alistair23-linux/arch/x86/kernel/dumpstack_64.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
 */
#include <linux/sched/debug.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/kdebug.h>
#include <linux/export.h>
#include <linux/ptrace.h>
#include <linux/kexec.h>
#include <linux/sysfs.h>
#include <linux/bug.h>
#include <linux/nmi.h>

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

static const char *exception_stack_names[N_EXCEPTION_STACKS] = {
		[ ESTACK_DF	]	= "#DF",
		[ ESTACK_NMI	]	= "NMI",
		[ ESTACK_DB	]	= "#DB",
		[ ESTACK_MCE	]	= "#MC",
};

const char *stack_type_name(enum stack_type type)
{
	BUILD_BUG_ON(N_EXCEPTION_STACKS != 4);

	if (type == STACK_TYPE_IRQ)
		return "IRQ";

	if (type == STACK_TYPE_ENTRY) {
		/*
		 * On 64-bit, we have a generic entry stack that we
		 * use for all the kernel entry points, including
		 * SYSENTER.
		 */
		return "ENTRY_TRAMPOLINE";
	}

	if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
		return exception_stack_names[type - STACK_TYPE_EXCEPTION];

	return NULL;
}

struct estack_layout {
	unsigned int	begin;
	unsigned int	end;
};

#define	ESTACK_ENTRY(x)	{						  \
	.begin	= offsetof(struct cea_exception_stacks, x## _stack),	  \
	.end	= offsetof(struct cea_exception_stacks, x## _stack_guard) \
	}

static const struct estack_layout layout[N_EXCEPTION_STACKS] = {
	[ ESTACK_DF	]	= ESTACK_ENTRY(DF),
	[ ESTACK_NMI	]	= ESTACK_ENTRY(NMI),
	[ ESTACK_DB	]	= ESTACK_ENTRY(DB),
	[ ESTACK_MCE	]	= ESTACK_ENTRY(MCE),
};

static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
{
	unsigned long estacks, begin, end, stk = (unsigned long)stack;
	struct pt_regs *regs;
	unsigned int k;

	BUILD_BUG_ON(N_EXCEPTION_STACKS != 4);

	estacks = (unsigned long)__this_cpu_read(cea_exception_stacks);

	for (k = 0; k < N_EXCEPTION_STACKS; k++) {
		begin = estacks + layout[k].begin;
		end   = estacks + layout[k].end;
		regs  = (struct pt_regs *)end - 1;

		if (stk < begin || stk >= end)
			continue;

		info->type	= STACK_TYPE_EXCEPTION + k;
		info->begin	= (unsigned long *)begin;
		info->end	= (unsigned long *)end;
		info->next_sp	= (unsigned long *)regs->sp;

		return true;
	}

	return false;
}

static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
{
	unsigned long *end   = (unsigned long *)this_cpu_read(irq_stack_ptr);
	unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));

	/*
	 * This is a software stack, so 'end' can be a valid stack pointer.
	 * It just means the stack is empty.
	 */
	if (stack < begin || stack >= end)
		return false;

	info->type	= STACK_TYPE_IRQ;
	info->begin	= begin;
	info->end	= end;

	/*
	 * The next stack pointer is the first thing pushed by the entry code
	 * after switching to the irq stack.
	 */
	info->next_sp = (unsigned long *)*(end - 1);

	return true;
}

int get_stack_info(unsigned long *stack, struct task_struct *task,
		   struct stack_info *info, unsigned long *visit_mask)
{
	if (!stack)
		goto unknown;

	task = task ? : current;

	if (in_task_stack(stack, task, info))
		goto recursion_check;

	if (task != current)
		goto unknown;

	if (in_exception_stack(stack, info))
		goto recursion_check;

	if (in_irq_stack(stack, info))
		goto recursion_check;

	if (in_entry_stack(stack, info))
		goto recursion_check;

	goto unknown;

recursion_check:
	/*
	 * Make sure we don't iterate through any given stack more than once.
	 * If it comes up a second time then there's something wrong going on:
	 * just break out and report an unknown stack type.
	 */
	if (visit_mask) {
		if (*visit_mask & (1UL << info->type)) {
			printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
			goto unknown;
		}
		*visit_mask |= 1UL << info->type;
	}

	return 0;

unknown:
	info->type = STACK_TYPE_UNKNOWN;
	return -EINVAL;
}