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[ELF] InX::BssRelRo should check section contents before marking relro 

When a linker script is used with a pattern like { *(.bss .bss.*) } the
InX::BssRelRo section will match against .bss.*. By matching on the name
only, in the same way that .data.rel.ro works we prevent this
from happening, but permit scripts that want to explicitly provide
a .bss.rel.ro OutputSection.
    
Differential Revision: https://reviews.llvm.org/D40735

llvm-svn: 319755
This commit is contained in:
Peter Smith 2017-12-05 11:15:58 +00:00
parent 86c40db49d
commit 7c40f93f38
2 changed files with 43 additions and 9 deletions
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12
lld/ELF/Writer.cpp
View File

@ -576,20 +576,14 @@ static bool isRelroSection(const OutputSection *Sec) {
if (Sec == InX::Dynamic->getParent())
return true;
// .bss.rel.ro is used for copy relocations for read-only symbols.
// Since the dynamic linker needs to process copy relocations, the
// section cannot be read-only, but once initialized, they shouldn't
// change.
if (Sec == InX::BssRelRo->getParent())
return true;
// Sections with some special names are put into RELRO. This is a
// bit unfortunate because section names shouldn't be significant in
// ELF in spirit. But in reality many linker features depend on
// magic section names.
StringRef S = Sec->Name;
return S == ".data.rel.ro" || S == ".ctors" || S == ".dtors" || S == ".jcr" ||
S == ".eh_frame" || S == ".openbsd.randomdata";
return S == ".data.rel.ro" || S == ".bss.rel.ro" || S == ".ctors" ||
S == ".dtors" || S == ".jcr" || S == ".eh_frame" ||
S == ".openbsd.randomdata";
}
// We compute a rank for each section. The rank indicates where the

40
lld/test/ELF/relro-copyrel-bss-script.s Normal file
View File

@ -0,0 +1,40 @@
// REQUIRES: x86
// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/shared.s -o %t.o
// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/copy-in-shared.s -o %t2.o
// RUN: ld.lld -shared %t.o %t2.o -o %t.so
// A linker script that will map .bss.rel.ro into .bss.
// RUN: echo "SECTIONS { \
// RUN: .bss : { *(.bss) *(.bss.*) } \
// RUN: } " > %t.script
// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t3.o
// RUN: ld.lld %t3.o %t.so -z relro -o %t --script=%t.script 2>&1
// RUN: llvm-readobj --program-headers %t | FileCheck %s
.section .text, "ax", @progbits
.global bar
.global foo
.global _start
_start:
callq bar
// Will produce .bss.rel.ro that will match in .bss, this will lose
// the relro property of the copy relocation.
.quad foo
// Non relro bss
.bss
// make large enough to affect PT_GNU_RELRO MemSize if this was marked
// as relro.
.space 0x2000
// CHECK: Type: PT_GNU_RELRO (0x6474E552)
// CHECK-NEXT: Offset:
// CHECK-NEXT: VirtualAddress:
// CHECK-NEXT: PhysicalAddress:
// CHECK-NEXT: FileSize:
// CHECK-NEXT: MemSize: 4096
// CHECK-NEXT: Flags [ (0x4)
// CHECK-NEXT: PF_R (0x4)
// CHECK-NEXT: ]
// CHECK-NEXT: Alignment: 1
// CHECK-NEXT: }