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

Allow adding start/end symbols to any section 

Allows adding start and/or end symbols to special output sections,
like .eh_frame_hdr, which aren't lists of regular input sections. 

Differential revision: https://reviews.llvm.org/D23716

llvm-svn: 280205
This commit is contained in:
Eugene Leviant 2016-08-31 08:13:33 +00:00
parent 1e3b086749
commit 20889c51b7
2 changed files with 89 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
lld/ELF/LinkerScript.cpp
View File

@ -310,10 +310,43 @@ void LinkerScript<ELFT>::createSections(OutputSectionFactory<ELFT> &Factory) {
}
}
template <class ELFT> void assignOffsets(OutputSectionBase<ELFT> *Sec) {
// Linker script may define start and end symbols for special section types,
// like .got, .eh_frame_hdr, .eh_frame and others. Those sections are not a list
// of regular input input sections, therefore our way of defining symbols for
// regular sections will not work. The approach we use for special section types
// is not perfect - it handles only start and end symbols.
template <class ELFT>
void addStartEndSymbols(OutputSectionCommand *Cmd,
OutputSectionBase<ELFT> *Sec) {
bool Start = true;
BaseCommand *PrevCmd = nullptr;
for (std::unique_ptr<BaseCommand> &Base : Cmd->Commands) {
if (auto *AssignCmd = dyn_cast<SymbolAssignment>(Base.get())) {
if (auto *Sym = cast_or_null<DefinedSynthetic<ELFT>>(AssignCmd->Sym)) {
Sym->Section = Sec;
Sym->Value =
AssignCmd->Expression(Sec->getVA() + (Start ? 0 : Sec->getSize())) -
Sec->getVA();
}
} else {
if (!Start && isa<SymbolAssignment>(PrevCmd))
error("section '" + Sec->getName() +
"' supports only start and end symbols");
Start = false;
}
PrevCmd = Base.get();
}
}
template <class ELFT>
void assignOffsets(OutputSectionCommand *Cmd, OutputSectionBase<ELFT> *Sec) {
auto *OutSec = dyn_cast<OutputSection<ELFT>>(Sec);
if (!OutSec) {
Sec->assignOffsets();
// This section is not regular output section. However linker script may
// have defined start/end symbols for it. This case is handled below.
addStartEndSymbols(Cmd, Sec);
return;
}
@ -404,19 +437,19 @@ template <class ELFT> void LinkerScript<ELFT>::assignAddresses() {
uintX_t TVA = Dot + ThreadBssOffset;
TVA = alignTo(TVA, Sec->getAlignment());
Sec->setVA(TVA);
assignOffsets(Sec);
assignOffsets(Cmd, Sec);
ThreadBssOffset = TVA - Dot + Sec->getSize();
continue;
}
if (!(Sec->getFlags() & SHF_ALLOC)) {
Sec->assignOffsets();
assignOffsets(Cmd, Sec);
continue;
}
Dot = alignTo(Dot, Sec->getAlignment());
Sec->setVA(Dot);
assignOffsets(Sec);
assignOffsets(Cmd, Sec);
MinVA = std::min(MinVA, Dot);
Dot += Sec->getSize();
}

