ftrace ported to PPC

The following two patches ports ftrace to PowerPC. I tested this on
both my PPC64 box as well as my 32bit PowerBook G4.

This applies to the latest sched-devel (with some extra hacks to get that
to boot on PPC).

This also depends on the CFLAGS_REMOVE_foo.o patches I sent earlier.

-- Steve

PPC doesn't have the irqs_disabled_flags needed by ftrace.
This patch adds it.

Signed-off-by: Steven Rostedt <redacted>
---
 include/asm-powerpc/hw_irq.h |   10 ++++++++++
 1 file changed, 10 insertions(+)

Index: linux-sched-devel.git/include/asm-powerpc/hw_irq.h
===================================================================

--- linux-sched-devel.git.orig/include/asm-powerpc/hw_irq.h	2008-05-14 18:12:21.000000000 -0700
+++ linux-sched-devel.git/include/asm-powerpc/hw_irq.h	2008-05-14 19:24:59.000000000 -0700

@@ -59,6 +59,11 @@ extern void iseries_handle_interrupts(vo
 		get_paca()->hard_enabled = 0;	\
 	} while(0)
 
+static inline int irqs_disabled_flags(unsigned long flags)
+{
+	return flags == 0;
+}
+
 #else
 
 #if defined(CONFIG_BOOKE)

@@ -113,6 +118,11 @@ static inline void local_irq_save_ptr(un
 #define hard_irq_enable()	local_irq_enable()
 #define hard_irq_disable()	local_irq_disable()
 
+static inline int irqs_disabled_flags(unsigned long flags)
+{
+	return (flags & MSR_EE) == 0;
+}
+
 #endif /* CONFIG_PPC64 */
 
 /*

-- 

This patch adds full support for ftrace for PowerPC (both 64 and 32 bit).
This includes dynamic tracing and function filtering.

Signed-off-by: Steven Rostedt <redacted>
---
 arch/powerpc/Kconfig                     |    5 
 arch/powerpc/kernel/Makefile             |   14 ++
 arch/powerpc/kernel/entry_32.S           |  130 ++++++++++++++++++++++++
 arch/powerpc/kernel/entry_64.S           |   62 +++++++++++
 arch/powerpc/kernel/ftrace.c             |  165 +++++++++++++++++++++++++++++++
 arch/powerpc/kernel/io.c                 |    3 
 arch/powerpc/kernel/irq.c                |    6 -
 arch/powerpc/kernel/setup_32.c           |   11 +-
 arch/powerpc/kernel/setup_64.c           |    5 
 arch/powerpc/platforms/powermac/Makefile |    5 
 kernel/trace/trace_selftest.c            |   11 +-
 11 files changed, 406 insertions(+), 11 deletions(-)

Index: linux-sched-devel.git/arch/powerpc/kernel/io.c
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/io.c	2008-05-14 19:30:53.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/io.c	2008-05-14 19:31:48.000000000 -0700

@@ -120,7 +120,8 @@ EXPORT_SYMBOL(_outsl_ns);
 
 #define IO_CHECK_ALIGN(v,a) ((((unsigned long)(v)) & ((a) - 1)) == 0)
 
-void _memset_io(volatile void __iomem *addr, int c, unsigned long n)
+notrace void
+_memset_io(volatile void __iomem *addr, int c, unsigned long n)
 {
 	void *p = (void __force *)addr;
 	u32 lc = c;

Index: linux-sched-devel.git/arch/powerpc/kernel/Makefile
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/Makefile	2008-05-14 19:30:53.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/Makefile	2008-05-14 19:31:56.000000000 -0700

@@ -12,6 +12,18 @@ CFLAGS_prom_init.o      += -fPIC
 CFLAGS_btext.o		+= -fPIC
 endif
 
+ifdef CONFIG_FTRACE
+# Do not trace early boot code
+CFLAGS_REMOVE_cputable.o = -pg
+CFLAGS_REMOVE_prom_init.o = -pg
+
+ifdef CONFIG_DYNAMIC_FTRACE
+# dynamic ftrace setup.
+CFLAGS_REMOVE_ftrace.o = -pg
+endif
+
+endif
+
 obj-y				:= cputable.o ptrace.o syscalls.o \
 				   irq.o align.o signal_32.o pmc.o vdso.o \
 				   init_task.o process.o systbl.o idle.o \

@@ -79,6 +91,8 @@ obj-$(CONFIG_KEXEC)		+= machine_kexec.o 
 obj-$(CONFIG_AUDIT)		+= audit.o
 obj64-$(CONFIG_AUDIT)		+= compat_audit.o
 
+obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o
+
 obj-$(CONFIG_8XX_MINIMAL_FPEMU) += softemu8xx.o
 
 ifneq ($(CONFIG_PPC_INDIRECT_IO),y)

Index: linux-sched-devel.git/arch/powerpc/platforms/powermac/Makefile
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/platforms/powermac/Makefile	2008-05-14 19:30:53.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/platforms/powermac/Makefile	2008-05-14 19:31:48.000000000 -0700

@@ -1,5 +1,10 @@
 CFLAGS_bootx_init.o  		+= -fPIC
 
+ifdef CONFIG_FTRACE
+# Do not trace early boot code
+CFLAGS_REMOVE_bootx_init.o = -pg
+endif
+
 obj-y				+= pic.o setup.o time.o feature.o pci.o \
 				   sleep.o low_i2c.o cache.o pfunc_core.o \
 				   pfunc_base.o

