// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/module.h>
#include <linux/objtool.h>
#include <linux/sort.h>
#include <asm/exception.h>
#include <asm/orc_header.h>
#include <asm/orc_lookup.h>
#include <asm/orc_types.h>
#include <asm/ptrace.h>
#include <asm/setup.h>
#include <asm/stacktrace.h>
#include <asm/tlb.h>
#include <asm/unwind.h>

ORC_HEADER;

#define orc_warn(fmt, ...) \
        printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)

extern int __start_orc_unwind_ip[];
extern int __stop_orc_unwind_ip[];
extern struct orc_entry __start_orc_unwind[];
extern struct orc_entry __stop_orc_unwind[];

static bool orc_init __ro_after_init;
static unsigned int lookup_num_blocks __ro_after_init;

/* Fake frame pointer entry -- used as a fallback for generated code */
static struct orc_entry orc_fp_entry = {
        .sp_reg         = ORC_REG_FP,
        .sp_offset      = 16,
        .fp_reg         = ORC_REG_PREV_SP,
        .fp_offset      = -16,
        .ra_reg         = ORC_REG_PREV_SP,
        .ra_offset      = -8,
        .type           = ORC_TYPE_CALL
};

/*
 * If we crash with IP==0, the last successfully executed instruction
 * was probably an indirect function call with a NULL function pointer,
 * and we don't have unwind information for NULL.
 * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function
 * pointer into its parent and then continue normally from there.
 */
static struct orc_entry orc_null_entry = {
        .sp_reg         = ORC_REG_SP,
        .sp_offset      = sizeof(long),
        .fp_reg         = ORC_REG_UNDEFINED,
        .type           = ORC_TYPE_CALL
};

static inline unsigned long orc_ip(const int *ip)
{
        return (unsigned long)ip + *ip;
}

static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
                                    unsigned int num_entries, unsigned long ip)
{
        int *first = ip_table;
        int *mid = first, *found = first;
        int *last = ip_table + num_entries - 1;

        if (!num_entries)
                return NULL;

        /*
         * Do a binary range search to find the rightmost duplicate of a given
         * starting address.  Some entries are section terminators which are
         * "weak" entries for ensuring there are no gaps.  They should be
         * ignored when they conflict with a real entry.
         */
        while (first <= last) {
                mid = first + ((last - first) / 2);

                if (orc_ip(mid) <= ip) {
                        found = mid;
                        first = mid + 1;
                } else
                        last = mid - 1;
        }

        return u_table + (found - ip_table);
}

#ifdef CONFIG_MODULES
static struct orc_entry *orc_module_find(unsigned long ip)
{
        struct module *mod;

        mod = __module_address(ip);
        if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip)
                return NULL;

        return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind, mod->arch.num_orcs, ip);
}
#else
static struct orc_entry *orc_module_find(unsigned long ip)
{
        return NULL;
}
#endif

#ifdef CONFIG_DYNAMIC_FTRACE
static struct orc_entry *orc_find(unsigned long ip);

/*
 * Ftrace dynamic trampolines do not have orc entries of their own.
 * But they are copies of the ftrace entries that are static and
 * defined in ftrace_*.S, which do have orc entries.
 *
 * If the unwinder comes across a ftrace trampoline, then find the
 * ftrace function that was used to create it, and use that ftrace
 * function's orc entry, as the placement of the return code in
 * the stack will be identical.
 */
static struct orc_entry *orc_ftrace_find(unsigned long ip)
{
        struct ftrace_ops *ops;
        unsigned long tramp_addr, offset;

        ops = ftrace_ops_trampoline(ip);
        if (!ops)
                return NULL;

        /* Set tramp_addr to the start of the code copied by the trampoline */
        if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
                tramp_addr = (unsigned long)ftrace_regs_caller;
        else
                tramp_addr = (unsigned long)ftrace_caller;

        /* Now place tramp_addr to the location within the trampoline ip is at */
        offset = ip - ops->trampoline;
        tramp_addr += offset;

