/*-
 * Copyright (c) 1989, 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software developed by the Computer Systems
 * Engineering group at Lawrence Berkeley Laboratory under DARPA contract
 * BG 91-66 and contributed to Berkeley.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/fnv_hash.h>

#define _WANT_VNET

#include <sys/user.h>
#include <sys/linker.h>
#include <sys/pcpu.h>
#include <sys/stat.h>
#include <sys/mman.h>

#include <stdbool.h>
#include <net/vnet.h>

#include <assert.h>
#include <fcntl.h>
#include <vm/vm.h>
#include <kvm.h>
#include <limits.h>
#include <paths.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdarg.h>
#include <inttypes.h>

#include "kvm_private.h"

/*
 * Routines private to libkvm.
 */

/* from src/lib/libc/gen/nlist.c */
int __fdnlist(int, struct nlist *);

/*
 * Report an error using printf style arguments.  "program" is kd->program
 * on hard errors, and 0 on soft errors, so that under sun error emulation,
 * only hard errors are printed out (otherwise, programs like gdb will
 * generate tons of error messages when trying to access bogus pointers).
 */
void
_kvm_err(kvm_t *kd, const char *program, const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        if (program != NULL) {
                (void)fprintf(stderr, "%s: ", program);
                (void)vfprintf(stderr, fmt, ap);
                (void)fputc('\n', stderr);
        } else
                (void)vsnprintf(kd->errbuf,
                    sizeof(kd->errbuf), fmt, ap);

        va_end(ap);
}

void
_kvm_syserr(kvm_t *kd, const char *program, const char *fmt, ...)
{
        va_list ap;
        int n;

        va_start(ap, fmt);
        if (program != NULL) {
                (void)fprintf(stderr, "%s: ", program);
                (void)vfprintf(stderr, fmt, ap);
                (void)fprintf(stderr, ": %s\n", strerror(errno));
        } else {
                char *cp = kd->errbuf;

                (void)vsnprintf(cp, sizeof(kd->errbuf), fmt, ap);
                n = strlen(cp);
                (void)snprintf(&cp[n], sizeof(kd->errbuf) - n, ": %s",
                    strerror(errno));
        }
        va_end(ap);
}

void *
_kvm_malloc(kvm_t *kd, size_t n)
{
        void *p;

        if ((p = calloc(n, sizeof(char))) == NULL)
                _kvm_err(kd, kd->program, "can't allocate %zu bytes: %s",
                         n, strerror(errno));
        return (p);
}

int
_kvm_probe_elf_kernel(kvm_t *kd, int class, int machine)
{

        return (kd->nlehdr.e_ident[EI_CLASS] == class &&
            ((machine == EM_PPC || machine == EM_PPC64) ?
             kd->nlehdr.e_type == ET_DYN : kd->nlehdr.e_type == ET_EXEC) &&
            kd->nlehdr.e_machine == machine);
}

int
_kvm_is_minidump(kvm_t *kd)
{
        char minihdr[8];

        if (kd->rawdump)
                return (0);
        if (pread(kd->pmfd, &minihdr, 8, 0) == 8 &&
            memcmp(&minihdr, "minidump", 8) == 0)
                return (1);
        return (0);
}

/*
 * The powerpc backend has a hack to strip a leading kerneldump
 * header from the core before treating it as an ELF header.
 *
 * We can add that here if we can get a change to libelf to support
 * an initial offset into the file.  Alternatively we could patch
 * savecore to extract cores from a regular file instead.
 */
int
_kvm_read_core_phdrs(kvm_t *kd, size_t *phnump, GElf_Phdr **phdrp)
{
        GElf_Ehdr ehdr;
        GElf_Phdr *phdr;
        Elf *elf;
        size_t i, phnum;

