2 * arch/arm64/kernel/ftrace.c
4 * Copyright (C) 2013 Linaro Limited
5 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/ftrace.h>
13 #include <linux/swab.h>
14 #include <linux/uaccess.h>
16 #include <asm/cacheflush.h>
17 #include <asm/ftrace.h>
20 #ifdef CONFIG_DYNAMIC_FTRACE
22 * Replace a single instruction, which may be a branch or NOP.
23 * If @validate == true, a replaced instruction is checked against 'old'.
25 static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
32 * Due to modules and __init, code can disappear and change,
33 * we need to protect against faulting as well as code changing.
34 * We do this by aarch64_insn_*() which use the probe_kernel_*().
36 * No lock is held here because all the modifications are run
37 * through stop_machine().
40 if (aarch64_insn_read((void *)pc, &replaced))
46 if (aarch64_insn_patch_text_nosync((void *)pc, new))
53 * Replace tracer function in ftrace_caller()
55 int ftrace_update_ftrace_func(ftrace_func_t func)
60 pc = (unsigned long)&ftrace_call;
61 new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func, true);
63 return ftrace_modify_code(pc, 0, new, false);
67 * Turn on the call to ftrace_caller() in instrumented function
69 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
71 unsigned long pc = rec->ip;
74 old = aarch64_insn_gen_nop();
75 new = aarch64_insn_gen_branch_imm(pc, addr, true);
77 return ftrace_modify_code(pc, old, new, true);
81 * Turn off the call to ftrace_caller() in instrumented function
83 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
86 unsigned long pc = rec->ip;
89 old = aarch64_insn_gen_branch_imm(pc, addr, true);
90 new = aarch64_insn_gen_nop();
92 return ftrace_modify_code(pc, old, new, true);
95 int __init ftrace_dyn_arch_init(void)
99 #endif /* CONFIG_DYNAMIC_FTRACE */
101 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
103 * function_graph tracer expects ftrace_return_to_handler() to be called
104 * on the way back to parent. For this purpose, this function is called
105 * in _mcount() or ftrace_caller() to replace return address (*parent) on
106 * the call stack to return_to_handler.
108 * Note that @frame_pointer is used only for sanity check later.
110 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
111 unsigned long frame_pointer)
113 unsigned long return_hooker = (unsigned long)&return_to_handler;
115 struct ftrace_graph_ent trace;
118 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
123 * No protection against faulting at *parent, which may be seen
124 * on other archs. It's unlikely on AArch64.
127 *parent = return_hooker;
129 trace.func = self_addr;
130 trace.depth = current->curr_ret_stack + 1;
132 /* Only trace if the calling function expects to */
133 if (!ftrace_graph_entry(&trace)) {
138 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
146 #ifdef CONFIG_DYNAMIC_FTRACE
148 * Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
149 * depending on @enable.
151 static int ftrace_modify_graph_caller(bool enable)
153 unsigned long pc = (unsigned long)&ftrace_graph_call;
156 branch = aarch64_insn_gen_branch_imm(pc,
157 (unsigned long)ftrace_graph_caller, false);
158 nop = aarch64_insn_gen_nop();
161 return ftrace_modify_code(pc, nop, branch, true);
163 return ftrace_modify_code(pc, branch, nop, true);
166 int ftrace_enable_ftrace_graph_caller(void)
168 return ftrace_modify_graph_caller(true);
171 int ftrace_disable_ftrace_graph_caller(void)
173 return ftrace_modify_graph_caller(false);
175 #endif /* CONFIG_DYNAMIC_FTRACE */
176 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */