arch/powerpc/kernel/ftrace.c - maze/linux - Git at Google

 /*
  * 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.
  *
  * Added function graph tracer code, taken from x86 that was written
  * by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
  *
  */

 #include <linux/spinlock.h>
 #include <linux/hardirq.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/ftrace.h>
 #include <linux/percpu.h>
 #include <linux/init.h>
 #include <linux/list.h>

 #include <asm/cacheflush.h>
 #include <asm/code-patching.h>
 #include <asm/ftrace.h>

 #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

 #ifdef CONFIG_DYNAMIC_FTRACE
 static unsigned int ftrace_nop_replace(void)
 {
 	return PPC_INST_NOP;
 }

 static unsigned int
 ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
 {
 	unsigned int op;

 	addr = GET_ADDR(addr);

 	/* if (link) set op to 'bl' else 'b' */
 	op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);

 	return op;
 }

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

 static int
 ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
 {
 	unsigned int replaced;

 	/*
 	 * Note: Due to modules and __init, code can
 	 *  disappear and change, we need to protect against faulting
 	 *  as well as code changing. We do this by using the
 	 *  probe_kernel_* functions.
 	 *
 	 * No real locking needed, this code is run through
 	 * kstop_machine, or before SMP starts.
 	 */

 	/* read the text we want to modify */
 	if (probe_kernel_read(&replaced, (void *)ip, MCOUNT_INSN_SIZE))
 		return -EFAULT;

 	/* Make sure it is what we expect it to be */
 	if (replaced != old)
 		return -EINVAL;

 	/* replace the text with the new text */
 	if (probe_kernel_write((void *)ip, &new, MCOUNT_INSN_SIZE))
 		return -EPERM;

 	flush_icache_range(ip, ip + 8);

 	return 0;
 }

 /*
  * Helper functions that are the same for both PPC64 and PPC32.
  */
 static int test_24bit_addr(unsigned long ip, unsigned long addr)
 {

 	/* use the create_branch to verify that this offset can be branched */
 	return create_branch((unsigned int *)ip, addr, 0);
 }

 #ifdef CONFIG_MODULES

 static int is_bl_op(unsigned int op)
 {
 	return (op & 0xfc000003) == 0x48000001;
 }

 static unsigned long find_bl_target(unsigned long ip, unsigned int op)
 {
 	static int offset;

 	offset = (op & 0x03fffffc);
 	/* make it signed */
 	if (offset & 0x02000000)
 		offset |= 0xfe000000;

 	return ip + (long)offset;
 }

 #ifdef CONFIG_PPC64
 static int
 __ftrace_make_nop(struct module *mod,
 		  struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned int op;
 	unsigned int jmp[5];
 	unsigned long ptr;
 	unsigned long ip = rec->ip;
 	unsigned long tramp;
 	int offset;

 	/* read where this goes */
 	if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
 		return -EFAULT;

 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
 		printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
 		return -EINVAL;
 	}

 	/* lets find where the pointer goes */
 	tramp = find_bl_target(ip, op);

 	/*
 	 * On PPC64 the trampoline looks like:
 	 * 0x3d, 0x82, 0x00, 0x00,    addis   r12,r2, <high>
 	 * 0x39, 0x8c, 0x00, 0x00,    addi    r12,r12, <low>
 	 *   Where the bytes 2,3,6 and 7 make up the 32bit offset
 	 *   to the TOC that holds the pointer.
 	 *   to jump to.
 	 * 0xf8, 0x41, 0x00, 0x28,    std     r2,40(r1)
 	 * 0xe9, 0x6c, 0x00, 0x20,    ld      r11,32(r12)
 	 *   The actually address is 32 bytes from the offset
 	 *   into the TOC.
 	 * 0xe8, 0x4c, 0x00, 0x28,    ld      r2,40(r12)
 	 */

 	pr_debug("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);

 	/* Find where the trampoline jumps to */
 	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
 		printk(KERN_ERR "Failed to read %lx\n", tramp);
 		return -EFAULT;
 	}

 	pr_debug(" %08x %08x", jmp[0], jmp[1]);

 	/* verify that this is what we expect it to be */
 	if (((jmp[0] & 0xffff0000) != 0x3d820000) ||
 	    ((jmp[1] & 0xffff0000) != 0x398c0000) ||
 	    (jmp[2] != 0xf8410028) ||
 	    (jmp[3] != 0xe96c0020) ||
 	    (jmp[4] != 0xe84c0028)) {
 		printk(KERN_ERR "Not a trampoline\n");
 		return -EINVAL;
 	}

 	/* The bottom half is signed extended */
 	offset = ((unsigned)((unsigned short)jmp[0]) << 16) +
 		(int)((short)jmp[1]);

 	pr_debug(" %x ", offset);

 	/* get the address this jumps too */
 	tramp = mod->arch.toc + offset + 32;
 	pr_debug("toc: %lx", tramp);

 	if (probe_kernel_read(jmp, (void *)tramp, 8)) {
 		printk(KERN_ERR "Failed to read %lx\n", tramp);
 		return -EFAULT;
 	}

 	pr_debug(" %08x %08x\n", jmp[0], jmp[1]);

 	ptr = ((unsigned long)jmp[0] << 32) + jmp[1];

 	/* This should match what was called */
 	if (ptr != GET_ADDR(addr)) {
 		printk(KERN_ERR "addr does not match %lx\n", ptr);
 		return -EINVAL;
 	}

 	/*
 	 * We want to nop the line, but the next line is
 	 *  0xe8, 0x41, 0x00, 0x28   ld r2,40(r1)
 	 * This needs to be turned to a nop too.
 	 */
 	if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))
 		return -EFAULT;

 	if (op != 0xe8410028) {
 		printk(KERN_ERR "Next line is not ld! (%08x)\n", op);
 		return -EINVAL;
 	}

 	/*
 	 * Milton Miller pointed out that we can not blindly do nops.
 	 * If a task was preempted when calling a trace function,
 	 * the nops will remove the way to restore the TOC in r2
 	 * and the r2 TOC will get corrupted.
 	 */

 	/*
 	 * Replace:
 	 *   bl <tramp>  <==== will be replaced with "b 1f"
 	 *   ld r2,40(r1)
 	 *  1:
 	 */
 	op = 0x48000008;	/* b +8 */

 	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
 		return -EPERM;


 	flush_icache_range(ip, ip + 8);

 	return 0;
 }

 #else /* !PPC64 */
 static int
 __ftrace_make_nop(struct module *mod,
 		  struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned int op;
 	unsigned int jmp[4];
 	unsigned long ip = rec->ip;
 	unsigned long tramp;

 	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
 		return -EFAULT;

 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
 		printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
 		return -EINVAL;
 	}

 	/* lets find where the pointer goes */
 	tramp = find_bl_target(ip, op);

 	/*
 	 * On PPC32 the trampoline looks like:
 	 *  0x3d, 0x60, 0x00, 0x00  lis r11,sym@ha
 	 *  0x39, 0x6b, 0x00, 0x00  addi r11,r11,sym@l
 	 *  0x7d, 0x69, 0x03, 0xa6  mtctr r11
 	 *  0x4e, 0x80, 0x04, 0x20  bctr
 	 */

 	pr_debug("ip:%lx jumps to %lx", ip, tramp);

 	/* Find where the trampoline jumps to */
 	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
 		printk(KERN_ERR "Failed to read %lx\n", tramp);
 		return -EFAULT;
 	}

 	pr_debug(" %08x %08x ", jmp[0], jmp[1]);

 	/* verify that this is what we expect it to be */
 	if (((jmp[0] & 0xffff0000) != 0x3d600000) ||
 	    ((jmp[1] & 0xffff0000) != 0x396b0000) ||
 	    (jmp[2] != 0x7d6903a6) ||
 	    (jmp[3] != 0x4e800420)) {
 		printk(KERN_ERR "Not a trampoline\n");
 		return -EINVAL;
 	}

 	tramp = (jmp[1] & 0xffff) |
 		((jmp[0] & 0xffff) << 16);
 	if (tramp & 0x8000)
 		tramp -= 0x10000;

 	pr_debug(" %lx ", tramp);

 	if (tramp != addr) {
 		printk(KERN_ERR
 		       "Trampoline location %08lx does not match addr\n",
 		       tramp);
 		return -EINVAL;
 	}

 	op = PPC_INST_NOP;

