Commit Graph

7 Commits

Author SHA1 Message Date
Fangrui Song f66b767abe [ELF][AArch64] Allow PT_LOAD to have overlapping p_offset ranges
Ported the D64906 technique to AArch64. It deletes 3 alignments at
PT_LOAD boundaries for the default case: the size of an aarch64 binary
decreases by at most 192kb.

If `sh_addralign(.tdata) < sh_addralign(.tbss)`,
we can potentially make `p_vaddr(PT_TLS)%p_align(PT_TLS) != 0`.

ld.so that are known to have problems if p_vaddr%p_align!=0:

* musl<=1.1.22
* FreeBSD 13.0-CURRENT (and before) rtld-elf arm64

New test aarch64-tls-vaddr-align.s checks that our workaround makes p_vaddr%p_align = 0.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D64930

llvm-svn: 369344
2019-08-20 08:34:56 +00:00
Fangrui Song 5387c2cd17 [llvm-objdump] Print newlines before and after "Disassembly of section ...:"
This improves readability and the behavior is consistent with GNU objdump.

The new test test/tools/llvm-objdump/X86/disassemble-section-name.s
checks we print newlines before and after "Disassembly of section ...:"

Differential Revision: https://reviews.llvm.org/D61127

llvm-svn: 359668
2019-05-01 10:40:48 +00:00
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
Jordan Rupprecht d768ecf5a7 [lld][NFC] Use explicit --symbols instead of -t in tests using llvm-readelf.
llvm-svn: 346260
2018-11-06 19:34:22 +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
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
Davide Italiano f681a8fa3a [AArch64] Implement R_AARCH64_ LD_PREL_LO19.
Fixes PR34660.

Differential Revision:  https://reviews.llvm.org/D38053

llvm-svn: 313841
2017-09-20 23:49:50 +00:00