coreboot-kgpe-d16/util/cbfstool/rmodule.c

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/*
;* Copyright (C) 2014 Google, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA, 02110-1301 USA
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "elfparsing.h"
#include "rmodule.h"
#include "../../src/include/rmodule-defs.h"
struct rmod_context;
struct arch_ops {
int arch;
/* Determine if relocation is a valid type for the architecture. */
int (*valid_type)(struct rmod_context *ctx, Elf64_Rela *rel);
/* Determine if relocation should be emitted. */
int (*should_emit)(struct rmod_context *ctx, Elf64_Rela *rel);
};
struct rmod_context {
/* Ops to process relocations. */
struct arch_ops *ops;
/* endian conversion ops */
struct xdr *xdr;
/* Parsed ELF sturcture. */
struct parsed_elf pelf;
/* Program segment. */
Elf64_Phdr *phdr;
/* Collection of relocation addresses fixup in the module. */
Elf64_Xword nrelocs;
Elf64_Addr *emitted_relocs;
/* The following fields are addresses within the linked program. */
Elf64_Addr link_addr;
Elf64_Addr entry;
Elf64_Addr parameters_begin;
Elf64_Addr parameters_end;
Elf64_Addr bss_begin;
Elf64_Addr bss_end;
Elf64_Xword size;
};
/*
* Architecture specific support operations.
*/
static int valid_reloc_386(struct rmod_context *ctx, Elf64_Rela *rel)
{
int type;
type = ELF64_R_TYPE(rel->r_info);
/* Only these 2 relocations are expected to be found. */
return (type == R_386_32 || type == R_386_PC32);
}
static int should_emit_386(struct rmod_context *ctx, Elf64_Rela *rel)
{
int type;
type = ELF64_R_TYPE(rel->r_info);
/* R_386_32 relocations are absolute. Must emit these. */
return (type == R_386_32);
}
static struct arch_ops reloc_ops[] = {
{
.arch = EM_386,
.valid_type = valid_reloc_386,
.should_emit = should_emit_386,
},
};
/*
* Relocation processing loops.
*/
static int for_each_reloc(struct rmod_context *ctx, int do_emit)
{
Elf64_Half i;
struct parsed_elf *pelf = &ctx->pelf;
for (i = 0; i < pelf->ehdr.e_shnum; i++) {
Elf64_Shdr *shdr;
Elf64_Rela *relocs;
Elf64_Xword nrelocs;
Elf64_Xword j;
relocs = pelf->relocs[i];
/* No relocations in this section. */
if (relocs == NULL)
continue;
shdr = &pelf->shdr[i];
nrelocs = shdr->sh_size / shdr->sh_entsize;
for (j = 0; j < nrelocs; j++) {
Elf64_Rela *r = &relocs[j];
if (!ctx->ops->valid_type(ctx, r)) {
ERROR("Invalid reloc type: %u\n",
(unsigned int)ELF64_R_TYPE(r->r_info));
return -1;
}
if (ctx->ops->should_emit(ctx, r)) {
int n = ctx->nrelocs;
if (do_emit)
ctx->emitted_relocs[n] = r->r_offset;
ctx->nrelocs++;
}
}
}
return 0;
}
static int find_program_segment(struct rmod_context *ctx)
{
int i;
int nsegments;
struct parsed_elf *pelf;
Elf64_Phdr *phdr;
pelf = &ctx->pelf;
/* There should only be a single loadable segment. */
nsegments = 0;
for (i = 0; i < pelf->ehdr.e_phnum; i++) {
if (pelf->phdr[i].p_type != PT_LOAD)
continue;
phdr = &pelf->phdr[i];
nsegments++;
}
if (nsegments != 1) {
ERROR("Unexepcted number of loadable segments: %d.\n",
nsegments);
return -1;
}
INFO("Segment at 0x%0llx, file size 0x%0llx, mem size 0x%0llx.\n",
(long long)phdr->p_vaddr, (long long)phdr->p_filesz,
(long long)phdr->p_memsz);
ctx->phdr = phdr;
return 0;
}
static int
filter_relocation_sections(struct rmod_context *ctx)
{
int i;
const char *shstrtab;
struct parsed_elf *pelf;
const Elf64_Phdr *phdr;
pelf = &ctx->pelf;
phdr = ctx->phdr;
shstrtab = buffer_get(pelf->strtabs[pelf->ehdr.e_shstrndx]);
/*
* Find all relocation sections that contain relocation entries
* for sections that fall within the bounds of the segment. For
* easier processing the pointer to the relocation array for the
* sections that don't fall within the loadable program are NULL'd
* out.
