// 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 * const exception_stack_names[] = {
                [ ESTACK_DF     ]       = "#DF",
                [ ESTACK_NMI    ]       = "NMI",
                [ ESTACK_DB     ]       = "#DB",
                [ ESTACK_MCE    ]       = "#MC",
                [ ESTACK_VC     ]       = "#VC",
                [ ESTACK_VC2    ]       = "#VC2",
};

const char *stack_type_name(enum stack_type type)
{
        BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);

        if (type == STACK_TYPE_TASK)
                return "TASK";

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

        if (type == STACK_TYPE_SOFTIRQ)
                return "SOFTIRQ";

        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_pages - Page descriptor for exception stacks
 * @offs:       Offset from the start of the exception stack area
 * @size:       Size of the exception stack
 * @type:       Type to store in the stack_info struct
 */
struct estack_pages {
        u32     offs;
        u16     size;
        u16     type;
};

#define EPAGERANGE(st)                                                  \
        [PFN_DOWN(CEA_ESTACK_OFFS(st)) ...                              \
         PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = {   \
                .offs   = CEA_ESTACK_OFFS(st),                          \
                .size   = CEA_ESTACK_SIZE(st),                          \
                .type   = STACK_TYPE_EXCEPTION + ESTACK_ ##st, }

/*
 * Array of exception stack page descriptors. If the stack is larger than
 * PAGE_SIZE, all pages covering a particular stack will have the same
 * info. The guard pages including the not mapped DB2 stack are zeroed
 * out.
 */
static const
struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
        EPAGERANGE(DF),
        EPAGERANGE(NMI),
        EPAGERANGE(DB),
        EPAGERANGE(MCE),
        EPAGERANGE(VC),
        EPAGERANGE(VC2),
};

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

        BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);

        begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
        /*
         * Handle the case where stack trace is collected _before_
         * cea_exception_stacks had been initialized.
         */
        if (!begin)
                return false;

        end = begin + sizeof(struct cea_exception_stacks);
        /* Bail if @stack is outside the exception stack area. */
        if (stk < begin || stk >= end)
                return false;

        /* Calc page offset from start of exception stacks */
        k = (stk - begin) >> PAGE_SHIFT;
        /* Lookup the page descriptor */
        ep = &estack_pages[k];
        /* Guard page? */
        if (!ep->size)
                return false;

        begin += (unsigned long)ep->offs;
        end = begin + (unsigned long)ep->size;
        regs = (struct pt_regs *)end - 1;

        info->type      = ep->type;
        info->begin     = (unsigned long *)begin;
        info->end       = (unsigned long *)end;
        info->next_sp   = (unsigned long *)regs->sp;
        return true;
}

static __always_inline bool in_irq_stack(unsigned long *stack, struct stack_info *info)
{
        unsigned long *end = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
        unsigned long *begin;

        /*
         * @end points directly to the top most stack entry to avoid a -8
         * adjustment in the stack switch hotpath. Adjust it back before
         * calculating @begin.
         */
        end++;
        begin = end - (IRQ_STACK_SIZE / sizeof(long));

        /*
         * Due to the switching logic RSP can never be == @end because the
         * final operation is 'popq %rsp' which means after that RSP points
         * to the original stack and not to @end.
         */
        if (stack < begin || stack >= end)
                return false;

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

        /*
         * The next stack pointer is stored at the top of the irq stack
         * before switching to the irq stack. Actual stack entries are all
         * below that.
         */
        info->next_sp = (unsigned long *)*(end - 1);

        return true;
}

bool noinstr get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
                                    struct stack_info *info)
{
        if (in_task_stack(stack, task, info))
                return true;

        if (task != current)
                return false;

        if (in_exception_stack(stack, info))
                return true;

        if (in_irq_stack(stack, info))
                return true;

        if (in_entry_stack(stack, info))
                return true;

        return false;
}

int get_stack_info(unsigned long *stack, struct task_struct *task,
                   struct stack_info *info, unsigned long *visit_mask)
{
        task = task ? : current;

        if (!stack)
                goto unknown;

        if (!get_stack_info_noinstr(stack, task, info))
                goto unknown;

        /*
         * 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)) {
                        if (task == current)
                                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;
}