From: Romeo Cane <romeo.cane.ext@xxxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit 1028ccf560b97adbf272381a61a67e17d44d1054 upstream.
Declaring sys_call_table as a pointer causes the compiler to generate
the wrong lookup code in arch_syscall_addr().
<arch_syscall_addr>:
lis r9,-16384
rlwinm r3,r3,2,0,29
- lwz r11,30640(r9)
- lwzx r3,r11,r3
+ addi r9,r9,30640
+ lwzx r3,r9,r3
blr
The actual sys_call_table symbol, declared in assembler, is an
array. If we lie about that to the compiler we get the wrong code
generated, as above.
This definition seems only to be used by the syscall tracing code in
kernel/trace/trace_syscalls.c. With this patch I can successfully use
the syscall tracepoints:
bash-3815 [002] .... 333.239082: sys_write -> 0x2
bash-3815 [002] .... 333.239087: sys_dup2(oldfd: a, newfd: 1)
bash-3815 [002] .... 333.239088: sys_dup2 -> 0x1
bash-3815 [002] .... 333.239092: sys_fcntl(fd: a, cmd: 1, arg: 0)
bash-3815 [002] .... 333.239093: sys_fcntl -> 0x1
bash-3815 [002] .... 333.239094: sys_close(fd: a)
bash-3815 [002] .... 333.239094: sys_close -> 0x0
Signed-off-by: Romeo Cane <romeo.cane.ext@xxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
arch/powerpc/include/asm/syscall.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index b54b2add07be..528ba9d8eed5 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -17,7 +17,7 @@
/* ftrace syscalls requires exporting the sys_call_table */
#ifdef CONFIG_FTRACE_SYSCALLS
-extern const unsigned long *sys_call_table;
+extern const unsigned long sys_call_table[];
#endif /* CONFIG_FTRACE_SYSCALLS */
static inline long syscall_get_nr(struct task_struct *task,
--
2.3.4
--
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