Commit Graph

15 Commits

Author SHA1 Message Date
Fangrui Song 011b785505 [ELF] Create readonly PT_LOAD in the presence of a SECTIONS command
This essentially drops the change by r288021 (discussed with Georgii Rymar
and Peter Smith and noted down in the release note of lld 10).

GNU ld>=2.31 enables -z separate-code by default for Linux x86. By
default (in the absence of a PHDRS command) a readonly PT_LOAD is
created, which is different from its traditional behavior.

Not emulating GNU ld's traditional behavior is good for us because it
improves code consistency (we create a readonly PT_LOAD in the absence
of a SECTIONS command).

Users can add --no-rosegment to restore the previous behavior (combined
readonly and read-executable sections in a single RX PT_LOAD).
2020-03-19 19:11:11 -07:00
Jordan Rupprecht 5bd334aef7 [lld][NFC] Update tests to use -S instead of -s when using llvm-readelf.
Summary: llvm-readobj/readelf accepts both -s and -S as aliases for --sections. However with GNU readelf only -S means --section, and -s means --symbols. I would like to make llvm-readelf more compatible.

Reviewers: MaskRay, espindola

Reviewed By: MaskRay

Subscribers: emaste, arichardson, steven_wu, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D54118

llvm-svn: 346164
2018-11-05 20:39:06 +00:00
Fangrui Song 3d87323a7e [ELF] Make non-writable non-executable PROGBITS sections closer to .text
This generalizes the old heuristic placing SHT_DYNSYM SHT_DYNSTR first in the readonly SHF_ALLOC segment.

Reviewers: espindola

Subscribers: emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D48406

llvm-svn: 335674
2018-06-26 22:13:32 +00:00
Fangrui Song 68fa4e8c34 [ELF] Assign RF_EXEC rank even if --no-rosegment or SECTIONS command is used
Summary:
Currently when --no-rosegment is specified or a linker script with SECTIONS command is used,
.rodata (A) .text (AX) are assigned the same rank and .rodata may be placed after .text .
This increases the gap between .text and .bss and can cause pc-relative relocation overflow (e.g. gcc crtbegin.o crtbegin.S have R_X86_64_PC32 relocation from .text to .bss).

This patch makes SingleRoRx affect only segment layout, not section layout. As a consequence, .rodata will be placed before .text regardless of SingleRoRx.

Reviewers: espindola, ruiu, grimar, echristo, javed.absar

Subscribers: emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D48405

llvm-svn: 335627
2018-06-26 17:04:47 +00:00
Fangrui Song 5ea154402e [ELF] Change test files for style consistency. NFC
* Move `REQUIRES:` line to the top
* llvm-mc ... -o %t -> llvm-mc ... -o %t.o
* Don't check "TEXT" "DATA" columns (they are bfd-style names that do
not fit into llvm well) in llvm-objdump output

llvm-svn: 335498
2018-06-25 17:07:40 +00:00
Fangrui Song 65c50074c2 [ELF] readobj -elf-output-style=GNU -> readelf
Style change for consistency. NFC

llvm-svn: 335494
2018-06-25 16:49:52 +00:00
Han Shen b56030ee9e [lld] Mitigate relocation overflow [part 1 of 2].
This CL places .dynsym and .dynstr at the beginning of SHF_ALLOC
sections. We do this to mitigate the possibility that huge .dynsym and
.dynstr sections placed between ro-data and text sections cause
relocation overflow.

Differential Revision: https://reviews.llvm.org/D45788

llvm-svn: 332374
2018-05-15 17:02:35 +00:00
George Rimar 4c9ae67bb7 [ELF] - Revert of: r332038, r332054, r332060, r332061, r332062, r332063
This reverts "Mitigate relocation overflow [part 1 of 2]." and the following commits which
were trying to fix the bots.

At the moment of r332082, bots are still failing and we need to find the reason of test case breakages first of all.
http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast/builds/17042/steps/test/logs/stdio
http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/29845/steps/test/logs/stdio

llvm-svn: 332085
2018-05-11 08:11:25 +00:00
Han Shen 6c0881c3cd Mitigate relocation overflow [part 1 of 2].
This CL is to mitigate R_X86_64_PC32 relocation overflow problems for huge binaries that has near 4G allocated sections.

By examining those binaries, there're 2 issues contributes to the problem:
1). huge ".dynsym" and ".dynstr" stands in the way between .rodata and .text
2). _init_array_start/end are placed at 0 if no ".init_array" presents, this causes .text relocation against them become more prone to overflow.

This CL addresses 1st problem (the 2nd will be addressed in another CL.) by assigning a smaller sortrank to .dynsym and .dynstr thus they no longer stand in between.

llvm-svn: 332038
2018-05-10 20:44:42 +00:00
George Rimar d46753e421 [ELF] - Do --hash-style=both by default.
Its PR34712,

GNU linkers recently changed default values to "both" of "sysv".
Patch do the same for all targets except MIPS, where .gnu.hash
section is not yet supported.

Code suggested by Rui Ueyama.

Differential revision: https://reviews.llvm.org/D38407

llvm-svn: 315051
2017-10-06 09:37:44 +00:00
Rafael Espindola 0347c0b874 Don't create a bogus PT_PHDR if we don't allocate the headers.
llvm-svn: 292644
2017-01-20 20:46:15 +00:00
Rafael Espindola e979fd1bf0 Don't put ro before rx when using linker scripts.
Since they end up going on the same PT_LOAD, there is no reason to
sort them. This matches bfd's behaviour and is user visible in the
placement of orphan sections.

llvm-svn: 282799
2016-09-29 22:48:55 +00:00
Rafael Espindola b45fd70ef1 Disable --rosegment when we have linker scripts.
Linker scripts are responsible for aliging '.'. Since they are
designed for bfd which has no --rosegment, they don't align the RO to
RX transition.

llvm-svn: 281978
2016-09-20 15:22:27 +00:00
Rafael Espindola aab6d5c52a Put SHF_ALLOC sections first, even with linker scripts.
This matches gold and bfd, and is pretty much required by some linker
scripts. They end with commands like

foo   0 : { *(bar) }

if we put any SHF_ALLOC sections after they can have an address that
is too low.

llvm-svn: 281778
2016-09-16 21:29:07 +00:00
Rafael Espindola 1d98d6292f Make sure we create all necessary PT_LOADs.
We were some times stopping early when using linker scripts.

llvm-svn: 281647
2016-09-15 19:36:01 +00:00