http://sourceware.org/bugzilla/show_bug.cgi?id=13470
Bug #: 13470
Summary: ld's powerpc32 relocation/dynsym output changed in
many bad ways with 2.22 (e.g. textrel added)
Product: binutils
Version: 2.22
Status: NEW
Severity: critical
Priority: P2
Component: ld
AssignedTo: amo...@gmail.com
ReportedBy: bernhard.kai...@thalesgroup.com
Classification: Unclassified
Host: all
Target: ppc/ppc32, possibly also ppc64
Build: all
Hello Alan
The cleanup which you posted as "powerpc backend tidy", included in
binutils-2.22, has quite wide-ranging effects on the powerpc32 backend of ld:
http://www.cygwin.com/ml/binutils/2011-07/msg00005.html
I have found that with this change, all ELF executables using for example
program_invocation_name which includes e.g all programs of GNU coreutils-8.14,
are affected:
* In their .dynsym section, the Ndx value of
__progname_full@GLIBC_2.0 and
program_invocation_name@GLIBC_2.0
changes from 24 to "UND" and the later's Bind field changes
from WEAK to GLOBAL.
* Their .rela.dyn sections get R_PPC_ADDR16_HA and
R_PPC_ADDR16_LO relocations for program_invocation_name
* They have a TEXTREL entry in their dynamic sections
* As the size of .rela.dyn is larger, the ELF file is larger
A minimal program triggering these effects is:
#define _GNU_SOURCE
#include <errno.h>
extern char *program_invocation_name;
main() {
const char a = *program_invocation_name;
}
>From a diff of readelf -a between an ld without and with "powerpc backend tidy"
on powerpc32, compiled using gcc-4.4.6, linked against glibc-2.11.3:
Here the changes to .dynsym in this program:
Symbol table '.dynsym' contains 6 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 00000000 0 NOTYPE LOCAL DEFAULT UND
- 1: 1001077c 4 OBJECT GLOBAL DEFAULT 24 __progname_full@GLIBC_2.0
(2)
+ 1: 00000000 0 OBJECT GLOBAL DEFAULT UND __progname_full@GLIBC_2.0
(2)
2: 00000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
- 3: 100005d8 4 OBJECT GLOBAL DEFAULT 13 _IO_stdin_used
+ 3: 100005e4 4 OBJECT GLOBAL DEFAULT 13 _IO_stdin_used
4: 00000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.0
(2)
- 5: 1001077c 4 OBJECT WEAK DEFAULT 24
program_invocation_name@GLIBC_2.0 (2)
+ 5: 00000000 0 OBJECT GLOBAL DEFAULT UND
program_invocation_name@GLIBC_2.0 (2)
Here the changes to '.rela.dyn':
-Relocation section '.rela.dyn' at offset 0x28c contains 2 entries:
+Relocation section '.rela.dyn' at offset 0x28c contains 3 entries:
Offset Info Type Sym.Value Sym. Name + Addend
-10010708 00000214 R_PPC_GLOB_DAT 00000000 __gmon_start__ + 0
-1001077c 00000113 R_PPC_COPY 1001077c __progname_full + 0
+10000466 00000506 R_PPC_ADDR16_HA 00000000 program_invocation_nam + 0
+1000046e 00000504 R_PPC_ADDR16_LO 00000000 program_invocation_nam + 0
+1001071c 00000214 R_PPC_GLOB_DAT 00000000 __gmon_start__ + 0
And here the resulting changes to the dynamic section:
-Dynamic section at offset 0x638 contains 20 entries:
+Dynamic section at offset 0x644 contains 21 entries:
Tag Type Name/Value
0x00000001 (NEEDED) Shared library: [libc.so.6]
- 0x0000000c (INIT) 0x100002bc
- 0x0000000d (FINI) 0x100005a8
+ 0x0000000c (INIT) 0x100002c8
+ 0x0000000d (FINI) 0x100005b4
0x00000004 (HASH) 0x10000164
0x00000005 (STRTAB) 0x100001f0
0x00000006 (SYMTAB) 0x10000190
0x0000000a (STRSZ) 109 (bytes)
0x0000000b (SYMENT) 16 (bytes)
0x00000015 (DEBUG) 0x0
- 0x00000003 (PLTGOT) 0x1001071c
+ 0x00000003 (PLTGOT) 0x10010730
0x00000002 (PLTRELSZ) 24 (bytes)
0x00000014 (PLTREL) RELA
- 0x00000017 (JMPREL) 0x100002a4
+ 0x00000017 (JMPREL) 0x100002b0
0x00000007 (RELA) 0x1000028c
- 0x00000008 (RELASZ) 48 (bytes)
+ 0x00000008 (RELASZ) 60 (bytes)
0x00000009 (RELAENT) 12 (bytes)
+ 0x00000016 (TEXTREL) 0x0
0x6ffffffe (VERNEED) 0x1000026c
0x6fffffff (VERNEEDNUM) 1
0x6ffffff0 (VERSYM) 0x1000025e
0x00000000 (NULL) 0x0
As the commit changed elf64-ppc.c (ppc64_elf_copy_indirect_symbol)
likewise, the ppc64 backend of ld may also be affected.
Of course, there may be even more effects, but as this was declared as a
cleanup, it should have had zero effect on the output, which it does not have
and must be fixed.
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