readelf.h

#pragma once

#include <elf.h>
#include <stdint.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>

struct elf {
    uint8_t *file;
    Elf64_Ehdr ehdr;
    Elf64_Phdr *phdrs;
    int n_phdrs;
    Elf64_Shdr *shdrs;
    int n_shdrs;
    char *shdr_names;
    Elf64_Sym *syms;
    int n_syms;
    char *sym_names;
};

char *get_shdr_name(struct elf *e, int i) {
    return &e->shdr_names[e->shdrs[i].sh_name];
}

void *get_sym_addr(struct elf *e, int i) {
    return (void *) e->syms[i].st_value;
}

char *get_sym_name(struct elf *e, int i) {
    return &e->sym_names[e->syms[i].st_name];
}

size_t get_sym_size(struct elf *e, int i) {
    return e->syms[i].st_size;
}

int get_sym_index(struct elf *e, char *name) {
    int i;

    for (i = 0; i < e->n_syms; i++) {
        if (!strcmp(name, get_sym_name(e, i))) return i;
    }

    return -1;
}

int at_symbol(struct elf *e, void *addr) {
    int i;

    for (i = 0; i < e->n_syms; i++) {
        if (get_sym_addr(e, i) == addr) return i;
    }

    return -1;
}

Elf64_Shdr *get_shdr(struct elf *e, char *name) {
    int i;

    for (i = 0; i < e->n_shdrs; i++) {
        if (!strcmp(name, get_shdr_name(e, i))) return &e->shdrs[i];
    }

    return NULL;
}

bool addr_in_section(struct elf *e, void *addr, char *name) {
    Elf64_Shdr *shdr;
    uint64_t sec_start, sec_end;

    shdr = get_shdr(e, name);
    sec_start = shdr->sh_addr;
    sec_end = sec_start + shdr->sh_size;

    return (uint64_t) addr >= sec_start && (uint64_t) addr < sec_end;
}

bool sym_in_section(struct elf *e, int i, char *name) {
    return addr_in_section(e, get_sym_addr(e, i), name);
}

uint8_t *bytes_from_addr_in_section(struct elf *e, void *addr, char *name) {
    Elf64_Shdr *shdr;

    shdr = get_shdr(e, name);

    return &e->file[(uint64_t) addr - (uint64_t) shdr->sh_addr + shdr->sh_offset];
}

struct elf *readelf(int fd) {
    struct stat st;
    struct elf *e;
    Elf64_Shdr *sym_hdr;

    e = malloc(sizeof(*e));

    fstat(fd, &st);
    e->file = malloc(st.st_size);
    read(fd, e->file, st.st_size);

    e->ehdr = *(Elf64_Ehdr *) e->file;

    e->phdrs = (Elf64_Phdr *) &e->file[e->ehdr.e_phoff];
    e->n_phdrs = e->ehdr.e_phnum;

    e->shdrs = (Elf64_Shdr *) &e->file[e->ehdr.e_shoff];
    e->n_shdrs = e->ehdr.e_shnum;
    e->shdr_names = &e->file[e->shdrs[e->ehdr.e_shstrndx].sh_offset];

    sym_hdr = get_shdr(e, ".symtab");

    e->syms = (Elf64_Sym *) &e->file[sym_hdr->sh_offset];
    e->n_syms = sym_hdr->sh_size / sym_hdr->sh_entsize;
    e->sym_names = &e->file[e->shdrs[sym_hdr->sh_link].sh_offset];

    return e;
}