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MIPS, Tracing: Clean up ftrace_make_nop()

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This moves the comments out of ftrace_make_nop() and cleans it.  At the
same time, a macro MCOUNT_OFFSET_INSNS is defined for sharing with the
next patch.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2008/
Signed-off-by: Ralf Baechle <ralf@duck.linux-mips.net>
This commit is contained in:
Wu Zhangjin 2011-01-20 03:28:31 +08:00 committed by Ralf Baechle
parent 2816e32596
commit 7f21a60968
1 changed files with 38 additions and 32 deletions
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70
arch/mips/kernel/ftrace.c
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@ -24,8 +24,6 @@
#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
#define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */
#define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */
#define INSN_NOP 0x00000000 /* nop */
#define INSN_JAL(addr) \
((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
@ -84,6 +82,42 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
return 0;
}
/*
* The details about the calling site of mcount on MIPS
*
* 1. For kernel:
*
* move at, ra
* jal _mcount --> nop
*
* 2. For modules:
*
* 2.1 For KBUILD_MCOUNT_RA_ADDRESS and 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
* 2.2 For the Other situations
*
* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
* addiu v1, v1, low_16bit_of_mcount
* move at, ra
* jalr v1
* nop | move $12, ra_address | sub sp, sp, 8
* 1: offset = 4 instructions
*/
#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
#define MCOUNT_OFFSET_INSNS 5
#else
#define MCOUNT_OFFSET_INSNS 4
#endif
#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
@ -94,36 +128,8 @@ int ftrace_make_nop(struct module *mod,
* If ip is in kernel space, no long call, otherwise, long call is
* needed.
*/
if (in_kernel_space(ip)) {
/*
* move at, ra
* jal _mcount --> nop
*/
new = INSN_NOP;
} else {
#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 = INSN_B_1F_5;
#else
/*
* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
* addiu v1, v1, low_16bit_of_mcount
* move at, ra
* jalr v1
* nop | move $12, ra_address | sub sp, sp, 8
* 1: offset = 4 instructions
*/
new = INSN_B_1F_4;
#endif
}
new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
return ftrace_modify_code(ip, new);
}