diff options
Diffstat (limited to 'resources/cbfstool/patch/rmodule.c')
| -rw-r--r-- | resources/cbfstool/patch/rmodule.c | 628 |
1 files changed, 628 insertions, 0 deletions
diff --git a/resources/cbfstool/patch/rmodule.c b/resources/cbfstool/patch/rmodule.c new file mode 100644 index 0000000..989da86 --- /dev/null +++ b/resources/cbfstool/patch/rmodule.c @@ -0,0 +1,628 @@ +/* + ;* 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 "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; +} |