backtrace.c

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#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/compat.h>
#include <linux/uaccess.h>

#include <asm/ptrace.h>
#include <asm/stacktrace.h>

static int backtrace_stack(void *data, char *name)
{
    /* Yes, we want all stacks */
    return 0;
}

static void backtrace_address(void *data, unsigned long addr, int reliable)
{
    unsigned int *depth = data;

    if ((*depth)--)
        oprofile_add_trace(addr);
}

static struct stacktrace_ops backtrace_ops = {
    .stack      = backtrace_stack,
    .address    = backtrace_address,
    .walk_stack = print_context_stack,
};

#ifdef CONFIG_COMPAT
static struct stack_frame_ia32 *
dump_user_backtrace_32(struct stack_frame_ia32 *head)
{
    /* Also check accessibility of one struct frame_head beyond: */
    struct stack_frame_ia32 bufhead[2];
    struct stack_frame_ia32 *fp;
    unsigned long bytes;

    bytes = copy_from_user_nmi(bufhead, head, sizeof(bufhead));
    if (bytes != sizeof(bufhead))
        return NULL;

    fp = (struct stack_frame_ia32 *) compat_ptr(bufhead[0].next_frame);

    oprofile_add_trace(bufhead[0].return_address);

    /* frame pointers should strictly progress back up the stack
    * (towards higher addresses) */
    if (head >= fp)
        return NULL;

    return fp;
}

static inline int
x86_backtrace_32(struct pt_regs * const regs, unsigned int depth)
{
    struct stack_frame_ia32 *head;

    /* User process is IA32 */
    if (!current || !test_thread_flag(TIF_IA32))
        return 0;

    head = (struct stack_frame_ia32 *) regs->bp;
    while (depth-- && head)
        head = dump_user_backtrace_32(head);

    return 1;
}

#else
static inline int
x86_backtrace_32(struct pt_regs * const regs, unsigned int depth)
{
    return 0;
}
#endif /* CONFIG_COMPAT */

static struct stack_frame *dump_user_backtrace(struct stack_frame *head)
{
    /* Also check accessibility of one struct frame_head beyond: */
    struct stack_frame bufhead[2];
    unsigned long bytes;

    bytes = copy_from_user_nmi(bufhead, head, sizeof(bufhead));
    if (bytes != sizeof(bufhead))
        return NULL;

    oprofile_add_trace(bufhead[0].return_address);

    /* frame pointers should strictly progress back up the stack
     * (towards higher addresses) */
    if (head >= bufhead[0].next_frame)
        return NULL;

    return bufhead[0].next_frame;
}

void
x86_backtrace(struct pt_regs * const regs, unsigned int depth)
{
    struct stack_frame *head = (struct stack_frame *)frame_pointer(regs);

    if (!user_mode_vm(regs)) {
        unsigned long stack = kernel_stack_pointer(regs);
        if (depth)
            dump_trace(NULL, regs, (unsigned long *)stack, 0,
                   &backtrace_ops, &depth);
        return;
    }

    if (x86_backtrace_32(regs, depth))
        return;

    while (depth-- && head)
        head = dump_user_backtrace(head);
}