freader_fetch
const void *freader_fetch(struct freader *r, loff_t file_off, size_t sz);
ptr = freader_fetch(&df->freader, offset + df->offset, len);
nhdr = freader_fetch(r, note_off, sizeof(Elf32_Nhdr) + note_name_sz);
data = freader_fetch(r, build_id_off, desc_sz);
ehdr = freader_fetch(r, 0, sizeof(Elf32_Ehdr));
phdr = freader_fetch(r, phoff + i * sizeof(Elf32_Phdr), sizeof(Elf32_Phdr));
ehdr = freader_fetch(r, 0, sizeof(Elf64_Ehdr));
phdr = freader_fetch(r, phoff + i * sizeof(Elf64_Phdr), sizeof(Elf64_Phdr));
ehdr = freader_fetch(&r, 0, offsetofend(Elf32_Ehdr, e_type));