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 * We are paranoid about modifying text, as if a bug were to happen, it
33 * could cause us to read or write to someplace that could cause harm.
34 * Carefully read and modify the code with aarch64_insn_*() which uses
35 * probe_kernel_*(), and make sure what we read is what we expected it
36 * to be before modifying it.
39 if (aarch64_insn_read((void *)pc, &replaced))
45 if (aarch64_insn_patch_text_nosync((void *)pc, new))
52 * Replace tracer function in ftrace_caller()
54 int ftrace_update_ftrace_func(ftrace_func_t func)
59 pc = (unsigned long)&ftrace_call;
60 new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
61 AARCH64_INSN_BRANCH_LINK);
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, AARCH64_INSN_BRANCH_LINK);
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, AARCH64_INSN_BRANCH_LINK);
90 new = aarch64_insn_gen_nop();
92 return ftrace_modify_code(pc, old, new, true);
95 void arch_ftrace_update_code(int command)
97 ftrace_modify_all_code(command);
100 int __init ftrace_dyn_arch_init(void)
104 #endif /* CONFIG_DYNAMIC_FTRACE */
106 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
108 * function_graph tracer expects ftrace_return_to_handler() to be called
109 * on the way back to parent. For this purpose, this function is called
110 * in _mcount() or ftrace_caller() to replace return address (*parent) on
111 * the call stack to return_to_handler.
113 * Note that @frame_pointer is used only for sanity check later.
115 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
116 unsigned long frame_pointer)
118 unsigned long return_hooker = (unsigned long)&return_to_handler;
120 struct ftrace_graph_ent trace;
123 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
128 * No protection against faulting at *parent, which may be seen
129 * on other archs. It's unlikely on AArch64.
133 trace.func = self_addr;
134 trace.depth = current->curr_ret_stack + 1;
136 /* Only trace if the calling function expects to */
137 if (!ftrace_graph_entry(&trace))
140 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
145 *parent = return_hooker;
148 #ifdef CONFIG_DYNAMIC_FTRACE
150 * Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
151 * depending on @enable.
153 static int ftrace_modify_graph_caller(bool enable)
155 unsigned long pc = (unsigned long)&ftrace_graph_call;
158 branch = aarch64_insn_gen_branch_imm(pc,
159 (unsigned long)ftrace_graph_caller,
160 AARCH64_INSN_BRANCH_NOLINK);
161 nop = aarch64_insn_gen_nop();
164 return ftrace_modify_code(pc, nop, branch, true);
166 return ftrace_modify_code(pc, branch, nop, true);
169 int ftrace_enable_ftrace_graph_caller(void)
171 return ftrace_modify_graph_caller(true);
174 int ftrace_disable_ftrace_graph_caller(void)
176 return ftrace_modify_graph_caller(false);
178 #endif /* CONFIG_DYNAMIC_FTRACE */
179 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */