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
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
In the r360676 "Apply clang format. NFC" I applied clang-format
for whole ELFDumper.cpp. It caused a little discussion,
one of the points mentioned was that previously nicely lined up
tables are not so nice now.
This patch reverts them.
llvm-svn: 360860
Summary: Currently, `llvm-readobj` do not support GNU style dumper for symbol versioning sections. In this patch, I would like to implement dumper for `.gnu.version` section
Reviewers: jhenderson, rupprecht, grimar
Reviewed By: jhenderson, rupprecht
Subscribers: llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59877
llvm-svn: 357578
Summary: Support reading notes that don't have a standard note name.
Reviewers: MaskRay
Reviewed By: MaskRay
Subscribers: llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59969
llvm-svn: 357271
The majority of the printRelocation and printDynamicRelocation functions
were identical. This patch factors this all out into a new function.
There are a couple of minor differences to do with printing of symbols
without names, but I think these are harmless, and in some cases a small
improvement.
Reviewed by: grimar, rupprecht, Higuoxing
Differential Revision: https://reviews.llvm.org/D59823
llvm-svn: 357246
Summary: When implementing `GNU style` dumper for `.gnu.version` section, we should find symbol version name by `vs_index`.
Reviewers: jhenderson, rupprecht
Reviewed By: rupprecht
Subscribers: arphaman, rupprecht, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59545
llvm-svn: 357164
Summary:
Currently, llvm-readobj can dump symbol version sections only in LLVM style. In this patch, I would like to separate these dumpers into GNU style and
LLVM style for future implementation.
Reviewers: grimar, jhenderson, mattd, rupprecht
Reviewed By: jhenderson, rupprecht
Subscribers: ormris, dyung, RKSimon, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59186
llvm-svn: 356881
Summary:
Currently, llvm-readobj can dump symbol version sections only in LLVM style. In this patch, I would like to separate these dumpers into GNU style and
LLVM style for future implementation.
Reviewers: grimar, jhenderson, mattd, rupprecht
Reviewed By: rupprecht
Subscribers: llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59186
llvm-svn: 356764
Summary:
This commit introduces a new AMDGPUPALMetadata class that:
* is inside the AMDGPU target;
* keeps an in-memory representation of PAL metadata;
* provides a method to read the frontend-supplied metadata from LLVM IR;
* provides methods for the asm printer to set metadata items;
* provides methods to write the metadata as a binary blob to put in a
.note record or as an asm directive;
* provides a method to read the metadata as a binary blob from a .note
record.
Because llvm-readobj cannot call directly into a target, I had to remove
llvm-readobj's ability to dump PAL metadata, pending a resolution to
https://reviews.llvm.org/D52821
Differential Revision: https://reviews.llvm.org/D57027
Change-Id: I756dc830894fcb6850324cdcfa87c0120eb2cf64
llvm-svn: 356582
Summary:
MsgPackDocument is the lighter-weight replacement for MsgPackTypes. This
commit switches AMDGPU HSA metadata processing to use MsgPackDocument
instead of MsgPackTypes.
Differential Revision: https://reviews.llvm.org/D57024
Change-Id: I0751668013abe8c87db01db1170831a76079b3a6
llvm-svn: 356081
Specifically, compute and Print Type and Section columns.
This is a re-commit of rL354833, after fixing the Asan problem found a a buildbot.
Differential Revision: https://reviews.llvm.org/D59060
llvm-svn: 355742
llvm-readelf prints relocation addends as:
<symbol value>[+-]<absolute addend>
where [+-] is determined from whether addend is less than zero or not.
However, it does not print the +/- if there is no symbol, which meant
that negative addends became their positive value with no indication
that this had happened. This patch stops the absolute conversion when
addends are negative and there is no associated symbol.
Reviewed by: Higuoxing, mattd, MaskRay
Differential Revision: https://reviews.llvm.org/D59095
llvm-svn: 355696
Summary:
This patch will obtain the section name for symbols that refer to a section. Prior to this patch the Name field for STT_SECTIONs was blank, now it is populated.
Before:
```
Symbol table '.symtab' contains 6 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 SECTION LOCAL DEFAULT 1
2: 0000000000000000 0 SECTION LOCAL DEFAULT 3
3: 0000000000000000 0 SECTION LOCAL DEFAULT 4
4: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND _GLOBAL_OFFSET_TABLE_
5: 0000000000000000 0 TLS GLOBAL DEFAULT UND sym
```
With this patch:
```
Symbol table '.symtab' contains 6 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 SECTION LOCAL DEFAULT 1 .text
2: 0000000000000000 0 SECTION LOCAL DEFAULT 3 .data
3: 0000000000000000 0 SECTION LOCAL DEFAULT 4 .bss
4: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND _GLOBAL_OFFSET_TABLE_
5: 0000000000000000 0 TLS GLOBAL DEFAULT UND sym
```
This fixes PR40788
Reviewers: jhenderson, rupprecht, espindola
Reviewed By: rupprecht
Subscribers: emaste, javed.absar, arichardson, MaskRay, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58796
llvm-svn: 355207
There's no reason to limit the DWARF CFI dumper to EM_386 and EM_X86_64;
ELF files could contain DWARF CFI on almost any platform (even 32-bit ARM;
NetBSD uses DWARF CFI on that platform). So start using the DWARF CFI dumper
unconditionally so that we can dump .eh_frame sections on the remaining ELF
platforms as well as in NetBSD binaries.
Differential Revision: https://reviews.llvm.org/D58761
llvm-svn: 355151
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
Summary:
This patch displays a hexadecimal section value (Elf_Shdr::sh_type) or section-relative offset when printing unknown sections.
Here is a subset of the output (ignoring the fields following "Type" when dumping an ELF's GNU `--section-headers` table).
Section Headers:
```
[Nr] Name Type
[16] android_rel LOOS+0x1
[17] android_rela LOOS+0x2
[27] unknown 0x1000: <unknown>
[28] loos LOOS+0
[30] hios VERSYM
[31] loproc LOPROC+0
[33] hiproc LOPROC+0xFFFFFFF
[34] louser LOUSER+0
[36] hiuser LOUSER+0x7FFFFFFF
```
As a comparison, the previous output looked something like the above, but with a blank "Type" field:
```
[Nr] Name Type
[27] unknown
[28] loos
[30] hios VERSYM
[31] loproc
[33] hiproc
[34] louser
[36] hiuser
```
This fixes PR40773
Reviewers: jhenderson, rupprecht, Bigcheese
Reviewed By: jhenderson, rupprecht, Bigcheese
Subscribers: MaskRay, Bigcheese, srhines, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58701
llvm-svn: 355014
Summary:
This is to be consistent with the display of other MIPS section types.
This string is also used by binutils-gdb/binutils/readelf.c:get_mips_section_type_name
Since we are here, reorder the two enum constatns because SHT_MIPS_DWARF < SHT_MIPS_ABIFLAGS.
Reviewers: jhenderson, atanasyan
Reviewed By: jhenderson
Subscribers: aprantl, sdardis, arichardson, rupprecht, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58496
llvm-svn: 354571
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
Summary:
The following patch introduces a new function `printSectionMapping` which is responsible for dumping just the section-to-segment mapping.
This patch also introduces a n option `-section-mapping` that outputs that mapping without the program headers.
Previously, this functionality was controlled by `printProgramHeaders`, and the output from `-program-headers` has not been changed. I am happy to change the option name, I copied the name that was displayed when outputting the mapping table.
Reviewers: khemant, jhenderson, grimar, rupprecht
Reviewed By: jhenderson, grimar, rupprecht
Subscribers: rupprecht, jhenderson, llvm-commits
Differential Revision: https://reviews.llvm.org/D57365
llvm-svn: 352896
We have a Field struct which has a StringRef member Str.
The code needs to create and keep alive the temporarily
std::string variables because of that.
That is not convenient and makes the code be more complicated
than it could be.
There seems to be no reason to keep Str be StringRef.
The patch changes it to be std::string and
rearranges the code around slightly.
Differential revision: https://reviews.llvm.org/D57447
llvm-svn: 352623
In r287786, a bug was introduced into llvm-readelf where it didn't print
the static symbol table if both --symbols and --dyn-symbols were
specified, even if there was no dynamic symbol table. This is obviously
incorrect.
This patch fixes this issue, by delegating the decision of which symbol
tables should be printed to the final dumper, rather than trying to
decide in the command-line option handling layer. The decision was made
to follow the approach taken in this patch because the LLVM style dumper
uses a different order to the original GNU style behaviour (and GNU
readelf) for ELF output. Other approaches resulted in behaviour changes
for other dumpers which felt wrong. In particular, I wanted to avoid
changing the order of the output for --symbols --dyn-symbols for LLVM
style, keep what is emitted by --symbols unchanged for all dumpers, and
avoid having different orders of .dynsym and .symtab dumping for GNU
"--symbols" and "--symbols --dyn-symbols".
Reviewed by: grimar, rupprecht
Differential Revision: https://reviews.llvm.org/D57016
llvm-svn: 351960
In r287786, the behaviour of --dyn-symbols in llvm-readelf (but not
llvm-readobj) was changed to print the dynamic symbols as derived from
the hash table, rather than to print the dynamic symbol table contents
directly. The original change was initially submitted without review,
and some comments were made on the commit mailing list implying that the
new behavious is GNU compatible. I argue that it is not:
1) It does not include a null symbol.
2) It prints the symbols based on an order derived from the hash
table.
3) It prints an extra column indicating which bucket it came from.
This could break parsers that expect a fixed number of columns,
with the first column being the symbol index.
4) If the input happens to have both .hash and .gnu.hash section, it
prints interpretations of them both, resulting in most symbols
being printed twice.
5) There is no way of just printing the raw dynamic symbol table,
because --symbols also prints the static symbol table.
This patch reverts the --dyn-symbols behaviour back to its old behaviour
of just printing the contents of the dynamic symbol table, similar to
what is printed by --symbols. As the hashed interpretation is still
desirable to validate the hash table, it puts it under a new switch
"--hash-symbols". This is a no-op on all output forms except for GNU
output style for ELF. If there is no hash table, it does nothing,
unlike the previous behaviour which printed the raw dynamic symbol
table, since the raw dynsym is available under --dyn-symbols.
The yaml input for the test is based on that in
test/tools/llvm-readobj/demangle.test, but stripped down to the bare
minimum to provide a valid dynamic symbol.
Note: some LLD tests needed updating. I will commit a separate patch for
those.
Reviewed by: grimar, rupprecht
Differential Revision: https://reviews.llvm.org/D56910
llvm-svn: 351789
George Rimar