*/
for (i = 0; i < pelf->ehdr.e_shnum; i++) {
Elf64_Shdr *shdr;
Elf64_Word sh_info;
const char *section_name;
shdr = &pelf->shdr[i];
/* Ignore non-relocation sections. */
if (shdr->sh_type != SHT_RELA && shdr->sh_type != SHT_REL)
continue;
/* Obtain section which relocations apply. */
sh_info = shdr->sh_info;
shdr = &pelf->shdr[sh_info];
section_name = &shstrtab[shdr->sh_name];
DEBUG("Relocation section found for '%s' section.\n",
section_name);
/* Do not process relocations for debug sections. */
if (strstr(section_name, ".debug") != NULL) {
pelf->relocs[i] = NULL;
continue;
}
/*
* If relocations apply to a non program section ignore the
* relocations for future processing.
*/
if (shdr->sh_type != SHT_PROGBITS) {
pelf->relocs[i] = NULL;
continue;
}
if (shdr->sh_addr < phdr->p_vaddr ||
((shdr->sh_addr + shdr->sh_size) >
(phdr->p_vaddr + phdr->p_memsz))) {
ERROR("Relocations being applied to section %d not "
"within segment region.\n", sh_info);
return -1;
}
}
return 0;
}
static int vaddr_cmp(const void *a, const void *b)
{
const Elf64_Addr *pa = a;
const Elf64_Addr *pb = b;
if (*pa < *pb)
return -1;
if (*pa > *pb)
return 1;
return 0;
}
static int collect_relocations(struct rmod_context *ctx)
{
int nrelocs;
/*
* The relocs array in the pelf should only contain relocations that
* apply to the program. Count the number relocations. Then collect
* them into the allocated buffer.
*/
if (for_each_reloc(ctx, 0))
return -1;
nrelocs = ctx->nrelocs;
INFO("%d relocations to be emitted.\n", nrelocs);
if (!nrelocs) {
ERROR("No valid relocations in file.\n");
return -1;
}
/* Reset the counter for indexing into the array. */
ctx->nrelocs = 0;
ctx->emitted_relocs = calloc(nrelocs, sizeof(Elf64_Addr));
/* Write out the relocations into the emitted_relocs array. */
if (for_each_reloc(ctx, 1))
return -1;
if (ctx->nrelocs != nrelocs) {
ERROR("Mismatch counted and emitted relocations: %zu vs %zu.\n",
(size_t)nrelocs, (size_t)ctx->nrelocs);
return -1;
}
/* Sort the relocations by their address. */
qsort(ctx->emitted_relocs, nrelocs, sizeof(Elf64_Addr), vaddr_cmp);
return 0;
}
static int
populate_sym(struct rmod_context *ctx, const char *sym_name, Elf64_Addr *addr,
int nsyms, const char *strtab)
{
int i;
Elf64_Sym *syms;
syms = ctx->pelf.syms;
for (i = 0; i < nsyms; i++) {
if (syms[i].st_name == 0)
continue;
if (strcmp(sym_name, &strtab[syms[i].st_name]))
continue;
DEBUG("%s -> 0x%llx\n", sym_name, (long long)syms[i].st_value);
*addr = syms[i].st_value;
return 0;
}
ERROR("symbol '%s' not found.\n", sym_name);
return -1;
}
static int populate_program_info(struct rmod_context *ctx)
{
int i;
const char *strtab;
struct parsed_elf *pelf;
Elf64_Ehdr *ehdr;
int nsyms;
pelf = &ctx->pelf;
ehdr = &pelf->ehdr;
/* Obtain the string table. */
strtab = NULL;
for (i = 0; i < ehdr->e_shnum; i++) {
if (ctx->pelf.strtabs[i] == NULL)
continue;
/* Don't use the section headers' string table. */
if (i == ehdr->e_shstrndx)
continue;
strtab = buffer_get(ctx->pelf.strtabs[i]);
break;
}
if (strtab == NULL) {
ERROR("No string table found.\n");
return -1;
}
/* Determine number of symbols. */
nsyms = 0;
for (i = 0; i < ehdr->e_shnum; i++) {
