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// SPDX-License-Identifier: GPL-2.0
/*
* Based on arch/arm64/kernel/ftrace.c
*
* Copyright (C) 2022 Loongson Technology Corporation Limited
*/
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <asm/inst.h>
static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, bool validate)
{
u32 replaced;
if (validate) {
if (larch_insn_read((void *)pc, &replaced))
return -EFAULT;
if (replaced != old)
return -EINVAL;
}
if (larch_insn_patch_text((void *)pc, new))
return -EPERM;
return 0;
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
{
u32 old, new;
unsigned long pc;
pc = rec->ip + LOONGARCH_INSN_SIZE;
new = larch_insn_gen_bl(pc, addr);
old = larch_insn_gen_bl(pc, old_addr);
return ftrace_modify_code(pc, old, new, true);
}
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
int ftrace_update_ftrace_func(ftrace_func_t func)
{
u32 new;
unsigned long pc;
pc = (unsigned long)&ftrace_call;
new = larch_insn_gen_bl(pc, (unsigned long)func);
return ftrace_modify_code(pc, 0, new, false);
}
/*
* The compiler has inserted 2 NOPs before the regular function prologue.
* T series registers are available and safe because of LoongArch's psABI.
*
* At runtime, we can replace nop with bl to enable ftrace call and replace bl
* with nop to disable ftrace call. The bl requires us to save the original RA
* value, so it saves RA at t0 here.
*
* Details are:
*
* | Compiled | Disabled | Enabled |
* +------------+------------------------+------------------------+
* | nop | move t0, ra | move t0, ra |
* | nop | nop | bl ftrace_caller |
* | func_body | func_body | func_body |
*
* The RA value will be recovered by ftrace_regs_entry, and restored into RA
* before returning to the regular function prologue. When a function is not
* being traced, the "move t0, ra" is not harmful.
*/
int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
{
u32 old, new;
unsigned long pc;
pc = rec->ip;
old = larch_insn_gen_nop();
new = larch_insn_gen_move(LOONGARCH_GPR_T0, LOONGARCH_GPR_RA);
return ftrace_modify_code(pc, old, new, true);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
u32 old, new;
unsigned long pc;
pc = rec->ip + LOONGARCH_INSN_SIZE;
old = larch_insn_gen_nop();
new = larch_insn_gen_bl(pc, addr);
return ftrace_modify_code(pc, old, new, true);
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
u32 old, new;
unsigned long pc;
pc = rec->ip + LOONGARCH_INSN_SIZE;
new = larch_insn_gen_nop();
old = larch_insn_gen_bl(pc, addr);
return ftrace_modify_code(pc, old, new, true);
}
void arch_ftrace_update_code(int command)
{
command |= FTRACE_MAY_SLEEP;
ftrace_modify_all_code(command);
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent)
{
unsigned long old;
unsigned long return_hooker = (unsigned long)&return_to_handler;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
old = *parent;
if (!function_graph_enter(old, self_addr, 0, NULL))
*parent = return_hooker;
}
static int ftrace_modify_graph_caller(bool enable)
{
u32 branch, nop;
unsigned long pc, func;
extern void ftrace_graph_call(void);
pc = (unsigned long)&ftrace_graph_call;
func = (unsigned long)&ftrace_graph_caller;
nop = larch_insn_gen_nop();
branch = larch_insn_gen_b(pc, func);
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_FUNCTION_GRAPH_TRACER */
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