bash-3.1$ cat foo.c
extern char x __attribute__((weak, visibility("hidden")));
void *_start(void) { return &x; }
bash-3.1$ make
gcc -fPIC -c -o foo.o foo.c
ld -Ttext 100000000 -o foo foo.o
objdump -dr foo.o
foo.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <_start>:
0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: 48 8d 05 00 00 00 00 lea 0(%rip),%rax # b <_start+0xb>
7: R_X86_64_PC32 x+0xfffffffffffffffc
b: c9 leaveq
c: c3 retq
objdump -d foo
foo: file format elf64-x86-64
Disassembly of section .text:
0000000100000000 <_start>:
100000000: 55 push %rbp
100000001: 48 89 e5 mov %rsp,%rbp
100000004: 48 8d 05 f5 ff ff ff lea -11(%rip),%rax # 100000000
<_start>
10000000b: c9 leaveq
10000000c: c3 retq
bash-3.1$
Linker ignores relocation overflow. As the result, &x is no longer 0. This
change was introduced by
http://sourceware.org/ml/binutils/2004-06/msg00199.html
--
Summary: x86-64 linker ignores relocation overflow
Product: binutils
Version: 2.18 (HEAD)
Status: NEW
Severity: normal
Priority: P2
Component: ld
AssignedTo: unassigned at sources dot redhat dot com
ReportedBy: hjl at lucon dot org
CC: amodra at bigpond dot net dot au,bug-binutils at gnu dot
org
http://sourceware.org/bugzilla/show_bug.cgi?id=3283
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