        /* Prevent unlikely recursion */
        if (ip == tramp_addr)
                return NULL;

        return orc_find(tramp_addr);
}
#else
static struct orc_entry *orc_ftrace_find(unsigned long ip)
{
        return NULL;
}
#endif

static struct orc_entry *orc_find(unsigned long ip)
{
        static struct orc_entry *orc;

        if (ip == 0)
                return &orc_null_entry;

        /* For non-init vmlinux addresses, use the fast lookup table: */
        if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
                unsigned int idx, start, stop;

                idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE;

                if (unlikely((idx >= lookup_num_blocks-1))) {
                        orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n",
                                 idx, lookup_num_blocks, (void *)ip);
                        return NULL;
                }

                start = orc_lookup[idx];
                stop = orc_lookup[idx + 1] + 1;

                if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) ||
                             (__start_orc_unwind + stop > __stop_orc_unwind))) {
                        orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n",
                                 idx, lookup_num_blocks, start, stop, (void *)ip);
                        return NULL;
                }

                return __orc_find(__start_orc_unwind_ip + start,
                                  __start_orc_unwind + start, stop - start, ip);
        }

        /* vmlinux .init slow lookup: */
        if (is_kernel_inittext(ip))
                return __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
                                  __stop_orc_unwind_ip - __start_orc_unwind_ip, ip);

        /* Module lookup: */
        orc = orc_module_find(ip);
        if (orc)
                return orc;

        return orc_ftrace_find(ip);
}

#ifdef CONFIG_MODULES

static DEFINE_MUTEX(sort_mutex);
static int *cur_orc_ip_table = __start_orc_unwind_ip;
static struct orc_entry *cur_orc_table = __start_orc_unwind;

static void orc_sort_swap(void *_a, void *_b, int size)
{
        int delta = _b - _a;
        int *a = _a, *b = _b, tmp;
        struct orc_entry *orc_a, *orc_b;

        /* Swap the .orc_unwind_ip entries: */
        tmp = *a;
        *a = *b + delta;
        *b = tmp - delta;

        /* Swap the corresponding .orc_unwind entries: */
        orc_a = cur_orc_table + (a - cur_orc_ip_table);
        orc_b = cur_orc_table + (b - cur_orc_ip_table);
        swap(*orc_a, *orc_b);
}

static int orc_sort_cmp(const void *_a, const void *_b)
{
        const int *a = _a, *b = _b;
        unsigned long a_val = orc_ip(a);
        unsigned long b_val = orc_ip(b);
        struct orc_entry *orc_a;

        if (a_val > b_val)
                return 1;
        if (a_val < b_val)
                return -1;

        /*
         * The "weak" section terminator entries need to always be first
         * to ensure the lookup code skips them in favor of real entries.
         * These terminator entries exist to handle any gaps created by
         * whitelisted .o files which didn't get objtool generation.
         */
        orc_a = cur_orc_table + (a - cur_orc_ip_table);

        return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
}

void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
                        void *_orc, size_t orc_size)
{
        int *orc_ip = _orc_ip;
        struct orc_entry *orc = _orc;
        unsigned int num_entries = orc_ip_size / sizeof(int);

        WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 ||
                     orc_size % sizeof(*orc) != 0 ||
                     num_entries != orc_size / sizeof(*orc));

        /*
         * The 'cur_orc_*' globals allow the orc_sort_swap() callback to
         * associate an .orc_unwind_ip table entry with its corresponding
         * .orc_unwind entry so they can both be swapped.
         */
        mutex_lock(&sort_mutex);
        cur_orc_ip_table = orc_ip;
        cur_orc_table = orc;
        sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap);
        mutex_unlock(&sort_mutex);

        mod->arch.orc_unwind_ip = orc_ip;
        mod->arch.orc_unwind = orc;
        mod->arch.num_orcs = num_entries;
}
#endif

void __init unwind_init(void)
{
        int i;
        size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind;
        size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip;
        size_t num_entries = orc_ip_size / sizeof(int);
        struct orc_entry *orc;

        if (!num_entries || orc_ip_size % sizeof(int) != 0 ||
            orc_size % sizeof(struct orc_entry) != 0 ||
            num_entries != orc_size / sizeof(struct orc_entry)) {
                orc_warn("WARNING: Bad or missing .orc_unwind table.  Disabling unwinder.\n");
                return;
        }

        /*
         * Note, the orc_unwind and orc_unwind_ip tables were already
         * sorted at build time via the 'sorttable' tool.
         * It's ready for binary search straight away, no need to sort it.
         */

        /* Initialize the fast lookup table: */
        lookup_num_blocks = orc_lookup_end - orc_lookup;
        for (i = 0; i < lookup_num_blocks-1; i++) {
                orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind,
                                 num_entries, LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i));
                if (!orc) {
                        orc_warn("WARNING: Corrupt .orc_unwind table.  Disabling unwinder.\n");
                        return;
                }

                orc_lookup[i] = orc - __start_orc_unwind;
        }

        /* Initialize the ending block: */
        orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries, LOOKUP_STOP_IP);
        if (!orc) {
                orc_warn("WARNING: Corrupt .orc_unwind table.  Disabling unwinder.\n");
                return;
        }
        orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind;

        orc_init = true;
}

static inline bool on_stack(struct stack_info *info, unsigned long addr, size_t len)
{
        unsigned long begin = info->begin;
        unsigned long end   = info->end;

        return (info->type != STACK_TYPE_UNKNOWN &&
                addr >= begin && addr < end && addr + len > begin && addr + len <= end);
}

static bool stack_access_ok(struct unwind_state *state, unsigned long addr, size_t len)
{
        struct stack_info *info = &state->stack_info;

        if (on_stack(info, addr, len))
                return true;

        return !get_stack_info(addr, state->task, info) && on_stack(info, addr, len);
}

unsigned long unwind_get_return_address(struct unwind_state *state)
{
        return __unwind_get_return_address(state);
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);

void unwind_start(struct unwind_state *state, struct task_struct *task,
                    struct pt_regs *regs)
{
        __unwind_start(state, task, regs);
        state->type = UNWINDER_ORC;
        if (!unwind_done(state) && !__kernel_text_address(state->pc))
                unwind_next_frame(state);
}
EXPORT_SYMBOL_GPL(unwind_start);

static inline unsigned long bt_address(unsigned long ra)
{
#if defined(CONFIG_NUMA) && !defined(CONFIG_PREEMPT_RT)
        int cpu;
        int vec_sz = sizeof(exception_handlers);

        for_each_possible_cpu(cpu) {
                if (!pcpu_handlers[cpu])
                        continue;

                if (ra >= pcpu_handlers[cpu] &&
                    ra < pcpu_handlers[cpu] + vec_sz) {
                        ra = ra + eentry - pcpu_handlers[cpu];
                        break;
                }
        }
#endif

        if (ra >= eentry && ra < eentry +  EXCCODE_INT_END * VECSIZE) {
                unsigned long func;
                unsigned long type = (ra - eentry) / VECSIZE;
                unsigned long offset = (ra - eentry) % VECSIZE;

                switch (type) {
                case 0 ... EXCCODE_INT_START - 1:
                        func = (unsigned long)exception_table[type];
                        break;
                case EXCCODE_INT_START ... EXCCODE_INT_END:
                        func = (unsigned long)handle_vint;
                        break;
                default:
                        func = (unsigned long)handle_reserved;
                        break;
                }

                ra = func + offset;
        }

        if (__kernel_text_address(ra))
                return ra;

        return 0;
}

bool unwind_next_frame(struct unwind_state *state)
{
        unsigned long *p, pc;
        struct pt_regs *regs;
        struct orc_entry *orc;
        struct stack_info *info = &state->stack_info;

        if (unwind_done(state))
                return false;

