314 lines
6.9 KiB
C
314 lines
6.9 KiB
C
/*
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* Dynamic function tracing support.
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*
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* Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
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* Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
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*
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* For licencing details, see COPYING.
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*
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* Defines low-level handling of mcount calls when the kernel
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* is compiled with the -pg flag. When using dynamic ftrace, the
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* mcount call-sites get patched with NOP till they are enabled.
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* All code mutation routines here are called under stop_machine().
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*/
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#include <linux/ftrace.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/stop_machine.h>
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#include <asm/cacheflush.h>
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#include <asm/opcodes.h>
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#include <asm/ftrace.h>
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#include <asm/insn.h>
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#include <asm/set_memory.h>
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#ifdef CONFIG_THUMB2_KERNEL
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#define NOP 0xf85deb04 /* pop.w {lr} */
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#else
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#define NOP 0xe8bd4000 /* pop {lr} */
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#endif
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#ifdef CONFIG_DYNAMIC_FTRACE
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static int __ftrace_modify_code(void *data)
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{
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int *command = data;
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set_kernel_text_rw();
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ftrace_modify_all_code(*command);
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set_kernel_text_ro();
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return 0;
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}
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void arch_ftrace_update_code(int command)
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{
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stop_machine(__ftrace_modify_code, &command, NULL);
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}
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#ifdef CONFIG_OLD_MCOUNT
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#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
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#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
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#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
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static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
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{
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return rec->arch.old_mcount ? OLD_NOP : NOP;
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}
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static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
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{
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if (!rec->arch.old_mcount)
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return addr;
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if (addr == MCOUNT_ADDR)
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addr = OLD_MCOUNT_ADDR;
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else if (addr == FTRACE_ADDR)
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addr = OLD_FTRACE_ADDR;
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return addr;
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}
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#else
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static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
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{
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return NOP;
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}
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static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
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{
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return addr;
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}
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#endif
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int ftrace_arch_code_modify_prepare(void)
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{
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set_all_modules_text_rw();
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return 0;
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}
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int ftrace_arch_code_modify_post_process(void)
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{
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set_all_modules_text_ro();
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/* Make sure any TLB misses during machine stop are cleared. */
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flush_tlb_all();
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return 0;
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}
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static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
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{
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return arm_gen_branch_link(pc, addr);
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}
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static int ftrace_modify_code(unsigned long pc, unsigned long old,
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unsigned long new, bool validate)
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{
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unsigned long replaced;
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if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
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old = __opcode_to_mem_thumb32(old);
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new = __opcode_to_mem_thumb32(new);
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} else {
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old = __opcode_to_mem_arm(old);
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new = __opcode_to_mem_arm(new);
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}
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if (validate) {
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if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
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return -EFAULT;
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if (replaced != old)
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return -EINVAL;
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}
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if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
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return -EPERM;
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flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
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return 0;
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}
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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unsigned long pc;
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unsigned long new;
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int ret;
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pc = (unsigned long)&ftrace_call;
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new = ftrace_call_replace(pc, (unsigned long)func);
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ret = ftrace_modify_code(pc, 0, new, false);
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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if (!ret) {
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pc = (unsigned long)&ftrace_regs_call;
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new = ftrace_call_replace(pc, (unsigned long)func);
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ret = ftrace_modify_code(pc, 0, new, false);
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}
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#endif
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#ifdef CONFIG_OLD_MCOUNT
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if (!ret) {
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pc = (unsigned long)&ftrace_call_old;
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new = ftrace_call_replace(pc, (unsigned long)func);
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ret = ftrace_modify_code(pc, 0, new, false);
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}
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#endif
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return ret;
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}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned long new, old;
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unsigned long ip = rec->ip;
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old = ftrace_nop_replace(rec);
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new = ftrace_call_replace(ip, adjust_address(rec, addr));
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return ftrace_modify_code(rec->ip, old, new, true);
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}
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
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unsigned long addr)
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{
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unsigned long new, old;
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unsigned long ip = rec->ip;
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old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
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new = ftrace_call_replace(ip, adjust_address(rec, addr));
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return ftrace_modify_code(rec->ip, old, new, true);
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}
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#endif
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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 long ip = rec->ip;
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unsigned long old;
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unsigned long new;
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int ret;
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old = ftrace_call_replace(ip, adjust_address(rec, addr));
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new = ftrace_nop_replace(rec);
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ret = ftrace_modify_code(ip, old, new, true);
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#ifdef CONFIG_OLD_MCOUNT
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if (ret == -EINVAL && addr == MCOUNT_ADDR) {
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rec->arch.old_mcount = true;
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old = ftrace_call_replace(ip, adjust_address(rec, addr));
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new = ftrace_nop_replace(rec);
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ret = ftrace_modify_code(ip, old, new, true);
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}
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#endif
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return ret;
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}
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int __init ftrace_dyn_arch_init(void)
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{
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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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void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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unsigned long frame_pointer)
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{
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unsigned long return_hooker = (unsigned long) &return_to_handler;
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struct ftrace_graph_ent trace;
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unsigned long old;
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int err;
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if (unlikely(atomic_read(¤t->tracing_graph_pause)))
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return;
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old = *parent;
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*parent = return_hooker;
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trace.func = self_addr;
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trace.depth = current->curr_ret_stack + 1;
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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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*parent = old;
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return;
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}
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err = ftrace_push_return_trace(old, self_addr, &trace.depth,
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frame_pointer, NULL);
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if (err == -EBUSY) {
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*parent = old;
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return;
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}
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}
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#ifdef CONFIG_DYNAMIC_FTRACE
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extern unsigned long ftrace_graph_call;
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extern unsigned long ftrace_graph_call_old;
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extern void ftrace_graph_caller_old(void);
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extern unsigned long ftrace_graph_regs_call;
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extern void ftrace_graph_regs_caller(void);
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static int __ftrace_modify_caller(unsigned long *callsite,
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void (*func) (void), bool enable)
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{
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unsigned long caller_fn = (unsigned long) func;
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unsigned long pc = (unsigned long) callsite;
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unsigned long branch = arm_gen_branch(pc, caller_fn);
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unsigned long nop = 0xe1a00000; /* mov r0, r0 */
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unsigned long old = enable ? nop : branch;
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unsigned long new = enable ? branch : nop;
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return ftrace_modify_code(pc, old, new, true);
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}
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static int ftrace_modify_graph_caller(bool enable)
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{
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int ret;
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ret = __ftrace_modify_caller(&ftrace_graph_call,
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ftrace_graph_caller,
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enable);
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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if (!ret)
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ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
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ftrace_graph_regs_caller,
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enable);
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#endif
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#ifdef CONFIG_OLD_MCOUNT
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if (!ret)
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ret = __ftrace_modify_caller(&ftrace_graph_call_old,
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ftrace_graph_caller_old,
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enable);
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#endif
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return ret;
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}
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int ftrace_enable_ftrace_graph_caller(void)
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{
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return ftrace_modify_graph_caller(true);
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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_graph_caller(false);
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}
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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