symbol-minimal.c

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// SPDX-License-Identifier: GPL-2.0
#include "symbol.h"
#include "util.h"

#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <byteswap.h>
#include <sys/stat.h>


static bool check_need_swap(int file_endian)
{
    const int data = 1;
    u8 *check = (u8 *)&data;
    int host_endian;

    if (check[0] == 1)
        host_endian = ELFDATA2LSB;
    else
        host_endian = ELFDATA2MSB;

    return host_endian != file_endian;
}

#define NOTE_ALIGN(sz) (((sz) + 3) & ~3)

#define NT_GNU_BUILD_ID 3

static int read_build_id(void *note_data, size_t note_len, void *bf,
             size_t size, bool need_swap)
{
    struct {
        u32 n_namesz;
        u32 n_descsz;
        u32 n_type;
    } *nhdr;
    void *ptr;

    ptr = note_data;
    while (ptr < (note_data + note_len)) {
        const char *name;
        size_t namesz, descsz;

        nhdr = ptr;
        if (need_swap) {
            nhdr->n_namesz = bswap_32(nhdr->n_namesz);
            nhdr->n_descsz = bswap_32(nhdr->n_descsz);
            nhdr->n_type = bswap_32(nhdr->n_type);
        }

        namesz = NOTE_ALIGN(nhdr->n_namesz);
        descsz = NOTE_ALIGN(nhdr->n_descsz);

        ptr += sizeof(*nhdr);
        name = ptr;
        ptr += namesz;
        if (nhdr->n_type == NT_GNU_BUILD_ID &&
            nhdr->n_namesz == sizeof("GNU")) {
            if (memcmp(name, "GNU", sizeof("GNU")) == 0) {
                size_t sz = min(size, descsz);
                memcpy(bf, ptr, sz);
                memset(bf + sz, 0, size - sz);
                return 0;
            }
        }
        ptr += descsz;
    }

    return -1;
}

int filename__read_debuglink(const char *filename __maybe_unused,
                 char *debuglink __maybe_unused,
                 size_t size __maybe_unused)
{
    return -1;
}

/*
 * Just try PT_NOTE header otherwise fails
 */
int filename__read_build_id(const char *filename, void *bf, size_t size)
{
    FILE *fp;
    int ret = -1;
    bool need_swap = false;
    u8 e_ident[EI_NIDENT];
    size_t buf_size;
    void *buf;
    int i;

    fp = fopen(filename, "r");
    if (fp == NULL)
        return -1;

    if (fread(e_ident, sizeof(e_ident), 1, fp) != 1)
        goto out;

    if (memcmp(e_ident, ELFMAG, SELFMAG) ||
        e_ident[EI_VERSION] != EV_CURRENT)
        goto out;

    need_swap = check_need_swap(e_ident[EI_DATA]);

    /* for simplicity */
    fseek(fp, 0, SEEK_SET);

    if (e_ident[EI_CLASS] == ELFCLASS32) {
        Elf32_Ehdr ehdr;
        Elf32_Phdr *phdr;

        if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
            goto out;

        if (need_swap) {
            ehdr.e_phoff = bswap_32(ehdr.e_phoff);
            ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
            ehdr.e_phnum = bswap_16(ehdr.e_phnum);
        }

        buf_size = ehdr.e_phentsize * ehdr.e_phnum;
        buf = malloc(buf_size);
        if (buf == NULL)
            goto out;

        fseek(fp, ehdr.e_phoff, SEEK_SET);
        if (fread(buf, buf_size, 1, fp) != 1)
            goto out_free;

        for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
            void *tmp;
            long offset;

            if (need_swap) {
                phdr->p_type = bswap_32(phdr->p_type);
                phdr->p_offset = bswap_32(phdr->p_offset);
                phdr->p_filesz = bswap_32(phdr->p_filesz);
            }

            if (phdr->p_type != PT_NOTE)
                continue;

            buf_size = phdr->p_filesz;
            offset = phdr->p_offset;
            tmp = realloc(buf, buf_size);
            if (tmp == NULL)
                goto out_free;

            buf = tmp;
            fseek(fp, offset, SEEK_SET);
            if (fread(buf, buf_size, 1, fp) != 1)
                goto out_free;

            ret = read_build_id(buf, buf_size, bf, size, need_swap);
            if (ret == 0)
                ret = size;
            break;
        }
    } else {
        Elf64_Ehdr ehdr;
        Elf64_Phdr *phdr;

        if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
            goto out;

        if (need_swap) {
            ehdr.e_phoff = bswap_64(ehdr.e_phoff);
            ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
            ehdr.e_phnum = bswap_16(ehdr.e_phnum);
        }

        buf_size = ehdr.e_phentsize * ehdr.e_phnum;
        buf = malloc(buf_size);
        if (buf == NULL)
            goto out;