        elf = elf_begin(kd->pmfd, ELF_C_READ, NULL);
        if (elf == NULL) {
                _kvm_err(kd, kd->program, "%s", elf_errmsg(0));
                return (-1);
        }
        if (elf_kind(elf) != ELF_K_ELF) {
                _kvm_err(kd, kd->program, "invalid core");
                goto bad;
        }
        if (gelf_getclass(elf) != kd->nlehdr.e_ident[EI_CLASS]) {
                _kvm_err(kd, kd->program, "invalid core");
                goto bad;
        }
        if (gelf_getehdr(elf, &ehdr) == NULL) {
                _kvm_err(kd, kd->program, "%s", elf_errmsg(0));
                goto bad;
        }
        if (ehdr.e_type != ET_CORE) {
                _kvm_err(kd, kd->program, "invalid core");
                goto bad;
        }
        if (ehdr.e_machine != kd->nlehdr.e_machine) {
                _kvm_err(kd, kd->program, "invalid core");
                goto bad;
        }

        if (elf_getphdrnum(elf, &phnum) == -1) {
                _kvm_err(kd, kd->program, "%s", elf_errmsg(0));
                goto bad;
        }

        phdr = calloc(phnum, sizeof(*phdr));
        if (phdr == NULL) {
                _kvm_err(kd, kd->program, "failed to allocate phdrs");
                goto bad;
        }

        for (i = 0; i < phnum; i++) {
                if (gelf_getphdr(elf, i, &phdr[i]) == NULL) {
                        free(phdr);
                        _kvm_err(kd, kd->program, "%s", elf_errmsg(0));
                        goto bad;
                }
        }
        elf_end(elf);
        *phnump = phnum;
        *phdrp = phdr;
        return (0);

bad:
        elf_end(elf);
        return (-1);
}

/*
 * Transform v such that only bits [bit0, bitN) may be set.  Generates a
 * bitmask covering the number of bits, then shifts so +bit0+ is the first.
 */
static uint64_t
bitmask_range(uint64_t v, uint64_t bit0, uint64_t bitN)
{
        if (bit0 == 0 && bitN == BITS_IN(v))
                return (v);

        return (v & (((1ULL << (bitN - bit0)) - 1ULL) << bit0));
}

/*
 * Returns the number of bits in a given byte array range starting at a
 * given base, from bit0 to bitN.  bit0 may be non-zero in the case of
 * counting backwards from bitN.
 */
static uint64_t
popcount_bytes(uint64_t *addr, uint32_t bit0, uint32_t bitN)
{
        uint32_t res = bitN - bit0;
        uint64_t count = 0;
        uint32_t bound;

        /* Align to 64-bit boundary on the left side if needed. */
        if ((bit0 % BITS_IN(*addr)) != 0) {
                bound = MIN(bitN, roundup2(bit0, BITS_IN(*addr)));
                count += __bitcount64(bitmask_range(*addr, bit0, bound));
                res -= (bound - bit0);
                addr++;
        }

        while (res > 0) {
                bound = MIN(res, BITS_IN(*addr));
                count += __bitcount64(bitmask_range(*addr, 0, bound));
                res -= bound;
                addr++;
        }

        return (count);
}

void *
_kvm_pmap_get(kvm_t *kd, u_long idx, size_t len)
{
        uintptr_t off = idx * len;

        if ((off_t)off >= kd->pt_sparse_off)
                return (NULL);
        return (void *)((uintptr_t)kd->page_map + off);
}

void *
_kvm_map_get(kvm_t *kd, u_long pa, unsigned int page_size)
{
        off_t off;
        uintptr_t addr;

        off = _kvm_pt_find(kd, pa, page_size);
        if (off == -1)
                return NULL;

        addr = (uintptr_t)kd->page_map + off;
        if (off >= kd->pt_sparse_off)
                addr = (uintptr_t)kd->sparse_map + (off - kd->pt_sparse_off);
        return (void *)addr;
}

int
_kvm_pt_init(kvm_t *kd, size_t dump_avail_size, off_t dump_avail_off,
    size_t map_len, off_t map_off, off_t sparse_off, int page_size)
{
        uint64_t *addr;
        uint32_t *popcount_bin;
        int bin_popcounts = 0;
        uint64_t pc_bins, res;
        ssize_t rd;

        kd->dump_avail_size = dump_avail_size;
        if (dump_avail_size > 0) {
                kd->dump_avail = mmap(NULL, kd->dump_avail_size, PROT_READ,
                    MAP_PRIVATE, kd->pmfd, dump_avail_off);
        } else {
                /*
                 * Older version minidumps don't provide dump_avail[],
                 * so the bitmap is fully populated from 0 to
                 * last_pa. Create an implied dump_avail that
                 * expresses this.
                 */
                kd->dump_avail = calloc(4, sizeof(uint64_t));
                kd->dump_avail[1] = _kvm64toh(kd, map_len * 8 * page_size);
        }

        /*
         * Map the bitmap specified by the arguments.
         */
        kd->pt_map = _kvm_malloc(kd, map_len);
        if (kd->pt_map == NULL) {
                _kvm_err(kd, kd->program, "cannot allocate %zu bytes for bitmap",
                    map_len);
                return (-1);
        }
        rd = pread(kd->pmfd, kd->pt_map, map_len, map_off);
        if (rd < 0 || rd != (ssize_t)map_len) {
                _kvm_err(kd, kd->program, "cannot read %zu bytes for bitmap",
                    map_len);
                return (-1);
        }
        kd->pt_map_size = map_len;

        /*
         * Generate a popcount cache for every POPCOUNT_BITS in the bitmap,
         * so lookups only have to calculate the number of bits set between
         * a cache point and their bit.  This reduces lookups to O(1),
         * without significantly increasing memory requirements.
         *
         * Round up the number of bins so that 'upper half' lookups work for
         * the final bin, if needed.  The first popcount is 0, since no bits
         * precede bit 0, so add 1 for that also.  Without this, extra work
         * would be needed to handle the first PTEs in _kvm_pt_find().
         */
        addr = kd->pt_map;
        res = map_len;
        pc_bins = 1 + (res * NBBY + POPCOUNT_BITS / 2) / POPCOUNT_BITS;
        kd->pt_popcounts = calloc(pc_bins, sizeof(uint32_t));
        if (kd->pt_popcounts == NULL) {
                _kvm_err(kd, kd->program, "cannot allocate popcount bins");
                return (-1);
        }

        for (popcount_bin = &kd->pt_popcounts[1]; res > 0;
            addr++, res -= sizeof(*addr)) {
                *popcount_bin += popcount_bytes(addr, 0,
                    MIN(res * NBBY, BITS_IN(*addr)));
                if (++bin_popcounts == POPCOUNTS_IN(*addr)) {
                        popcount_bin++;
                        *popcount_bin = *(popcount_bin - 1);
                        bin_popcounts = 0;
                }
        }

        assert(pc_bins * sizeof(*popcount_bin) ==
            ((uintptr_t)popcount_bin - (uintptr_t)kd->pt_popcounts));

        kd->pt_sparse_off = sparse_off;
        kd->pt_sparse_size = (uint64_t)*popcount_bin * page_size;
        kd->pt_page_size = page_size;

        /*
         * Map the sparse page array.  This is useful for performing point
         * lookups of specific pages, e.g. for kvm_walk_pages.  Generally,
         * this is much larger than is reasonable to read in up front, so
         * mmap it in instead.
         */
        kd->sparse_map = mmap(NULL, kd->pt_sparse_size, PROT_READ,
            MAP_PRIVATE, kd->pmfd, kd->pt_sparse_off);
        if (kd->sparse_map == MAP_FAILED) {
                _kvm_err(kd, kd->program, "cannot map %" PRIu64
                    " bytes from fd %d offset %jd for sparse map: %s",
                    kd->pt_sparse_size, kd->pmfd,
                    (intmax_t)kd->pt_sparse_off, strerror(errno));
                return (-1);
        }
        return (0);
}

int
_kvm_pmap_init(kvm_t *kd, uint32_t pmap_size, off_t pmap_off)
{
        ssize_t exp_len = pmap_size;

        kd->page_map_size = pmap_size;
        kd->page_map_off = pmap_off;
        kd->page_map = _kvm_malloc(kd, pmap_size);
        if (kd->page_map == NULL) {
                _kvm_err(kd, kd->program, "cannot allocate %u bytes "
                    "for page map", pmap_size);
                return (-1);
        }
        if (pread(kd->pmfd, kd->page_map, pmap_size, pmap_off) != exp_len) {
                _kvm_err(kd, kd->program, "cannot read %d bytes from "
                    "offset %jd for page map", pmap_size, (intmax_t)pmap_off);
                return (-1);
        }
        return (0);
}

static inline uint64_t
dump_avail_n(kvm_t *kd, long i)
{
        return (_kvm64toh(kd, kd->dump_avail[i]));
}

uint64_t
_kvm_pa_bit_id(kvm_t *kd, uint64_t pa, unsigned int page_size)
{
        uint64_t adj;
        long i;

        adj = 0;
        for (i = 0; dump_avail_n(kd, i + 1) != 0; i += 2) {
                if (pa >= dump_avail_n(kd, i + 1)) {
                        adj += howmany(dump_avail_n(kd, i + 1), page_size) -
                            dump_avail_n(kd, i) / page_size;
                } else {
                        return (pa / page_size -
                            dump_avail_n(kd, i) / page_size + adj);
                }
        }
        return (_KVM_BIT_ID_INVALID);
}

uint64_t
_kvm_bit_id_pa(kvm_t *kd, uint64_t bit_id, unsigned int page_size)
{
        uint64_t sz;
        long i;

        for (i = 0; dump_avail_n(kd, i + 1) != 0; i += 2) {
                sz = howmany(dump_avail_n(kd, i + 1), page_size) -
                    dump_avail_n(kd, i) / page_size;
                if (bit_id < sz) {
                        return (rounddown2(dump_avail_n(kd, i), page_size) +
                            bit_id * page_size);
                }
                bit_id -= sz;
        }
        return (_KVM_PA_INVALID);
}

/*
 * Find the offset for the given physical page address; returns -1 otherwise.
 *
 * A page's offset is represented by the sparse page base offset plus the
 * number of bits set before its bit multiplied by page size.  This means
 * that if a page exists in the dump, it's necessary to know how many pages
 * in the dump precede it.  Reduce this O(n) counting to O(1) by caching the
 * number of bits set at POPCOUNT_BITS intervals.
 *
 * Then to find the number of pages before the requested address, simply
 * index into the cache and count the number of bits set between that cache
 * bin and the page's bit.  Halve the number of bytes that have to be
 * checked by also counting down from the next higher bin if it's closer.
 */
off_t
_kvm_pt_find(kvm_t *kd, uint64_t pa, unsigned int page_size)
{
        uint64_t *bitmap = kd->pt_map;
        uint64_t pte_bit_id = _kvm_pa_bit_id(kd, pa, page_size);
        uint64_t pte_u64 = pte_bit_id / BITS_IN(*bitmap);
        uint64_t popcount_id = pte_bit_id / POPCOUNT_BITS;
        uint64_t pte_mask = 1ULL << (pte_bit_id % BITS_IN(*bitmap));
        uint64_t bitN;
        uint32_t count;

        /* Check whether the page address requested is in the dump. */
        if (pte_bit_id == _KVM_BIT_ID_INVALID ||
            pte_bit_id >= (kd->pt_map_size * NBBY) ||
            (bitmap[pte_u64] & pte_mask) == 0)
                return (-1);

