diff mbox

[3/7,RFC] powerpc64, tracing: add function graph tracer with dynamic tracing

Message ID 20090212011343.074329920@goodmis.org (mailing list archive)
State Accepted, archived
Commit 465428884765b43d642a967915e16c6c7cacbe8e
Headers show

Commit Message

Steven Rostedt Feb. 12, 2009, 1:10 a.m. UTC 
From: Steven Rostedt <srostedt@redhat.com>

This is the port of the function graph tracer to PowerPC with
dynamic tracing.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 arch/powerpc/Kconfig           |    2 +-
 arch/powerpc/kernel/entry_64.S |    8 ++++++-
 arch/powerpc/kernel/ftrace.c   |   47 ++++++++++++++++++++++++++++++++++-----
 3 files changed, 49 insertions(+), 8 deletions(-)

Comments

Benjamin Herrenschmidt Feb. 13, 2009, 4:15 a.m. UTC | #1 
> @@ -55,8 +56,9 @@ static unsigned char *ftrace_call_replace(unsigned
> long ip, unsigned long addr)
>  	 */
>  	addr = GET_ADDR(addr);
>  
> -	/* Set to "bl addr" */
> -	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
> +	/* if (link) set op to 'bl' else 'b' */
> +	op = 0x48000000 | (link ? 1 : 0);
> +	op |= (ftrace_calc_offset(ip, addr) & 0x03fffffc);

Any reason why you aren't using the code in
arch/powerpc/lib/code-patching.c here ?

> 	new = ftrace_call_replace(ip, stub, 0);
> +	memcpy(old, new, MCOUNT_INSN_SIZE);
> +	new = ftrace_call_replace(ip, addr, 0);
> +
> +	return ftrace_modify_code(ip, old, new);
> +}

Heh, memcpy of 4 bytes :-) I hope gcc is smart enough to turn that into
a simple load/store ..

Cheers,
Ben.
Steven Rostedt Feb. 13, 2009, 4:20 a.m. UTC | #2 
On Fri, 13 Feb 2009, Benjamin Herrenschmidt wrote:

> 
> > @@ -55,8 +56,9 @@ static unsigned char *ftrace_call_replace(unsigned
> > long ip, unsigned long addr)
> >  	 */
> >  	addr = GET_ADDR(addr);
> >  
> > -	/* Set to "bl addr" */
> > -	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
> > +	/* if (link) set op to 'bl' else 'b' */
> > +	op = 0x48000000 | (link ? 1 : 0);
> > +	op |= (ftrace_calc_offset(ip, addr) & 0x03fffffc);
> 
> Any reason why you aren't using the code in
> arch/powerpc/lib/code-patching.c here ?
> 
> > 	new = ftrace_call_replace(ip, stub, 0);
> > +	memcpy(old, new, MCOUNT_INSN_SIZE);
> > +	new = ftrace_call_replace(ip, addr, 0);
> > +
> > +	return ftrace_modify_code(ip, old, new);
> > +}
> 
> Heh, memcpy of 4 bytes :-) I hope gcc is smart enough to turn that into
> a simple load/store ..

hehe, I hated writing that. I just did not want to touch the (already 
working code) of the dynamic ftrace. I guess I could still use longs and 
then typecast them to char pointers for the ftrace_modify_code.

Thanks,

-- Steve
Steven Rostedt Feb. 13, 2009, 5:22 a.m. UTC | #3 
On Fri, 13 Feb 2009, Benjamin Herrenschmidt wrote:

> 
> > @@ -55,8 +56,9 @@ static unsigned char *ftrace_call_replace(unsigned
> > long ip, unsigned long addr)
> >  	 */
> >  	addr = GET_ADDR(addr);
> >  
> > -	/* Set to "bl addr" */
> > -	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
> > +	/* if (link) set op to 'bl' else 'b' */
> > +	op = 0x48000000 | (link ? 1 : 0);
> > +	op |= (ftrace_calc_offset(ip, addr) & 0x03fffffc);
> 
> Any reason why you aren't using the code in
> arch/powerpc/lib/code-patching.c here ?

