From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Fri, 14 May 2010 11:08:30 +0000 (+0800)
Subject: MIPS: Tracing: Fix 32-bit support with -mmcount-ra-address
X-Git-Tag: v2.6.35-rc5~20^2~10
X-Git-Url: https://bbs.cooldavid.org/git/?p=net-next-2.6.git;a=commitdiff_plain;h=3a2af2dc1bcbfe86b1f39e9e5f9c2c5447943f16

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>
---

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) {