        fseek(fp, ehdr.e_phoff, SEEK_SET);
        if (fread(buf, buf_size, 1, fp) != 1)
            goto out_free;

        for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
            void *tmp;
            long offset;

            if (need_swap) {
                phdr->p_type = bswap_32(phdr->p_type);
                phdr->p_offset = bswap_64(phdr->p_offset);
                phdr->p_filesz = bswap_64(phdr->p_filesz);
            }

            if (phdr->p_type != PT_NOTE)
                continue;

            buf_size = phdr->p_filesz;
            offset = phdr->p_offset;
            tmp = realloc(buf, buf_size);
            if (tmp == NULL)
                goto out_free;

            buf = tmp;
            fseek(fp, offset, SEEK_SET);
            if (fread(buf, buf_size, 1, fp) != 1)
                goto out_free;

            ret = read_build_id(buf, buf_size, bf, size, need_swap);
            if (ret == 0)
                ret = size;
            break;
        }
    }
out_free:
    free(buf);
out:
    fclose(fp);
    return ret;
}

int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
{
    int fd;
    int ret = -1;
    struct stat stbuf;
    size_t buf_size;
    void *buf;

    fd = open(filename, O_RDONLY);
    if (fd < 0)
        return -1;

    if (fstat(fd, &stbuf) < 0)
        goto out;

    buf_size = stbuf.st_size;
    buf = malloc(buf_size);
    if (buf == NULL)
        goto out;

    if (read(fd, buf, buf_size) != (ssize_t) buf_size)
        goto out_free;

    ret = read_build_id(buf, buf_size, build_id, size, false);
out_free:
    free(buf);
out:
    close(fd);
    return ret;
}

int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
             enum dso_binary_type type)
{
    int fd = open(name, O_RDONLY);
    if (fd < 0)
        goto out_errno;

    ss->name = strdup(name);
    if (!ss->name)
        goto out_close;

    ss->fd = fd;
    ss->type = type;

    return 0;
out_close:
    close(fd);
out_errno:
    dso->load_errno = errno;
    return -1;
}

bool symsrc__possibly_runtime(struct symsrc *ss __maybe_unused)
{
    /* Assume all sym sources could be a runtime image. */
    return true;
}

bool symsrc__has_symtab(struct symsrc *ss __maybe_unused)
{
    return false;
}

void symsrc__destroy(struct symsrc *ss)
{
    zfree(&ss->name);
    close(ss->fd);
}

int dso__synthesize_plt_symbols(struct dso *dso __maybe_unused,
                struct symsrc *ss __maybe_unused)
{
    return 0;
}

static int fd__is_64_bit(int fd)
{
    u8 e_ident[EI_NIDENT];

    if (lseek(fd, 0, SEEK_SET))
        return -1;

    if (readn(fd, e_ident, sizeof(e_ident)) != sizeof(e_ident))
        return -1;

    if (memcmp(e_ident, ELFMAG, SELFMAG) ||
        e_ident[EI_VERSION] != EV_CURRENT)
        return -1;

    return e_ident[EI_CLASS] == ELFCLASS64;
}

enum dso_type dso__type_fd(int fd)
{
    Elf64_Ehdr ehdr;
    int ret;

    ret = fd__is_64_bit(fd);
    if (ret < 0)
        return DSO__TYPE_UNKNOWN;

    if (ret)
        return DSO__TYPE_64BIT;

    if (readn(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
        return DSO__TYPE_UNKNOWN;

    if (ehdr.e_machine == EM_X86_64)
        return DSO__TYPE_X32BIT;

    return DSO__TYPE_32BIT;
}

int dso__load_sym(struct dso *dso, struct map *map __maybe_unused,
          struct symsrc *ss,
          struct symsrc *runtime_ss __maybe_unused,
          int kmodule __maybe_unused)
{
    unsigned char build_id[BUILD_ID_SIZE];
    int ret;

    ret = fd__is_64_bit(ss->fd);
    if (ret >= 0)
        dso->is_64_bit = ret;

    if (filename__read_build_id(ss->name, build_id, BUILD_ID_SIZE) > 0) {
        dso__set_build_id(dso, build_id);
    }
    return 0;
}

int file__read_maps(int fd __maybe_unused, bool exe __maybe_unused,
            mapfn_t mapfn __maybe_unused, void *data __maybe_unused,
            bool *is_64_bit __maybe_unused)
{
    return -1;
}

int kcore_extract__create(struct kcore_extract *kce __maybe_unused)
{
    return -1;
}

void kcore_extract__delete(struct kcore_extract *kce __maybe_unused)
{
}

int kcore_copy(const char *from_dir __maybe_unused,
           const char *to_dir __maybe_unused)
{
    return -1;
}

void symbol__elf_init(void)
{
}

char *dso__demangle_sym(struct dso *dso __maybe_unused,
            int kmodule __maybe_unused,
            const char *elf_name __maybe_unused)
{
    return NULL;
}