        /*
         * Add/sub popcounts from the bitmap until the PTE's bit is reached.
         * For bits that are in the upper half between the calculated
         * popcount id and the next one, use the next one and subtract to
         * minimize the number of popcounts required.
         */
        if ((pte_bit_id % POPCOUNT_BITS) < (POPCOUNT_BITS / 2)) {
                count = kd->pt_popcounts[popcount_id] + popcount_bytes(
                    bitmap + popcount_id * POPCOUNTS_IN(*bitmap),
                    0, pte_bit_id - popcount_id * POPCOUNT_BITS);
        } else {
                /*
                 * Counting in reverse is trickier, since we must avoid
                 * reading from bytes that are not in range, and invert.
                 */
                uint64_t pte_u64_bit_off = pte_u64 * BITS_IN(*bitmap);

                popcount_id++;
                bitN = MIN(popcount_id * POPCOUNT_BITS,
                    kd->pt_map_size * BITS_IN(uint8_t));
                count = kd->pt_popcounts[popcount_id] - popcount_bytes(
                    bitmap + pte_u64,
                    pte_bit_id - pte_u64_bit_off, bitN - pte_u64_bit_off);
        }

        /*
         * This can only happen if the core is truncated.  Treat these
         * entries as if they don't exist, since their backing doesn't.
         */
        if (count >= (kd->pt_sparse_size / page_size))
                return (-1);

        return (kd->pt_sparse_off + (uint64_t)count * page_size);
}

static int
kvm_fdnlist(kvm_t *kd, struct kvm_nlist *list)
{
        kvaddr_t addr;
        int error, nfail;

        if (kd->resolve_symbol == NULL) {
                struct nlist *nl;
                int count, i;

                for (count = 0; list[count].n_name != NULL &&
                     list[count].n_name[0] != '\0'; count++)
                        ;
                nl = calloc(count + 1, sizeof(*nl));
                for (i = 0; i < count; i++)
                        nl[i].n_name = list[i].n_name;
                nfail = __fdnlist(kd->nlfd, nl);
                for (i = 0; i < count; i++) {
                        list[i].n_type = nl[i].n_type;
                        list[i].n_value = nl[i].n_value;
                }
                free(nl);
                return (nfail);
        }

        nfail = 0;
        while (list->n_name != NULL && list->n_name[0] != '\0') {
                error = kd->resolve_symbol(list->n_name, &addr);
                if (error != 0) {
                        nfail++;
                        list->n_value = 0;
                        list->n_type = 0;
                } else {
                        list->n_value = addr;
                        list->n_type = N_DATA | N_EXT;
                }
                list++;
        }
        return (nfail);
}

/*
 * Walk the list of unresolved symbols, generate a new list and prefix the
 * symbol names, try again, and merge back what we could resolve.
 */
static int
kvm_fdnlist_prefix(kvm_t *kd, struct kvm_nlist *nl, int missing,
    const char *prefix, kvaddr_t (*validate_fn)(kvm_t *, kvaddr_t))
{
        struct kvm_nlist *n, *np, *p;
        char *cp, *ce;
        const char *ccp;
        size_t len;
        int slen, unresolved;

        /*
         * Calculate the space we need to malloc for nlist and names.
         * We are going to store the name twice for later lookups: once
         * with the prefix and once the unmodified name delmited by \0.
         */
        len = 0;
        unresolved = 0;
        for (p = nl; p->n_name && p->n_name[0]; ++p) {
                if (p->n_type != N_UNDF)
                        continue;
                len += sizeof(struct kvm_nlist) + strlen(prefix) +
                    2 * (strlen(p->n_name) + 1);
                unresolved++;
        }
        if (unresolved == 0)
                return (unresolved);
        /* Add space for the terminating nlist entry. */
        len += sizeof(struct kvm_nlist);
        unresolved++;

