/*
 * Ftrace support for Microblaze.
 *
 * Copyright (C) 2009 Michal Simek <monstr@monstr.eu>
 * Copyright (C) 2009 PetaLogix
 *
 * Based on MIPS and PowerPC ftrace code
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License. See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#include <asm/cacheflush.h>
#include <linux/ftrace.h>

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
 * Hook the return address and push it in the stack of return addrs
 * in current thread info.
 */
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
{
        unsigned long old;
        int faulted, err;
        struct ftrace_graph_ent trace;
        unsigned long return_hooker = (unsigned long)
                                &return_to_handler;

        if (unlikely(ftrace_graph_is_dead()))
                return;

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

        /*
         * Protect against fault, even if it shouldn't
         * happen. This tool is too much intrusive to
         * ignore such a protection.
         */
        asm volatile("  1:      lwi     %0, %2, 0;"             \
                        "2:     swi     %3, %2, 0;"             \
                        "       addik   %1, r0, 0;"             \
                        "3:"                                    \
                        "       .section .fixup, \"ax\";"       \
                        "4:     brid    3b;"                    \
                        "       addik   %1, r0, 1;"             \
                        "       .previous;"                     \
                        "       .section __ex_table,\"a\";"     \
                        "       .word   1b,4b;"                 \
                        "       .word   2b,4b;"                 \
                        "       .previous;"                     \
                        : "=&r" (old), "=r" (faulted)
                        : "r" (parent), "r" (return_hooker)
        );

        flush_dcache_range((u32)parent, (u32)parent + 4);
        flush_icache_range((u32)parent, (u32)parent + 4);

        if (unlikely(faulted)) {
                ftrace_graph_stop();
                WARN_ON(1);
                return;
        }

        err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0, 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;
        }
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

#ifdef CONFIG_DYNAMIC_FTRACE
/* save value to addr - it is save to do it in asm */
static int ftrace_modify_code(unsigned long addr, unsigned int value)
{
        int faulted = 0;

        __asm__ __volatile__("  1:      swi     %2, %1, 0;"             \
                                "       addik   %0, r0, 0;"             \
                                "2:"                                    \
                                "       .section .fixup, \"ax\";"       \
                                "3:     brid    2b;"                    \
                                "       addik   %0, r0, 1;"             \
                                "       .previous;"                     \
                                "       .section __ex_table,\"a\";"     \
                                "       .word   1b,3b;"                 \
                                "       .previous;"                     \
                                : "=r" (faulted)
                                : "r" (addr), "r" (value)
        );

        if (unlikely(faulted))
                return -EFAULT;

        flush_dcache_range(addr, addr + 4);
        flush_icache_range(addr, addr + 4);

        return 0;
}

#define MICROBLAZE_NOP 0x80000000
#define MICROBLAZE_BRI 0xb800000C

static unsigned int recorded; /* if save was or not */
static unsigned int imm; /* saving whole imm instruction */

/* There are two approaches howto solve ftrace_make nop function - look below */
#undef USE_FTRACE_NOP

#ifdef USE_FTRACE_NOP
static unsigned int bralid; /* saving whole bralid instruction */
#endif

int ftrace_make_nop(struct module *mod,
                        struct dyn_ftrace *rec, unsigned long addr)
{
        /* we have this part of code which we are working with
         * b000c000        imm     -16384
         * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
         * 80000000        or      r0, r0, r0
         *
         * The first solution (!USE_FTRACE_NOP-could be called branch solution)
         * b000c000        bri  12 (0xC - jump to any other instruction)
         * b9fc8e30        bralid  r15, -29136     // c0008e30 <_mcount>
         * 80000000        or      r0, r0, r0
         * any other instruction
         *
         * The second solution (USE_FTRACE_NOP) - no jump just nops
         * 80000000        or      r0, r0, r0
         * 80000000        or      r0, r0, r0
         * 80000000        or      r0, r0, r0
         */
        int ret = 0;

        if (recorded == 0) {
                recorded = 1;
                imm = *(unsigned int *)rec->ip;
                pr_debug("%s: imm:0x%x\n", __func__, imm);
#ifdef USE_FTRACE_NOP
                bralid = *(unsigned int *)(rec->ip + 4);
                pr_debug("%s: bralid 0x%x\n", __func__, bralid);
#endif /* USE_FTRACE_NOP */
        }

#ifdef USE_FTRACE_NOP
        ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
        ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
#else /* USE_FTRACE_NOP */
        ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
#endif /* USE_FTRACE_NOP */
        return ret;
}

/* I believe that first is called ftrace_make_nop before this function */
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
        int ret;
        pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
                __func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
        ret = ftrace_modify_code(rec->ip, imm);
#ifdef USE_FTRACE_NOP
        pr_debug("%s: bralid:0x%x\n", __func__, bralid);
        ret += ftrace_modify_code(rec->ip + 4, bralid);
#endif /* USE_FTRACE_NOP */
        return ret;
}

int __init ftrace_dyn_arch_init(void)
{
        return 0;
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
        unsigned long ip = (unsigned long)(&ftrace_call);
        unsigned int upper = (unsigned int)func;
        unsigned int lower = (unsigned int)func;
        int ret = 0;

        /* create proper saving to ftrace_call poll */
        upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
        lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */

        pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
                __func__, (unsigned int)func, (unsigned int)ip, upper, lower);

        /* save upper and lower code */
        ret = ftrace_modify_code(ip, upper);
        ret += ftrace_modify_code(ip + 4, lower);

        /* We just need to replace the rtsd r15, 8 with NOP */
        ret += ftrace_modify_code((unsigned long)&ftrace_caller,
                                  MICROBLAZE_NOP);

        return ret;
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
unsigned int old_jump; /* saving place for jump instruction */

int ftrace_enable_ftrace_graph_caller(void)
{
        unsigned int ret;
        unsigned long ip = (unsigned long)(&ftrace_call_graph);

        old_jump = *(unsigned int *)ip; /* save jump over instruction */
        ret = ftrace_modify_code(ip, MICROBLAZE_NOP);

        pr_debug("%s: Replace instruction: 0x%x\n", __func__, old_jump);
        return ret;
}

int ftrace_disable_ftrace_graph_caller(void)
{
        unsigned int ret;
        unsigned long ip = (unsigned long)(&ftrace_call_graph);

        ret = ftrace_modify_code(ip, old_jump);

        pr_debug("%s\n", __func__);
        return ret;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#endif /* CONFIG_DYNAMIC_FTRACE */