ftrace.c

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#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/list.h>
#include <trace/syscall.h>

#include <asm/ftrace.h>

#ifdef CONFIG_DYNAMIC_FTRACE
static const u32 ftrace_nop = 0x01000000;

static u32 ftrace_call_replace(unsigned long ip, unsigned long addr)
{
    u32 call;
    s32 off;

    off = ((s32)addr - (s32)ip);
    call = 0x40000000 | ((u32)off >> 2);

    return call;
}

static int ftrace_modify_code(unsigned long ip, u32 old, u32 new)
{
    u32 replaced;
    int faulted;

    __asm__ __volatile__(
    "1: cas [%[ip]], %[old], %[new]\n"
    "   flush   %[ip]\n"
    "   mov 0, %[faulted]\n"
    "2:\n"
    "   .section .fixup,#alloc,#execinstr\n"
    "   .align  4\n"
    "3: sethi   %%hi(2b), %[faulted]\n"
    "   jmpl    %[faulted] + %%lo(2b), %%g0\n"
    "    mov    1, %[faulted]\n"
    "   .previous\n"
    "   .section __ex_table,\"a\"\n"
    "   .align  4\n"
    "   .word   1b, 3b\n"
    "   .previous\n"
    : "=r" (replaced), [faulted] "=r" (faulted)
    : [new] "0" (new), [old] "r" (old), [ip] "r" (ip)
    : "memory");

    if (replaced != old && replaced != new)
        faulted = 2;

    return faulted;
}

int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
    unsigned long ip = rec->ip;
    u32 old, new;

    old = ftrace_call_replace(ip, addr);
    new = ftrace_nop;
    return ftrace_modify_code(ip, old, new);
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
    unsigned long ip = rec->ip;
    u32 old, new;

    old = ftrace_nop;
    new = ftrace_call_replace(ip, addr);
    return ftrace_modify_code(ip, old, new);
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
    unsigned long ip = (unsigned long)(&ftrace_call);
    u32 old, new;

    old = *(u32 *) &ftrace_call;
    new = ftrace_call_replace(ip, (unsigned long)func);
    return ftrace_modify_code(ip, old, new);
}

int __init ftrace_dyn_arch_init(void *data)
{
    unsigned long *p = data;

    *p = 0;

    return 0;
}
#endif

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);

int ftrace_enable_ftrace_graph_caller(void)
{
    unsigned long ip = (unsigned long)(&ftrace_graph_call);
    u32 old, new;

    old = *(u32 *) &ftrace_graph_call;
    new = ftrace_call_replace(ip, (unsigned long) &ftrace_graph_caller);
    return ftrace_modify_code(ip, old, new);
}

int ftrace_disable_ftrace_graph_caller(void)
{
    unsigned long ip = (unsigned long)(&ftrace_graph_call);
    u32 old, new;

    old = *(u32 *) &ftrace_graph_call;
    new = ftrace_call_replace(ip, (unsigned long) &ftrace_stub);

    return ftrace_modify_code(ip, old, new);
}

#endif /* !CONFIG_DYNAMIC_FTRACE */

/*
 * Hook the return address and push it in the stack of return addrs
 * in current thread info.
 */
unsigned long 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;

    if (unlikely(atomic_read(&current->tracing_graph_pause)))
        return parent + 8UL;

    if (ftrace_push_return_trace(parent, self_addr, &trace.depth,
                     frame_pointer) == -EBUSY)
        return parent + 8UL;

    trace.func = self_addr;

    /* Only trace if the calling function expects to */
    if (!ftrace_graph_entry(&trace)) {
        current->curr_ret_stack--;
        return parent + 8UL;
    }

    return return_hooker;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */