/*
 * Copyright 2012 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 *
 * TILE-Gx specific ftrace support
 */

#include <linux/ftrace.h>
#include <linux/uaccess.h>

#include <asm/cacheflush.h>
#include <asm/ftrace.h>
#include <asm/sections.h>
#include <asm/insn.h>

#include <arch/opcode.h>

#ifdef CONFIG_DYNAMIC_FTRACE

static int machine_stopped __read_mostly;

int ftrace_arch_code_modify_prepare(void)
{
        machine_stopped = 1;
        return 0;
}

int ftrace_arch_code_modify_post_process(void)
{
        flush_icache_range(0, CHIP_L1I_CACHE_SIZE());
        machine_stopped = 0;
        return 0;
}

/*
 * Put { move r10, lr; jal ftrace_caller } in a bundle, this lets dynamic
 * tracer just add one cycle overhead to every kernel function when disabled.
 */
static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
                                       bool link)
{
        tilegx_bundle_bits opcode_x0, opcode_x1;
        long pcrel_by_instr = (addr - pc) >> TILEGX_LOG2_BUNDLE_SIZE_IN_BYTES;

        if (link) {
                /* opcode: jal addr */
                opcode_x1 =
                        create_Opcode_X1(JUMP_OPCODE_X1) |
                        create_JumpOpcodeExtension_X1(JAL_JUMP_OPCODE_X1) |
                        create_JumpOff_X1(pcrel_by_instr);
        } else {
                /* opcode: j addr */
                opcode_x1 =
                        create_Opcode_X1(JUMP_OPCODE_X1) |
                        create_JumpOpcodeExtension_X1(J_JUMP_OPCODE_X1) |
                        create_JumpOff_X1(pcrel_by_instr);
        }

        /*
         * Also put { move r10, lr; jal ftrace_stub } in a bundle, which
         * is used to replace the instruction in address ftrace_call.
         */
        if (addr == FTRACE_ADDR || addr == (unsigned long)ftrace_stub) {
                /* opcode: or r10, lr, zero */
                opcode_x0 =
                        create_Dest_X0(10) |
                        create_SrcA_X0(TREG_LR) |
                        create_SrcB_X0(TREG_ZERO) |
                        create_RRROpcodeExtension_X0(OR_RRR_0_OPCODE_X0) |
                        create_Opcode_X0(RRR_0_OPCODE_X0);
        } else {
                /* opcode: fnop */
                opcode_x0 =
                        create_UnaryOpcodeExtension_X0(FNOP_UNARY_OPCODE_X0) |
                        create_RRROpcodeExtension_X0(UNARY_RRR_0_OPCODE_X0) |
                        create_Opcode_X0(RRR_0_OPCODE_X0);
        }

        return opcode_x1 | opcode_x0;
}

static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
        return NOP();
}

static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
{
        return ftrace_gen_branch(pc, addr, true);
}

static int ftrace_modify_code(unsigned long pc, unsigned long old,
                              unsigned long new)
{
        unsigned long pc_wr;

        /* Check if the address is in kernel text space and module space. */
        if (!kernel_text_address(pc))
                return -EINVAL;

        /* Operate on writable kernel text mapping. */
        pc_wr = ktext_writable_addr(pc);

        if (probe_kernel_write((void *)pc_wr, &new, MCOUNT_INSN_SIZE))
                return -EPERM;

        smp_wmb();

        if (!machine_stopped && num_online_cpus() > 1)
                flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);

        return 0;
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
        unsigned long pc, old;
        unsigned long new;
        int ret;

        pc = (unsigned long)&ftrace_call;
        memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
        new = ftrace_call_replace(pc, (unsigned long)func);

        ret = ftrace_modify_code(pc, old, new);

        return ret;
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
        unsigned long new, old;
        unsigned long ip = rec->ip;

        old = ftrace_nop_replace(rec);
        new = ftrace_call_replace(ip, addr);

        return ftrace_modify_code(rec->ip, old, new);
}

int ftrace_make_nop(struct module *mod,
                    struct dyn_ftrace *rec, unsigned long addr)
{
        unsigned long ip = rec->ip;
        unsigned long old;
        unsigned long new;
        int ret;

        old = ftrace_call_replace(ip, addr);
        new = ftrace_nop_replace(rec);
        ret = ftrace_modify_code(ip, old, new);

        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;
        struct ftrace_graph_ent trace;
        unsigned long old;
        int err;

        if (unlikely(atomic_read(&current->tracing_graph_pause)))
                return;

        old = *parent;
        *parent = return_hooker;

        err = ftrace_push_return_trace(old, self_addr, &trace.depth,
                                       frame_pointer, NULL);
        if (err == -EBUSY) {
                *parent = old;
                return;
        }

        trace.func = self_addr;

        /* Only trace if the calling function expects to */
        if (!ftrace_graph_entry(&trace)) {
                current->curr_ret_stack--;
                *parent = old;
        }
}

#ifdef CONFIG_DYNAMIC_FTRACE
extern unsigned long ftrace_graph_call;

static int __ftrace_modify_caller(unsigned long *callsite,
                                  void (*func) (void), bool enable)
{
        unsigned long caller_fn = (unsigned long) func;
        unsigned long pc = (unsigned long) callsite;
        unsigned long branch = ftrace_gen_branch(pc, caller_fn, false);
        unsigned long nop = NOP();
        unsigned long old = enable ? nop : branch;
        unsigned long new = enable ? branch : nop;

        return ftrace_modify_code(pc, old, new);
}

static int ftrace_modify_graph_caller(bool enable)
{
        int ret;

        ret = __ftrace_modify_caller(&ftrace_graph_call,
                                     ftrace_graph_caller,
                                     enable);

        return ret;
}

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_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */