maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[ELF] Define __ehdr_start unconditionally even when using linker script 

This behavior differs from the semantics implemented by GNU linkers
which only define this symbol iff ELF headers are in the memory
mapped segment.

Differential Revision: https://reviews.llvm.org/D33019

llvm-svn: 302687
This commit is contained in:
Petr Hosek 2017-05-10 16:20:33 +00:00
parent 40c012654e
commit 6b936bf6c7
2 changed files with 17 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
lld/ELF/Writer.cpp
View File

@ -859,13 +859,16 @@ template <class ELFT> void Writer<ELFT>::addReservedSymbols() {
if (!In<ELFT>::DynSymTab)
Symtab<ELFT>::X->addIgnored("__tls_get_addr");
// __ehdr_start is the location of ELF file headers. Note that we define
// this symbol unconditionally even when using a linker script, which
// differs from the behavior implemented by GNU linker which only define
// this symbol if ELF headers are in the memory mapped segment.
addOptionalRegular<ELFT>("__ehdr_start", Out::ElfHeader, 0, STV_HIDDEN);
// If linker script do layout we do not need to create any standart symbols.
if (Script->Opt.HasSections)
return;
// __ehdr_start is the location of ELF file headers.
addOptionalRegular<ELFT>("__ehdr_start", Out::ElfHeader, 0, STV_HIDDEN);
auto Add = [](StringRef S) {
return addOptionalRegular<ELFT>(S, Out::ElfHeader, 0, STV_DEFAULT);
};

14
lld/test/ELF/linkerscript/ehdr_start.s
View File

@ -2,9 +2,17 @@
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
# RUN: echo "SECTIONS { }" > %t.script
# RUN: not ld.lld %t.o -script %t.script -o %t 2>&1 | FileCheck %s
# CHECK: error: undefined symbol: __ehdr_start
# CHECK: >>> referenced by {{.*}}:(.text+0x0)
# RUN: ld.lld %t.o -script %t.script -o %t
# RUN: llvm-readobj -symbols %t | FileCheck %s
# CHECK: Name: __ehdr_start (1)
# CHECK-NEXT: Value: 0x0
# CHECK-NEXT: Size: 0
# CHECK-NEXT: Binding: Local (0x0)
# CHECK-NEXT: Type: None (0x0)
# CHECK-NEXT: Other [ (0x2)
# CHECK-NEXT: STV_HIDDEN (0x2)
# CHECK-NEXT: ]
# CHECK-NEXT: Section: .text (0x1)
.text
.global _start, __ehdr_start