[lld] r283760 - [ELF] Don't emit empty PT_LOAD segment
Eugene Leviant via llvm-commits
llvm-commits at lists.llvm.org
Mon Oct 10 08:09:45 PDT 2016
Author: evgeny777
Date: Mon Oct 10 10:09:44 2016
New Revision: 283760
URL: http://llvm.org/viewvc/llvm-project?rev=283760&view=rev
Log:
[ELF] Don't emit empty PT_LOAD segment
Sometimes the very first PT_LOAD segment, created by lld, can be empty.
This happens when (all conditions met):
- Linker script is used
- First section in ELF image is not RO
- Not enough space for program headers.
Differential revision: https://reviews.llvm.org/D25330
Added:
lld/trunk/test/ELF/linkerscript/empty-load.s
Modified:
lld/trunk/ELF/LinkerScript.cpp
Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=283760&r1=283759&r2=283760&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Mon Oct 10 10:09:44 2016
@@ -655,6 +655,17 @@ void LinkerScript<ELFT>::assignAddresses
FirstPTLoad->First = Out<ELFT>::ElfHeader;
if (!FirstPTLoad->Last)
FirstPTLoad->Last = Out<ELFT>::ProgramHeaders;
+ } else if (!FirstPTLoad->First) {
+ // Sometimes the very first PT_LOAD segment can be empty.
+ // This happens if (all conditions met):
+ // - Linker script is used
+ // - First section in ELF image is not RO
+ // - Not enough space for program headers.
+ // The code below removes empty PT_LOAD segment and updates
+ // program headers size.
+ Phdrs.erase(FirstPTLoad);
+ Out<ELFT>::ProgramHeaders->setSize(sizeof(typename ELFT::Phdr) *
+ Phdrs.size());
}
}
Added: lld/trunk/test/ELF/linkerscript/empty-load.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/empty-load.s?rev=283760&view=auto
==============================================================================
--- lld/trunk/test/ELF/linkerscript/empty-load.s (added)
+++ lld/trunk/test/ELF/linkerscript/empty-load.s Mon Oct 10 10:09:44 2016
@@ -0,0 +1,22 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: echo "SECTIONS { .rw : { *(.rw) } .text : { *(.text) } }" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -private-headers %t1 | FileCheck %s
+
+## We expect 2 PT_LOAD segments
+# CHECK: PHDR
+# CHECK-NEXT: filesz {{0x[0-9a-f]+}} memsz {{0x[0-9a-f]+}} flags r--
+# CHECK-NEXT: LOAD
+# CHECK-NEXT: filesz {{0x[0-9a-f]+}} memsz {{0x[0-9a-f]+}} flags rw-
+# CHECK-NEXT: LOAD
+# CHECK-NEXT: filesz {{0x[0-9a-f]+}} memsz {{0x[0-9a-f]+}} flags r-x
+# CHECK-NEXT: STACK
+# CHECK-NEXT: filesz
+
+.globl _start
+_start:
+ jmp _start
+
+.section .rw, "aw"
+ .quad 0
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