ftrace: support for PowerPC

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 <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/powerpc/kernel/ftrace.c

@@ -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;
+}
+