 	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
 		return -EPERM;

 	flush_icache_range(ip, ip + 8);

 	return 0;
 }
 #endif /* PPC64 */
 #endif /* CONFIG_MODULES */

 int ftrace_make_nop(struct module *mod,
 		    struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long ip = rec->ip;
 	unsigned int old, new;

 	/*
 	 * If the calling address is more that 24 bits away,
 	 * then we had to use a trampoline to make the call.
 	 * Otherwise just update the call site.
 	 */
 	if (test_24bit_addr(ip, addr)) {
 		/* within range */
 		old = ftrace_call_replace(ip, addr, 1);
 		new = ftrace_nop_replace();
 		return ftrace_modify_code(ip, old, new);
 	}

 #ifdef CONFIG_MODULES
 	/*
 	 * Out of range jumps are called from modules.
 	 * We should either already have a pointer to the module
 	 * or it has been passed in.
 	 */
 	if (!rec->arch.mod) {
 		if (!mod) {
 			printk(KERN_ERR "No module loaded addr=%lx\n",
 			       addr);
 			return -EFAULT;
 		}
 		rec->arch.mod = mod;
 	} else if (mod) {
 		if (mod != rec->arch.mod) {
 			printk(KERN_ERR
 			       "Record mod %p not equal to passed in mod %p\n",
 			       rec->arch.mod, mod);
 			return -EINVAL;
 		}
 		/* nothing to do if mod == rec->arch.mod */
 	} else
 		mod = rec->arch.mod;

 	return __ftrace_make_nop(mod, rec, addr);
 #else
 	/* We should not get here without modules */
 	return -EINVAL;
 #endif /* CONFIG_MODULES */
 }

 #ifdef CONFIG_MODULES
 #ifdef CONFIG_PPC64
 static int
 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned int op[2];
 	unsigned long ip = rec->ip;

 	/* read where this goes */
 	if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))
 		return -EFAULT;

 	/*
 	 * It should be pointing to two nops or
 	 *  b +8; ld r2,40(r1)
 	 */
 	if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
 	    ((op[0] != PPC_INST_NOP) || (op[1] != PPC_INST_NOP))) {
 		printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
 		return -EINVAL;
 	}

 	/* If we never set up a trampoline to ftrace_caller, then bail */
 	if (!rec->arch.mod->arch.tramp) {
 		printk(KERN_ERR "No ftrace trampoline\n");
 		return -EINVAL;
 	}

 	/* create the branch to the trampoline */
 	op[0] = create_branch((unsigned int *)ip,
 			      rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
 	if (!op[0]) {
 		printk(KERN_ERR "REL24 out of range!\n");
 		return -EINVAL;
 	}

 	/* ld r2,40(r1) */
 	op[1] = 0xe8410028;

 	pr_debug("write to %lx\n", rec->ip);

 	if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))
 		return -EPERM;

 	flush_icache_range(ip, ip + 8);

 	return 0;
 }
 #else
 static int
 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned int op;
 	unsigned long ip = rec->ip;

 	/* read where this goes */
 	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
 		return -EFAULT;

 	/* It should be pointing to a nop */
 	if (op != PPC_INST_NOP) {
 		printk(KERN_ERR "Expected NOP but have %x\n", op);
 		return -EINVAL;
 	}

 	/* If we never set up a trampoline to ftrace_caller, then bail */
 	if (!rec->arch.mod->arch.tramp) {
 		printk(KERN_ERR "No ftrace trampoline\n");
 		return -EINVAL;
 	}

 	/* create the branch to the trampoline */
 	op = create_branch((unsigned int *)ip,
 			   rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
 	if (!op) {
 		printk(KERN_ERR "REL24 out of range!\n");
 		return -EINVAL;
 	}

 	pr_debug("write to %lx\n", rec->ip);

