MIPS: Tracing: Fix 32-bit support with -mmcount-ra-address

For 32-bit kernel the -mmcount-ra-address option of gcc 4.5 emits one
extra instruction before calling to _mcount so we need to use a different
"b 1f" for it.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips <linux-mips@linux-mips.org>
Cc: David Daney <david.s.daney@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/1228/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index e9e64e0ff7a..37aa7677e76 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -62,14 +62,26 @@ int ftrace_make_nop(struct module *mod,
                                 return -EFAULT;
                 }
 
+#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
+                /* lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
+                 * addiu v1, v1, low_16bit_of_mcount
+                 * move at, ra
+                 * move $12, ra_address
+                 * jalr v1
+                 *  sub sp, sp, 8
+                 *                                  1: offset = 5 instructions
+                 */
+                new = 0x10000005;
+#else
                 /* lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
                  * addiu v1, v1, low_16bit_of_mcount
                  * move at, ra
                  * jalr v1
-                 * nop
-                 *                                   1f: (ip + 12)
+                 *  nop | move $12, ra_address | sub sp, sp, 8
+                 *                                  1: offset = 4 instructions
                  */
                 new = 0x10000004;
+#endif
         } else {
                 /* record/calculate it for ftrace_make_call */
                 if (jal_mcount == 0) {