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ELF: Omit PT_GNU_STACK segment if -z execstack is provided. 

In the previous patch (r254003), I made the linker emit PT_GNU_STACK
unconditionally. But sometimes you want to have a control over the
presence of the segment. With this patch, you can omit the segment
by passing -z execstack option.

llvm-svn: 254039
This commit is contained in:
Rui Ueyama 2015-11-24 23:42:33 +00:00
parent 28b700373e
commit a46566f2db
2 changed files with 28 additions and 43 deletions
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13
lld/ELF/Writer.cpp
View File

@ -933,12 +933,11 @@ template <class ELFT> void Writer<ELFT>::assignAddresses() {
// PT_GNU_STACK is a special section to tell the loader to make the // PT_GNU_STACK is a special section to tell the loader to make the
// pages for the stack non-executable. // pages for the stack non-executable.
Elf_Phdr *PH = &Phdrs[++PhdrIdx]; if (!Config->ZExecStack) {
PH->p_type = PT_GNU_STACK; Elf_Phdr *PH = &Phdrs[++PhdrIdx];
if (Config->ZExecStack) PH->p_type = PT_GNU_STACK;
PH->p_flags = PF_R | PF_W | PF_X;
else
PH->p_flags = PF_R | PF_W; PH->p_flags = PF_R | PF_W;
}
// Fix up PT_INTERP as we now know the address of .interp section. // Fix up PT_INTERP as we now know the address of .interp section.
if (Interp) { if (Interp) {
@ -962,11 +961,13 @@ template <class ELFT> void Writer<ELFT>::assignAddresses() {
// Returns the number of PHDR entries. // Returns the number of PHDR entries.
template <class ELFT> int Writer<ELFT>::getPhdrsNum() const { template <class ELFT> int Writer<ELFT>::getPhdrsNum() const {
bool Tls = false; bool Tls = false;
int I = 3; // 3 for PT_PHDR, first PT_LOAD and PT_GNU_STACK int I = 2; // 2 for PT_PHDR and first PT_LOAD
if (needsInterpSection()) if (needsInterpSection())
++I; ++I;
if (isOutputDynamic()) if (isOutputDynamic())
++I; ++I;
if (!Config->ZExecStack)
++I;
uintX_t Last = PF_R; uintX_t Last = PF_R;
for (OutputSectionBase<ELFT> *Sec : OutputSections) { for (OutputSectionBase<ELFT> *Sec : OutputSections) {
if (!needsPhdr<ELFT>(Sec)) if (!needsPhdr<ELFT>(Sec))

58
lld/test/ELF/gnustack.s
View File

@ -1,46 +1,30 @@
# REQUIRES: x86 # REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1
# RUN: ld.lld %t1 -z execstack -o %t # RUN: ld.lld %t1 -z execstack -o %t
# RUN: llvm-readobj --program-headers -s %t | FileCheck --check-prefix=CHECK_RWX %s # RUN: llvm-readobj --program-headers -s %t | FileCheck --check-prefix=RWX %s
# RUN: ld.lld %t1 -o %t # RUN: ld.lld %t1 -o %t
# RUN: llvm-readobj --program-headers -s %t | FileCheck --check-prefix=CHECK_RW %s # RUN: llvm-readobj --program-headers -s %t | FileCheck --check-prefix=RW %s
# CHECK_RW: Sections [ # RW: Sections [
# CHECK_RW-NOT: Name: .note.GNU-stack # RW-NOT: Name: .note.GNU-stack
# CHECK_RW: ProgramHeaders [ # RW: ProgramHeaders [
# CHECK_RW: ProgramHeader { # RW: ProgramHeader {
# CHECK_RW: Type: PT_GNU_STACK # RW: Type: PT_GNU_STACK
# CHECK_RW-NEXT: Offset: 0x0 # RW-NEXT: Offset: 0x0
# CHECK_RW-NEXT: VirtualAddress: 0x0 # RW-NEXT: VirtualAddress: 0x0
# CHECK_RW-NEXT: PhysicalAddress: 0x0 # RW-NEXT: PhysicalAddress: 0x0
# CHECK_RW-NEXT: FileSize: 0 # RW-NEXT: FileSize: 0
# CHECK_RW-NEXT: MemSize: 0 # RW-NEXT: MemSize: 0
# CHECK_RW-NEXT: Flags [ # RW-NEXT: Flags [
# CHECK_RW-NEXT: PF_R # RW-NEXT: PF_R
# CHECK_RW-NEXT: PF_W # RW-NEXT: PF_W
# CHECK_RW-NEXT: ] # RW-NEXT: ]
# CHECK_RW-NEXT: Alignment: 0 # RW-NEXT: Alignment: 0
# CHECK_RW-NEXT: } # RW-NEXT: }
# CHECK_RW-NEXT: ] # RW-NEXT: ]
# CHECK_RWX: Sections [ # RWX-NOT: Name: .note.GNU-stack
# CHECK_RWX-NOT: Name: .note.GNU-stack # RWX-NOT: Type: PT_GNU_STACK
# CHECK_RWX: ProgramHeaders [
# CHECK_RWX: ProgramHeader {
# CHECK_RWX: Type: PT_GNU_STACK
# CHECK_RWX-NEXT: Offset: 0x0
# CHECK_RWX-NEXT: VirtualAddress: 0x0
# CHECK_RWX-NEXT: PhysicalAddress: 0x0
# CHECK_RWX-NEXT: FileSize: 0
# CHECK_RWX-NEXT: MemSize: 0
# CHECK_RWX-NEXT: Flags [
# CHECK_RWX-NEXT: PF_R
# CHECK_RWX-NEXT: PF_W
# CHECK_RWX-NEXT: PF_X
# CHECK_RWX-NEXT: ]
# CHECK_RWX-NEXT: Alignment: 0
# CHECK_RWX-NEXT: }
# CHECK_RWX-NEXT: ]
.globl _start .globl _start
_start: _start: