// 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(&current->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);