backtrace.c

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

#define STACK_SP(STACK)     *(STACK)

#define STACK_LR64(STACK)   *((unsigned long *)(STACK) + 2)
#define STACK_LR32(STACK)   *((unsigned int *)(STACK) + 1)

#ifdef CONFIG_PPC64
#define STACK_LR(STACK)     STACK_LR64(STACK)
#else
#define STACK_LR(STACK)     STACK_LR32(STACK)
#endif

static unsigned int user_getsp32(unsigned int sp, int is_first)
{
    unsigned int stack_frame[2];
    void __user *p = compat_ptr(sp);

    if (!access_ok(VERIFY_READ, p, sizeof(stack_frame)))
        return 0;

    /*
     * The most likely reason for this is that we returned -EFAULT,
     * which means that we've done all that we can do from
     * interrupt context.
     */
    if (__copy_from_user_inatomic(stack_frame, p, sizeof(stack_frame)))
        return 0;

    if (!is_first)
        oprofile_add_trace(STACK_LR32(stack_frame));

    /*
     * We do not enforce increasing stack addresses here because
     * we may transition to a different stack, eg a signal handler.
     */
    return STACK_SP(stack_frame);
}

#ifdef CONFIG_PPC64
static unsigned long user_getsp64(unsigned long sp, int is_first)
{
    unsigned long stack_frame[3];

    if (!access_ok(VERIFY_READ, (void __user *)sp, sizeof(stack_frame)))
        return 0;

    if (__copy_from_user_inatomic(stack_frame, (void __user *)sp,
                    sizeof(stack_frame)))
        return 0;

    if (!is_first)
        oprofile_add_trace(STACK_LR64(stack_frame));

    return STACK_SP(stack_frame);
}
#endif

static unsigned long kernel_getsp(unsigned long sp, int is_first)
{
    unsigned long *stack_frame = (unsigned long *)sp;

    if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
        return 0;

    if (!is_first)
        oprofile_add_trace(STACK_LR(stack_frame));

    /*
     * We do not enforce increasing stack addresses here because
     * we might be transitioning from an interrupt stack to a kernel
     * stack. validate_sp() is designed to understand this, so just
     * use it.
     */
    return STACK_SP(stack_frame);
}

void op_powerpc_backtrace(struct pt_regs * const regs, unsigned int depth)
{
    unsigned long sp = regs->gpr[1];
    int first_frame = 1;

    /* We ditch the top stackframe so need to loop through an extra time */
    depth += 1;

    if (!user_mode(regs)) {
        while (depth--) {
            sp = kernel_getsp(sp, first_frame);
            if (!sp)
                break;
            first_frame = 0;
        }
    } else {
#ifdef CONFIG_PPC64
        if (!is_32bit_task()) {
            while (depth--) {
                sp = user_getsp64(sp, first_frame);
                if (!sp)
                    break;
                first_frame = 0;
            }

            return;
        }
#endif

        while (depth--) {
            sp = user_getsp32(sp, first_frame);
            if (!sp)
                break;
            first_frame = 0;
        }
    }
}