/*
   * 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>

  #include <asm-generic/sections.h>

  #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
  #define MCOUNT_OFFSET_INSNS 5
  #else
  #define MCOUNT_OFFSET_INSNS 4
  #endif
  
  /*
   * Check if the address is in kernel space
   *
   * Clone core_kernel_text() from kernel/extable.c, but doesn't call
   * init_kernel_text() for Ftrace doesn't trace functions in init sections.
   */
  static inline int in_kernel_space(unsigned long ip)
  {
  	if (ip >= (unsigned long)_stext &&
  	    ip <= (unsigned long)_etext)
  		return 1;
  	return 0;
  }

  #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 JUMP_RANGE_MASK ((1UL << 28) - 1)

  #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) & JUMP_RANGE_MASK);

  
  #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 & JUMP_RANGE_MASK);

  #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;
  }

  /*
   * The details about the calling site of mcount on MIPS
   *
   * 1. For kernel:
   *
   * move at, ra
   * jal _mcount		--> nop
   *
   * 2. For modules:
   *
   * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and 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
   * 2.2 For the Other situations
   *
   * 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
   */

  #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)

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

  	/*

  	 * If ip is in kernel space, no long call, otherwise, long call is
  	 * needed.

  	 */

  	new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;

  	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;

  	new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
  		insn_lui_v1_hi16_mcount;

  
  	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_ra_addr(unsigned long self_ra, unsigned long
  		old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)

  {

  	unsigned long sp, ip, tmp;

  	unsigned int code;

  	int faulted;

  	/*

  	 * For module, move the ip from the return address after the

  	 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
  	 * kernel, move after the instruction "move ra, at"(offset is 16)

  	 */

  	ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);

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

  	do {

  		/* 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_ra_addr;

  		/* Move to the next instruction */
  		ip -= 4;
  	} while ((code & S_RA_SP) != S_RA_SP);

  
  	sp = fp + (code & OFFSET_MASK);

  	/* tmp = *(unsigned long *)sp; */
  	safe_load_stack(tmp, sp, faulted);

  	if (unlikely(faulted))
  		return 0;

  	if (tmp == old_parent_ra)

  		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_ra_addr, unsigned long self_ra,

  			   unsigned long fp)
  {

  	unsigned long old_parent_ra;

  	struct ftrace_graph_ent trace;
  	unsigned long return_hooker = (unsigned long)
  	    &return_to_handler;

  	int faulted, insns;

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

  	/*

  	 * "parent_ra_addr" 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_ra = *parent_ra_addr; */
  	safe_load_stack(old_parent_ra, parent_ra_addr, faulted);

  	if (unlikely(faulted))
  		goto out;

  #ifndef KBUILD_MCOUNT_RA_ADDRESS

  	parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
  			old_parent_ra, (unsigned long)parent_ra_addr, fp);

  	/*
  	 * If fails when getting the stack address of the non-leaf function's
  	 * ra, stop function graph tracer and return
  	 */

  	if (parent_ra_addr == 0)

  		goto out;

  #endif

  	/* *parent_ra_addr = return_hooker; */
  	safe_store_stack(return_hooker, parent_ra_addr, faulted);

  	if (unlikely(faulted))
  		goto out;

  	if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
  	    == -EBUSY) {
  		*parent_ra_addr = old_parent_ra;

  		return;
  	}

  	/*
  	 * Get the recorded ip of the current mcount calling site in the
  	 * __mcount_loc section, which will be used to filter the function
  	 * entries configured through the tracing/set_graph_function interface.
  	 */
  
  	insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
  	trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);

  
  	/* Only trace if the calling function expects to */
  	if (!ftrace_graph_entry(&trace)) {
  		current->curr_ret_stack--;

  		*parent_ra_addr = old_parent_ra;

  	}

  	return;
  out:
  	ftrace_graph_stop();
  	WARN_ON(1);

  }

  #endif	/* CONFIG_FUNCTION_GRAPH_TRACER */