This moves the comments out of ftrace_make_nop() and make it cleaner.
At the same time, a macro MCOUNT_OFFSET_INSNS is defined for sharing
with the next patch.
Signed-off-by: Wu Zhangjin <wuzhangjin@xxxxxxxxx>
---
arch/mips/kernel/ftrace.c | 70 ++++++++++++++++++++++++--------------------
1 files changed, 38 insertions(+), 32 deletions(-)
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 40ef34c..bc91e4a 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -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);
}
--
1.7.1
