[PATCH] D18330: [ELF/AArch64] Implemented set of R_AARCH64_TLSDESC_* relocations.

[Adhemerval Zanella via llvm-commits]

zatrazz created this revision.
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This patch implements next relocations:

R_AARCH64_TLSDESC_ADR_PAGE21, R_AARCH64_TLSDESC_LD64_LO12_NC,
R_AARCH64_TLSDESC_ADD_LO12_NC, R_AARCH64_TLSDESC_CALL.

They have lazy relocation nature, so require entries in got.plt. Each one
is double sized. Also special Plt entry with resolver is created in
addition to single got entry. A module that uses lazy TLSDESC relocations
must define next two entries in dynamic section:

 DT_TLSDESC_PLT - Location of PLT entry for TLS descriptor resolver calls.
DT_TLSDESC_GOT - Location of GOT entry used by TLS descriptor resolver PLT entry.

More information can be found in "Thread-Local Storage Descriptors for IA32 and
AMD64/EM64T" and "Thread-Local Storage Descriptors for the ARM platform"
(http://www.fsfla.org/~lxoliva/writeups/TLS/RFC-TLSDESC-x86.txt,
http://www.fsfla.org/~lxoliva/writeups/TLS/RFC-TLSDESC-ARM.txt)

Sample app to see them on AArch64 is:
__thread int foo;
int main() {
  foo = 5;
}
aarch64-linux-gnu-g++ -fPIC test.cpp -S -o test.s

PS: this patch is based on http://reviews.llvm.org/D16201

Repository:
  rL LLVM

http://reviews.llvm.org/D18330

Files:
  ELF/InputSection.cpp
  ELF/OutputSections.cpp
  ELF/OutputSections.h
  ELF/Symbols.cpp
  ELF/Symbols.h
  ELF/Target.cpp
  ELF/Target.h
  ELF/Writer.cpp
  test/ELF/aarch64-tls-desc.s

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