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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: Wu 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: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Wu Zhangjin 2010-05-14 19:08:33 +08:00 committed by Ralf Baechle
parent e424054000
commit 68ccf7521d
1 changed files with 26 additions and 22 deletions
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44
arch/mips/kernel/ftrace.c
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@ -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