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[ELF] Add sh_link field to .ARM.exidx sections for relocatable links 

When doing a relocatable link the .ARM.exidx sections with the
SHF_LINK_ORDER flag set need to set the sh_link field to the executable
section they describe. We find the appropriate OutputSection by
following the sh_link field of the .ARM.exidx InputSections.
    
The getOutputSectionName() function rules make sure that when there are
multiple .ARM.exidx InputSections in an OutputSection they all have the
same sh_link field.

Differential revision: https://reviews.llvm.org/D25825

llvm-svn: 284820
This commit is contained in:
Peter Smith 2016-10-21 11:25:33 +00:00
parent eb01a169c2
commit 580ba95b16
2 changed files with 113 additions and 3 deletions
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18
lld/ELF/OutputSections.cpp
View File

@ -933,9 +933,21 @@ OutputSection<ELFT>::OutputSection(StringRef Name, uint32_t Type, uintX_t Flags)
template <class ELFT> void OutputSection<ELFT>::finalize() {
uint32_t Type = this->Header.sh_type;
// SHF_LINK_ORDER only has meaning in relocatable objects
if (!Config->Relocatable)
this->Header.sh_flags &= ~SHF_LINK_ORDER;
if (this->Header.sh_flags & SHF_LINK_ORDER) {
if (!Config->Relocatable) {
// SHF_LINK_ORDER only has meaning in relocatable objects
this->Header.sh_flags &= ~SHF_LINK_ORDER;
}
else if (!this->Sections.empty()) {
// When doing a relocatable link we must preserve the link order
// dependency of sections with the SHF_LINK_ORDER flag. The dependency
// is indicated by the sh_link field. We need to translate the
// InputSection sh_link to the OutputSection sh_link, all InputSections
// in the OutputSection have the same dependency.
if (auto *D = this->Sections.front()->getLinkOrderDep())
this->Header.sh_link = D->OutSec->SectionIndex;
}
}
if (Type != SHT_RELA && Type != SHT_REL)
return;
this->Header.sh_link = Out<ELFT>::SymTab->SectionIndex;

98
lld/test/ELF/arm-exidx-relocatable.s Normal file
View File

@ -0,0 +1,98 @@
// RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %s -o %t
// RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %S/Inputs/arm-exidx-cantunwind.s -o %tcantunwind
// Check that relocatable link maintains SHF_LINK_ORDER
// RUN: ld.lld -r %t %tcantunwind -o %t4 2>&1
// RUN: llvm-readobj -s %t4 | FileCheck %s
// REQUIRES: arm
// Each assembler created .ARM.exidx section has the SHF_LINK_ORDER flag set
// with the sh_link containing the section index of the executable section
// containing the function it describes. To maintain this property in
// relocatable links we pass through the .ARM.exidx section, the section it
// it has a sh_link to, and the associated relocation sections uncombined.
.syntax unified
.section .text, "ax",%progbits
.globl _start
_start:
.fnstart
bx lr
.cantunwind
.fnend
.section .text.f1, "ax", %progbits
.globl f1
f1:
.fnstart
bx lr
.cantunwind
.fnend
.section .text.f2, "ax", %progbits
.globl f2
f2:
.fnstart
bx lr
.cantunwind
.fnend
.globl f3
f3:
.fnstart
bx lr
.cantunwind
.fnend
// CHECK: Name: .ARM.exidx
// CHECK-NEXT: Type: SHT_ARM_EXIDX (0x70000001)
// CHECK-NEXT: Flags [ (0x82)
// CHECK-NEXT: SHF_ALLOC (0x2)
// CHECK-NEXT: SHF_LINK_ORDER (0x80)
// CHECK: Size: 24
// CHECK-NEXT: Link: 7
// CHECK: Name: .ARM.exidx.text.f1
// CHECK-NEXT: Type: SHT_ARM_EXIDX (0x70000001)
// CHECK-NEXT: Flags [ (0x82)
// CHECK-NEXT: SHF_ALLOC (0x2)
// CHECK-NEXT: SHF_LINK_ORDER (0x80)
// CHECK: Size: 8
// CHECK-NEXT: Link: 8
// CHECK: Name: .ARM.exidx.text.f2
// CHECK-NEXT: Type: SHT_ARM_EXIDX (0x70000001)
// CHECK-NEXT: Flags [ (0x82)
// CHECK-NEXT: SHF_ALLOC (0x2)
// CHECK-NEXT: SHF_LINK_ORDER (0x80)
// CHECK: Size: 16
// CHECK-NEXT: Link: 9
// CHECK: Name: .ARM.exidx.func1
// CHECK-NEXT: Type: SHT_ARM_EXIDX (0x70000001)
// CHECK-NEXT: Flags [ (0x82)
// CHECK-NEXT: SHF_ALLOC (0x2)
// CHECK-NEXT: SHF_LINK_ORDER (0x80)
// CHECK: Size: 8
// CHECK-NEXT: Link: 10
// CHECK: Name: .ARM.exidx.func2
// CHECK-NEXT: Type: SHT_ARM_EXIDX (0x70000001)
// CHECK-NEXT: Flags [ (0x82)
// CHECK-NEXT: SHF_ALLOC (0x2)
// CHECK-NEXT: SHF_LINK_ORDER (0x80)
// CHECK: Size: 8
// CHECK-NEXT: Link: 11
// CHECK: Name: .ARM.exidx.func3
// CHECK-NEXT: Type: SHT_ARM_EXIDX (0x70000001)
// CHECK-NEXT: Flags [ (0x82)
// CHECK-NEXT: SHF_ALLOC (0x2)
// CHECK-NEXT: SHF_LINK_ORDER (0x80)
// CHECK: Size: 8
// CHECK-NEXT: Link: 12
// CHECK: Index: 7
// CHECK-NEXT: Name: .text
// CHECK: Index: 8
// CHECK-NEXT: Name: .text.f1
// CHECK: Index: 9
// CHECK-NEXT: Name: .text.f2
// CHECK: Index: 10
// CHECK-NEXT: Name: .func1
// CHECK: Index: 11
// CHECK-NEXT: Name: .func2
// CHECK: Index: 12
// CHECK-NEXT: Name: .func3