 	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
 		return -EPERM;

 	flush_icache_range(ip, ip + 8);

 	return 0;
 }
 #endif /* CONFIG_PPC64 */
 #endif /* CONFIG_MODULES */

 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long ip = rec->ip;
 	unsigned int old, new;

 	/*
 	 * If the calling address is more that 24 bits away,
 	 * then we had to use a trampoline to make the call.
 	 * Otherwise just update the call site.
 	 */
 	if (test_24bit_addr(ip, addr)) {
 		/* within range */
 		old = ftrace_nop_replace();
 		new = ftrace_call_replace(ip, addr, 1);
 		return ftrace_modify_code(ip, old, new);
 	}

 #ifdef CONFIG_MODULES
 	/*
 	 * Out of range jumps are called from modules.
 	 * Being that we are converting from nop, it had better
 	 * already have a module defined.
 	 */
 	if (!rec->arch.mod) {
 		printk(KERN_ERR "No module loaded\n");
 		return -EINVAL;
 	}

 	return __ftrace_make_call(rec, addr);
 #else
 	/* We should not get here without modules */
 	return -EINVAL;
 #endif /* CONFIG_MODULES */
 }

 int ftrace_update_ftrace_func(ftrace_func_t func)
 {
 	unsigned long ip = (unsigned long)(&ftrace_call);
 	unsigned int old, new;
 	int ret;

 	old = *(unsigned int *)&ftrace_call;
 	new = ftrace_call_replace(ip, (unsigned long)func, 1);
 	ret = ftrace_modify_code(ip, old, new);

 	return ret;
 }

 int __init ftrace_dyn_arch_init(void *data)
 {
 	/* caller expects data to be zero */
 	unsigned long *p = data;

 	*p = 0;

 	return 0;
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

 #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 int old, new;

 	old = ftrace_call_replace(ip, stub, 0);
 	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 int old, new;

 	old = ftrace_call_replace(ip, addr, 0);
 	new = ftrace_call_replace(ip, stub, 0);

 	return ftrace_modify_code(ip, old, new);
 }
 #endif /* CONFIG_DYNAMIC_FTRACE */

 #ifdef CONFIG_PPC64
 extern void mod_return_to_handler(void);
 #endif

 /*
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.
  */
 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 {
 	unsigned long old;
 	int faulted;
 	struct ftrace_graph_ent trace;
 	unsigned long return_hooker = (unsigned long)&return_to_handler;

 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		return;

 #ifdef CONFIG_PPC64
 	/* non core kernel code needs to save and restore the TOC */
 	if (REGION_ID(self_addr) != KERNEL_REGION_ID)
 		return_hooker = (unsigned long)&mod_return_to_handler;
 #endif

 	return_hooker = GET_ADDR(return_hooker);

 	/*
 	 * Protect against fault, even if it shouldn't
 	 * happen. This tool is too much intrusive to
 	 * ignore such a protection.
 	 */
 	asm volatile(
 		"1: " PPC_LL "%[old], 0(%[parent])\n"
 		"2: " PPC_STL "%[return_hooker], 0(%[parent])\n"
 		"   li %[faulted], 0\n"
 		"3:\n"

 		".section .fixup, \"ax\"\n"
 		"4: li %[faulted], 1\n"
 		"   b 3b\n"
 		".previous\n"

 		".section __ex_table,\"a\"\n"
 			PPC_LONG_ALIGN "\n"
 			PPC_LONG "1b,4b\n"
 			PPC_LONG "2b,4b\n"
 		".previous"

 		: [old] "=r" (old), [faulted] "=r" (faulted)
 		: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
 		: "memory"
 	);

 	if (unlikely(faulted)) {
 		ftrace_graph_stop();
 		WARN_ON(1);
 		return;
 	}

 	if (ftrace_push_return_trace(old, self_addr, &trace.depth) == -EBUSY) {
 		*parent = old;
 		return;
 	}

 	trace.func = self_addr;

