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Commit 56b49cd3 authored by Wu Zhangjin's avatar Wu Zhangjin Committed by Ralf Baechle
Browse files

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: default avatarWu 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: default avatarRalf Baechle <ralf@linux-mips.org>
parent 042e571d

arch/mips/kernel/mcount.S

+9 −3
Original line number Diff line number Diff line
@@ -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: 


	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 @@ NESTED(ftrace_graph_caller, PT_SIZE, ra) 
#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 */