linux/arch/powerpc/oprofile/backtrace.c

// SPDX-License-Identifier: GPL-2.0-or-later
/**
 * Copyright (C) 2005 Brian Rogan <bcr6@cornell.edu>, IBM
 *
**/

#include <linux/time.h>
#include <linux/oprofile.h>
#include <linux/sched.h>
#include <asm/processor.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
#include <asm/oprofile_impl.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);

	/*
	 * 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 (probe_user_read(stack_frame, (void __user *)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 (probe_user_read(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;
		}
	}
}