 	/* Only trace if the calling function expects to */
 	if (!ftrace_graph_entry(&trace)) {
 		current->curr_ret_stack--;
 		*parent = old;
 	}
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
	/*
	* 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.
	*
	* Added function graph tracer code, taken from x86 that was written
	* by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
	*
	*/

	#include <linux/spinlock.h>
	#include <linux/hardirq.h>
	#include <linux/uaccess.h>
	#include <linux/module.h>
	#include <linux/ftrace.h>
	#include <linux/percpu.h>
	#include <linux/init.h>
	#include <linux/list.h>

	#include <asm/cacheflush.h>
	#include <asm/code-patching.h>
	#include <asm/ftrace.h>

	#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

	#ifdef CONFIG_DYNAMIC_FTRACE
	static unsigned int ftrace_nop_replace(void)
	{
	return PPC_INST_NOP;
	}

	static unsigned int
	ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
	{
	unsigned int op;

	addr = GET_ADDR(addr);

	/* if (link) set op to 'bl' else 'b' */
	op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);

	return op;
	}

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

	static int
	ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
	{
	unsigned int replaced;

	/*
	* Note: Due to modules and __init, code can
	* disappear and change, we need to protect against faulting
	* as well as code changing. We do this by using the
	* probe_kernel_* functions.
	*
	* No real locking needed, this code is run through
	* kstop_machine, or before SMP starts.
	*/

	/* read the text we want to modify */
	if (probe_kernel_read(&replaced, (void *)ip, MCOUNT_INSN_SIZE))
	return -EFAULT;

	/* Make sure it is what we expect it to be */
	if (replaced != old)
	return -EINVAL;

	/* replace the text with the new text */
	if (probe_kernel_write((void *)ip, &new, MCOUNT_INSN_SIZE))
	return -EPERM;

	flush_icache_range(ip, ip + 8);

	return 0;
	}

	/*
	* Helper functions that are the same for both PPC64 and PPC32.
	*/
	static int test_24bit_addr(unsigned long ip, unsigned long addr)
	{

	/* use the create_branch to verify that this offset can be branched */
	return create_branch((unsigned int *)ip, addr, 0);
	}

	#ifdef CONFIG_MODULES

	static int is_bl_op(unsigned int op)
	{
	return (op & 0xfc000003) == 0x48000001;
	}

	static unsigned long find_bl_target(unsigned long ip, unsigned int op)
	{
	static int offset;

	offset = (op & 0x03fffffc);
	/* make it signed */
	if (offset & 0x02000000)
	offset \|= 0xfe000000;

	return ip + (long)offset;
	}

	#ifdef CONFIG_PPC64
	static int
	__ftrace_make_nop(struct module *mod,
	struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned int op;
	unsigned int jmp[5];
	unsigned long ptr;
	unsigned long ip = rec->ip;
	unsigned long tramp;
	int offset;

	/* read where this goes */
	if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
	return -EFAULT;

	/* Make sure that that this is still a 24bit jump */
	if (!is_bl_op(op)) {
	printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
	return -EINVAL;
	}

	/* lets find where the pointer goes */
	tramp = find_bl_target(ip, op);

	/*
	* On PPC64 the trampoline looks like:
	* 0x3d, 0x82, 0x00, 0x00, addis r12,r2, <high>
	* 0x39, 0x8c, 0x00, 0x00, addi r12,r12, <low>
	* Where the bytes 2,3,6 and 7 make up the 32bit offset
	* to the TOC that holds the pointer.
	* to jump to.
	* 0xf8, 0x41, 0x00, 0x28, std r2,40(r1)
	* 0xe9, 0x6c, 0x00, 0x20, ld r11,32(r12)
	* The actually address is 32 bytes from the offset
	* into the TOC.
	* 0xe8, 0x4c, 0x00, 0x28, ld r2,40(r12)
	*/

	pr_debug("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);

	/* Find where the trampoline jumps to */
	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
	printk(KERN_ERR "Failed to read %lx\n", tramp);
	return -EFAULT;
	}

	pr_debug(" %08x %08x", jmp[0], jmp[1]);

	/* verify that this is what we expect it to be */
	if (((jmp[0] & 0xffff0000) != 0x3d820000) \|\|
	((jmp[1] & 0xffff0000) != 0x398c0000) \|\|
	(jmp[2] != 0xf8410028) \|\|
	(jmp[3] != 0xe96c0020) \|\|
	(jmp[4] != 0xe84c0028)) {
	printk(KERN_ERR "Not a trampoline\n");
	return -EINVAL;
	}

	/* The bottom half is signed extended */
	offset = ((unsigned)((unsigned short)jmp[0]) << 16) +
	(int)((short)jmp[1]);

	pr_debug(" %x ", offset);

	/* get the address this jumps too */
	tramp = mod->arch.toc + offset + 32;
	pr_debug("toc: %lx", tramp);

	if (probe_kernel_read(jmp, (void *)tramp, 8)) {
	printk(KERN_ERR "Failed to read %lx\n", tramp);
	return -EFAULT;
	}

	pr_debug(" %08x %08x\n", jmp[0], jmp[1]);

	ptr = ((unsigned long)jmp[0] << 32) + jmp[1];

	/* This should match what was called */
	if (ptr != GET_ADDR(addr)) {
	printk(KERN_ERR "addr does not match %lx\n", ptr);
	return -EINVAL;
	}

	/*
	* We want to nop the line, but the next line is
	* 0xe8, 0x41, 0x00, 0x28 ld r2,40(r1)
	* This needs to be turned to a nop too.
	*/
	if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))
	return -EFAULT;

	if (op != 0xe8410028) {
	printk(KERN_ERR "Next line is not ld! (%08x)\n", op);
	return -EINVAL;
	}

	/*
	* Milton Miller pointed out that we can not blindly do nops.
	* If a task was preempted when calling a trace function,
	* the nops will remove the way to restore the TOC in r2
	* and the r2 TOC will get corrupted.
	*/

	/*
	* Replace:
	* bl <tramp> <==== will be replaced with "b 1f"
	* ld r2,40(r1)
	* 1:
	*/
	op = 0x48000008; /* b +8 */

	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
	return -EPERM;


	flush_icache_range(ip, ip + 8);

	return 0;
	}

	#else /* !PPC64 */
	static int
	__ftrace_make_nop(struct module *mod,
	struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned int op;
	unsigned int jmp[4];
	unsigned long ip = rec->ip;
	unsigned long tramp;

	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
	return -EFAULT;

	/* Make sure that that this is still a 24bit jump */
	if (!is_bl_op(op)) {
	printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
	return -EINVAL;
	}

	/* lets find where the pointer goes */
	tramp = find_bl_target(ip, op);

	/*
	* On PPC32 the trampoline looks like:
	* 0x3d, 0x60, 0x00, 0x00 lis r11,sym@ha
	* 0x39, 0x6b, 0x00, 0x00 addi r11,r11,sym@l
	* 0x7d, 0x69, 0x03, 0xa6 mtctr r11
	* 0x4e, 0x80, 0x04, 0x20 bctr
	*/

	pr_debug("ip:%lx jumps to %lx", ip, tramp);

	/* Find where the trampoline jumps to */
	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
	printk(KERN_ERR "Failed to read %lx\n", tramp);
	return -EFAULT;
	}

	pr_debug(" %08x %08x ", jmp[0], jmp[1]);

	/* verify that this is what we expect it to be */
	if (((jmp[0] & 0xffff0000) != 0x3d600000) \|\|
	((jmp[1] & 0xffff0000) != 0x396b0000) \|\|
	(jmp[2] != 0x7d6903a6) \|\|
	(jmp[3] != 0x4e800420)) {
	printk(KERN_ERR "Not a trampoline\n");
	return -EINVAL;
	}

	tramp = (jmp[1] & 0xffff) \|
	((jmp[0] & 0xffff) << 16);
	if (tramp & 0x8000)
	tramp -= 0x10000;

	pr_debug(" %lx ", tramp);

	if (tramp != addr) {
	printk(KERN_ERR
	"Trampoline location %08lx does not match addr\n",
	tramp);
	return -EINVAL;
	}

	op = PPC_INST_NOP;

