diff options
Diffstat (limited to 'arch/mips/kernel/ftrace.c')
| -rw-r--r-- | arch/mips/kernel/ftrace.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c index 5459a783837..65a3f8a8992 100644 --- a/arch/mips/kernel/ftrace.c +++ b/arch/mips/kernel/ftrace.c @@ -13,6 +13,8 @@ #include <linux/ftrace.h> #include <asm/cacheflush.h> +#include <asm/asm.h> +#include <asm/asm-offsets.h> #ifdef CONFIG_DYNAMIC_FTRACE @@ -110,3 +112,107 @@ int __init ftrace_dyn_arch_init(void *data) return 0; } #endif /* CONFIG_DYNAMIC_FTRACE */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + +#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; + + /* 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; + } + + /* 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; + + /* 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; + + if (ra == parent) + return sp; + + return 0; +} + +/* + * 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; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + + /* "parent" is the stack address saved the return address of the caller + * of _mcount, for a leaf function 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 will save the + * return address to the its stack space, so, we can not hijack the + * "parent" directly, but need to find the real stack address, + * ftrace_get_parent_addr() does it! + */ + + old = *parent; + + 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) { + ftrace_graph_stop(); + WARN_ON(1); + return; + } + + *parent = return_hooker; + + 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; + } +} +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |