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[ELF] Do not skip relocation scanning checking if the symbol gets dynamic COPY relocation already

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It is possible that the same symbol referenced by two kinds of
relocations at the same time. The first type requires say GOT entry
creation, the second type requires dynamic copy relocation. For MIPS
targets they might be R_MIPS_GOT16 and R_MIPS_HI16 relocations. For X86
target they might be R_386_GOT32 and R_386_32 respectively.

Now LLD never creates GOT entry for a symbol if this symbol already has
related copy relocation. This patch solves this problem.

Differential Revision: http://reviews.llvm.org/D18862

llvm-svn: 265910
This commit is contained in:
Simon Atanasyan
2016-04-10 21:48:55 +00:00
parent f9e4576e08
commit 2615c3846f
3 changed files with 80 additions and 4 deletions
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7
lld/ELF/Writer.cpp
View File

@@ -382,10 +382,9 @@ void Writer<ELFT>::scanRelocs(InputSectionBase<ELFT> &C, ArrayRef<RelTy> Rels) {
// If a symbol in a DSO is referenced directly instead of through GOT,
// we need to create a copy relocation for the symbol.
if (auto *B = dyn_cast<SharedSymbol<ELFT>>(&Body)) {
if (B->needsCopy())
continue;
if (Target->needsCopyRel<ELFT>(Type, *B)) {
addCopyRelSymbol(B);
if (Target->needsCopyRel<ELFT>(Type, Body)) {
if (!B->needsCopy())
addCopyRelSymbol(B);
continue;
}
}

26
lld/test/ELF/i386-got-and-copy.s Normal file
View File

@@ -0,0 +1,26 @@
# REQUIRES: x86
# If there are two relocations such that the first one requires
# dynamic COPY relocation, the second one requires GOT entry
# creation, linker should create both - dynamic relocation
# and GOT entry.
# RUN: llvm-mc -filetype=obj -triple=i386-pc-linux \
# RUN: %S/Inputs/copy-in-shared.s -o %t.so.o
# RUN: llvm-mc -filetype=obj -triple=i386-pc-linux %s -o %t.o
# RUN: ld.lld %t.so.o -shared -o %t.so
# RUN: ld.lld %t.o %t.so -o %t.exe
# RUN: llvm-readobj -r %t.exe | FileCheck %s
# CHECK: Relocations [
# CHECK-NEXT: Section (4) .rel.dyn {
# CHECK-NEXT: 0x{{[0-9A-F]+}} R_386_COPY foo
# CHECK-NEXT: 0x{{[0-9A-F]+}} R_386_GLOB_DAT foo
# CHECK-NEXT: }
# CHECK-NEXT: ]
.text
.global _start
_start:
movl $foo, (%esp) # R_386_32 - requires R_386_COPY relocation
movl foo@GOT, %eax # R_386_GOT32 - requires GOT entry

51
lld/test/ELF/mips-got-and-copy.s Normal file
View File

@@ -0,0 +1,51 @@
# REQUIRES: mips
# If there are two relocations such that the first one requires
# dynamic COPY relocation, the second one requires GOT entry
# creation, linker should create both - dynamic relocation
# and GOT entry.
# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux \
# RUN: %S/Inputs/mips-dynamic.s -o %t.so.o
# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t.o
# RUN: ld.lld %t.so.o -shared -o %t.so
# RUN: ld.lld %t.o %t.so -o %t.exe
# RUN: llvm-readobj -r -mips-plt-got %t.exe | FileCheck %s
# CHECK: Relocations [
# CHECK-NEXT: Section (7) .rel.dyn {
# CHECK-NEXT: 0x{{[0-9A-F]+}} R_MIPS_COPY data0
# CHECK-NEXT: 0x{{[0-9A-F]+}} R_MIPS_COPY data1
# CHECK-NEXT: }
# CHECK-NEXT: ]
# CHECK-NEXT: Primary GOT {
# CHECK-NEXT: Canonical gp value: 0x37FF0
# CHECK-NEXT: Reserved entries [
# CHECK: ]
# CHECK-NEXT: Local entries [
# CHECK-NEXT: ]
# CHECK-NEXT: Global entries [
# CHECK-NEXT: Entry {
# CHECK: Section: .bss
# CHECK-NEXT: Name: data0
# CHECK-NEXT: }
# CHECK-NEXT: Entry {
# CHECK: Section: .bss
# CHECK-NEXT: Name: data1
# CHECK-NEXT: }
# CHECK-NEXT: ]
# CHECK-NEXT: Number of TLS and multi-GOT entries: 0
# CHECK-NEXT: }
.text
.global __start
__start:
# Case A: 'got' relocation goes before 'copy' relocation
lui $t0,%hi(data0) # R_MIPS_HI16 - requires R_MISP_COPY relocation
addi $t0,$t0,%lo(data0)
lw $t0,%got(data0)($gp) # R_MIPS_GOT16 - requires GOT entry
# Case B: 'copy' relocation goes before 'got' relocation
lw $t0,%got(data1)($gp) # R_MIPS_GOT16 - requires GOT entry
lui $t0,%hi(data1) # R_MIPS_HI16 - requires R_MISP_COPY relocation
addi $t0,$t0,%lo(data1)