	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
	return -EPERM;

	flush_icache_range(ip, ip + 8);

	return 0;
	}
	#endif /* PPC64 */
	#endif /* CONFIG_MODULES */

	int ftrace_make_nop(struct module *mod,
	struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned long ip = rec->ip;
	unsigned int old, new;

	/*
	* If the calling address is more that 24 bits away,
	* then we had to use a trampoline to make the call.
	* Otherwise just update the call site.
	*/
	if (test_24bit_addr(ip, addr)) {
	/* within range */
	old = ftrace_call_replace(ip, addr, 1);
	new = ftrace_nop_replace();
	return ftrace_modify_code(ip, old, new);
	}

	#ifdef CONFIG_MODULES
	/*
	* Out of range jumps are called from modules.
	* We should either already have a pointer to the module
	* or it has been passed in.
	*/
	if (!rec->arch.mod) {
	if (!mod) {
	printk(KERN_ERR "No module loaded addr=%lx\n",
	addr);
	return -EFAULT;
	}
	rec->arch.mod = mod;
	} else if (mod) {
	if (mod != rec->arch.mod) {
	printk(KERN_ERR
	"Record mod %p not equal to passed in mod %p\n",
	rec->arch.mod, mod);
	return -EINVAL;
	}
	/* nothing to do if mod == rec->arch.mod */
	} else
	mod = rec->arch.mod;

	return __ftrace_make_nop(mod, rec, addr);
	#else
	/* We should not get here without modules */
	return -EINVAL;
	#endif /* CONFIG_MODULES */
	}

	#ifdef CONFIG_MODULES
	#ifdef CONFIG_PPC64
	static int
	__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned int op[2];
	unsigned long ip = rec->ip;

	/* read where this goes */
	if (probe_kernel_read(op, (void )ip, MCOUNT_INSN_SIZE 2))
	return -EFAULT;

	/*
	* It should be pointing to two nops or
	* b +8; ld r2,40(r1)
	*/
	if (((op[0] != 0x48000008) \|\| (op[1] != 0xe8410028)) &&
	((op[0] != PPC_INST_NOP) \|\| (op[1] != PPC_INST_NOP))) {
	printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
	return -EINVAL;
	}

	/* If we never set up a trampoline to ftrace_caller, then bail */
	if (!rec->arch.mod->arch.tramp) {
	printk(KERN_ERR "No ftrace trampoline\n");
	return -EINVAL;
	}

	/* create the branch to the trampoline */
	op[0] = create_branch((unsigned int *)ip,
	rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
	if (!op[0]) {
	printk(KERN_ERR "REL24 out of range!\n");
	return -EINVAL;
	}

	/* ld r2,40(r1) */
	op[1] = 0xe8410028;

	pr_debug("write to %lx\n", rec->ip);

	if (probe_kernel_write((void )ip, op, MCOUNT_INSN_SIZE 2))
	return -EPERM;

	flush_icache_range(ip, ip + 8);

	return 0;
	}
	#else
	static int
	__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned int op;
	unsigned long ip = rec->ip;

	/* read where this goes */
	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
	return -EFAULT;

	/* It should be pointing to a nop */
	if (op != PPC_INST_NOP) {
	printk(KERN_ERR "Expected NOP but have %x\n", op);
	return -EINVAL;
	}

	/* If we never set up a trampoline to ftrace_caller, then bail */
	if (!rec->arch.mod->arch.tramp) {
	printk(KERN_ERR "No ftrace trampoline\n");
	return -EINVAL;
	}

	/* create the branch to the trampoline */
	op = create_branch((unsigned int *)ip,
	rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
	if (!op) {
	printk(KERN_ERR "REL24 out of range!\n");
	return -EINVAL;
	}

	pr_debug("write to %lx\n", rec->ip);