if (pelf->shdr[i].sh_type != SHT_SYMTAB)
continue;
nsyms = pelf->shdr[i].sh_size / pelf->shdr[i].sh_entsize;
break;
}
if (populate_sym(ctx, "_module_params_begin", &ctx->parameters_begin,
nsyms, strtab))
return -1;
if (populate_sym(ctx, "_module_params_end", &ctx->parameters_end,
nsyms, strtab))
return -1;
if (populate_sym(ctx, "_bss", &ctx->bss_begin, nsyms, strtab))
return -1;
if (populate_sym(ctx, "_ebss", &ctx->bss_end, nsyms, strtab))
return -1;
if (populate_sym(ctx, "__rmodule_entry", &ctx->entry, nsyms, strtab))
return -1;
/* Link address is the virtual address of the program segment. */
ctx->link_addr = ctx->phdr->p_vaddr;
/* The program size is the memsz of the program segment. */
ctx->size = ctx->phdr->p_memsz;
return 0;
}
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;
}
static int
write_elf(const struct rmod_context *ctx, const struct buffer *in,
struct buffer *out)
{
int i;
int ret;
int bit64;
size_t loc;
size_t rmod_data_size;
struct elf_writer *ew;
struct buffer rmod_data;
struct buffer rmod_header;
struct buffer program;
struct buffer relocs;
Elf64_Xword total_size;
Elf64_Addr addr;
Elf64_Ehdr ehdr;
bit64 = ctx->pelf.ehdr.e_ident[EI_CLASS] == ELFCLASS64;
/*
* 3 sections will be added to the ELF file.
* +------------------+
* | rmodule header |
* +------------------+
* | program |
* +------------------+
* | relocations |
* +------------------+
*/
/* Create buffer for header and relocations. */
rmod_data_size = sizeof(struct rmodule_header);
if (bit64)
rmod_data_size += ctx->nrelocs * sizeof(Elf64_Addr);
else
rmod_data_size += ctx->nrelocs * sizeof(Elf32_Addr);
if (buffer_create(&rmod_data, rmod_data_size, "rmod"))
return -1;
buffer_splice(&rmod_header, &rmod_data,
0, sizeof(struct rmodule_header));
buffer_clone(&relocs, &rmod_data);
buffer_seek(&relocs, sizeof(struct rmodule_header));
/* Reset current location. */
buffer_set_size(&rmod_header, 0);
buffer_set_size(&relocs, 0);
/* Program contents. */
buffer_splice(&program, in, ctx->phdr->p_offset, ctx->phdr->p_filesz);
/* Create ELF writer with modified entry point. */
memcpy(&ehdr, &ctx->pelf.ehdr, sizeof(ehdr));
ehdr.e_entry = ctx->entry;
ew = elf_writer_init(&ehdr);
if (ew == NULL) {
ERROR("Failed to create ELF writer.\n");
buffer_delete(&rmod_data);
return -1;
}
/* Write out rmodule_header. */
ctx->xdr->put16(&rmod_header, RMODULE_MAGIC);
ctx->xdr->put8(&rmod_header, RMODULE_VERSION_1);
ctx->xdr->put8(&rmod_header, 0);
/* payload_begin_offset */
loc = sizeof(struct rmodule_header);
ctx->xdr->put32(&rmod_header, loc);
/* payload_end_offset */
loc += ctx->phdr->p_filesz;
ctx->xdr->put32(&rmod_header, loc);
/* relocations_begin_offset */
ctx->xdr->put32(&rmod_header, loc);
/* relocations_end_offset */
if (bit64)
loc += ctx->nrelocs * sizeof(Elf64_Addr);
else
loc += ctx->nrelocs * sizeof(Elf32_Addr);
ctx->xdr->put32(&rmod_header, loc);
/* module_link_start_address */
ctx->xdr->put32(&rmod_header, ctx->link_addr);
/* module_program_size */
ctx->xdr->put32(&rmod_header, ctx->size);
/* module_entry_point */
ctx->xdr->put32(&rmod_header, ctx->entry);
/* parameters_begin */
ctx->xdr->put32(&rmod_header, ctx->parameters_begin);
/* parameters_end */
ctx->xdr->put32(&rmod_header, ctx->parameters_end);
/* bss_begin */
ctx->xdr->put32(&rmod_header, ctx->bss_begin);
/* bss_end */
ctx->xdr->put32(&rmod_header, ctx->bss_end);
/* padding[4] */
ctx->xdr->put32(&rmod_header, 0);
ctx->xdr->put32(&rmod_header, 0);
ctx->xdr->put32(&rmod_header, 0);
ctx->xdr->put32(&rmod_header, 0);
/* Write the relocations. */
for (i = 0; i < ctx->nrelocs; i++) {
if (bit64)
ctx->xdr->put64(&relocs, ctx->emitted_relocs[i]);
else
ctx->xdr->put32(&relocs, ctx->emitted_relocs[i]);
}
total_size = 0;
addr = 0;
/*
* There are 2 cases to deal with. The program has a large NOBITS
* section and the relocations can fit entirely within occupied memory
* region for the program. The other is that the relocations increase
* the memory footprint of the program if it was loaded directly into
* the region it would run. The rmdoule header is a fixed cost that
* is considered a part of the program.
*/
total_size += buffer_size(&rmod_header);
total_size += ctx->phdr->p_memsz;
if (buffer_size(&relocs) + ctx->phdr->p_filesz > total_size) {
total_size -= ctx->phdr->p_memsz;
total_size += buffer_size(&relocs);
total_size += ctx->phdr->p_filesz;
}
ret = add_section(ew, &rmod_header, ".header", addr,
buffer_size(&rmod_header));
if (ret < 0)
goto out;
addr += buffer_size(&rmod_header);
ret = add_section(ew, &program, ".program", addr, ctx->phdr->p_filesz);
if (ret < 0)
goto out;
addr += ctx->phdr->p_filesz;
ret = add_section(ew, &relocs, ".relocs", addr, buffer_size(&relocs));
if (ret < 0)
goto out;
addr += buffer_size(&relocs);
if (total_size != addr) {
ret = add_section(ew, NULL, ".empty", addr, total_size - addr);
if (ret < 0)
goto out;
}
/*
* Ensure last section has a memory usage that meets the required
* total size of the program in memory.
*/
ret = elf_writer_serialize(ew, out);
if (ret < 0)
ERROR("Failed to serialize ELF to buffer.\n");
out:
buffer_delete(&rmod_data);
elf_writer_destroy(ew);
return ret;
}
int rmodule_create(const struct buffer *elfin, struct buffer *elfout)
{
struct rmod_context ctx;
struct parsed_elf *pelf;
int i;
int ret;
ret = -1;
memset(&ctx, 0, sizeof(ctx));
pelf = &ctx.pelf;
if (parse_elf(elfin, pelf, ELF_PARSE_ALL)) {
ERROR("Couldn't parse ELF!\n");
return -1;
}
/* Only allow executables to be turned into rmodules. */
if (pelf->ehdr.e_type != ET_EXEC) {
ERROR("ELF is not an executable: %u.\n", pelf->ehdr.e_type);
goto out;
}
/* Determine if architecture is supported. */
for (i = 0; i < ARRAY_SIZE(reloc_ops); i++) {
if (reloc_ops[i].arch == pelf->ehdr.e_machine) {
ctx.ops = &reloc_ops[i];
break;
}
}
if (ctx.ops == NULL) {
ERROR("ELF is unsupported arch: %u.\n", pelf->ehdr.e_machine);
goto out;
}
/* Set the endian ops. */
if (ctx.pelf.ehdr.e_ident[EI_DATA] == ELFDATA2MSB)
ctx.xdr = &xdr_be;
else
ctx.xdr = &xdr_le;
if (find_program_segment(&ctx))
goto out;
if (filter_relocation_sections(&ctx))
goto out;
if (collect_relocations(&ctx))
goto out;
if (populate_program_info(&ctx))
goto out;
if (write_elf(&ctx, elfin, elfout))
goto out;
ret = 0;
out:
free(ctx.emitted_relocs);
parsed_elf_destroy(pelf);
return ret;
}