tequilaOS/platform_bionic
2
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

Merge "Overalign the TLS segment using crtbegin"

Browse source 
am: fc5535074d

Change-Id: I78ec892457e29a88fdb5c75a173f5728ba92aa31
This commit is contained in:
Ryan Prichard 2019-05-28 16:57:22 -07:00 committed by android-build-merger
commit 55cac03181
1 changed files with 39 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

39
libc/arch-common/bionic/crtbegin.c
View file

@ -63,6 +63,45 @@ __asm__(PRE "movq %rsp,%rdi; andq $~0xf,%rsp; callq _start_main" POST);
#undef PRE
#undef POST
// On arm32 and arm64, when targeting Q and up, overalign the TLS segment to
// (8 * sizeof(void*)), which reserves enough space between the thread pointer
// and the executable's TLS segment for Bionic's TLS slots. It has the side
// effect of placing a 0-sized TLS segment into Android executables that don't
// use TLS, but this should be harmless.
//
// To ensure that the .tdata input section isn't deleted, the .text input
// section (which contains _start) has a relocation to the .tdata input section.
//
// TODO: This file currently uses TPREL relocations from .text to ensure that
// --gc-sections doesn't remove the .tdata input section. The relocations are
// resolved by the static linker. (They don't appear in the executable.) Replace
// the TPREL relocations with R_{ARM,AARCH64}_NONE once the toolchain has been
// updated to support them:
// - https://reviews.llvm.org/D61992 (Support .reloc *, R_ARM_NONE, *)
// - https://reviews.llvm.org/D61973 (Support .reloc *, R_AARCH64_NONE, *)
// - https://reviews.llvm.org/D62052 (lld -r: fix R_*_NONE to section symbols on Elf*_Rel targets)
#if __ANDROID_API__ >= __ANDROID_API_Q__
#if defined(__arm__)
asm(" .section .tdata,\"awT\",%progbits\n"
" .p2align 5\n"
"__tls_align:\n"
" .text\n"
" .type __tls_align_reference,%function\n"
"__tls_align_reference:\n"
" .long __tls_align(TPOFF)\n"
" .size __tls_align_reference, .-__tls_align_reference\n");
#elif defined(__aarch64__)
asm(" .section .tdata,\"awT\",@progbits\n"
" .p2align 6\n"
"__tls_align:\n"
" .text\n"
" .type __tls_align_reference,%function\n"
"__tls_align_reference:\n"
" add x0, x0, :tprel_lo12_nc:__tls_align\n"
" .size __tls_align_reference, .-__tls_align_reference\n");
#endif
#endif
#include "__dso_handle.h"
#include "atexit.h"
#include "pthread_atfork.h"