	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
	return -EPERM;

	flush_icache_range(ip, ip + 8);

	return 0;
	}
	#endif /* CONFIG_PPC64 */
	#endif /* CONFIG_MODULES */

	int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
	{
	unsigned long ip = rec->ip;
	unsigned int old, new;

	/*
	* If the calling address is more that 24 bits away,
	* then we had to use a trampoline to make the call.
	* Otherwise just update the call site.
	*/
	if (test_24bit_addr(ip, addr)) {
	/* within range */
	old = ftrace_nop_replace();
	new = ftrace_call_replace(ip, addr, 1);
	return ftrace_modify_code(ip, old, new);
	}

	#ifdef CONFIG_MODULES
	/*
	* Out of range jumps are called from modules.
	* Being that we are converting from nop, it had better
	* already have a module defined.
	*/
	if (!rec->arch.mod) {
	printk(KERN_ERR "No module loaded\n");
	return -EINVAL;
	}

	return __ftrace_make_call(rec, addr);
	#else
	/* We should not get here without modules */
	return -EINVAL;
	#endif /* CONFIG_MODULES */
	}

	int ftrace_update_ftrace_func(ftrace_func_t func)
	{
	unsigned long ip = (unsigned long)(&ftrace_call);
	unsigned int old, new;
	int ret;

	old = (unsigned int )&ftrace_call;
	new = ftrace_call_replace(ip, (unsigned long)func, 1);
	ret = ftrace_modify_code(ip, old, new);

	return ret;
	}

	int __init ftrace_dyn_arch_init(void *data)
	{
	/* caller expects data to be zero */
	unsigned long *p = data;

	*p = 0;

	return 0;
	}
	#endif /* CONFIG_DYNAMIC_FTRACE */

	#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 int old, new;

	old = ftrace_call_replace(ip, stub, 0);
	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 int old, new;

	old = ftrace_call_replace(ip, addr, 0);
	new = ftrace_call_replace(ip, stub, 0);

	return ftrace_modify_code(ip, old, new);
	}
	#endif /* CONFIG_DYNAMIC_FTRACE */

	#ifdef CONFIG_PPC64
	extern void mod_return_to_handler(void);
	#endif

	/*
	* Hook the return address and push it in the stack of return addrs
	* in current thread info.
	*/
	void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
	{
	unsigned long old;
	int faulted;
	struct ftrace_graph_ent trace;
	unsigned long return_hooker = (unsigned long)&return_to_handler;

	if (unlikely(atomic_read(&current->tracing_graph_pause)))
	return;

	#ifdef CONFIG_PPC64
	/* non core kernel code needs to save and restore the TOC */
	if (REGION_ID(self_addr) != KERNEL_REGION_ID)
	return_hooker = (unsigned long)&mod_return_to_handler;
	#endif

	return_hooker = GET_ADDR(return_hooker);

	/*
	* Protect against fault, even if it shouldn't
	* happen. This tool is too much intrusive to
	* ignore such a protection.
	*/
	asm volatile(
	"1: " PPC_LL "%[old], 0(%[parent])\n"
	"2: " PPC_STL "%[return_hooker], 0(%[parent])\n"
	" li %[faulted], 0\n"
	"3:\n"

	".section .fixup, \"ax\"\n"
	"4: li %[faulted], 1\n"
	" b 3b\n"
	".previous\n"

	".section __ex_table,\"a\"\n"
	PPC_LONG_ALIGN "\n"
	PPC_LONG "1b,4b\n"
	PPC_LONG "2b,4b\n"
	".previous"

	: [old] "=r" (old), [faulted] "=r" (faulted)
	: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
	: "memory"
	);

	if (unlikely(faulted)) {
	ftrace_graph_stop();
	WARN_ON(1);
	return;
	}

	if (ftrace_push_return_trace(old, self_addr, &trace.depth) == -EBUSY) {
	*parent = old;
	return;
	}

	trace.func = self_addr;

	/* Only trace if the calling function expects to */
	if (!ftrace_graph_entry(&trace)) {
	current->curr_ret_stack--;
	*parent = old;
	}
	}
	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */