arch/mips/kernel/ftrace.c - linux - Git at Google

 /*
  * Code for replacing ftrace calls with jumps.
  *
  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
  * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
  * Author: Wu Zhangjin <wuzhangjin@gmail.com>
  *
  * Thanks goes to Steven Rostedt for writing the original x86 version.
  */

 #include <linux/uaccess.h>
 #include <linux/init.h>
 #include <linux/ftrace.h>

 #include <asm/asm.h>
 #include <asm/asm-offsets.h>
 #include <asm/cacheflush.h>
 #include <asm/uasm.h>

 /*
  * If the Instruction Pointer is in module space (0xc0000000), return true;
  * otherwise, it is in kernel space (0x80000000), return false.
  *
  * FIXME: This will not work when the kernel space and module space are the
  * same. If they are the same, we need to modify scripts/recordmcount.pl,
  * ftrace_make_nop/call() and the other related parts to ensure the
  * enabling/disabling of the calling site to _mcount is right for both kernel
  * and module.
  */

 static inline int in_module(unsigned long ip)
 {
 	return ip & 0x40000000;
 }

 #ifdef CONFIG_DYNAMIC_FTRACE

 #define JAL 0x0c000000		/* jump & link: ip --> ra, jump to target */
 #define ADDR_MASK 0x03ffffff	/*  op_code|addr : 31...26|25 ....0 */

 #define INSN_B_1F_4 0x10000004	/* b 1f; offset = 4 */
 #define INSN_B_1F_5 0x10000005	/* b 1f; offset = 5 */
 #define INSN_NOP 0x00000000	/* nop */
 #define INSN_JAL(addr)	\
 	((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))

 static unsigned int insn_jal_ftrace_caller __read_mostly;
 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;

 static inline void ftrace_dyn_arch_init_insns(void)
 {
 	u32 *buf;
 	unsigned int v1;

 	/* lui v1, hi16_mcount */
 	v1 = 3;
 	buf = (u32 *)&insn_lui_v1_hi16_mcount;
 	UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);

 	/* jal (ftrace_caller + 8), jump over the first two instruction */
 	buf = (u32 *)&insn_jal_ftrace_caller;
 	uasm_i_jal(&buf, (FTRACE_ADDR + 8));

 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	/* j ftrace_graph_caller */
 	buf = (u32 *)&insn_j_ftrace_graph_caller;
 	uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
 #endif
 }

 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
 {
 	int faulted;

 	/* *(unsigned int *)ip = new_code; */
 	safe_store_code(new_code, ip, faulted);

 	if (unlikely(faulted))
 		return -EFAULT;

 	flush_icache_range(ip, ip + 8);

 	return 0;
 }

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

 	/*
 	 * We have compiled module with -mlong-calls, but compiled the kernel
 	 * without it, we need to cope with them respectively.
 	 */
 	if (in_module(ip)) {
 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
 		/*
 		 * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 		 * addiu v1, v1, low_16bit_of_mcount
 		 * move at, ra
 		 * move $12, ra_address
 		 * jalr v1
 		 *  sub sp, sp, 8
 		 *                                  1: offset = 5 instructions
 		 */
 		new = INSN_B_1F_5;
 #else
 		/*
 		 * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 		 * addiu v1, v1, low_16bit_of_mcount
 		 * move at, ra
 		 * jalr v1
 		 *  nop | move $12, ra_address | sub sp, sp, 8
 		 *                                  1: offset = 4 instructions
 		 */
 		new = INSN_B_1F_4;
 #endif
 	} else {
 		/*
 		 * move at, ra
 		 * jal _mcount		--> nop
 		 */
 		new = INSN_NOP;
 	}
 	return ftrace_modify_code(ip, new);
 }

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

 	/* ip, module: 0xc0000000, kernel: 0x80000000 */
 	new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;

 	return ftrace_modify_code(ip, new);
 }

 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))

 int ftrace_update_ftrace_func(ftrace_func_t func)
 {
 	unsigned int new;

 	new = INSN_JAL((unsigned long)func);

 	return ftrace_modify_code(FTRACE_CALL_IP, new);
 }

 int __init ftrace_dyn_arch_init(void *data)
 {
 	/* Encode the instructions when booting */
 	ftrace_dyn_arch_init_insns();

 	/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
 	ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);

 	/* The return code is retured via data */
 	*(unsigned long *)data = 0;

 	return 0;
 }
 #endif	/* CONFIG_DYNAMIC_FTRACE */

 #ifdef CONFIG_FUNCTION_GRAPH_TRACER

 #ifdef CONFIG_DYNAMIC_FTRACE

 extern void ftrace_graph_call(void);
 #define FTRACE_GRAPH_CALL_IP	((unsigned long)(&ftrace_graph_call))

 int ftrace_enable_ftrace_graph_caller(void)
 {
 	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
 			insn_j_ftrace_graph_caller);
 }

 int ftrace_disable_ftrace_graph_caller(void)
 {
 	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
 }

 #endif	/* CONFIG_DYNAMIC_FTRACE */

 #ifndef KBUILD_MCOUNT_RA_ADDRESS

 #define S_RA_SP	(0xafbf << 16)	/* s{d,w} ra, offset(sp) */
 #define S_R_SP	(0xafb0 << 16)  /* s{d,w} R, offset(sp) */
 #define OFFSET_MASK	0xffff	/* stack offset range: 0 ~ PT_SIZE */

 unsigned long ftrace_get_parent_addr(unsigned long self_addr,
 				     unsigned long parent,
 				     unsigned long parent_addr,
 				     unsigned long fp)
 {
 	unsigned long sp, ip, ra;
 	unsigned int code;
 	int faulted;

 	/*
 	 * For module, move the ip from calling site of mcount to the
 	 * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
 	 * kernel, move to the instruction "move ra, at"(offset is 12)
 	 */
 	ip = self_addr - (in_module(self_addr) ? 20 : 12);

 	/*
 	 * search the text until finding the non-store instruction or "s{d,w}
 	 * ra, offset(sp)" instruction
 	 */
 	do {
 		ip -= 4;

 		/* get the code at "ip": code = *(unsigned int *)ip; */
 		safe_load_code(code, ip, faulted);

 		if (unlikely(faulted))
 			return 0;
 		/*
 		 * If we hit the non-store instruction before finding where the
 		 * ra is stored, then this is a leaf function and it does not
 		 * store the ra on the stack
 		 */
 		if ((code & S_R_SP) != S_R_SP)
 			return parent_addr;

 	} while (((code & S_RA_SP) != S_RA_SP));

 	sp = fp + (code & OFFSET_MASK);

 	/* ra = *(unsigned long *)sp; */
 	safe_load_stack(ra, sp, faulted);
 	if (unlikely(faulted))
 		return 0;

 	if (ra == parent)
 		return sp;
 	return 0;
 }

 #endif	/* !KBUILD_MCOUNT_RA_ADDRESS */

 /*
  * 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 fp)
 {
 	unsigned long old;
 	struct ftrace_graph_ent trace;
 	unsigned long return_hooker = (unsigned long)
 	    &return_to_handler;
 	int faulted;

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

 	/*
 	 * "parent" is the stack address saved the return address of the caller
 	 * of _mcount.
 	 *
 	 * if the gcc < 4.5, a leaf function does not save the return address
 	 * in the stack address, so, we "emulate" one in _mcount's stack space,
 	 * and hijack it directly, but for a non-leaf function, it save the
 	 * return address to the its own stack space, we can not hijack it
 	 * directly, but need to find the real stack address,
 	 * ftrace_get_parent_addr() does it!
 	 *
 	 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
 	 * non-leaf function, the location of the return address will be saved
 	 * to $12 for us, and for a leaf function, only put a zero into $12. we
 	 * do it in ftrace_graph_caller of mcount.S.
 	 */

 	/* old = *parent; */
 	safe_load_stack(old, parent, faulted);
 	if (unlikely(faulted))
 		goto out;
 #ifndef KBUILD_MCOUNT_RA_ADDRESS
 	parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
 			(unsigned long)parent, fp);
 	/*
 	 * If fails when getting the stack address of the non-leaf function's
 	 * ra, stop function graph tracer and return
 	 */
 	if (parent == 0)
 		goto out;
 #endif
 	/* *parent = return_hooker; */
 	safe_store_stack(return_hooker, parent, faulted);
 	if (unlikely(faulted))
 		goto out;

 	if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
 	    -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;
 	}
 	return;
 out:
 	ftrace_graph_stop();
 	WARN_ON(1);
 }
 #endif	/* CONFIG_FUNCTION_GRAPH_TRACER */
	/*
	* Code for replacing ftrace calls with jumps.
	*
	* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
	* Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
	* Author: Wu Zhangjin <wuzhangjin@gmail.com>
	*
	* Thanks goes to Steven Rostedt for writing the original x86 version.
	*/

	#include <linux/uaccess.h>
	#include <linux/init.h>
	#include <linux/ftrace.h>

	#include <asm/asm.h>
	#include <asm/asm-offsets.h>
	#include <asm/cacheflush.h>
	#include <asm/uasm.h>

	/*
	* If the Instruction Pointer is in module space (0xc0000000), return true;
	* otherwise, it is in kernel space (0x80000000), return false.
	*
	* FIXME: This will not work when the kernel space and module space are the
	* same. If they are the same, we need to modify scripts/recordmcount.pl,
	* ftrace_make_nop/call() and the other related parts to ensure the
	* enabling/disabling of the calling site to _mcount is right for both kernel
	* and module.
	*/

	static inline int in_module(unsigned long ip)
	{
	return ip & 0x40000000;
	}

	#ifdef CONFIG_DYNAMIC_FTRACE

	#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
	#define ADDR_MASK 0x03ffffff /* op_code\|addr : 31...26\|25 ....0 */

	#define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */
	#define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */
	#define INSN_NOP 0x00000000 /* nop */
	#define INSN_JAL(addr) \
	((unsigned int)(JAL \| (((addr) >> 2) & ADDR_MASK)))

	static unsigned int insn_jal_ftrace_caller __read_mostly;
	static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
	static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;

	static inline void ftrace_dyn_arch_init_insns(void)
	{
	u32 *buf;
	unsigned int v1;

	/* lui v1, hi16_mcount */
	v1 = 3;
	buf = (u32 *)&insn_lui_v1_hi16_mcount;
	UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);

	/* jal (ftrace_caller + 8), jump over the first two instruction */
	buf = (u32 *)&insn_jal_ftrace_caller;
	uasm_i_jal(&buf, (FTRACE_ADDR + 8));

	#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	/* j ftrace_graph_caller */
	buf = (u32 *)&insn_j_ftrace_graph_caller;
	uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
	#endif
	}

	static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
	{
	int faulted;

	/* (unsigned int )ip = new_code; */
	safe_store_code(new_code, ip, faulted);

	if (unlikely(faulted))
	return -EFAULT;

	flush_icache_range(ip, ip + 8);

	return 0;
	}

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

	/*
	* We have compiled module with -mlong-calls, but compiled the kernel
	* without it, we need to cope with them respectively.
	*/
	if (in_module(ip)) {
	#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
	/*
	* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
	* addiu v1, v1, low_16bit_of_mcount
	* move at, ra
	* move $12, ra_address
	* jalr v1
	* sub sp, sp, 8
	* 1: offset = 5 instructions
	*/
	new = INSN_B_1F_5;
	#else
	/*
	* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
	* addiu v1, v1, low_16bit_of_mcount
	* move at, ra
	* jalr v1
	* nop \| move $12, ra_address \| sub sp, sp, 8
	* 1: offset = 4 instructions
	*/
	new = INSN_B_1F_4;
	#endif
	} else {
	/*
	* move at, ra
	* jal _mcount --> nop
	*/
	new = INSN_NOP;
	}
	return ftrace_modify_code(ip, new);
	}

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

	/* ip, module: 0xc0000000, kernel: 0x80000000 */
	new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;

	return ftrace_modify_code(ip, new);
	}

	#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))

	int ftrace_update_ftrace_func(ftrace_func_t func)
	{
	unsigned int new;

	new = INSN_JAL((unsigned long)func);

	return ftrace_modify_code(FTRACE_CALL_IP, new);
	}

	int __init ftrace_dyn_arch_init(void *data)
	{
	/* Encode the instructions when booting */
	ftrace_dyn_arch_init_insns();

	/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
	ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);

	/* The return code is retured via data */
	(unsigned long )data = 0;

	return 0;
	}
	#endif /* CONFIG_DYNAMIC_FTRACE */

	#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	#ifdef CONFIG_DYNAMIC_FTRACE

	extern void ftrace_graph_call(void);
	#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))

	int ftrace_enable_ftrace_graph_caller(void)
	{
	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
	insn_j_ftrace_graph_caller);
	}

	int ftrace_disable_ftrace_graph_caller(void)
	{
	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
	}

	#endif /* CONFIG_DYNAMIC_FTRACE */

	#ifndef KBUILD_MCOUNT_RA_ADDRESS

	#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
	#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
	#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */

	unsigned long ftrace_get_parent_addr(unsigned long self_addr,
	unsigned long parent,
	unsigned long parent_addr,
	unsigned long fp)
	{
	unsigned long sp, ip, ra;
	unsigned int code;
	int faulted;

	/*
	* For module, move the ip from calling site of mcount to the
	* instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
	* kernel, move to the instruction "move ra, at"(offset is 12)
	*/
	ip = self_addr - (in_module(self_addr) ? 20 : 12);

	/*
	* search the text until finding the non-store instruction or "s{d,w}
	* ra, offset(sp)" instruction
	*/
	do {
	ip -= 4;

	/* get the code at "ip": code = (unsigned int )ip; */
	safe_load_code(code, ip, faulted);

	if (unlikely(faulted))
	return 0;
	/*
	* If we hit the non-store instruction before finding where the
	* ra is stored, then this is a leaf function and it does not
	* store the ra on the stack
	*/
	if ((code & S_R_SP) != S_R_SP)
	return parent_addr;

	} while (((code & S_RA_SP) != S_RA_SP));

	sp = fp + (code & OFFSET_MASK);

	/* ra = (unsigned long )sp; */
	safe_load_stack(ra, sp, faulted);
	if (unlikely(faulted))
	return 0;

	if (ra == parent)
	return sp;
	return 0;
	}

	#endif /* !KBUILD_MCOUNT_RA_ADDRESS */

	/*
	* 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 fp)
	{
	unsigned long old;
	struct ftrace_graph_ent trace;
	unsigned long return_hooker = (unsigned long)
	&return_to_handler;
	int faulted;

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

	/*
	* "parent" is the stack address saved the return address of the caller
	* of _mcount.
	*
	* if the gcc < 4.5, a leaf function does not save the return address
	* in the stack address, so, we "emulate" one in _mcount's stack space,
	* and hijack it directly, but for a non-leaf function, it save the
	* return address to the its own stack space, we can not hijack it
	* directly, but need to find the real stack address,
	* ftrace_get_parent_addr() does it!
	*
	* if gcc>= 4.5, with the new -mmcount-ra-address option, for a
	* non-leaf function, the location of the return address will be saved
	* to $12 for us, and for a leaf function, only put a zero into $12. we
	* do it in ftrace_graph_caller of mcount.S.
	*/

	/* old = parent; /
	safe_load_stack(old, parent, faulted);
	if (unlikely(faulted))
	goto out;
	#ifndef KBUILD_MCOUNT_RA_ADDRESS
	parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
	(unsigned long)parent, fp);
	/*
	* If fails when getting the stack address of the non-leaf function's
	* ra, stop function graph tracer and return
	*/
	if (parent == 0)
	goto out;
	#endif
	/* parent = return_hooker; /
	safe_store_stack(return_hooker, parent, faulted);
	if (unlikely(faulted))
	goto out;

	if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
	-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;
	}
	return;
	out:
	ftrace_graph_stop();
	WARN_ON(1);
	}
	#endif /* CONFIG_FUNCTION_GRAPH_TRACER */