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Subject[PATCH v7 13/17] tracing: add dynamic function graph tracer for MIPS
Date
From: Wu Zhangjin <wuzhangjin@gmail.com>

This patch make function graph tracer work with dynamic function tracer.

To share the source code of dynamic function tracer(MCOUNT_SAVE_REGS),
and avoid restoring the whole saved registers, we need to restore the ra
register from the stack.

(NOTE: This not work with 32bit! need to ensure why!)

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
arch/mips/kernel/ftrace.c | 21 +++++++++++++++++++++
arch/mips/kernel/mcount.S | 14 ++++++++++++--
2 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 50ba128..af3ceed 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -92,6 +92,27 @@ int __init ftrace_dyn_arch_init(void *data)

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

+#ifdef CONFIG_DYNAMIC_FTRACE
+
+extern void ftrace_graph_call(void);
+#define JMP 0x08000000 /* jump to target directly */
+#define CALL_FTRACE_GRAPH_CALLER \
+ jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
+#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
+ CALL_FTRACE_GRAPH_CALLER);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, ftrace_nop);
+}
+
+#endif /* !CONFIG_DYNAMIC_FTRACE */
+
#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index b50e38d..98d4690 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -77,6 +77,13 @@ ftrace_call:
nop /* a placeholder for the call to a real tracing function */
move a1, AT /* arg2: the caller's next ip, parent */

+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ .globl ftrace_graph_call
+ftrace_graph_call:
+ nop
+ nop
+#endif
+
MCOUNT_RESTORE_REGS
.globl ftrace_stub
ftrace_stub:
@@ -124,10 +131,13 @@ ftrace_stub:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER

NESTED(ftrace_graph_caller, PT_SIZE, ra)
+#ifdef CONFIG_DYNAMIC_FTRACE
+ PTR_L a1, PT_R31(sp) /* load the original ra from the stack */
+#else
MCOUNT_SAVE_REGS
-
- PTR_LA a0, PT_R1(sp) /* arg1: &AT -> a0 */
move a1, ra /* arg2: next ip, selfaddr */
+#endif
+ PTR_LA a0, PT_R1(sp) /* arg1: &AT -> a0 */
jal prepare_ftrace_return
move a2, fp /* arg3: frame pointer */

--
1.6.2.1


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