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[ELF] - Do not ignore discarding of .rela.plt/.rela.dyn, allow doing custom layout for them. 

Currently when we build input sections list in linker script
we ignore all rel[a] sections. That was done to support
scripts like .rela.dyn : { *(.rela.data) } for emit relocs.

Though as a result following scripts were also silently ignored:

/DISCARD/ : { *(.rela.plt)
/DISCARD/ : { *(.rela.dyn)

and we produced output with this sections. That is not ideal.
The solution this patch suggests is simple: do not ignore synthetic
rel[a] sections. That way we can enable common discarding logic
for them and report a proper error.

Differential revision: https://reviews.llvm.org/D41640

llvm-svn: 328419
This commit is contained in:
George Rimar 2018-03-24 13:10:19 +00:00
parent 96d81916b0
commit d8281379f9
3 changed files with 31 additions and 2 deletions
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7
lld/ELF/LinkerScript.cpp
View File

@ -380,7 +380,10 @@ LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
// For -emit-relocs we have to ignore entries like
// .rela.dyn : { *(.rela.data) }
// which are common because they are in the default bfd script.
if (Sec->Type == SHT_REL || Sec->Type == SHT_RELA)
// We do not ignore SHT_REL[A] linker-synthesized sections here because
// want to support scripts that do custom layout for them.
if (!isa<SyntheticSection>(Sec) &&
(Sec->Type == SHT_REL || Sec->Type == SHT_RELA))
continue;
std::string Filename = getFilename(Sec->File);
@ -405,7 +408,7 @@ LinkerScript::computeInputSections(const InputSectionDescription *Cmd) {
void LinkerScript::discard(ArrayRef<InputSection *> V) {
for (InputSection *S : V) {
if (S == InX::ShStrTab || S == InX::Dynamic || S == InX::DynSymTab ||
S == InX::DynStrTab)
S == InX::DynStrTab || S == InX::RelaPlt || S == InX::RelaDyn)
error("discarding " + S->Name + " section is not allowed");
// You can discard .hash and .gnu.hash sections by linker scripts. Since

10
lld/test/ELF/linkerscript/discard-section-err.s
View File

@ -22,4 +22,14 @@
# RUN: FileCheck -check-prefix=DYNSTR %s
# DYNSTR: discarding .dynstr section is not allowed
# RUN: echo "SECTIONS { /DISCARD/ : { *(.rela.plt) } }" > %t.script
# RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \
# RUN: FileCheck -check-prefix=RELAPLT %s
# RELAPLT: discarding .rela.plt section is not allowed
# RUN: echo "SECTIONS { /DISCARD/ : { *(.rela.dyn) } }" > %t.script
# RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \
# RUN: FileCheck -check-prefix=RELADYN %s
# RELADYN: discarding .rela.dyn section is not allowed
.comm foo,4,4

16
lld/test/ELF/linkerscript/synthetic-relsec-layout.s Normal file
View File

@ -0,0 +1,16 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
# RUN: echo "SECTIONS { .foo : { *(.rela.dyn) } }" > %t.script
# RUN: ld.lld -T %t.script %t.o -o %t.so -shared
# RUN: llvm-readobj -r %t.so | FileCheck %s
# Check we are able to do custom layout for synthetic sections.
# (here we check we can place synthetic .rela.dyn into .foo).
# CHECK: Relocations [
# CHECK: Section ({{.*}}) .foo {
# CHECK: R_X86_64_64 .foo 0x0
# CHECK: }
.data
.quad .foo