[lld] r280205 - Allow adding start/end symbols to any section
Eugene Leviant via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 31 01:13:33 PDT 2016
Author: evgeny777
Date: Wed Aug 31 03:13:33 2016
New Revision: 280205
URL: http://llvm.org/viewvc/llvm-project?rev=280205&view=rev
Log:
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
Modified:
lld/trunk/ELF/LinkerScript.cpp
lld/trunk/test/ELF/linkerscript/linkerscript-symbols-synthetic.s
Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=280205&r1=280204&r2=280205&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Wed Aug 31 03:13:33 2016
@@ -310,10 +310,43 @@ void LinkerScript<ELFT>::createSections(
}
}
-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<
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();
}
Modified: lld/trunk/test/ELF/linkerscript/linkerscript-symbols-synthetic.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/linkerscript-symbols-synthetic.s?rev=280205&r1=280204&r2=280205&view=diff
==============================================================================
--- lld/trunk/test/ELF/linkerscript/linkerscript-symbols-synthetic.s (original)
+++ lld/trunk/test/ELF/linkerscript/linkerscript-symbols-synthetic.s Wed Aug 31 03:13:33 2016
@@ -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", at progbits
+ .cfi_startproc
+ nop
+ .cfi_endproc
+
+.global _begin_sec, _end_sec
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