Index: linux-sched-devel.git/arch/powerpc/Kconfig
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/Kconfig	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/Kconfig	2008-05-14 19:31:56.000000000 -0700

@@ -106,11 +106,12 @@ config PPC
 	bool
 	default y
 	select HAVE_IDE
-	select HAVE_OPROFILE
+	select HAVE_IMMEDIATE
+	select HAVE_FTRACE
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
 	select HAVE_LMB
-	select HAVE_IMMEDIATE
+	select HAVE_OPROFILE
 
 config EARLY_PRINTK
 	bool

Index: linux-sched-devel.git/arch/powerpc/kernel/entry_32.S
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/entry_32.S	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/entry_32.S	2008-05-14 19:31:56.000000000 -0700

@@ -1035,3 +1035,133 @@ machine_check_in_rtas:
 	/* XXX load up BATs and panic */
 
 #endif /* CONFIG_PPC_RTAS */
+
+#ifdef CONFIG_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+	stwu	r1,-48(r1)
+	stw	r3, 12(r1)
+	stw	r4, 16(r1)
+	stw	r5, 20(r1)
+	stw	r6, 24(r1)
+	mflr	r3
+	stw	r7, 28(r1)
+	mfcr	r5
+	stw	r8, 32(r1)
+	stw	r9, 36(r1)
+	stw	r10,40(r1)
+	stw	r3, 44(r1)
+	stw	r5, 8(r1)
+	.globl mcount_call
+mcount_call:
+	bl	ftrace_stub
+	nop
+	lwz	r6, 8(r1)
+	lwz	r0, 44(r1)
+	lwz	r3, 12(r1)
+	mtctr	r0
+	lwz	r4, 16(r1)
+	mtcr	r6
+	lwz	r5, 20(r1)
+	lwz	r6, 24(r1)
+	lwz	r0, 52(r1)
+	lwz	r7, 28(r1)
+	lwz	r8, 32(r1)
+	mtlr	r0
+	lwz	r9, 36(r1)
+	lwz	r10,40(r1)
+	addi	r1, r1, 48
+	bctr
+
+_GLOBAL(ftrace_caller)
+	/* Based off of objdump optput from glibc */
+	stwu	r1,-48(r1)
+	stw	r3, 12(r1)
+	stw	r4, 16(r1)
+	stw	r5, 20(r1)
+	stw	r6, 24(r1)
+	mflr	r3
+	lwz	r4, 52(r1)
+	mfcr	r5
+	stw	r7, 28(r1)
+	stw	r8, 32(r1)
+	stw	r9, 36(r1)
+	stw	r10,40(r1)
+	stw	r3, 44(r1)
+	stw	r5, 8(r1)
+.globl ftrace_call
+ftrace_call:
+	bl	ftrace_stub
+	nop
+	lwz	r6, 8(r1)
+	lwz	r0, 44(r1)
+	lwz	r3, 12(r1)
+	mtctr	r0
+	lwz	r4, 16(r1)
+	mtcr	r6
+	lwz	r5, 20(r1)
+	lwz	r6, 24(r1)
+	lwz	r0, 52(r1)
+	lwz	r7, 28(r1)
+	lwz	r8, 32(r1)
+	mtlr	r0
+	lwz	r9, 36(r1)
+	lwz	r10,40(r1)
+	addi	r1, r1, 48
+	bctr
+#else
+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+	stwu	r1,-48(r1)
+	stw	r3, 12(r1)
+	stw	r4, 16(r1)
+	stw	r5, 20(r1)
+	stw	r6, 24(r1)
+	mflr	r3
+	lwz	r4, 52(r1)
+	mfcr	r5
+	stw	r7, 28(r1)
+	stw	r8, 32(r1)
+	stw	r9, 36(r1)
+	stw	r10,40(r1)
+	stw	r3, 44(r1)
+	stw	r5, 8(r1)
+
+	LOAD_REG_ADDR(r5, ftrace_trace_function)
+#if 0
+	mtctr	r3
+	mr	r1, r5
+	bctrl
+#endif
+	lwz	r5,0(r5)
+#if 1
+	mtctr	r5
+	bctrl
+#else
+	bl	ftrace_stub
+#endif
+	nop
+
+	lwz	r6, 8(r1)
+	lwz	r0, 44(r1)
+	lwz	r3, 12(r1)
+	mtctr	r0
+	lwz	r4, 16(r1)
+	mtcr	r6
+	lwz	r5, 20(r1)
+	lwz	r6, 24(r1)
+	lwz	r0, 52(r1)
+	lwz	r7, 28(r1)
+	lwz	r8, 32(r1)
+	mtlr	r0
+	lwz	r9, 36(r1)
+	lwz	r10,40(r1)
+	addi	r1, r1, 48
+	bctr
+#endif
+
+_GLOBAL(ftrace_stub)
+	blr
+
+#endif /* CONFIG_MCOUNT */

Index: linux-sched-devel.git/arch/powerpc/kernel/entry_64.S
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/entry_64.S	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/entry_64.S	2008-05-14 19:31:56.000000000 -0700

