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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2013 Linaro Limited
* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
* Copyright (C) 2017 Andes Technology Corporation
*/
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#ifdef CONFIG_DYNAMIC_FTRACE
static int ftrace_check_current_call(unsigned long hook_pos,
unsigned int *expected)
{
unsigned int replaced[2];
unsigned int nops[2] = {NOP4, NOP4};
/* we expect nops at the hook position */
if (!expected)
expected = nops;
/*
* Read the text we want to modify;
* return must be -EFAULT on read error
*/
if (probe_kernel_read(replaced, (void *)hook_pos, MCOUNT_INSN_SIZE))
return -EFAULT;
/*
* Make sure it is what we expect it to be;
* return must be -EINVAL on failed comparison
*/
if (memcmp(expected, replaced, sizeof(replaced))) {
pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n",
(void *)hook_pos, expected[0], expected[1], replaced[0],
replaced[1]);
return -EINVAL;
}
return 0;
}
static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
bool enable)
{
unsigned int call[2];
unsigned int nops[2] = {NOP4, NOP4};
int ret = 0;
make_call(hook_pos, target, call);
/* replace the auipc-jalr pair at once */
ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
MCOUNT_INSN_SIZE);
/* return must be -EPERM on write error */
if (ret)
return -EPERM;
smp_mb();
flush_icache_range((void *)hook_pos, (void *)hook_pos + MCOUNT_INSN_SIZE);
return 0;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
int ret = ftrace_check_current_call(rec->ip, NULL);
if (ret)
return ret;
return __ftrace_modify_call(rec->ip, addr, true);
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
unsigned int call[2];
int ret;
make_call(rec->ip, addr, call);
ret = ftrace_check_current_call(rec->ip, call);
if (ret)
return ret;
return __ftrace_modify_call(rec->ip, addr, false);
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
(unsigned long)func, true);
if (!ret) {
ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
(unsigned long)func, true);
}
return ret;
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#endif
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
unsigned int call[2];
int ret;
make_call(rec->ip, old_addr, call);
ret = ftrace_check_current_call(rec->ip, call);
if (ret)
return ret;
return __ftrace_modify_call(rec->ip, addr, true);
}
#endif
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* Most of this function is copied from arm64.
*/
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;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
/*
* We don't suffer access faults, so no extra fault-recovery assembly
* is needed here.
*/
old = *parent;
if (function_graph_enter(old, self_addr, frame_pointer, parent))
*parent = return_hooker;
}
#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);
int ftrace_enable_ftrace_graph_caller(void)
{
unsigned int call[2];
static int init_graph = 1;
int ret;
make_call(&ftrace_graph_call, &ftrace_stub, call);
/*
* When enabling graph tracer for the first time, ftrace_graph_call
* should contains a call to ftrace_stub. Once it has been disabled,
* the 8-bytes at the position becomes NOPs.
*/
if (init_graph) {
ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
call);
init_graph = 0;
} else {
ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
NULL);
}
if (ret)
return ret;
return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
(unsigned long)&prepare_ftrace_return, true);
}
int ftrace_disable_ftrace_graph_caller(void)
{
unsigned int call[2];
int ret;
make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
/*
* This is to make sure that ftrace_enable_ftrace_graph_caller
* did the right thing.
*/
ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
call);
if (ret)
return ret;
return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
(unsigned long)&prepare_ftrace_return, false);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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