ftrace.c

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/*
 * Ftrace support for Microblaze.
 *
 * Copyright (C) 2009 Michal Simek <[email protected]>
 * 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(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);
    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 *data)
{
    /* The return code is retured via data */
    *(unsigned long *)data = 0;

    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 */