
what is itself good, but not for dumper tools, that might want to dump the information,
even if some pieces are broken/unexpected.

This patch introduces a warning handler which can be passed to ELFFile<ELFT> methods
and can allow skipping the non-critical errors when needed/possible.

For demonstration, I removed the duplication from llvm-readobj and implemented a warning using
the new custom warning handler. It also deduplicates the strings printed, making the output less verbose.

Differential revision: https://reviews.llvm.org/D65515

llvm-svn: 368260
2019-08-08 07:17:35 +00:00
Igor Kudrin
3f5a065dda Remove support for 32-bit offsets in utility classes (5/5)
Differential Revision: https://reviews.llvm.org/D65641

llvm-svn: 368156
2019-08-07 11:44:47 +00:00
Fangrui Song
1622ba3df6 [llvm-readelf] --notes: move 'Data size' column left by 1
readelf -n:

```
// "Data size" is not left justified
  Owner                 Data size       Description
  GNU                  0x00000010       NT_GNU_ABI_TAG (ABI version tag)
```

llvm-readelf -n (before):
```
// "Data size" column shifted by 1
  Owner                 Data size        Description
  GNU                   0x00000010       NT_GNU_ABI_TAG (ABI version tag)
```

llvm-readelf -n (after):
```
  Owner                Data size        Description
  GNU                  0x00000010       NT_GNU_ABI_TAG (ABI version tag)
```

This change is made to reduce the diff with readelf -n, so that it is
slightly easier to check what features readelf implements but we don't.

Reviewed By: grimar, jhenderson

Differential Revision: https://reviews.llvm.org/D65847

llvm-svn: 368138
2019-08-07 09:13:11 +00:00
Igor Kudrin
2f7af9b01c Switch LLVM to use 64-bit offsets (2/5)
This updates all libraries and tools in LLVM Core to use 64-bit offsets
which directly or indirectly come to DataExtractor.

Differential Revision: https://reviews.llvm.org/D65638

llvm-svn: 368014
2019-08-06 10:49:40 +00:00
Wolfgang Pieb
205f1a60c6 [llvm-readelf] Support dumping of stack sizes sections with readelf --stack-sizes
Reviewers: jhenderson, grimar, rupprecht

Differential Revision: https://reviews.llvm.org/D65313

llvm-svn: 367942
2019-08-05 22:47:07 +00:00
Jordan Rupprecht
5703017478 [llvm-readelf] Fix core note descriptions
Summary:
Core files have different descriptions for note values. llvm-readelf currently prints the generic note type, which is wrong when using it to read a core file.

To verify the constants/strings, see:
Values: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=include/elf/common.h;h=75c4fb7e9d7c0f780d635ac305f579546b7b071b;hb=HEAD#l571
Strings: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=binutils/readelf.c;h=c31a5c1266b7bb62a485895b01b49e1f832ade35;hb=HEAD#l16881

Note: this does not handle printing the note data for NT_FILE, it just fixes the descriptions.

Reviewers: MaskRay

Reviewed By: MaskRay

Subscribers: labath, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65608

llvm-svn: 367878
2019-08-05 15:43:20 +00:00
George Rimar
e8c8550933 [llvm-readelf] - A fix for: "--hash-symbols asserts for 64-bit ELFs"
Fixes https://bugs.llvm.org/show_bug.cgi?id=42622.
(--hash-symbols switch is currently broken for 64-bit ELF files, due to r352630.)

Differential revision: https://reviews.llvm.org/D64788

llvm-svn: 366558
2019-07-19 10:15:03 +00:00
Yuanfang Chen
728d845f5f [NFC][llvm-readobj] Refactor dynamic string table indexing into a function.
Restore printDynamicString removed in rL363868. It provides better
error handling whenever indexing dynamic string table is needed.

Reviewers: jhenderson, MaskRay, grimar

Reviewed by: jhenderson, MaskRay, grimar

Differential Revision: https://reviews.llvm.org/D64674

llvm-svn: 366464
2019-07-18 17:04:28 +00:00
George Rimar
3781086e1e [Object/llvm-readelf/llvm-readobj] - Improve error reporting when e_shstrndx is broken.
When e_shstrndx is broken, it is impossible to get a section name.
In this patch I improved the error message we show and 
added tests for Object and for llvm-readelf/llvm-readobj

Message was changed in two places:
1) llvm-readelf/llvm-readobj previously used a code from Object/ELF.h,
now they have a modified version of it (it has less checks and allows
dumping broken things).
2) Code in Object/ELF.h is still used for generic cases.

Differential revision: https://reviews.llvm.org/D64714

llvm-svn: 366203
2019-07-16 11:07:30 +00:00
Yuanfang Chen
373457fb8b [llvm-readelf] Print "File: lib.a(file.o)" info when dumping archive files.
Match GNU readelf.

https://bugs.llvm.org/show_bug.cgi?id=35351

Reviewers: jhenderson, grimar, MaskRay, rupprecht

Reviewed by: jhenderson, MaskRay, grimar

Differential Revision: https://reviews.llvm.org/D64361

llvm-svn: 366147
2019-07-15 22:52:01 +00:00
George Rimar
44f982eeb2 [llvm-readobj/llvm-readelf] - Report a warning instead of a error when dumping a broken dynamic section.
It does not make sence to stop dumping the object if the broken
dynamic section was found. In this patch I changed the behavior from
"report an error" to "report a warning". This matches GNU.

Differential revision: https://reviews.llvm.org/D64472

llvm-svn: 365762
2019-07-11 12:26:48 +00:00
Stanislav Mekhanoshin
a7f5d761c5 [AMDGPU] gfx908 target
Differential Revision: https://reviews.llvm.org/D64429

llvm-svn: 365525
2019-07-09 18:10:06 +00:00
Sean Fertile
aa1c5e5087 [Object][XCOFF] Add support for 64-bit file header and section header dumping.
Adds a readobj dumper for 32-bit and 64-bit section header tables, and extend
support for the file-header dumping to include 64-bit object files. Also
refactors the binary file parsing to be done in a helper function in an attempt
to cleanup error handeling.

Differential Revision: https://reviews.llvm.org/D63843

llvm-svn: 365524
2019-07-09 18:09:11 +00:00
James Henderson
33503da181 [binutils] Add response file option to help and docs
Many LLVM-based tools already support response files (i.e. files
containing a list of options, specified with '@'). This change simply
updates the documentation and help text for some of these tools to
include it. I haven't attempted to fix all tools, just a selection that
I am interested in.

I've taken the opportunity to add some tests for --help behaviour, where
they were missing. We could expand these tests, but I don't think that's
within scope of this patch.

This fixes https://bugs.llvm.org/show_bug.cgi?id=42233 and
https://bugs.llvm.org/show_bug.cgi?id=42236.

Reviewed by: grimar, MaskRay, jkorous

Differential Revision: https://reviews.llvm.org/D63597

llvm-svn: 364036
2019-06-21 11:49:20 +00:00
Yuanfang Chen
0685dae273 [llvm-readobj] Match GNU output for DT_RPATH and DT_RUNPATH when dumping dynamic symbol table.
Reviewers: jhenderson, grimar, MaskRay, rupprecht, espindola

Subscribers: emaste, nemanjai, arichardson, kbarton, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63347

llvm-svn: 363868
2019-06-19 19:31:07 +00:00
Reid Kleckner
4260bafcbb [PDB] Ignore .debug$S subsections with high bit set
Some versions of the Visual C++ 2015 runtime have line tables with the
subsection kind of 0x800000F2. In cvinfo.h, 0x80000000 is documented to
be DEBUG_S_IGNORE. This appears to implement the intended behavior.

llvm-svn: 363724
2019-06-18 19:41:25 +00:00
Fangrui Song
dbbc693bbe [llvm-readobj] Allow --hex-dump/--string-dump to dump multiple sections
1) `-x foo` currently dumps one `foo`. This change makes it dump all `foo`.
2) `-x foo -x foo` currently dumps `foo` twice. This change makes it dump `foo` once.
   In addition, if foo has section index 9, `-x foo -x 9` dumps `foo` once.
3) Give a warning instead of an error if `foo` does not exist.

The new behaviors match GNU readelf.

Also, print a new line as a separator between two section dumps.
GNU readelf uses two lines, but one seems good enough.

Reviewed By: grimar, jhenderson

Differential Revision: https://reviews.llvm.org/D63475

llvm-svn: 363683
2019-06-18 14:01:03 +00:00
James Henderson
7d7dfda2cc [llvm-readobj] Don't abort printing of dynamic table if string reference is invalid
If dynamic table is missing, output "dynamic strtab not found'. If the index is
out of range, output "Invalid Offset<..>".

https://bugs.llvm.org/show_bug.cgi?id=40807

Reviewed by: jhenderson, grimar, MaskRay

Differential Revision: https://reviews.llvm.org/D63084

Patch by Yuanfang Chen.

llvm-svn: 363374
2019-06-14 12:02:01 +00:00
George Rimar
bb7e4e3aa6 [llvm-readobj] - Do not fail to dump the object which has wrong type of .shstrtab.
Imagine we have object that has .shstrtab with type != SHT_STRTAB.
In this case, we fail to dump the object, though GNU readelf dumps it without
any issues and warnings.

This patch fixes that. It adds a code to ELFDumper.cpp which is based on the implementation of getSectionName from the ELF.h:

https://github.com/llvm-mirror/llvm/blob/master/include/llvm/Object/ELF.h#L608
https://github.com/llvm-mirror/llvm/blob/master/include/llvm/Object/ELF.h#L431
https://github.com/llvm-mirror/llvm/blob/master/include/llvm/Object/ELF.h#L539

The difference is that all non critical errors are ommitted what allows us to
improve the dumping on a tool side. Also, this opens a road for a follow-up that
should allow us to dump the section headers, but drop the section names in case if .shstrtab is completely absent and/or broken.

Differential revision: https://reviews.llvm.org/D63266

llvm-svn: 363371
2019-06-14 11:56:10 +00:00
Stanislav Mekhanoshin
3e11a165dc [AMDGPU] gfx1011/gfx1012 targets
Differential Revision: https://reviews.llvm.org/D63307

llvm-svn: 363344
2019-06-14 00:33:31 +00:00
Jordan Rupprecht
28c60062c8 [llvm-readobj] Fix output interleaving issue caused by using multiple streams at the same time.
Summary:
Use llvm::fouts() as the default stream for outputing. No new stream
should be constructed to output at the same time.

https://bugs.llvm.org/show_bug.cgi?id=42140

Reviewers: jhenderson, grimar, MaskRay, phosek, rupprecht

Reviewed By: rupprecht

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63115

Patch by Yuanfang Chen!

llvm-svn: 363198
2019-06-12 20:16:22 +00:00
George Rimar
bc0552b9e6 [llvm-readobj/llvm-readelf] - Don't fail to dump the object if .dynsym has broken sh_link field.
This is https://bugs.llvm.org/show_bug.cgi?id=42215.

GNU readelf allows to dump the objects in that case,
but llvm-readobj/llvm-readelf reports an error and stops.

The patch fixes that.

Differential revision: https://reviews.llvm.org/D63074

llvm-svn: 362938
2019-06-10 14:23:46 +00:00
Peter Smith
b65ead9186 [AArch64][ELF][llvm-readobj] Add support for BTI and PAC dynamic tags
ELF for the 64-bit Arm Architecture defines two processor-specific dynamic
tags:
DT_AARCH64_BTI_PLT 0x70000001, d_val
DT_AARCH64_PAC_PLT 0x70000003, d_val

These presence of these tags indicate that PLT sequences have been
protected using Branch Target Identification and Pointer Authentication
respectively. The presence of both indicates that the PLT sequences have
been protected with both Branch Target Identification and Pointer
Authentication.

This patch adds the tags and tests for llvm-readobj and yaml2obj.

As some of the processor specific dynamic tags overlap, this patch splits
them up, keeping their original default value if they were not previously
mentioned explicitly in a switch case.

Differential Revision: https://reviews.llvm.org/D62596

llvm-svn: 362493
2019-06-04 11:44:33 +00:00
Peter Smith
09220df774 [AARCH64][ELF][llvm-readobj] Support for AArch64 .note.gnu.property
ELF for the 64-bit Arm Architecture defines a processor specific property
type GNU_PROPERTY_AARCH64_FEATURE_1_AND as GNU_PROPERTY_LOPROC. This
property works in a similar way to the existing X86 processor specific
property GNU_PROPERTY_GNU_X86_FEATURE_1_AND.

Two feature bits are defined for GNU_PROPERTY_AARCH64_FEATURE_1_AND:
- GNU_PROPERTY_AARCH64_FEATURE_1_BTI 0x1
- GNU_PROPERTY_AARCH64_FEATURE_1_PAC 0x2

This patch defines the property, feature bits and implements support for
printing in llvm-readobj.

Differential Revision: https://reviews.llvm.org/D62595

llvm-svn: 362490
2019-06-04 11:28:22 +00:00
George Rimar
04348b844e [llvm-readobj] - An attemp to fix BB.
BB failed:
http://lab.llvm.org:8011/builders/clang-armv7-linux-build-cache/builds/15062/steps/build%20stage%201/logs/stdio

Error was:
/home/buildslave/buildslave/clang-armv7-linux-build-cache/llvm/tools/llvm-readobj/ELFDumper.cpp:3540:7:
error: non-constant-expression cannot be narrowed from type 'llvm::support::detail::packed_endian_specific_integral<unsigned long long,
llvm::support::endianness::little, 1>::value_type' (aka 'unsigned long long') to 'size_t' (aka 'unsigned int') in initializer list [-Wc++11-narrowing]
      StrTabSec->sh_size};

llvm-svn: 362084
2019-05-30 10:42:47 +00:00
George Rimar
0e04335923 [llvm-readobj/llvm-readelf] - Implement GNU style dumper of the SHT_GNU_verdef section.
It was not implemented yet, we had only LLVM style dumper implemented.
Section description is here: https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/symversion.html

Differential revision: https://reviews.llvm.org/D62520

llvm-svn: 362082
2019-05-30 10:36:52 +00:00
George Rimar
aa6e098e39 [llvm-readobj/llvm-readelf] - Implement GNU style dumper of the SHT_GNU_verneed section.
It was not implemented yet, we had only LLVM style dumper implemented.
Section description is here: https://refspecs.linuxfoundation.org/LSB_2.0.1/LSB-Core/LSB-Core/symverrqmts.html

Differential revision: https://reviews.llvm.org/D62516

llvm-svn: 362080
2019-05-30 10:14:41 +00:00
George Rimar
f9d10cdb6f [llvm-readelf] - Allow dumping of the .dynamic section even if there is no PT_DYNAMIC header.
It is now possible after D61937 was landed and was discussed
in it's review comments. It is not consistent with GNU, which
does not output .dynamic section content in this case for
no visible reason.

Differential revision: https://reviews.llvm.org/D62179

llvm-svn: 361943
2019-05-29 10:31:46 +00:00
Fangrui Song
c129acb59b [llvm-readobj] -u: don't crash when dumping SHT_ARM_EXIDX if .symtab doesn't exist
Reviewed By: kongyi

Differential Revision: https://reviews.llvm.org/D62567

llvm-svn: 361929
2019-05-29 06:18:34 +00:00
Peter Collingbourne
7fb6630c25 Change ELF tools to allow multiple sections per file.
This is how multi-partition combined output files are going to look. If we
see multiple sections, the tools will just read the first one.

Differential Revision: https://reviews.llvm.org/D62349

llvm-svn: 361869
2019-05-28 20:01:25 +00:00
Jason Liu
7fa2c0c182 [XCOFF] Implement parsing symbol table for xcoffobjfile and output as yaml format
Summary:
This patch implement parsing symbol table for xcoffobjfile and
output as yaml format. Parsing auxiliary entries of a symbol
will be in a separate patch.

The XCOFF object file (aix_xcoff.o) used in the test comes from
-bash-4.2$ cat test.c
extern int i;
extern int TestforXcoff;
int main()
{
i++;
TestforXcoff--;
}

Patch by DiggerLin

Reviewers: sfertile, hubert.reinterpretcast, MaskRay, daltenty

Differential Revision: https://reviews.llvm.org/D61532

llvm-svn: 361832
2019-05-28 14:37:59 +00:00
Hans Wennborg
81ee9ec427 Cleanups for r361807 that I somehow failed to commit
llvm-svn: 361812
2019-05-28 12:30:35 +00:00
Hans Wennborg
4dc1a77230 Fix some llvm-readelf tests after r361633
They were failing on 32-bit Windows. In the cases where I've changed
test expectations, I've checked that they match the output of GNU
readelf.

llvm-svn: 361807
2019-05-28 11:24:20 +00:00
Simon Atanasyan
8a7e514b76 [llvm-readobj] Implement GNU-style output for dynamic table
GNU readelf tool prints slightly different dynamic table "header" and
surrounds dynamic tag names by brackets. This patch implements the same
formatting for GNU-style output of the `llvm-readobj`.

LLVM
```
DynamicSection [ (13 entries)
  Tag        Type                 Name/Value
  0x00000006 SYMTAB               0x168
  ...
]
```

GNU
```
Dynamic section at offset 0x1d0 contains 13 entries:
  Tag        Type                 Name/Value
  0x00000006 (SYMTAB)             0x168
  ...
```

Differential Revision: https://reviews.llvm.org/D62256

llvm-svn: 361633
2019-05-24 12:22:53 +00:00
George Rimar
641f2653c4 Revert r361630 "[llvm-readelf] - Allow dumping of the .dynamic section even if there is no PT_DYNAMIC header."
It broke BB:
http://lab.llvm.org:8011/builders/ppc64le-lld-multistage-test/builds/3748

llvm-svn: 361631
2019-05-24 11:24:42 +00:00
George Rimar
e624c6dcd2 [llvm-readelf] - Allow dumping of the .dynamic section even if there is no PT_DYNAMIC header.
It is now possible after D61937 was landed and was discussed
in it's review comments. It is not consistent with GNU, which
does not output .dynamic section content in this case for
no visible reason.

Differential revision: https://reviews.llvm.org/D62179

llvm-svn: 361630
2019-05-24 11:12:50 +00:00
Simon Atanasyan
dc34fe0303 [llvm-readobj][mips] Align GOT columns headers properly in 64-bit case
llvm-svn: 361626
2019-05-24 10:26:48 +00:00
George Rimar
96e8534d94 [llvm-readelf] - Rework how we parse the .dynamic section.
This is a result of what I found during my work on https://bugs.llvm.org/show_bug.cgi?id=41679.

Previously LLVM readelf took the information about .dynamic section
from its PT_DYNAMIC segment only. GNU tools have a bit different logic.
They also use the information from the .dynamic section header if it is available.
This patch changes the code to improve the compatibility with the GNU Binutils.

Differential revision: https://reviews.llvm.org/D61937

llvm-svn: 361165
2019-05-20 15:41:48 +00:00
Ben Dunbobbin
2aa2767ebe [ELF] Implement Dependent Libraries Feature
This patch implements a limited form of autolinking primarily designed to allow
either the --dependent-library compiler option, or "comment lib" pragmas (
https://docs.microsoft.com/en-us/cpp/preprocessor/comment-c-cpp?view=vs-2017) in
C/C++ e.g. #pragma comment(lib, "foo"), to cause an ELF linker to automatically
add the specified library to the link when processing the input file generated
by the compiler.

Currently this extension is unique to LLVM and LLD. However, care has been taken
to design this feature so that it could be supported by other ELF linkers.

The design goals were to provide:

- A simple linking model for developers to reason about.
- The ability to to override autolinking from the linker command line.
- Source code compatibility, where possible, with "comment lib" pragmas in other
  environments (MSVC in particular).

Dependent library support is implemented differently for ELF platforms than on
the other platforms. Primarily this difference is that on ELF we pass the
dependent library specifiers directly to the linker without manipulating them.
This is in contrast to other platforms where they are mapped to a specific
linker option by the compiler. This difference is a result of the greater
variety of ELF linkers and the fact that ELF linkers tend to handle libraries in
a more complicated fashion than on other platforms. This forces us to defer
handling the specifiers to the linker.

In order to achieve a level of source code compatibility with other platforms
we have restricted this feature to work with libraries that meet the following
"reasonable" requirements:

1. There are no competing defined symbols in a given set of libraries, or
   if they exist, the program owner doesn't care which is linked to their
   program.
2. There may be circular dependencies between libraries.

The binary representation is a mergeable string section (SHF_MERGE,
SHF_STRINGS), called .deplibs, with custom type SHT_LLVM_DEPENDENT_LIBRARIES
(0x6fff4c04). The compiler forms this section by concatenating the arguments of
the "comment lib" pragmas and --dependent-library options in the order they are
encountered. Partial (-r, -Ur) links are handled by concatenating .deplibs
sections with the normal mergeable string section rules. As an example, #pragma
comment(lib, "foo") would result in:

.section ".deplibs","MS",@llvm_dependent_libraries,1
         .asciz "foo"

For LTO, equivalent information to the contents of a the .deplibs section can be
retrieved by the LLD for bitcode input files.

LLD processes the dependent library specifiers in the following way:

1. Dependent libraries which are found from the specifiers in .deplibs sections
   of relocatable object files are added when the linker decides to include that
   file (which could itself be in a library) in the link. Dependent libraries
   behave as if they were appended to the command line after all other options. As
   a consequence the set of dependent libraries are searched last to resolve
   symbols.
2. It is an error if a file cannot be found for a given specifier.
3. Any command line options in effect at the end of the command line parsing apply
   to the dependent libraries, e.g. --whole-archive.
4. The linker tries to add a library or relocatable object file from each of the
   strings in a .deplibs section by; first, handling the string as if it was
   specified on the command line; second, by looking for the string in each of the
   library search paths in turn; third, by looking for a lib<string>.a or
   lib<string>.so (depending on the current mode of the linker) in each of the
   library search paths.
5. A new command line option --no-dependent-libraries tells LLD to ignore the
   dependent libraries.

Rationale for the above points:

1. Adding the dependent libraries last makes the process simple to understand
   from a developers perspective. All linkers are able to implement this scheme.
2. Error-ing for libraries that are not found seems like better behavior than
   failing the link during symbol resolution.
3. It seems useful for the user to be able to apply command line options which
   will affect all of the dependent libraries. There is a potential problem of
   surprise for developers, who might not realize that these options would apply
   to these "invisible" input files; however, despite the potential for surprise,
   this is easy for developers to reason about and gives developers the control
   that they may require.
4. This algorithm takes into account all of the different ways that ELF linkers
   find input files. The different search methods are tried by the linker in most
   obvious to least obvious order.
5. I considered adding finer grained control over which dependent libraries were
   ignored (e.g. MSVC has /nodefaultlib:<library>); however, I concluded that this
   is not necessary: if finer control is required developers can fall back to using
   the command line directly.

RFC thread: http://lists.llvm.org/pipermail/llvm-dev/2019-March/131004.html.

Differential Revision: https://reviews.llvm.org/D60274

llvm-svn: 360984
2019-05-17 03:44:15 +00:00