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/*
* arch/arm64/kernel/ftrace.c
*
* Copyright (C) 2013 Linaro Limited
* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/ftrace.h>
#include <linux/swab.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/ftrace.h>
#include <asm/insn.h>
#ifdef CONFIG_DYNAMIC_FTRACE
/*
* Replace a single instruction, which may be a branch or NOP.
* If @validate == true, a replaced instruction is checked against 'old'.
*/
static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
bool validate)
{
u32 replaced;
/*
* Note:
* We are paranoid about modifying text, as if a bug were to happen, it
* could cause us to read or write to someplace that could cause harm.
* Carefully read and modify the code with aarch64_insn_*() which uses
* probe_kernel_*(), and make sure what we read is what we expected it
* to be before modifying it.
*/
if (validate) {
if (aarch64_insn_read((void *)pc, &replaced))
return -EFAULT;
if (replaced != old)
return -EINVAL;
}
if (aarch64_insn_patch_text_nosync((void *)pc, new))
return -EPERM;
return 0;
}
/*
* Replace tracer function in ftrace_caller()
*/
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long pc;
u32 new;
pc = (unsigned long)&ftrace_call;
new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
AARCH64_INSN_BRANCH_LINK);
return ftrace_modify_code(pc, 0, new, false);
}
/*
* Turn on the call to ftrace_caller() in instrumented function
*/
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long pc = rec->ip;
u32 old, new;
old = aarch64_insn_gen_nop();
new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
return ftrace_modify_code(pc, old, new, true);
}
/*
* Turn off the call to ftrace_caller() in instrumented function
*/
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
unsigned long pc = rec->ip;
u32 old, new;
old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
new = aarch64_insn_gen_nop();
return ftrace_modify_code(pc, old, new, true);
}
void arch_ftrace_update_code(int command)
{
ftrace_modify_all_code(command);
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* function_graph tracer expects ftrace_return_to_handler() to be called
* on the way back to parent. For this purpose, this function is called
* in _mcount() or ftrace_caller() to replace return address (*parent) on
* the call stack to return_to_handler.
*
* Note that @frame_pointer is used only for sanity check later.
*/
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
unsigned long frame_pointer)
{
unsigned long return_hooker = (unsigned long)&return_to_handler;
unsigned long old;
struct ftrace_graph_ent trace;
int err;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
/*
* Note:
* No protection against faulting at *parent, which may be seen
* on other archs. It's unlikely on AArch64.
*/
old = *parent;
*parent = return_hooker;
trace.func = self_addr;
trace.depth = current->curr_ret_stack + 1;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
*parent = old;
return;
}
err = ftrace_push_return_trace(old, self_addr, &trace.depth,
frame_pointer);
if (err == -EBUSY) {
*parent = old;
return;
}
}
#ifdef CONFIG_DYNAMIC_FTRACE
/*
* Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
* depending on @enable.
*/
static int ftrace_modify_graph_caller(bool enable)
{
unsigned long pc = (unsigned long)&ftrace_graph_call;
u32 branch, nop;
branch = aarch64_insn_gen_branch_imm(pc,
(unsigned long)ftrace_graph_caller,
AARCH64_INSN_BRANCH_NOLINK);
nop = aarch64_insn_gen_nop();
if (enable)
return ftrace_modify_code(pc, nop, branch, true);
else
return ftrace_modify_code(pc, branch, nop, true);
}
int ftrace_enable_ftrace_graph_caller(void)
{
return ftrace_modify_graph_caller(true);
}
int ftrace_disable_ftrace_graph_caller(void)
{
return ftrace_modify_graph_caller(false);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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