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Commit 68ccf752 authored by Wu Zhangjin's avatar Wu Zhangjin Committed by Ralf Baechle
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MIPS: Tracing: Cleanup of function graph tracer 



Cleans up comments and ftrace_get_parent_addr() of function graph tracer.

Signed-off-by: default avatarWu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips <linux-mips@linux-mips.org>
Cc: David Daney <david.s.daney@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/1231/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent e4240540

arch/mips/kernel/ftrace.c

+26 −22
Original line number Diff line number Diff line
@@ -166,9 +166,10 @@ int ftrace_disable_ftrace_graph_caller(void) 
	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);

}



#endif				/* !CONFIG_DYNAMIC_FTRACE */

#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 */
@@ -182,17 +183,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr, 
	unsigned int code;

	int faulted;



	/* in module or kernel? */

	if (self_addr & 0x40000000) {

		/* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */

		ip = self_addr - 20;

	} else {

		/* kernel: move to the instruction "move ra, at" */

		ip = self_addr - 12;

	}

	/*

	 * 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 - ((self_addr & 0x40000000) ? 20 : 12);



	/* search the text until finding the non-store instruction or "s{d,w}

	 * ra, offset(sp)" instruction */

	/*

	 * search the text until finding the non-store instruction or "s{d,w}

	 * ra, offset(sp)" instruction

	 */

	do {

		ip -= 4;
@@ -201,10 +202,11 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr, 


		if (unlikely(faulted))

			return 0;



		/* If we hit the non-store instruction before finding where the

		/*

		 * 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. */

		 * store the ra on the stack

		 */

		if ((code & S_R_SP) != S_R_SP)

			return parent_addr;
@@ -222,7 +224,7 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr, 
	return 0;

}



#endif

#endif	/* !KBUILD_MCOUNT_RA_ADDRESS */



/*

 * Hook the return address and push it in the stack of return addrs
@@ -240,7 +242,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
	if (unlikely(atomic_read(&current->tracing_graph_pause)))

		return;



	/* "parent" is the stack address saved the return address of the caller

	/*

	 * "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
@@ -262,10 +265,11 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
		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 */

			(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