        /* Don't let modules unload while we're reading their ORC data. */
        guard(rcu)();

        orc = orc_find(state->pc);
        if (!orc) {
                /*
                 * As a fallback, try to assume this code uses a frame pointer.
                 * This is useful for generated code, like BPF, which ORC
                 * doesn't know about.  This is just a guess, so the rest of
                 * the unwind is no longer considered reliable.
                 */
                orc = &orc_fp_entry;
                state->error = true;
        } else {
                if (orc->type == ORC_TYPE_UNDEFINED)
                        goto err;

                if (orc->type == ORC_TYPE_END_OF_STACK)
                        goto end;
        }

        switch (orc->sp_reg) {
        case ORC_REG_SP:
                if (info->type == STACK_TYPE_IRQ && state->sp == info->end)
                        orc->type = ORC_TYPE_REGS;
                else
                        state->sp = state->sp + orc->sp_offset;
                break;
        case ORC_REG_FP:
                state->sp = state->fp;
                break;
        default:
                orc_warn("unknown SP base reg %d at %pB\n", orc->sp_reg, (void *)state->pc);
                goto err;
        }

        switch (orc->fp_reg) {
        case ORC_REG_PREV_SP:
                p = (unsigned long *)(state->sp + orc->fp_offset);
                if (!stack_access_ok(state, (unsigned long)p, sizeof(unsigned long)))
                        goto err;

                state->fp = *p;
                break;
        case ORC_REG_UNDEFINED:
                /* Nothing. */
                break;
        default:
                orc_warn("unknown FP base reg %d at %pB\n", orc->fp_reg, (void *)state->pc);
                goto err;
        }

        switch (orc->type) {
        case ORC_TYPE_CALL:
                if (orc->ra_reg == ORC_REG_PREV_SP) {
                        p = (unsigned long *)(state->sp + orc->ra_offset);
                        if (!stack_access_ok(state, (unsigned long)p, sizeof(unsigned long)))
                                goto err;

                        pc = unwind_graph_addr(state, *p, state->sp);
                        pc -= LOONGARCH_INSN_SIZE;
                } else if (orc->ra_reg == ORC_REG_UNDEFINED) {
                        if (!state->ra || state->ra == state->pc)
                                goto err;

                        pc = unwind_graph_addr(state, state->ra, state->sp);
                        pc -=  LOONGARCH_INSN_SIZE;
                        state->ra = 0;
                } else {
                        orc_warn("unknown ra base reg %d at %pB\n", orc->ra_reg, (void *)state->pc);
                        goto err;
                }
                break;
        case ORC_TYPE_REGS:
                if (info->type == STACK_TYPE_IRQ && state->sp == info->end)
                        regs = (struct pt_regs *)info->next_sp;
                else
                        regs = (struct pt_regs *)state->sp;

                if (!stack_access_ok(state, (unsigned long)regs, sizeof(*regs)))
                        goto err;

                if ((info->end == (unsigned long)regs + sizeof(*regs)) &&
                    !regs->regs[3] && !regs->regs[1])
                        goto end;

                if (user_mode(regs))
                        goto end;

                pc = regs->csr_era;
                if (!__kernel_text_address(pc))
                        goto err;

                state->sp = regs->regs[3];
                state->ra = regs->regs[1];
                state->fp = regs->regs[22];
                get_stack_info(state->sp, state->task, info);

                break;
        default:
                orc_warn("unknown .orc_unwind entry type %d at %pB\n", orc->type, (void *)state->pc);
                goto err;
        }

        state->pc = bt_address(pc);
        if (!state->pc) {
                pr_err("cannot find unwind pc at %px\n", (void *)pc);
                goto err;
        }

        return true;

err:
        state->error = true;

end:
        state->stack_info.type = STACK_TYPE_UNKNOWN;
        return false;
}
EXPORT_SYMBOL_GPL(unwind_next_frame);