        /* Alloc one chunk for (nlist, [names]) and setup pointers. */
        n = np = malloc(len);
        bzero(n, len);
        if (n == NULL)
                return (missing);
        cp = ce = (char *)np;
        cp += unresolved * sizeof(struct kvm_nlist);
        ce += len;

        /* Generate shortened nlist with special prefix. */
        unresolved = 0;
        for (p = nl; p->n_name && p->n_name[0]; ++p) {
                if (p->n_type != N_UNDF)
                        continue;
                *np = *p;
                /* Save the new\0orig. name so we can later match it again. */
                slen = snprintf(cp, ce - cp, "%s%s%c%s", prefix,
                    (prefix[0] != '\0' && p->n_name[0] == '_') ?
                        (p->n_name + 1) : p->n_name, '\0', p->n_name);
                if (slen < 0 || slen >= ce - cp)
                        continue;
                np->n_name = cp;
                cp += slen + 1;
                np++;
                unresolved++;
        }

        /* Do lookup on the reduced list. */
        np = n;
        unresolved = kvm_fdnlist(kd, np);

        /* Check if we could resolve further symbols and update the list. */
        if (unresolved >= 0 && unresolved < missing) {
                /* Find the first freshly resolved entry. */
                for (; np->n_name && np->n_name[0]; np++)
                        if (np->n_type != N_UNDF)
                                break;
                /*
                 * The lists are both in the same order,
                 * so we can walk them in parallel.
                 */
                for (p = nl; np->n_name && np->n_name[0] &&
                    p->n_name && p->n_name[0]; ++p) {
                        if (p->n_type != N_UNDF)
                                continue;
                        /* Skip expanded name and compare to orig. one. */
                        ccp = np->n_name + strlen(np->n_name) + 1;
                        if (strcmp(ccp, p->n_name) != 0)
                                continue;
                        /* Update nlist with new, translated results. */
                        p->n_type = np->n_type;
                        if (validate_fn)
                                p->n_value = (*validate_fn)(kd, np->n_value);
                        else
                                p->n_value = np->n_value;
                        missing--;
                        /* Find next freshly resolved entry. */
                        for (np++; np->n_name && np->n_name[0]; np++)
                                if (np->n_type != N_UNDF)
                                        break;
                }
        }
        /* We could assert missing = unresolved here. */

        free(n);
        return (unresolved);
}

int
_kvm_nlist(kvm_t *kd, struct kvm_nlist *nl, int initialize)
{
        struct kvm_nlist *p;
        int nvalid;
        struct kld_sym_lookup lookup;
        int error;
        const char *prefix = "";
        char symname[1024]; /* XXX-BZ symbol name length limit? */
        int tried_vnet, tried_dpcpu;

        /*
         * If we can't use the kld symbol lookup, revert to the
         * slow library call.
         */
        if (!ISALIVE(kd)) {
                error = kvm_fdnlist(kd, nl);
                if (error <= 0)                 /* Hard error or success. */
                        return (error);

                if (_kvm_vnet_initialized(kd, initialize))
                        error = kvm_fdnlist_prefix(kd, nl, error,
                            VNET_SYMPREFIX, _kvm_vnet_validaddr);

                if (error > 0 && _kvm_dpcpu_initialized(kd, initialize))
                        error = kvm_fdnlist_prefix(kd, nl, error,
                            DPCPU_SYMPREFIX, _kvm_dpcpu_validaddr);

                return (error);
        }

        /*
         * We can use the kld lookup syscall.  Go through each nlist entry
         * and look it up with a kldsym(2) syscall.
         */
        nvalid = 0;
        tried_vnet = 0;
        tried_dpcpu = 0;
again:
        for (p = nl; p->n_name && p->n_name[0]; ++p) {
                if (p->n_type != N_UNDF)
                        continue;

                lookup.version = sizeof(lookup);
                lookup.symvalue = 0;
                lookup.symsize = 0;

