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Subject[PATCH v1 3/5] mips function graph tracer support
Date
From: Wu Zhangjin <wuzj@lemote.com>

this works something like -finstrument-functions does, instead of using

void __cyg_profile_func_enter (void *this_fn,
void *call_site);
void __cyg_profile_func_exit (void *this_fn,
void *call_site);

-pg use _mcount, so some tricks are adoptive by the author of orignal function
graph tracer:

the _mcount function will call prepare_function_return to save the
parent_ip, ip and calltime in a tracing array, if success, the
address of a hooker function named return_to_handler will be
substitued to the parent_ip, so, after return from _mcount it will
call the return_to_handler, not back to the parent_ip, but calling
ftrace_return_to_handler to remember the rettime, and return the
parent_ip to let return_to_handler go back to the real parent.

Signed-off-by: Wu Zhangjin <wuzj@lemote.com>
---
arch/mips/Kconfig | 1 +
arch/mips/kernel/ftrace.c | 72 ++++++++++++++++++++++++++++++++++++++++
arch/mips/kernel/mcount.S | 58 +++++++++++++++++++++++++++++++-
arch/mips/kernel/vmlinux.lds.S | 1 +
4 files changed, 131 insertions(+), 1 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 0c00536..ac1437e 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -9,6 +9,7 @@ config MIPS
select HAVE_DYNAMIC_FTRACE
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
+ select HAVE_FUNCTION_GRAPH_TRACER
# Horrible source of confusion. Die, die, die ...
select EMBEDDED
select RTC_LIB
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 827c128..e7f15f7 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -215,3 +215,75 @@ int __init ftrace_dyn_arch_init(void *data)
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+#define JMP 0x08000000 /* jump to target directly */
+extern void ftrace_graph_call(void);
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ unsigned long ip = (unsigned long) (&ftrace_graph_call);
+ unsigned char old[MCOUNT_INSN_SIZE], *new;
+ int ret;
+
+ /* j ftrace_stub */
+ memcpy(old, (unsigned long *) ip, MCOUNT_INSN_SIZE);
+ new = ftrace_call_replace(JMP, (unsigned long) ftrace_graph_caller);
+
+ ret = ftrace_modify_code(ip, old, new);
+
+ return ret;
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ unsigned long ip = (unsigned long) (&ftrace_graph_call);
+ unsigned char old[MCOUNT_INSN_SIZE], *new;
+ int ret;
+
+ /* j ftrace_graph_caller */
+ memcpy(old, (unsigned long *) ip, MCOUNT_INSN_SIZE);
+ new = ftrace_call_replace(JMP, (unsigned long) ftrace_stub);
+
+ ret = ftrace_modify_code(ip, old, new);
+
+ return ret;
+}
+
+#endif /* !CONFIG_DYNAMIC_FTRACE */
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+
+unsigned long prepare_ftrace_return(unsigned long ip,
+ unsigned long parent_ip)
+{
+ struct ftrace_graph_ent trace;
+
+ /* Nmi's are currently unsupported */
+ if (unlikely(in_nmi()))
+ goto out;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ goto out;
+
+ if (ftrace_push_return_trace(parent_ip, ip, &trace.depth) == -EBUSY)
+ goto out;
+
+ trace.func = ip;
+
+ /* Only trace if the calling function expects to */
+ if (!ftrace_graph_entry(&trace)) {
+ current->curr_ret_stack--;
+ goto out;
+ }
+ return (unsigned long) &return_to_handler;
+out:
+ return parent_ip;
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index ce8a0ba..bd58f16 100644
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -28,6 +28,10 @@
PTR_SUBU sp, PT_SIZE
PTR_S ra, PT_R31(sp)
PTR_S $1, PT_R1(sp)
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ PTR_S v0, PT_R2(sp)
+ PTR_S v1, PT_R3(sp)
+#endif
PTR_S a0, PT_R4(sp)
PTR_S a1, PT_R5(sp)
PTR_S a2, PT_R6(sp)
@@ -43,6 +47,10 @@
.macro MCOUNT_RESTORE_REGS
PTR_L ra, PT_R31(sp)
PTR_L $1, PT_R1(sp)
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ PTR_L v0, PT_R2(sp)
+ PTR_L v1, PT_R3(sp)
+#endif
PTR_L a0, PT_R4(sp)
PTR_L a1, PT_R5(sp)
PTR_L a2, PT_R6(sp)
@@ -89,6 +97,14 @@ ftrace_call:
nop

MCOUNT_RESTORE_REGS
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ .globl ftrace_graph_call
+ftrace_graph_call:
+ j ftrace_stub
+ nop
+#endif
+
.globl ftrace_stub
ftrace_stub:
RETURN_BACK
@@ -106,7 +122,15 @@ NESTED(_mcount, PT_SIZE, ra)
PTR_L t1, ftrace_trace_function /* please don't use t1 later, safe? */
bne t0, t1, static_trace
nop
-
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ PTR_L t2, ftrace_graph_return
+ bne t0, t2, ftrace_graph_caller
+ nop
+ PTR_LA t0, ftrace_graph_entry_stub
+ PTR_L t2, ftrace_graph_entry
+ bne t0, t2, ftrace_graph_caller
+ nop
+#endif
j ftrace_stub
nop

@@ -125,5 +149,37 @@ ftrace_stub:

#endif /* ! CONFIG_DYNAMIC_FTRACE */

+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+NESTED(ftrace_graph_caller, PT_SIZE, ra)
+ MCOUNT_SAVE_REGS
+
+ MCOUNT_SET_ARGS
+ jal prepare_ftrace_return
+ nop
+
+ /* overwrite the parent as &return_to_handler: v0 -> $1(at) */
+ PTR_S v0, PT_R1(sp)
+
+ MCOUNT_RESTORE_REGS
+ RETURN_BACK
+ END(ftrace_graph_caller)
+
+ .align 2
+ .globl return_to_handler
+return_to_handler:
+ MCOUNT_SAVE_REGS
+
+ jal ftrace_return_to_handler
+ nop
+
+ /* restore the real parent address: v0 -> ra */
+ PTR_S v0, PT_R31(sp)
+
+ MCOUNT_RESTORE_REGS
+ RETURN_BACK
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
.set at
.set reorder
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 58738c8..67435e5 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -36,6 +36,7 @@ SECTIONS
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
+ IRQENTRY_TEXT
*(.text.*)
*(.fixup)
*(.gnu.warning)
--
1.6.0.4


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