Yes, because I did not know about it ;-)

I'll write up a patch to change this. But I'll post this series as is for 
now.

Thanks,

-- Steve
diff mbox

Patch

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index ca4647e..6e1ee1b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -111,7 +111,7 @@  config PPC
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FUNCTION_TRACER
-	select HAVE_FUNCTION_GRAPH_TRACER if !DYNAMIC_FTRACE && PPC64
+	select HAVE_FUNCTION_GRAPH_TRACER if PPC64
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select HAVE_IDE
 	select HAVE_IOREMAP_PROT
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index a32699e..9f61fd6 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -908,6 +908,12 @@  _GLOBAL(ftrace_caller)
 ftrace_call:
 	bl	ftrace_stub
 	nop
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.globl ftrace_graph_call
+ftrace_graph_call:
+	b	ftrace_graph_stub
+_GLOBAL(ftrace_graph_stub)
+#endif
 	ld	r0, 128(r1)
 	mtlr	r0
 	addi	r1, r1, 112
@@ -946,7 +952,7 @@  _GLOBAL(ftrace_stub)
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-ftrace_graph_caller:
+_GLOBAL(ftrace_graph_caller)
 	/* load r4 with local address */
 	ld	r4, 128(r1)
 	subi	r4, r4, MCOUNT_INSN_SIZE
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index c9b1547..7538b94 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -43,7 +43,8 @@  static unsigned char *ftrace_nop_replace(void)
 	return (char *)&ftrace_nop;
 }
 
-static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+static unsigned char *
+ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
 {
 	static unsigned int op;
 
@@ -55,8 +56,9 @@  static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
 	 */
 	addr = GET_ADDR(addr);
 
-	/* Set to "bl addr" */
-	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
+	/* if (link) set op to 'bl' else 'b' */
+	op = 0x48000000 | (link ? 1 : 0);
+	op |= (ftrace_calc_offset(ip, addr) & 0x03fffffc);
 
 	/*
 	 * No locking needed, this must be called via kstop_machine
@@ -344,7 +346,7 @@  int ftrace_make_nop(struct module *mod,
 	 */
 	if (test_24bit_addr(ip, addr)) {
 		/* within range */
-		old = ftrace_call_replace(ip, addr);
+		old = ftrace_call_replace(ip, addr, 1);
 		new = ftrace_nop_replace();
 		return ftrace_modify_code(ip, old, new);
 	}
@@ -484,7 +486,7 @@  int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 	if (test_24bit_addr(ip, addr)) {
 		/* within range */
 		old = ftrace_nop_replace();
-		new = ftrace_call_replace(ip, addr);
+		new = ftrace_call_replace(ip, addr, 1);
 		return ftrace_modify_code(ip, old, new);
 	}
 
@@ -513,7 +515,7 @@  int ftrace_update_ftrace_func(ftrace_func_t func)
 	int ret;
 
 	memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
-	new = ftrace_call_replace(ip, (unsigned long)func);
+	new = ftrace_call_replace(ip, (unsigned long)func, 1);
 	ret = ftrace_modify_code(ip, old, new);
 
 	return ret;
@@ -532,6 +534,39 @@  int __init ftrace_dyn_arch_init(void *data)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+extern void ftrace_graph_stub(void);
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+	unsigned long ip = (unsigned long)(&ftrace_graph_call);
+	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
+	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
+	unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+	new = ftrace_call_replace(ip, stub, 0);
+	memcpy(old, new, MCOUNT_INSN_SIZE);
+	new = ftrace_call_replace(ip, addr, 0);
+
+	return ftrace_modify_code(ip, old, new);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	unsigned long ip = (unsigned long)(&ftrace_graph_call);
+	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
+	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
+	unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+	new = ftrace_call_replace(ip, addr, 0);
+	memcpy(old, new, MCOUNT_INSN_SIZE);
+	new = ftrace_call_replace(ip, stub, 0);
+
+	return ftrace_modify_code(ip, old, new);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
 /*
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.