[PATCH] D41105: [ELF] Prevent crash in writing an .ARM.exidx sentinel entry.
Igor Kudrin via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Dec 13 22:24:32 PST 2017
This revision was not accepted when it landed; it landed in state "Needs Review".
This revision was automatically updated to reflect the committed changes.
Closed by commit rLLD320668: [ELF] Prevent crash in writing an .ARM.exidx sentinel entry. (authored by ikudrin, committed by ).
Changed prior to commit:
https://reviews.llvm.org/D41105?vs=126704&id=126895#toc
Repository:
rLLD LLVM Linker
https://reviews.llvm.org/D41105
Files:
ELF/SyntheticSections.cpp
test/ELF/linkerscript/arm-exidx-sentinel-and-assignment.s
Index: test/ELF/linkerscript/arm-exidx-sentinel-and-assignment.s
===================================================================
--- test/ELF/linkerscript/arm-exidx-sentinel-and-assignment.s
+++ test/ELF/linkerscript/arm-exidx-sentinel-and-assignment.s
@@ -0,0 +1,24 @@
+# REQUIRES: arm
+# RUN: llvm-mc -filetype=obj -triple=armv7a-none-linux-gnueabi %s -o %t.o
+# RUN: echo "SECTIONS { \
+# RUN: .ARM.exidx 0x1000 : { *(.ARM.exidx*) foo = .; } \
+# RUN: .text 0x2000 : { *(.text*) } \
+# RUN: }" > %t.script
+## We used to crash if the last output section command for .ARM.exidx
+## was anything but an input section description.
+# RUN: ld.lld -T %t.script %t.o -shared -o %t.so
+# RUN: llvm-objdump -s -triple=armv7a-none-linux-gnueabi %t.so | FileCheck %s
+
+ .syntax unified
+ .text
+ .global _start
+_start:
+ .fnstart
+ .cantunwind
+ bx lr
+ .fnend
+
+// CHECK: Contents of section .ARM.exidx:
+// 1000 + 1000 = 0x2000 = _start
+// 1008 + 0ffc = 0x2004 = _start + sizeof(_start)
+// CHECK-NEXT: 1000 00100000 01000000 fc0f0000 01000000
Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -2569,16 +2569,22 @@
void ARMExidxSentinelSection::writeTo(uint8_t *Buf) {
// The Sections are sorted in order of ascending PREL31 address with the
// sentinel last. We need to find the InputSection that precedes the
- // sentinel. By construction the Sentinel is in the last
- // InputSectionDescription as the InputSection that precedes it.
+ // sentinel.
OutputSection *C = getParent();
- auto ISD =
- std::find_if(C->SectionCommands.rbegin(), C->SectionCommands.rend(),
- [](const BaseCommand *Base) {
- return isa<InputSectionDescription>(Base);
- });
- auto L = cast<InputSectionDescription>(*ISD);
- InputSection *Highest = L->Sections[L->Sections.size() - 2];
+ InputSection *Highest = nullptr;
+ int Skip = 1;
+ for (const BaseCommand *Base : llvm::reverse(C->SectionCommands)) {
+ if (!isa<InputSectionDescription>(Base))
+ continue;
+ auto L = cast<InputSectionDescription>(Base);
+ if (Skip >= L->Sections.size()) {
+ Skip -= L->Sections.size();
+ continue;
+ }
+ Highest = L->Sections[L->Sections.size() - Skip - 1];
+ break;
+ }
+ assert(Highest);
InputSection *LS = Highest->getLinkOrderDep();
uint64_t S = LS->getParent()->Addr + LS->getOffset(LS->getSize());
uint64_t P = getVA();
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