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// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#ifdef CONFIG_DYNAMIC_FTRACE
#define NOP 0x4000
#define NOP32_HI 0xc400
#define NOP32_LO 0x4820
#define PUSH_LR 0x14d0
#define MOVIH_LINK 0xea3a
#define ORI_LINK 0xef5a
#define JSR_LINK 0xe8fa
#define BSR_LINK 0xe000
/*
* Gcc-csky with -pg will insert stub in function prologue:
* push lr
* jbsr _mcount
* nop32
* nop32
*
* If the (callee - current_pc) is less then 64MB, we'll use bsr:
* push lr
* bsr _mcount
* nop32
* nop32
* else we'll use (movih + ori + jsr):
* push lr
* movih r26, ...
* ori r26, ...
* jsr r26
*
* (r26 is our reserved link-reg)
*
*/
static inline void make_jbsr(unsigned long callee, unsigned long pc,
uint16_t *call, bool nolr)
{
long offset;
call[0] = nolr ? NOP : PUSH_LR;
offset = (long) callee - (long) pc;
if (unlikely(offset < -67108864 || offset > 67108864)) {
call[1] = MOVIH_LINK;
call[2] = callee >> 16;
call[3] = ORI_LINK;
call[4] = callee & 0xffff;
call[5] = JSR_LINK;
call[6] = 0;
} else {
offset = offset >> 1;
call[1] = BSR_LINK |
((uint16_t)((unsigned long) offset >> 16) & 0x3ff);
call[2] = (uint16_t)((unsigned long) offset & 0xffff);
call[3] = call[5] = NOP32_HI;
call[4] = call[6] = NOP32_LO;
}
}
static uint16_t nops[7] = {NOP, NOP32_HI, NOP32_LO, NOP32_HI, NOP32_LO,
NOP32_HI, NOP32_LO};
static int ftrace_check_current_nop(unsigned long hook)
{
uint16_t olds[7];
unsigned long hook_pos = hook - 2;
if (probe_kernel_read((void *)olds, (void *)hook_pos, sizeof(nops)))
return -EFAULT;
if (memcmp((void *)nops, (void *)olds, sizeof(nops))) {
pr_err("%p: nop but get (%04x %04x %04x %04x %04x %04x %04x)\n",
(void *)hook_pos,
olds[0], olds[1], olds[2], olds[3], olds[4], olds[5],
olds[6]);
return -EINVAL;
}
return 0;
}
static int ftrace_modify_code(unsigned long hook, unsigned long target,
bool enable, bool nolr)
{
uint16_t call[7];
unsigned long hook_pos = hook - 2;
int ret = 0;
make_jbsr(target, hook, call, nolr);
ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
sizeof(nops));
if (ret)
return -EPERM;
flush_icache_range(hook_pos, hook_pos + MCOUNT_INSN_SIZE);
return 0;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
int ret = ftrace_check_current_nop(rec->ip);
if (ret)
return ret;
return ftrace_modify_code(rec->ip, addr, true, false);
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
return ftrace_modify_code(rec->ip, addr, false, false);
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
int ret = ftrace_modify_code((unsigned long)&ftrace_call,
(unsigned long)func, true, true);
return ret;
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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;
old = *parent;
if (!function_graph_enter(old, self_addr,
*(unsigned long *)frame_pointer, parent)) {
/*
* For csky-gcc function has sub-call:
* subi sp, sp, 8
* stw r8, (sp, 0)
* mov r8, sp
* st.w r15, (sp, 0x4)
* push r15
* jl _mcount
* We only need set *parent for resume
*
* For csky-gcc function has no sub-call:
* subi sp, sp, 4
* stw r8, (sp, 0)
* mov r8, sp
* push r15
* jl _mcount
* We need set *parent and *(frame_pointer + 4) for resume,
* because lr is resumed twice.
*/
*parent = return_hooker;
frame_pointer += 4;
if (*(unsigned long *)frame_pointer == old)
*(unsigned long *)frame_pointer = return_hooker;
}
}
#ifdef CONFIG_DYNAMIC_FTRACE
int ftrace_enable_ftrace_graph_caller(void)
{
return ftrace_modify_code((unsigned long)&ftrace_graph_call,
(unsigned long)&ftrace_graph_caller, true, true);
}
int ftrace_disable_ftrace_graph_caller(void)
{
return ftrace_modify_code((unsigned long)&ftrace_graph_call,
(unsigned long)&ftrace_graph_caller, false, true);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
/* _mcount is defined in abi's mcount.S */
EXPORT_SYMBOL(_mcount);
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