From: slyich--- via Libc-alpha <libc-alpha@sourceware.org>
To: libc-alpha@sourceware.org
Cc: Sergei Trofimovich <slyfox@gentoo.org>
Subject: [PATCH] ia64: fix dl-sysdep miscompilation on gcc-10
Date: Sat, 16 May 2020 14:53:32 +0100 [thread overview]
Message-ID: <20200516135332.3969575-1-slyich@gmail.com> (raw)
From: Sergei Trofimovich <slyfox@gentoo.org>
gcc-10 enabled -fno-common by default. This caused glibc link failure:
```
$ ia64-unknown-linux-gnu-gcc -pipe -O2 -nostdlib -nostartfiles \
-static -o .../elf/sln ...
libc.a(dl-support.o): in function `setup_vdso':
glibc-2.31/elf/setup-vdso.h:116:(.text+0x1322):
relocation truncated to fit: GPREL22 against `.text'
collect2: error: ld returned 1 exit status
```
The difference between gcc-9 and gcc-10 is the way relocation is
generated for ia64-specific symbol '_dl_sysinfo_break', defined as:
```c
32 #ifndef __ASSEMBLER__
33 /* Don't declare this as a function---we want it's entry-point, not
34 it's function descriptor... */
35 extern int _dl_sysinfo_break attribute_hidden;
36 # define DL_SYSINFO_DEFAULT ((uintptr_t) &_dl_sysinfo_break)
37 # define DL_SYSINFO_IMPLEMENTATION \
38 asm (".text\n\t" \
39 ".hidden _dl_sysinfo_break\n\t" \
40 ".proc _dl_sysinfo_break\n\t" \
```
Note: it's declared as ".sdata" (defined nearby GOT) but assumed
to be defined in ".text" as it's really a direct function address.
As a result generated relocation changed from:
from `GPREL64I`:
```
1390: 05 00 84 1e 98 11 [MLX] st8 [r15]=r33
1391: GPREL64I .text
1396: 00 00 00 00 00 e0 movl r15=0x0;;
139c: 01 00 00 60
13a0: 0b 78 04 1e 00 20 [MMI] add r15=r1,r15;;
```
to `GPREL22`:
```
if (GLRO(dl_sysinfo) == DL_SYSINFO_DEFAULT)
1320: 0b 80 00 1c 18 10 [MMI] ld8 r16=[r14];;
1322: GPREL22 .text
1326: 00 08 3d 30 23 e0 st8 [r15]=r33
132c: 01 08 00 90 addl r15=0,r1;;
```
This change explicitly declares symbol to be in ".text" section.
That allows gcc to generate far relocations.
Regression tested on glibc-master and gcc-10.1.0 on rx3600.
Bug: https://bugs.gentoo.org/723268
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
---
sysdeps/unix/sysv/linux/ia64/dl-sysdep.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h b/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h
index 78fa6dd2c9..e526e02ff4 100644
--- a/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h
+++ b/sysdeps/unix/sysv/linux/ia64/dl-sysdep.h
@@ -32,7 +32,9 @@
#ifndef __ASSEMBLER__
/* Don't declare this as a function---we want it's entry-point, not
it's function descriptor... */
-extern int _dl_sysinfo_break attribute_hidden;
+/* Use section ".text" to force far GPREL64 relocation instead of
+ GPREL22 . */
+extern int _dl_sysinfo_break attribute_hidden __attribute__((section(".text")));
# define DL_SYSINFO_DEFAULT ((uintptr_t) &_dl_sysinfo_break)
# define DL_SYSINFO_IMPLEMENTATION \
asm (".text\n\t" \
--
2.26.2
next reply other threads:[~2020-05-16 13:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-16 13:53 slyich--- via Libc-alpha [this message]
2020-05-20 19:45 ` [PATCH] ia64: fix dl-sysdep miscompilation on gcc-10 Adhemerval Zanella via Libc-alpha
2020-05-31 19:34 ` Sergei Trofimovich via Libc-alpha
2020-05-31 21:40 ` Sergei Trofimovich via Libc-alpha
2020-06-05 18:44 ` Adhemerval Zanella via Libc-alpha
2020-06-05 21:31 ` Sergei Trofimovich via Libc-alpha
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