@@ -870,3 +870,65 @@ _GLOBAL(enter_prom)
 	ld	r0,16(r1)
 	mtlr    r0
         blr
+
+#ifdef CONFIG_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+	/* Taken from output of objdump from lib64/glibc */
+	mflr	r3
+	stdu	r1, -112(r1)
+	std	r3, 128(r1)
+	.globl mcount_call
+mcount_call:
+	bl	ftrace_stub
+	nop
+	ld	r0, 128(r1)
+	mtlr	r0
+	addi	r1, r1, 112
+	blr
+
+_GLOBAL(ftrace_caller)
+	/* Taken from output of objdump from lib64/glibc */
+	mflr	r3
+	ld	r11, 0(r1)
+	stdu	r1, -112(r1)
+	std	r3, 128(r1)
+	ld	r4, 16(r11)
+.globl ftrace_call
+ftrace_call:
+	bl	ftrace_stub
+	nop
+	ld	r0, 128(r1)
+	mtlr	r0
+	addi	r1, r1, 112
+_GLOBAL(ftrace_stub)
+	blr
+#else
+_GLOBAL(mcount)
+	blr
+
+_GLOBAL(_mcount)
+	/* Taken from output of objdump from lib64/glibc */
+	mflr	r3
+	ld	r11, 0(r1)
+	stdu	r1, -112(r1)
+	std	r3, 128(r1)
+	ld	r4, 16(r11)
+
+
+	LOAD_REG_ADDR(r5,ftrace_trace_function)
+	ld	r5,0(r5)
+	ld	r5,0(r5)
+	mtctr	r5
+	bctrl
+
+	nop
+	ld	r0, 128(r1)
+	mtlr	r0
+	addi	r1, r1, 112
+_GLOBAL(ftrace_stub)
+	blr
+
+#endif
+#endif

Index: linux-sched-devel.git/arch/powerpc/kernel/ftrace.c
===================================================================

--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-sched-devel.git/arch/powerpc/kernel/ftrace.c	2008-05-14 19:31:56.000000000 -0700

@@ -0,0 +1,165 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
+ *
+ */
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/ftrace.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/list.h>
+
+#include <asm/cacheflush.h>
+
+#define CALL_BACK		4
+
+static unsigned int ftrace_nop = 0x60000000;
+
+#ifdef CONFIG_PPC32
+# define GET_ADDR(addr) addr
+#else
+/* PowerPC64's functions are data that points to the functions */
+# define GET_ADDR(addr) *(unsigned long *)addr
+#endif
+
+notrace int ftrace_ip_converted(unsigned long ip)
+{
+	unsigned int save;
+
+	ip -= CALL_BACK;
+	save = *(unsigned int *)ip;
+
+	return save == ftrace_nop;
+}
+
+static unsigned int notrace ftrace_calc_offset(long ip, long addr)
+{
+	return (int)((addr + CALL_BACK) - ip);
+}
+
+notrace unsigned char *ftrace_nop_replace(void)
+{
+	return (char *)&ftrace_nop;
+}
+
+notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+	static unsigned int op;
+
+	addr = GET_ADDR(addr);
+
+	/* Set to "bl addr" */
+	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffe);
+
+	/*
+	 * No locking needed, this must be called via kstop_machine
+	 * which in essence is like running on a uniprocessor machine.
+	 */
+	return (unsigned char *)&op;
+}
+
+#ifdef CONFIG_PPC64
+# define _ASM_ALIGN	" .align 3 "
+# define _ASM_PTR	" .llong "
+#else
+# define _ASM_ALIGN	" .align 2 "
+# define _ASM_PTR	" .long "
+#endif
+
+notrace int
+ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+		   unsigned char *new_code)
+{
+	unsigned replaced;
+	unsigned old = *(unsigned *)old_code;
+	unsigned new = *(unsigned *)new_code;
+	int faulted = 0;
+
+	/* move the IP back to the start of the call */
+	ip -= CALL_BACK;
+
+	/*
+	 * Note: Due to modules and __init, code can
+	 *  disappear and change, we need to protect against faulting
+	 *  as well as code changing.
+	 *
+	 * No real locking needed, this code is run through
+	 * kstop_machine.
+	 */
+	asm volatile (
+		"1: lwz		%1, 0(%2)\n"
+		"   cmpw	%1, %5\n"
+		"   bne		2f\n"
+		"   stwu	%3, 0(%2)\n"
+		"2:\n"
+		".section .fixup, \"ax\"\n"
+		"3:	li %0, 1\n"
+		"	b 2b\n"
+		".previous\n"
+		".section __ex_table,\"a\"\n"
+		_ASM_ALIGN "\n"
+		_ASM_PTR "1b, 3b\n"
+		".previous"
+		: "=r"(faulted), "=r"(replaced)
+		: "r"(ip), "r"(new),
+		  "0"(faulted), "r"(old)
+		: "memory");
+
+	if (replaced != old && replaced != new)
+		faulted = 2;
+
+	if (!faulted)
+		flush_icache_range(ip, ip + 8);
+
+	return faulted;
+}
+
+notrace int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	unsigned long ip = (unsigned long)(&ftrace_call);
+	unsigned char old[4], *new;
+	int ret;
+
+	ip += CALL_BACK;
+
+	memcpy(old, &ftrace_call, 4);
+	new = ftrace_call_replace(ip, (unsigned long)func);
+	ret = ftrace_modify_code(ip, old, new);
+
+	return ret;
+}
+
+notrace int ftrace_mcount_set(unsigned long *data)
+{
+	unsigned long ip = (long)(&mcount_call);
+	unsigned long *addr = data;
+	unsigned char old[4], *new;
+
+	/* ip is at the location, but modify code will subtact this */
+	ip += CALL_BACK;
+
+	/*
+	 * Replace the mcount stub with a pointer to the
+	 * ip recorder function.
+	 */
+	memcpy(old, &mcount_call, 4);
+	new = ftrace_call_replace(ip, *addr);
+	*addr = ftrace_modify_code(ip, old, new);
+
+	return 0;
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+	/* This is running in kstop_machine */
+
+	ftrace_mcount_set(data);
+
+	return 0;
+}
+

