276 lines
6.9 KiB
C
276 lines
6.9 KiB
C
/*
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* Code for replacing ftrace calls with jumps.
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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* Copyright (C) 2009 DSLab, Lanzhou University, China
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* Author: Wu Zhangjin <wuzhangjin@gmail.com>
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*
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* Thanks goes to Steven Rostedt for writing the original x86 version.
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*/
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#include <linux/uaccess.h>
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#include <linux/init.h>
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#include <linux/ftrace.h>
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#include <asm/cacheflush.h>
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#include <asm/asm.h>
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#include <asm/asm-offsets.h>
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#ifdef CONFIG_DYNAMIC_FTRACE
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#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
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#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
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#define jump_insn_encode(op_code, addr) \
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((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK)))
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static unsigned int ftrace_nop = 0x00000000;
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static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
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{
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int faulted;
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/* *(unsigned int *)ip = new_code; */
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safe_store_code(new_code, ip, faulted);
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if (unlikely(faulted))
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return -EFAULT;
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flush_icache_range(ip, ip + 8);
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return 0;
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}
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static int lui_v1;
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static int jal_mcount;
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int new;
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int faulted;
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unsigned long ip = rec->ip;
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/* We have compiled module with -mlong-calls, but compiled the kernel
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* without it, we need to cope with them respectively. */
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if (ip & 0x40000000) {
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/* record it for ftrace_make_call */
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if (lui_v1 == 0) {
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/* lui_v1 = *(unsigned int *)ip; */
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safe_load_code(lui_v1, ip, faulted);
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if (unlikely(faulted))
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return -EFAULT;
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}
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/* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
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* addiu v1, v1, low_16bit_of_mcount
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* move at, ra
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* jalr v1
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* nop
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* 1f: (ip + 12)
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*/
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new = 0x10000004;
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} else {
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/* record/calculate it for ftrace_make_call */
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if (jal_mcount == 0) {
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/* We can record it directly like this:
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* jal_mcount = *(unsigned int *)ip;
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* Herein, jump over the first two nop instructions */
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jal_mcount = jump_insn_encode(JAL, (MCOUNT_ADDR + 8));
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}
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/* move at, ra
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* jalr v1 --> nop
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*/
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new = ftrace_nop;
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}
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return ftrace_modify_code(ip, new);
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}
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static int modified; /* initialized as 0 by default */
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int new;
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unsigned long ip = rec->ip;
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/* We just need to remove the "b ftrace_stub" at the fist time! */
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if (modified == 0) {
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modified = 1;
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ftrace_modify_code(addr, ftrace_nop);
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}
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/* ip, module: 0xc0000000, kernel: 0x80000000 */
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new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
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return ftrace_modify_code(ip, new);
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}
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#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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unsigned int new;
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new = jump_insn_encode(JAL, (unsigned long)func);
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return ftrace_modify_code(FTRACE_CALL_IP, new);
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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/* The return code is retured via data */
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*(unsigned long *)data = 0;
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return 0;
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}
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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#ifdef CONFIG_DYNAMIC_FTRACE
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extern void ftrace_graph_call(void);
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#define JMP 0x08000000 /* jump to target directly */
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#define CALL_FTRACE_GRAPH_CALLER \
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jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
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#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
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int ftrace_enable_ftrace_graph_caller(void)
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{
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return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
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CALL_FTRACE_GRAPH_CALLER);
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}
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int ftrace_disable_ftrace_graph_caller(void)
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{
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return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, ftrace_nop);
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}
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#endif /* !CONFIG_DYNAMIC_FTRACE */
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#ifndef KBUILD_MCOUNT_RA_ADDRESS
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#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
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#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
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#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
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unsigned long ftrace_get_parent_addr(unsigned long self_addr,
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unsigned long parent,
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unsigned long parent_addr,
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unsigned long fp)
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{
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unsigned long sp, ip, ra;
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unsigned int code;
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int faulted;
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/* in module or kernel? */
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if (self_addr & 0x40000000) {
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/* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */
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ip = self_addr - 20;
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} else {
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/* kernel: move to the instruction "move ra, at" */
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ip = self_addr - 12;
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}
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/* search the text until finding the non-store instruction or "s{d,w}
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* ra, offset(sp)" instruction */
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do {
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ip -= 4;
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/* get the code at "ip": code = *(unsigned int *)ip; */
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safe_load_code(code, ip, faulted);
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if (unlikely(faulted))
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return 0;
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/* If we hit the non-store instruction before finding where the
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* ra is stored, then this is a leaf function and it does not
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* store the ra on the stack. */
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if ((code & S_R_SP) != S_R_SP)
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return parent_addr;
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} while (((code & S_RA_SP) != S_RA_SP));
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sp = fp + (code & OFFSET_MASK);
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/* ra = *(unsigned long *)sp; */
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safe_load_stack(ra, sp, faulted);
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if (unlikely(faulted))
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return 0;
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if (ra == parent)
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return sp;
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return 0;
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}
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#endif
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/*
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* Hook the return address and push it in the stack of return addrs
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* in current thread info.
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*/
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void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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unsigned long fp)
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{
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unsigned long old;
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struct ftrace_graph_ent trace;
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unsigned long return_hooker = (unsigned long)
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&return_to_handler;
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int faulted;
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if (unlikely(atomic_read(¤t->tracing_graph_pause)))
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return;
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/* "parent" is the stack address saved the return address of the caller
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* of _mcount.
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*
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* if the gcc < 4.5, a leaf function does not save the return address
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* in the stack address, so, we "emulate" one in _mcount's stack space,
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* and hijack it directly, but for a non-leaf function, it save the
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* return address to the its own stack space, we can not hijack it
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* directly, but need to find the real stack address,
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* ftrace_get_parent_addr() does it!
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*
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* if gcc>= 4.5, with the new -mmcount-ra-address option, for a
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* non-leaf function, the location of the return address will be saved
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* to $12 for us, and for a leaf function, only put a zero into $12. we
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* do it in ftrace_graph_caller of mcount.S.
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*/
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/* old = *parent; */
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safe_load_stack(old, parent, faulted);
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if (unlikely(faulted))
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goto out;
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#ifndef KBUILD_MCOUNT_RA_ADDRESS
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parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
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(unsigned long)parent,
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fp);
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/* If fails when getting the stack address of the non-leaf function's
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* ra, stop function graph tracer and return */
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if (parent == 0)
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goto out;
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#endif
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/* *parent = return_hooker; */
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safe_store_stack(return_hooker, parent, faulted);
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if (unlikely(faulted))
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goto out;
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if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
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-EBUSY) {
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*parent = old;
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return;
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}
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trace.func = self_addr;
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/* Only trace if the calling function expects to */
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if (!ftrace_graph_entry(&trace)) {
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current->curr_ret_stack--;
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*parent = old;
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}
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return;
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out:
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ftrace_graph_stop();
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WARN_ON(1);
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}
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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