static int
add_section(struct elf_writer *ew, struct buffer *data, const char *name,
Elf64_Addr addr, Elf64_Word size)
{
Elf64_Shdr shdr;
int ret;
memset(&shdr, 0, sizeof(shdr));
if (data != NULL) {
shdr.sh_type = SHT_PROGBITS;
shdr.sh_flags = SHF_ALLOC | SHF_WRITE | SHF_EXECINSTR;
} else {
shdr.sh_type = SHT_NOBITS;
shdr.sh_flags = SHF_ALLOC;
}
shdr.sh_addr = addr;
shdr.sh_offset = addr;
shdr.sh_size = size;
ret = elf_writer_add_section(ew, &shdr, data, name);
if (ret)
ERROR("Could not add '%s' section.\n", name);
return ret;
}
struct elf_writer *elf_writer_init(const Elf64_Ehdr *ehdr)
{
struct elf_writer *ew;
Elf64_Shdr shdr;
struct buffer empty_buffer;
if (!iself(ehdr))
return NULL;
ew = calloc(1, sizeof(*ew));
memcpy(&ew->ehdr, ehdr, sizeof(ew->ehdr));
ew->bit64 = ew->ehdr.e_ident[EI_CLASS] == ELFCLASS64;
/* Set the endinan ops. */
if (ew->ehdr.e_ident[EI_DATA] == ELFDATA2MSB)
ew->xdr = &xdr_be;
else
ew->xdr = &xdr_le;
/* Reset count and offsets */
ew->ehdr.e_phoff = 0;
ew->ehdr.e_shoff = 0;
ew->ehdr.e_shnum = 0;
ew->ehdr.e_phnum = 0;
memset(&empty_buffer, 0, sizeof(empty_buffer));
memset(&shdr, 0, sizeof(shdr));
/* Add SHT_NULL section header. */
shdr.sh_type = SHT_NULL;
elf_writer_add_section(ew, &shdr, &empty_buffer, NULL);
/* Add section header string table and maintain reference to it. */
shdr.sh_type = SHT_STRTAB;
elf_writer_add_section(ew, &shdr, &empty_buffer, ".shstrtab");
ew->ehdr.e_shstrndx = ew->num_secs - 1;
ew->shstrtab = &ew->sections[ew->ehdr.e_shstrndx];
return ew;
}
int rmodule_stage_to_elf(Elf64_Ehdr *ehdr, struct buffer *buff)
{
struct buffer reader;
struct buffer elf_out;
struct rmodule_header rmod;
struct xdr *xdr;
struct elf_writer *ew;
Elf64_Shdr shdr;
int bit64;
size_t payload_sz;
const char *section_name = ".program";
const size_t input_sz = buffer_size(buff);
buffer_clone(&reader, buff);
xdr = (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) ? &xdr_be : &xdr_le;
bit64 = ehdr->e_ident[EI_CLASS] == ELFCLASS64;
rmod_deserialize(&rmod, &reader, xdr);
/* Indicate that file is not an rmodule if initial checks fail. */
if (rmod.magic != RMODULE_MAGIC)
return 1;
if (rmod.version != RMODULE_VERSION_1)
return 1;
if (rmod.payload_begin_offset > input_sz ||
rmod.payload_end_offset > input_sz ||
rmod.relocations_begin_offset > input_sz ||
rmod.relocations_end_offset > input_sz) {
ERROR("Rmodule fields out of bounds.\n");
return -1;
}
ehdr->e_entry = rmod.module_entry_point;
ew = elf_writer_init(ehdr);
if (ew == NULL)
return -1;
payload_sz = rmod.payload_end_offset - rmod.payload_begin_offset;
memset(&shdr, 0, sizeof(shdr));
shdr.sh_type = SHT_PROGBITS;
shdr.sh_flags = SHF_WRITE | SHF_ALLOC | SHF_EXECINSTR;
shdr.sh_addr = rmod.module_link_start_address;
shdr.sh_size = payload_sz;
buffer_splice(&reader, buff, rmod.payload_begin_offset, payload_sz);
if (elf_writer_add_section(ew, &shdr, &reader, section_name)) {
ERROR("Unable to add ELF section: %s\n", section_name);
elf_writer_destroy(ew);
return -1;
}
if (payload_sz != rmod.module_program_size) {
struct buffer b;
buffer_init(&b, NULL, NULL, 0);
memset(&shdr, 0, sizeof(shdr));
shdr.sh_type = SHT_NOBITS;
shdr.sh_flags = SHF_WRITE | SHF_ALLOC;
shdr.sh_addr = rmod.module_link_start_address + payload_sz;
shdr.sh_size = rmod.module_program_size - payload_sz;
if (elf_writer_add_section(ew, &shdr, &b, ".empty")) {
ERROR("Unable to add ELF section: .empty\n");
elf_writer_destroy(ew);
return -1;
}
}
/* Provide a section symbol so the relcoations can reference that. */
if (elf_writer_add_symbol(ew, section_name, section_name, shdr.sh_addr,
0, STB_LOCAL, STT_SECTION)) {
ERROR("Unable to add section symbol to ELF.\n");
elf_writer_destroy(ew);
return -1;
}
/* Add symbols for the parameters if they are non-zero. */
if (rmod.parameters_begin != rmod.parameters_end) {
int ret = 0;
ret |= elf_writer_add_symbol(ew, "_rmodule_params",
section_name,
rmod.parameters_begin, 0,
STB_GLOBAL, STT_NOTYPE);
ret |= elf_writer_add_symbol(ew, "_ermodule_params",
section_name,
rmod.parameters_end, 0,
STB_GLOBAL, STT_NOTYPE);
if (ret != 0) {
ERROR("Unable to add module params symbols to ELF\n");
elf_writer_destroy(ew);
return -1;
}
}
if (elf_writer_add_symbol(ew, "_bss", section_name, rmod.bss_begin, 0,
STB_GLOBAL, STT_NOTYPE) ||
elf_writer_add_symbol(ew, "_ebss", section_name, rmod.bss_end, 0,
STB_GLOBAL, STT_NOTYPE)) {
ERROR("Unable to add bss symbols to ELF\n");
elf_writer_destroy(ew);
return -1;
}
ssize_t relocs_sz = rmod.relocations_end_offset;
relocs_sz -= rmod.relocations_begin_offset;
buffer_splice(&reader, buff, rmod.relocations_begin_offset, relocs_sz);
while (relocs_sz > 0) {
Elf64_Addr addr;
if (bit64) {
relocs_sz -= sizeof(Elf64_Addr);
addr = xdr->get64(&reader);
} else {
relocs_sz -= sizeof(Elf32_Addr);
addr = xdr->get32(&reader);
}
/* Skip any relocations that are below the link address. */
if (addr < rmod.module_link_start_address)
continue;
if (elf_writer_add_rel(ew, section_name, addr)) {
ERROR("Relocation addition failure.\n");
elf_writer_destroy(ew);
return -1;
}
}
if (elf_writer_serialize(ew, &elf_out)) {
ERROR("ELF writer serialize failure.\n");
elf_writer_destroy(ew);
return -1;
}
elf_writer_destroy(ew);
/* Flip buffer with the created ELF one. */
buffer_delete(buff);
*buff = elf_out;
return 0;
}