Index: linux-sched-devel.git/arch/powerpc/kernel/irq.c
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/irq.c	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/irq.c	2008-05-14 19:31:56.000000000 -0700

@@ -98,7 +98,7 @@ EXPORT_SYMBOL(irq_desc);
 
 int distribute_irqs = 1;
 
-static inline unsigned long get_hard_enabled(void)
+static inline notrace unsigned long get_hard_enabled(void)
 {
 	unsigned long enabled;
 

@@ -108,13 +108,13 @@ static inline unsigned long get_hard_ena
 	return enabled;
 }
 
-static inline void set_soft_enabled(unsigned long enable)
+static inline notrace void set_soft_enabled(unsigned long enable)
 {
 	__asm__ __volatile__("stb %0,%1(13)"
 	: : "r" (enable), "i" (offsetof(struct paca_struct, soft_enabled)));
 }
 
-void raw_local_irq_restore(unsigned long en)
+notrace void raw_local_irq_restore(unsigned long en)
 {
 	/*
 	 * get_paca()->soft_enabled = en;

Index: linux-sched-devel.git/arch/powerpc/kernel/setup_32.c
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/setup_32.c	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/setup_32.c	2008-05-14 19:31:56.000000000 -0700

@@ -47,6 +47,11 @@
 #include <asm/kgdb.h>
 #endif
 
+#ifdef CONFIG_FTRACE
+extern void _mcount(void);
+EXPORT_SYMBOL(_mcount);
+#endif
+
 extern void bootx_init(unsigned long r4, unsigned long phys);
 
 int boot_cpuid;

@@ -81,7 +86,7 @@ int ucache_bsize;
  * from the address that it was linked at, so we must use RELOC/PTRRELOC
  * to access static data (including strings).  -- paulus
  */
-unsigned long __init early_init(unsigned long dt_ptr)
+notrace unsigned long __init early_init(unsigned long dt_ptr)
 {
 	unsigned long offset = reloc_offset();
 	struct cpu_spec *spec;

@@ -111,7 +116,7 @@ unsigned long __init early_init(unsigned
  * This is called very early on the boot process, after a minimal
  * MMU environment has been set up but before MMU_init is called.
  */
-void __init machine_init(unsigned long dt_ptr, unsigned long phys)
+notrace void __init machine_init(unsigned long dt_ptr, unsigned long phys)
 {
 	/* Enable early debugging if any specified (see udbg.h) */
 	udbg_early_init();

@@ -133,7 +138,7 @@ void __init machine_init(unsigned long d
 
 #ifdef CONFIG_BOOKE_WDT
 /* Checks wdt=x and wdt_period=xx command-line option */
-int __init early_parse_wdt(char *p)
+notrace int __init early_parse_wdt(char *p)
 {
 	if (p && strncmp(p, "0", 1) != 0)
 	       booke_wdt_enabled = 1;

Index: linux-sched-devel.git/arch/powerpc/kernel/setup_64.c
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/setup_64.c	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/setup_64.c	2008-05-14 19:31:56.000000000 -0700

@@ -85,6 +85,11 @@ struct ppc64_caches ppc64_caches = {
 };
 EXPORT_SYMBOL_GPL(ppc64_caches);
 
+#ifdef CONFIG_FTRACE
+extern void _mcount(void);
+EXPORT_SYMBOL(_mcount);
+#endif
+
 /*
  * These are used in binfmt_elf.c to put aux entries on the stack
  * for each elf executable being started.

Index: linux-sched-devel.git/kernel/trace/trace_selftest.c
===================================================================

--- linux-sched-devel.git.orig/kernel/trace/trace_selftest.c	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/kernel/trace/trace_selftest.c	2008-05-14 19:31:56.000000000 -0700

@@ -123,6 +123,7 @@ int trace_selftest_startup_dynamic_traci
 	int ret;
 	int save_ftrace_enabled = ftrace_enabled;
 	int save_tracer_enabled = tracer_enabled;
+	char *func_name;
 
 	/* The ftrace test PASSED */
 	printk(KERN_CONT "PASSED\n");

@@ -142,9 +143,15 @@ int trace_selftest_startup_dynamic_traci
 		return ret;
 	}
 
+	/*
+	 * Some archs *cough*PowerPC*cough* add charachters to the
+	 * start of the function names. We simply put a '*' to
+	 * accomodate them.
+	 */
+	func_name = "*" STR(DYN_FTRACE_TEST_NAME);
+
 	/* filter only on our function */
-	ftrace_set_filter(STR(DYN_FTRACE_TEST_NAME),
-			  sizeof(STR(DYN_FTRACE_TEST_NAME)), 1);
+	ftrace_set_filter(func_name, strlen(func_name), 1);
 
 	/* enable tracing */
 	tr->ctrl = 1;

-- 

Steven Rostedt writes:

The following two patches ports ftrace to PowerPC. I tested this on
both my PPC64 box as well as my 32bit PowerBook G4.

