135 lines
2.7 KiB
C
135 lines
2.7 KiB
C
#include <merror.h>
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#include <melf.h>
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#include <elf.h>
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#include <sys/mman.h>
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#include "link.h"
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/**
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* Read the phdr for this segment
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*/
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static int load_phdr(struct object *obj, struct segment *seg, size_t index)
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{
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if (index >= obj->phdr_len) {
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ERROR("phdr index [%d] out of bounds", index);
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return M_ERROR;
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}
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seg->phdr = &obj->phdr[index];
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seg->phdr_idx = index;
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return M_SUCCESS;
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}
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/**
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* Read the shdr for this segment
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*/
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static int load_shdr(struct object *obj, struct segment *seg, size_t index)
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{
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bool found = false;
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for (size_t i = 0; i < obj->shdr_len; i++) {
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Elf32_Shdr *hdr = &obj->shdr[i];
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// find shdr that matches the offset in phdr
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if (seg->phdr->p_offset != hdr->sh_offset)
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continue;
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// get name
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uint32_t name = B32(hdr->sh_name);
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if (name >= obj->shstrtab->len) {
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ERROR("section name index [%d] out of bounds", name);
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return M_ERROR;
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}
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seg->name = &obj->shstrtab->data[name];
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// map bytes
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uint32_t len = B32(hdr->sh_size);
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uint32_t off = B32(hdr->sh_offset);
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seg->bytes = (unsigned char *) (obj->mapped + off);
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if (BOUND_CHK(obj, len, off)) {
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ERROR("cannot map seg %s:%d", seg->name, index);
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return M_ERROR;
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}
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found = true;
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seg->shdr = hdr;
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seg->shdr_idx = i;
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break;
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}
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if (!found) {
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ERROR("cannot find shdr for segment [%d]", index);
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return M_ERROR;
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}
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return M_SUCCESS;
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}
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/**
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* Read the relocation table for this segment (if one exists)
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*/
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static int load_reltab(struct object *obj, struct segment *seg)
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{
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// default to none
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seg->reltab.len = 0;
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for (size_t i = 0; i < obj->shdr_len; i++) {
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Elf32_Shdr *hdr = &obj->shdr[i];
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uint32_t type = B32(hdr->sh_type);
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if (type != SHT_REL && type != SHT_RELA)
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continue;
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if (B32(hdr->sh_info) != seg->shdr_idx)
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continue;
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uint32_t symtab_idx = B32(hdr->sh_link);
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if (symtab_idx >= obj->shdr_len) {
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ERROR("reltab [%d] symtab index [%d] out of bounds",
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i, symtab_idx);
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return M_ERROR;
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}
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struct symbol_table *symtab = &obj->symtabs[symtab_idx];
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if (symtab->len < 1) {
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ERROR("reltab [%d] symtab is empty or invalid", i);
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return M_ERROR;
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}
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uint32_t len = B32(hdr->sh_size);
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uint32_t off = B32(hdr->sh_offset);
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seg->reltab.symtab = symtab;
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seg->reltab.len = len;
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seg->reltab.raw = obj->mapped + off;
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seg->reltab.type = type;
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if (BOUND_CHK(obj, len, off)) {
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ERROR("cannot map reltab [%d] for %s",
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i, seg->name);
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return M_ERROR;
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}
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break;
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}
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return M_SUCCESS;
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}
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int segment_load(struct object *obj, struct segment *seg, size_t index)
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{
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if (load_phdr(obj, seg, index))
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return M_ERROR;
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if (load_shdr(obj, seg, index))
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return M_ERROR;
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if (load_reltab(obj, seg))
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return M_ERROR;
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return M_SUCCESS;
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}
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