66
lld/test/ELF/linkerscript/linkerscript-symbols-synthetic.s
View File

@ -1,36 +1,69 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
# Simple symbol assignment within input section list. The '.' symbol
# is not location counter but offset from the beginning of output
# section .foo
# RUN: echo "SECTIONS { \
# RUN: .foo : { \
# RUN: begin_foo = .; \
# RUN: PROVIDE(_begin_foo = .); \
# RUN: PROVIDE(_begin_sec = .); \
# RUN: *(.foo) \
# RUN: end_foo = .; \
# RUN: PROVIDE_HIDDEN(_end_foo = .); \
# RUN: PROVIDE_HIDDEN(_end_sec = .); \
# RUN: size_foo_1 = SIZEOF(.foo); \
# RUN: . = ALIGN(0x1000); \
# RUN: begin_bar = .; \
# RUN: *(.bar) \
# RUN: end_bar = .; \
# RUN: size_foo_2 = SIZEOF(.foo); \
# RUN: } \
# RUN: size_foo_3 = SIZEOF(.foo); }" > %t.script
# RUN: ld.lld -o %t1 --script %t.script %t
# RUN: size_foo_2 = SIZEOF(.foo); } \
# RUN: size_foo_3 = SIZEOF(.foo); \
# RUN: .eh_frame_hdr : { \
# RUN: __eh_frame_hdr_start = .; \
# RUN: __eh_frame_hdr_start2 = ALIGN(0x10); \
# RUN: *(.eh_frame_hdr) \
# RUN: __eh_frame_hdr_end = .; \
# RUN: __eh_frame_hdr_end2 = ALIGN(0x10); } \
# RUN: }" > %t.script
# RUN: ld.lld -o %t1 --eh-frame-hdr --script %t.script %t
# RUN: llvm-objdump -t %t1 | FileCheck --check-prefix=SIMPLE %s
# SIMPLE: 0000000000000128 .foo 00000000 .hidden _end_foo
# SIMPLE: 0000000000000120 .foo 00000000 _begin_foo
# SIMPLE-NEXT: 0000000000000120 .foo 00000000 begin_foo
# SIMPLE-NEXT: 0000000000000128 .foo 00000000 end_foo
# The script below contains symbols in the middle of .eh_frame_hdr section.
# We don't support this.
# RUN: echo "SECTIONS { \
# RUN: .eh_frame_hdr : { \
# RUN: PROVIDE_HIDDEN(_begin_sec = .); \
# RUN: __eh_frame_hdr_start = .; \
# RUN: *(.eh_frame_hdr) \
# RUN: __eh_frame_hdr_end = .; \
# RUN: *(.eh_frame_hdr) } \
# RUN: PROVIDE_HIDDEN(_end_sec = .); \
# RUN: }" > %t.script
# RUN: not ld.lld -o %t1 --eh-frame-hdr --script %t.script %t 2>&1 | FileCheck --check-prefix=ERROR %s
# Check that the following script is processed without errors
# RUN: echo "SECTIONS { \
# RUN: .eh_frame_hdr : { \
# RUN: PROVIDE_HIDDEN(_begin_sec = .); \
# RUN: *(.eh_frame_hdr) \
# RUN: *(.eh_frame_hdr) \
# RUN: PROVIDE_HIDDEN(_end_sec = .); } \
# RUN: }" > %t.script
# RUN: ld.lld -o %t1 --eh-frame-hdr --script %t.script %t
# SIMPLE: 0000000000000160 .foo 00000000 .hidden _end_sec
# SIMPLE: 0000000000000158 .foo 00000000 _begin_sec
# SIMPLE-NEXT: 0000000000000158 .foo 00000000 begin_foo
# SIMPLE-NEXT: 0000000000000160 .foo 00000000 end_foo
# SIMPLE-NEXT: 0000000000000008 .foo 00000000 size_foo_1
# SIMPLE-NEXT: 0000000000001000 .foo 00000000 begin_bar
# SIMPLE-NEXT: 0000000000001004 .foo 00000000 end_bar
# SIMPLE-NEXT: 0000000000000ee4 .foo 00000000 size_foo_2
# SIMPLE-NEXT: 0000000000000ee4 *ABS* 00000000 size_foo_3
# SIMPLE-NEXT: 0000000000000eac .foo 00000000 size_foo_2
# SIMPLE-NEXT: 0000000000000eac *ABS* 00000000 size_foo_3
# SIMPLE-NEXT: 0000000000001004 .eh_frame_hdr 00000000 __eh_frame_hdr_start
# SIMPLE-NEXT: 0000000000001010 .eh_frame_hdr 00000000 __eh_frame_hdr_start2
# SIMPLE-NEXT: 0000000000001018 .eh_frame_hdr 00000000 __eh_frame_hdr_end
# SIMPLE-NEXT: 0000000000001020 .eh_frame_hdr 00000000 __eh_frame_hdr_end2
# ERROR: section '.eh_frame_hdr' supports only start and end symbols
.global _start
_start:
@ -42,4 +75,9 @@ _start:
.section .bar,"a"
.long 0
.global _begin_foo, _end_foo
.section .dah,"ax",@progbits
.cfi_startproc
nop
.cfi_endproc
.global _begin_sec, _end_sec