Very cool!  Thanks.

This applies to the latest sched-devel (with some extra hacks to get that
to boot on PPC).

This also depends on the CFLAGS_REMOVE_foo.o patches I sent earlier.

Ingo, when do you intend to send the ftrace stuff to Linus?  In the
next merge window?

Paul.

From: Steven Rostedt <rostedt@goodmis.org>
Date: Wed, 14 May 2008 23:49:44 -0400

Yikes, that's really expensive.

Can't you do a tail call and let the function you end
up calling do all the callee-saved register pops onto
the stack?

That's what I did on sparc.

On Wed, 14 May 2008, David Miller wrote:

From: Steven Rostedt <rostedt@goodmis.org>
Date: Wed, 14 May 2008 23:49:44 -0400

quoted

+#ifdef CONFIG_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+	stwu	r1,-48(r1)
+	stw	r3, 12(r1)
+	stw	r4, 16(r1)
+	stw	r5, 20(r1)
+	stw	r6, 24(r1)
+	mflr	r3
+	stw	r7, 28(r1)
+	mfcr	r5
+	stw	r8, 32(r1)
+	stw	r9, 36(r1)
+	stw	r10,40(r1)
+	stw	r3, 44(r1)
+	stw	r5, 8(r1)

Yikes, that's really expensive.

Well, at least with dynamic ftrace, it's only expensive when tracing is
enabled.

Can't you do a tail call and let the function you end
up calling do all the callee-saved register pops onto
the stack?

Not sure PPC has such a thing. I'm only a hobby PPC hacker (did it full
time in another life). If there is such a way, I'll be happy to Ack any
patches.

That's what I did on sparc.

So that was your secret! ;-)

-- Steve

On Wed, May 14, 2008 at 10:28:57PM -0700, David Miller wrote:

From: Steven Rostedt <rostedt@goodmis.org>
Date: Wed, 14 May 2008 23:49:44 -0400

quoted

+#ifdef CONFIG_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+	stwu	r1,-48(r1)
+	stw	r3, 12(r1)
+	stw	r4, 16(r1)
+	stw	r5, 20(r1)
+	stw	r6, 24(r1)
+	mflr	r3
+	stw	r7, 28(r1)
+	mfcr	r5
+	stw	r8, 32(r1)
+	stw	r9, 36(r1)
+	stw	r10,40(r1)
+	stw	r3, 44(r1)
+	stw	r5, 8(r1)

Yikes, that's really expensive.

Can't you do a tail call and let the function you end
up calling do all the callee-saved register pops onto
the stack?

The PPC32 ABI seems to (unfortunately) suggest that, with mcount, all
registers are callee-saved (except for the modifiable-during-function-linkage
registers like r0, r11, and r12) -- so mcount has to save the registers that
the callee won't (because they're normally volatile).

-Scott

* Paul Mackerras [off-list ref] wrote:

Steven Rostedt writes:

quoted

The following two patches ports ftrace to PowerPC. I tested this on 
both my PPC64 box as well as my 32bit PowerBook G4.

Very cool!  Thanks.

great - could you please send an Acked-by line for those patches?

quoted

This applies to the latest sched-devel (with some extra hacks to get 
that to boot on PPC).

This also depends on the CFLAGS_REMOVE_foo.o patches I sent earlier.

Ingo, when do you intend to send the ftrace stuff to Linus?  In the 
next merge window?

yeah, that's the plan, this merge window was too hot already. Right now 
there's an ftrace topic in the -tip tree:

    http://people.redhat.com/mingo/tip.git/README

that contains the latest ftrace patches. Please holler if you see 
something weird in it.

	Ingo

* Steven Rostedt [off-list ref] wrote:

PPC doesn't have the irqs_disabled_flags needed by ftrace. This patch 
adds it.

applied, thanks.

	Ingo

* Steven Rostedt [off-list ref] wrote:

This patch adds full support for ftrace for PowerPC (both 64 and 32 
bit). This includes dynamic tracing and function filtering.

applied, thanks. Nice stuff! :)

	Ingo

On Wed, 2008-05-14 at 23:49 -0400, Steven Rostedt wrote:

plain text document attachment (ftrace-powerpc-port.patch)
This patch adds full support for ftrace for PowerPC (both 64 and 32 bit).
This includes dynamic tracing and function filtering.

Hi Steven,

Just a few comments inline ..

Why do we not want to trace early boot? Just because it's not useful? 

.. snip

#if 0, #if 1 ?

I don't grok what you're doing with CALL_BACK, you add it in places and
subtract in others - and it looks like you could do neither, but I haven't
gone over it in detail.

