MIPS: Tracing: Fix argument passing of the 32bit support with gcc 4.5
As documented in the GCC 4.5 docs [1] -mmcount-ra-address uses register
$12 to pass the stack offset of the return address to the _mcount function.
On 64-bit kernels $12 is t0 but in 32-bit kernels it is t4 so we need to
use $12 instead of t0 here to be correct for both kernel types.
[1] GCC documentation: MIPS Options
http://gcc.gnu.org/onlinedocs/gcc/MIPS-Options.html
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/1227/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index 9a029d4..6bfcb7a 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -57,6 +57,12 @@
move ra, AT
.endm
+/*
+ * The -mmcount-ra-address option of gcc 4.5 uses register $12 to pass
+ * the location of the parent's return address.
+ */
+#define MCOUNT_RA_ADDRESS_REG $12
+
#ifdef CONFIG_DYNAMIC_FTRACE
NESTED(ftrace_caller, PT_SIZE, ra)
@@ -70,7 +76,7 @@
MCOUNT_SAVE_REGS
#ifdef KBUILD_MCOUNT_RA_ADDRESS
- PTR_S t0, PT_R12(sp) /* save location of parent's return address */
+ PTR_S MCOUNT_RA_ADDRESS_REG, PT_R12(sp)
#endif
move a0, ra /* arg1: self return address */
@@ -142,9 +148,9 @@
#ifdef CONFIG_DYNAMIC_FTRACE
PTR_L a0, PT_R12(sp)
#else
- move a0, t0
+ move a0, MCOUNT_RA_ADDRESS_REG
#endif
- bnez a0, 1f /* non-leaf func: stored in t0 */
+ bnez a0, 1f /* non-leaf func: stored in MCOUNT_RA_ADDRESS_REG */
nop
#endif
PTR_LA a0, PT_R1(sp) /* leaf func: the location in current stack */
