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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 <linux/memory.h>
#include <asm/cacheflush.h>
#include <asm/patch.h>
#ifdef CONFIG_DYNAMIC_FTRACE
void ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
{
mutex_lock(&text_mutex);
/*
* The code sequences we use for ftrace can't be patched while the
* kernel is running, so we need to use stop_machine() to modify them
* for now. This doesn't play nice with text_mutex, we use this flag
* to elide the check.
*/
riscv_patch_in_stop_machine = true;
}
void ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
{
riscv_patch_in_stop_machine = false;
mutex_unlock(&text_mutex);
}
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 (copy_from_kernel_nofault(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, bool ra)
{
unsigned int call[2];
unsigned int nops[2] = {NOP4, NOP4};
if (ra)
make_call_ra(hook_pos, target, call);
else
make_call_t0(hook_pos, target, call);
/* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
if (patch_text_nosync
((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
return -EPERM;
return 0;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int call[2];
make_call_t0(rec->ip, addr, call);
if (patch_text_nosync((void *)rec->ip, call, MCOUNT_INSN_SIZE))
return -EPERM;
return 0;
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
unsigned int nops[2] = {NOP4, NOP4};
if (patch_text_nosync((void *)rec->ip, nops, MCOUNT_INSN_SIZE))
return -EPERM;
return 0;
}
/*
* This is called early on, and isn't wrapped by
* ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold
* text_mutex, which triggers a lockdep failure. SMP isn't running so we could
* just directly poke the text, but it's simpler to just take the lock
* ourselves.
*/
int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
{
int out;
mutex_lock(&text_mutex);
out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
mutex_unlock(&text_mutex);
return out;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
(unsigned long)func, true, true);
if (!ret) {
ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
(unsigned long)func, true, true);
}
return ret;
}
#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];
unsigned long caller = rec->ip;
int ret;
make_call_t0(caller, old_addr, call);
ret = ftrace_check_current_call(caller, call);
if (ret)
return ret;
return __ftrace_modify_call(caller, addr, true, false);
}
#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
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs)
{
struct pt_regs *regs = arch_ftrace_get_regs(fregs);
unsigned long *parent = (unsigned long *)®s->ra;
prepare_ftrace_return(parent, ip, frame_pointer(regs));
}
#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
extern void ftrace_graph_call(void);
int ftrace_enable_ftrace_graph_caller(void)
{
return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
(unsigned long)&prepare_ftrace_return, true, true);
}
int ftrace_disable_ftrace_graph_caller(void)
{
return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
(unsigned long)&prepare_ftrace_return, false, true);
}
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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