+static unsigned int ftrace_nop = 0x60000000;

I should really add a #define for that.

And that.

.. snip

0x03fffffe should be 0x03fffffc, if you set bit 1 you'll end with a "bla" instruction,
ie. branch absolute and link. That shouldn't happen as long as ip and addr are
properly aligned, but still.

In fact I think you should just use create_function_call() or create_branch() from
include/asm-powerpc/system.h

We already have a #define for .long, it's called PPC_LONG (asm/asm-compat.h)

Perhaps we should add one for .align, PPC_LONG_ALIGN or something?

Or perhaps we just need a macro for adding exception table entries.

Can you please put the extern in a header, and the EXPORT_SYMBOL in arch/powerpc/kernel/ftrace.c?

Ditto.


cheers


-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

Why do we not want to trace early boot? Just because it's not useful? 

Not running at the linked address... might be causing trouble.

Ben.

On Wed, 21 May 2008, Michael Ellerman wrote:

On Wed, 2008-05-14 at 23:49 -0400, Steven Rostedt wrote:

quoted

plain text document attachment (ftrace-powerpc-port.patch)
This patch adds full support for ftrace for PowerPC (both 64 and 32 bit).
This includes dynamic tracing and function filtering.

Hi Steven,

Just a few comments inline ..

Hi Michael,

I really appreciate this. It's been a few years since I did any real PPC
programming, so any comments are most definitely welcome.

quoted

Index: linux-sched-devel.git/arch/powerpc/kernel/Makefile
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/Makefile	2008-05-14 19:30:53.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/Makefile	2008-05-14 19:31:56.000000000 -0700

@@ -12,6 +12,18 @@ CFLAGS_prom_init.o      += -fPIC
 CFLAGS_btext.o		+= -fPIC
 endif

+ifdef CONFIG_FTRACE
+# Do not trace early boot code
+CFLAGS_REMOVE_cputable.o = -pg
+CFLAGS_REMOVE_prom_init.o = -pg

Why do we not want to trace early boot? Just because it's not useful?

The -pg flag makes calls to the mcount code. I didn't look too deeply, but
at least in my first prototypes the early boot up code would crash when
calling mcount. I found that simply keeping them from calling mcount made
things OK. Perhaps I'm just hiding the problem, but the tracing wont
happen anyway that early. We need to set up memory before tracing starts.

quoted

Index: linux-sched-devel.git/arch/powerpc/kernel/entry_32.S
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/entry_32.S	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/entry_32.S	2008-05-14 19:31:56.000000000 -0700

@@ -1035,3 +1035,133 @@ machine_check_in_rtas:
 	/* XXX load up BATs and panic */

... snip

quoted

+_GLOBAL(mcount)
+_GLOBAL(_mcount)
+	stwu	r1,-48(r1)
+	stw	r3, 12(r1)
+	stw	r4, 16(r1)
+	stw	r5, 20(r1)
+	stw	r6, 24(r1)
+	mflr	r3
+	lwz	r4, 52(r1)
+	mfcr	r5
+	stw	r7, 28(r1)
+	stw	r8, 32(r1)
+	stw	r9, 36(r1)
+	stw	r10,40(r1)
+	stw	r3, 44(r1)
+	stw	r5, 8(r1)
+
+	LOAD_REG_ADDR(r5, ftrace_trace_function)
+#if 0
+	mtctr	r3
+	mr	r1, r5
+	bctrl
+#endif
+	lwz	r5,0(r5)
+#if 1
+	mtctr	r5
+	bctrl
+#else
+	bl	ftrace_stub
+#endif

2 more quoted lines

Ouch! Thanks, that's leftover from debugging.

quoted

Index: linux-sched-devel.git/arch/powerpc/kernel/ftrace.c
===================================================================

--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-sched-devel.git/arch/powerpc/kernel/ftrace.c	2008-05-14 19:31:56.000000000 -0700

@@ -0,0 +1,165 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
+ *
+ */
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/ftrace.h>
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/list.h>
+
+#include <asm/cacheflush.h>
+
+#define CALL_BACK		4

I don't grok what you're doing with CALL_BACK, you add it in places and
subtract in others - and it looks like you could do neither, but I haven't
gone over it in detail.

I tried hard to make most of the complex logic stay in generic code.

What dynamic ftrace does is at start up the code is simply a nop. Then
after initialization of ftrace, it calls kstop-machine that will call into
the arch code to convert the nop to a call to a "record_ip" function.
That record_ip function will start recording the return address of the
mcount function (__builtin_return_address(0)).

Then later, once a second the ftraced wakes up and checks if any new
functions have been recorded. If they have been, then it calls
kstop_machine againg and for each recorded function, it passes in the
address that was recorded.

The arch is responsible for knowning how to translate the
__builtin_return_address(0) into the address of the location of the call,
to be able to modify that code.

On boot up, all functions call "mcount". The ftraced daemon will convert
those calls to nop, and when tracing is enabled, then they will be
converted to point directly to the tracing function.

This helps tremondously in making ftrace efficient.

quoted

+static unsigned int ftrace_nop = 0x60000000;

I should really add a #define for that.

quoted

+#ifdef CONFIG_PPC32
+# define GET_ADDR(addr) addr
+#else
+/* PowerPC64's functions are data that points to the functions */
+# define GET_ADDR(addr) *(unsigned long *)addr
+#endif

And that.

... snip

quoted

+notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+	static unsigned int op;
+
+	addr = GET_ADDR(addr);
+
+	/* Set to "bl addr" */
+	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffe);

0x03fffffe should be 0x03fffffc, if you set bit 1 you'll end with a "bla" instruction,
ie. branch absolute and link. That shouldn't happen as long as ip and addr are
properly aligned, but still.

Thanks for the update. I guess I miss read the documents I have.

In fact I think you should just use create_function_call() or create_branch() from
include/asm-powerpc/system.h

Also good to know. I'll look into replacing them with these.

quoted

+#ifdef CONFIG_PPC64
+# define _ASM_ALIGN	" .align 3 "
+# define _ASM_PTR	" .llong "
+#else
+# define _ASM_ALIGN	" .align 2 "
+# define _ASM_PTR	" .long "
+#endif

We already have a #define for .long, it's called PPC_LONG (asm/asm-compat.h)

Perhaps we should add one for .align, PPC_LONG_ALIGN or something?

Ah, thanks. I'll wait till I see a PPC_LONG_ALIGN ;-)

quoted

+notrace int
+ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+		   unsigned char *new_code)
+{
+	unsigned replaced;
+	unsigned old = *(unsigned *)old_code;
+	unsigned new = *(unsigned *)new_code;
+	int faulted = 0;
+
+	/* move the IP back to the start of the call */
+	ip -= CALL_BACK;
+
+	/*
+	 * Note: Due to modules and __init, code can
+	 *  disappear and change, we need to protect against faulting
+	 *  as well as code changing.
+	 *
+	 * No real locking needed, this code is run through
+	 * kstop_machine.
+	 */
+	asm volatile (
+		"1: lwz		%1, 0(%2)\n"
+		"   cmpw	%1, %5\n"
+		"   bne		2f\n"
+		"   stwu	%3, 0(%2)\n"
+		"2:\n"
+		".section .fixup, \"ax\"\n"
+		"3:	li %0, 1\n"
+		"	b 2b\n"
+		".previous\n"
+		".section __ex_table,\"a\"\n"
+		_ASM_ALIGN "\n"
+		_ASM_PTR "1b, 3b\n"
+		".previous"

Or perhaps we just need a macro for adding exception table entries.

Yeah, that was taken from what x86 does.

quoted

+		: "=r"(faulted), "=r"(replaced)
+		: "r"(ip), "r"(new),
+		  "0"(faulted), "r"(old)
+		: "memory");
+
+	if (replaced != old && replaced != new)
+		faulted = 2;
+
+	if (!faulted)
+		flush_icache_range(ip, ip + 8);
+
+	return faulted;
+}

quoted

Index: linux-sched-devel.git/arch/powerpc/kernel/setup_32.c
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/setup_32.c	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/setup_32.c	2008-05-14 19:31:56.000000000 -0700

@@ -47,6 +47,11 @@
 #include <asm/kgdb.h>
 #endif

+#ifdef CONFIG_FTRACE
+extern void _mcount(void);
+EXPORT_SYMBOL(_mcount);
+#endif

Can you please put the extern in a header, and the EXPORT_SYMBOL in
arch/powerpc/kernel/ftrace.c?

Actually, I think Ingo added this into the generic code. I'll see what's
in there now.

quoted

Index: linux-sched-devel.git/arch/powerpc/kernel/setup_64.c
===================================================================

--- linux-sched-devel.git.orig/arch/powerpc/kernel/setup_64.c	2008-05-14 19:30:50.000000000 -0700
+++ linux-sched-devel.git/arch/powerpc/kernel/setup_64.c	2008-05-14 19:31:56.000000000 -0700

@@ -85,6 +85,11 @@ struct ppc64_caches ppc64_caches = {
 };
 EXPORT_SYMBOL_GPL(ppc64_caches);

+#ifdef CONFIG_FTRACE
+extern void _mcount(void);
+EXPORT_SYMBOL(_mcount);
+#endif

Ditto.

Ditto too ;-)


Thanks a lot for you feedback!

-- Steve

On Tue, 20 May 2008, Benjamin Herrenschmidt wrote:

quoted

Why do we not want to trace early boot? Just because it's not useful?

Not running at the linked address... might be causing trouble.

I figured it was something like that, so I didn't look too deep into it,
and decided that it was best just not to trace it.

-- Steve

This patch cleans up the ftrace code in PowerPC based on the comments from
Michael Ellerman.

Signed-off-by: Steven Rostedt <redacted>
---
 -0700                           |binary
 arch/powerpc/kernel/entry_32.S  |   11 ++---------
 arch/powerpc/kernel/ftrace.c    |    8 +++++++-
 arch/powerpc/kernel/ppc_ksyms.c |    5 +++++
 arch/powerpc/kernel/setup_32.c  |    5 -----
 arch/powerpc/kernel/setup_64.c  |    5 -----
 include/asm-powerpc/ftrace.h    |    6 ++++++
 6 files changed, 20 insertions(+), 20 deletions(-)

Index: linux-tip.git/arch/powerpc/kernel/entry_32.S
===================================================================

--- linux-tip.git.orig/arch/powerpc/kernel/entry_32.S	2008-05-22 09:17:51.000000000 -0700
+++ linux-tip.git/arch/powerpc/kernel/entry_32.S	2008-05-22 09:18:21.000000000 -0700

@@ -1129,18 +1129,11 @@ _GLOBAL(_mcount)
 	stw	r5, 8(r1)

 	LOAD_REG_ADDR(r5, ftrace_trace_function)
-#if 0
-	mtctr	r3
-	mr	r1, r5
-	bctrl
-#endif
 	lwz	r5,0(r5)
-#if 1
+
 	mtctr	r5
 	bctrl
-#else
-	bl	ftrace_stub
-#endif
+
 	nop

 	lwz	r6, 8(r1)

Index: linux-tip.git/arch/powerpc/kernel/ftrace.c
===================================================================

--- linux-tip.git.orig/arch/powerpc/kernel/ftrace.c	2008-05-22 09:19:12.000000000 -0700
+++ linux-tip.git/arch/powerpc/kernel/ftrace.c	2008-05-22 09:29:45.000000000 -0700

@@ -51,10 +51,16 @@ notrace unsigned char *ftrace_call_repla
 {
 	static unsigned int op;

+	/*
+	 * It would be nice to just use create_function_call, but that will
+	 * update the code itself. Here we need to just return the
+	 * instruction that is going to be modified, without modifying the
+	 * code.
+	 */
 	addr = GET_ADDR(addr);

 	/* Set to "bl addr" */
-	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffe);
+	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);

 	/*
 	 * No locking needed, this must be called via kstop_machine

Index: linux-tip.git/arch/powerpc/kernel/ppc_ksyms.c
===================================================================

--- linux-tip.git.orig/arch/powerpc/kernel/ppc_ksyms.c	2008-05-22 09:37:28.000000000 -0700
+++ linux-tip.git/arch/powerpc/kernel/ppc_ksyms.c	2008-05-22 11:07:36.000000000 -0700

@@ -43,6 +43,7 @@
 #include <asm/div64.h>
 #include <asm/signal.h>
 #include <asm/dcr.h>
+#include <asm/ftrace.h>

 #ifdef CONFIG_PPC32
 extern void transfer_to_handler(void);

@@ -68,6 +69,10 @@ EXPORT_SYMBOL(single_step_exception);
 EXPORT_SYMBOL(sys_sigreturn);
 #endif

+#ifdef CONFIG_FTRACE
+EXPORT_SYMBOL(_mcount);
+#endif
+
 EXPORT_SYMBOL(strcpy);
 EXPORT_SYMBOL(strncpy);
 EXPORT_SYMBOL(strcat);

Index: linux-tip.git/arch/powerpc/kernel/setup_64.c
===================================================================

--- linux-tip.git.orig/arch/powerpc/kernel/setup_64.c	2008-05-22 09:35:30.000000000 -0700
+++ linux-tip.git/arch/powerpc/kernel/setup_64.c	2008-05-22 11:25:30.000000000 -0700

@@ -85,11 +85,6 @@ struct ppc64_caches ppc64_caches = {
 };
 EXPORT_SYMBOL_GPL(ppc64_caches);

-#ifdef CONFIG_FTRACE
-extern void _mcount(void);
-EXPORT_SYMBOL(_mcount);
-#endif
-
 /*
  * These are used in binfmt_elf.c to put aux entries on the stack
  * for each elf executable being started.

Index: linux-tip.git/include/asm-powerpc/ftrace.h
===================================================================

--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-tip.git/include/asm-powerpc/ftrace.h	2008-05-22 09:39:39.000000000 -0700

@@ -0,0 +1,6 @@
+#ifndef _ASM_POWERPC_FTRACE
+#define _ASM_POWERPC_FTRACE
+
+extern void _mcount(void);
+
+#endif

Index: linux-tip.git/arch/powerpc/kernel/setup_32.c
===================================================================

--- linux-tip.git.orig/arch/powerpc/kernel/setup_32.c	2008-05-22 09:35:30.000000000 -0700
+++ linux-tip.git/arch/powerpc/kernel/setup_32.c	2008-05-22 11:25:39.000000000 -0700

@@ -47,11 +47,6 @@
 #include <asm/kgdb.h>
 #endif

-#ifdef CONFIG_FTRACE
-extern void _mcount(void);
-EXPORT_SYMBOL(_mcount);
-#endif
-
 extern void bootx_init(unsigned long r4, unsigned long phys);

 int boot_cpuid;

On Thu, 22 May 2008, Steven Rostedt wrote:

This patch cleans up the ftrace code in PowerPC based on the comments from
Michael Ellerman.

Applied, thanks

	 tglx

On Thu, 2008-05-22 at 14:31 -0400, Steven Rostedt wrote:

This patch cleans up the ftrace code in PowerPC based on the comments from
Michael Ellerman.

Hi Steven,

Thanks for that.

I posted some patches last week, also in my git tree[1], that should
allow you to use create_branch() in your code (and also facilitate some
other things I wanted to do). I also added a #define for NOP also.

If/when my patches go into powerpc-next I'll do a patch against
linux-next for ftrace to use them.

cheers

[1]: http://git.kernel.org/?p=linux/kernel/git/mpe/linux-2.6.git;a=summary

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person