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Fangrui Song 07f8daf05e [ELF] Simplify RelRo, TLS, NOBITS section ranks and make RW PT_LOAD start with RelRo 
Old: PT_LOAD(.data | PT_GNU_RELRO(.data.rel.ro .bss.rel.ro) | .bss)
New: PT_LOAD(PT_GNU_RELRO(.data.rel.ro .bss.rel.ro) | .data .bss)

The placement of | indicates page alignment caused by PT_GNU_RELRO. The
new layout has simpler rules and saves space for many cases.

Old size: roundup(.data) + roundup(.data.rel.ro)
New size: roundup(.data.rel.ro + .bss.rel.ro) + .data

Other advantages:

* At runtime the 3 memory mappings decrease to 2.
* start(PT_TLS) = start(PT_GNU_RELRO) = start(RW PT_LOAD). This
  simplifies binary manipulation tools.
  GNU strip before 2.31 discards PT_GNU_RELRO if its
  address is not equal to the start of its associated PT_LOAD.
  This has been fixed by https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f2731e0c374e5323ce4cdae2bcc7b7fe22da1a6f
  But with this change, we will be compatible with GNU strip before 2.31
* Before, .got.plt (non-relro by default) was placed before .got (relro
  by default), which made it impossible to have _GLOBAL_OFFSET_TABLE_
  (start of .got.plt on x86-64) equal to the end of .got (R_GOT*_FROM_END)
  (https://bugs.llvm.org/show_bug.cgi?id=36555). With the new ordering, we
  can improve on this regard if we'd like to.

Reviewers: ruiu, espindola, pcc

Subscribers: emaste, arichardson, llvm-commits, joerg, jdoerfert

Differential Revision: https://reviews.llvm.org/D56828

llvm-svn: 356117
 		2019-03-14 03:47:45 +00:00
..
COFF lld-link: Only print demangled symbol names by default 2019-03-11 23:02:18 +00:00
Common Fail early if an output file is not writable 2019-03-11 16:30:55 +00:00
ELF [ELF] Simplify RelRo, TLS, NOBITS section ranks and make RW PT_LOAD start with RelRo 2019-03-14 03:47:45 +00:00
MinGW [MinGW] Hook up the --exclude-all-symbols option 2019-02-19 21:57:49 +00:00
cmake/modules [CMake] Properly conditionalize installation of lld libraries 2018-03-09 13:09:36 +00:00
docs Reland "[Remarks] Add -foptimization-record-passes to filter remark emission" 2019-03-12 21:22:27 +00:00
include/lld Fail early if an output file is not writable 2019-03-11 16:30:55 +00:00
lib Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
test [ELF] Simplify RelRo, TLS, NOBITS section ranks and make RW PT_LOAD start with RelRo 2019-03-14 03:47:45 +00:00
tools/lld Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
unittests Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
utils Update the file headers across all of the LLVM projects in the monorepo 2019-01-19 08:50:56 +00:00
wasm [WebAssembly] Improve support for "needed" list in dylink section 2019-03-13 21:29:20 +00:00
.arcconfig
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.clang-format
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.gitignore
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CMakeLists.txt
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CODE_OWNERS.TXT
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LICENSE.TXT Fix typos throughout the license files that somehow I and my reviewers 2019-01-21 09:52:34 +00:00
README.md
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README.md

LLVM Linker (lld)

This directory and its subdirectories contain source code for the LLVM Linker, a modular cross platform linker which is built as part of the LLVM compiler infrastructure project.

lld is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt.

Benchmarking

In order to make sure various developers can evaluate patches over the same tests, we create a collection of self contained programs.

It is hosted at https://s3-us-west-2.amazonaws.com/linker-tests/lld-speed-test.tar.xz

The current sha256 is 10eec685463d5a8bbf08d77f4ca96282161d396c65bd97dc99dbde644a31610f.