                error = snprintf(symname, sizeof(symname), "%s%s", prefix,
                    (prefix[0] != '\0' && p->n_name[0] == '_') ?
                        (p->n_name + 1) : p->n_name);
                if (error < 0 || error >= (int)sizeof(symname))
                        continue;
                lookup.symname = symname;
                if (lookup.symname[0] == '_')
                        lookup.symname++;

                if (kldsym(0, KLDSYM_LOOKUP, &lookup) != -1) {
                        p->n_type = N_TEXT;
                        if (_kvm_vnet_initialized(kd, initialize) &&
                            strcmp(prefix, VNET_SYMPREFIX) == 0)
                                p->n_value =
                                    _kvm_vnet_validaddr(kd, lookup.symvalue);
                        else if (_kvm_dpcpu_initialized(kd, initialize) &&
                            strcmp(prefix, DPCPU_SYMPREFIX) == 0)
                                p->n_value =
                                    _kvm_dpcpu_validaddr(kd, lookup.symvalue);
                        else
                                p->n_value = lookup.symvalue;
                        ++nvalid;
                        /* lookup.symsize */
                }
        }

        /*
         * Check the number of entries that weren't found. If they exist,
         * try again with a prefix for virtualized or DPCPU symbol names.
         */
        error = ((p - nl) - nvalid);
        if (error && _kvm_vnet_initialized(kd, initialize) && !tried_vnet) {
                tried_vnet = 1;
                prefix = VNET_SYMPREFIX;
                goto again;
        }
        if (error && _kvm_dpcpu_initialized(kd, initialize) && !tried_dpcpu) {
                tried_dpcpu = 1;
                prefix = DPCPU_SYMPREFIX;
                goto again;
        }

        /*
         * Return the number of entries that weren't found. If they exist,
         * also fill internal error buffer.
         */
        error = ((p - nl) - nvalid);
        if (error)
                _kvm_syserr(kd, kd->program, "kvm_nlist");
        return (error);
}

int
_kvm_bitmap_init(struct kvm_bitmap *bm, u_long bitmapsize, u_long *idx)
{

        *idx = ULONG_MAX;
        bm->map = calloc(bitmapsize, sizeof *bm->map);
        if (bm->map == NULL)
                return (0);
        bm->size = bitmapsize;
        return (1);
}

void
_kvm_bitmap_set(struct kvm_bitmap *bm, u_long bm_index)
{
        uint8_t *byte = &bm->map[bm_index / 8];

        if (bm_index / 8 < bm->size)
                *byte |= (1UL << (bm_index % 8));
}

int
_kvm_bitmap_next(struct kvm_bitmap *bm, u_long *idx)
{
        u_long first_invalid = bm->size * CHAR_BIT;

        if (*idx == ULONG_MAX)
                *idx = 0;
        else
                (*idx)++;

        /* Find the next valid idx. */
        for (; *idx < first_invalid; (*idx)++) {
                unsigned int mask = 1U << (*idx % CHAR_BIT);
                if ((bm->map[*idx / CHAR_BIT] & mask) != 0)
                        break;
        }

        return (*idx < first_invalid);
}

void
_kvm_bitmap_deinit(struct kvm_bitmap *bm)
{

        free(bm->map);
}

int
_kvm_visit_cb(kvm_t *kd, kvm_walk_pages_cb_t *cb, void *arg, u_long pa,
    u_long kmap_vaddr, u_long dmap_vaddr, vm_prot_t prot, size_t len,
    unsigned int page_size)
{
        unsigned int pgsz = page_size ? page_size : len;
        struct kvm_page p = {
                .kp_version = LIBKVM_WALK_PAGES_VERSION,
                .kp_paddr = pa,
                .kp_kmap_vaddr = kmap_vaddr,
                .kp_dmap_vaddr = dmap_vaddr,
                .kp_prot = prot,
                .kp_offset = _kvm_pt_find(kd, pa, pgsz),
                .kp_len = len,
        };

        return cb(&p, arg);
}