dont require phdr to link
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parent
853a1ba612
commit
fb07130990
GPG key ID:
744AB800E383AE52
5 changed files with 154 additions and 63 deletions
46
mld/link.c
46
mld/link.c
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@ -12,8 +12,6 @@
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#include "link.h"
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#include "mips.h"
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#define SEC_ALIGN 0x1000
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static int load_objects(struct linker *linker)
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{
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int max_entries = linker->args->in_count + 1;
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@ -168,7 +166,7 @@ static int relocate_symbol(struct linker *linker, struct object *obj,
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struct symbol_table *symtab, const Elf32_Sym *sym)
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{
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size_t shndx = B16(sym->st_shndx);
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if (shndx == 0)
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if (shndx == 0 || shndx == SHN_ABS)
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return M_SUCCESS; // ignore this symbol
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// find the given section
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@ -184,11 +182,9 @@ static int relocate_symbol(struct linker *linker, struct object *obj,
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return M_ERROR;
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}
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Elf32_Shdr const *shdr = &obj->shdr[shndx];
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struct segment *sec = NULL;
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for (size_t i = 0; i < obj->phdr_len; i++) {
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Elf32_Phdr *temp = &obj->phdr[i];
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if (PHDR_SHDR_MATCH(temp, shdr)) {
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if (obj->phdr_to_shdr_mapping[i] == shndx) {
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sec = &obj->segments[i];
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break;
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}
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@ -219,6 +215,20 @@ static int relocate_symbol(struct linker *linker, struct object *obj,
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new.st_shndx = B16(new_shndx);
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new.st_size = 0;
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// rename symbol if its name is empty to perm placeholder
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//if (B32(sym->st_name) == 0) {
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// #define __MAX 512
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// char name[__MAX];
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// memset(name, 0, __MAX);
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// strcat(name, "__sym");
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// snprintf(name + strlen(name), __MAX - strlen(name), "%d",
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// B32(sym->st_value));
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// if (strtab_push(linker->symtab.strtab, name, &str_off))
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// return M_ERROR;
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// new.st_name = B32(str_off);
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// #undef __MAX
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//}
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if (symtab_get(&linker->symtab, NULL, name, obj->index) == M_SUCCESS) {
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ERROR("cannot link doubly defiend symbol '%s'", name);
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return M_ERROR;
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@ -447,33 +457,38 @@ static int relocate_instruction_rela(struct linker *linker,
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// 16bit absolute
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if (vaddr_abs > UINT16_MAX)
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warn = true;
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ins.immd = (uint16_t)vaddr_abs;
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ins.immd += (uint16_t)vaddr_abs;
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break;
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case R_MIPS_PC16:
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// 16bit relative shifted
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if (vaddr_rel > INT16_MAX || vaddr_rel < INT16_MIN)
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warn = true;
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ins.offset = vaddr_rel;
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ins.offset += vaddr_rel;
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break;
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case R_MIPS_26:
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case R_MIPS_JALR:
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// 26bit absolute shifted
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if (vaddr_abs >= (1 << 25))
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warn = true;
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ins.target = (vaddr_abs & 0x0FFFFFFF) >> 2;
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ins.target += (vaddr_abs & 0x0FFFFFFF) >> 2;
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break;
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case R_MIPS_PC26_S2:
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// 26bit relative shifted
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if (vaddr_rel >= (1 << 24) || -vaddr_rel > (1 << 24))
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warn = true;
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ins.offs26 = vaddr_rel;
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ins.offs26 += vaddr_rel;
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break;
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case R_MIPS_LO16:
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// lo 16bit absolute
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ins.immd = (uint16_t)(vaddr_abs & 0xFFFF);
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ins.immd += (uint16_t)(vaddr_abs & 0xFFFF);
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break;
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case R_MIPS_HI16:
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// hi 16bit absolute
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ins.immd = (uint16_t)(vaddr_abs >> 16);
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ins.immd += (uint16_t)(vaddr_abs >> 16);
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break;
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case R_MIPS_32:
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// 32bit absolute
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ins.raw = vaddr_abs;
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break;
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default:
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ERROR("do not know how do handle relocation type [%d]", typ);
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@ -596,9 +611,6 @@ static void update_offsets(struct linker *linker)
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static int write_file(struct linker *linker)
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{
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extern char *current_file;
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current_file = linker->args->out_file;
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int fd = open(linker->args->out_file, O_RDWR | O_CREAT, 0711);
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if (fd < 0) {
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PERROR("cannot write");
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@ -739,12 +751,16 @@ static void linker_free(struct linker *linker)
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int link_files(struct linker_arguments args) {
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struct linker linker;
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extern char *current_file;
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int res = M_SUCCESS;
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if (res == M_SUCCESS)
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res = linker_init(&linker, &args);
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if (res == M_SUCCESS)
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res = load_objects(&linker);
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current_file = args.out_file;
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if (res == M_SUCCESS)
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res = relocate_segments(&linker);
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if (res == M_SUCCESS)
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@ -35,6 +35,9 @@
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#define TEXT_VADDR_MIN 0x00400000
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#define DATA_VADDR_MIN 0x10000000
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// alignment of a section
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#define SEC_ALIGN 0x1000
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// pre define
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struct linker;
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struct object;
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@ -42,6 +45,7 @@ struct segment;
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struct string_table;
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struct symbol_table;
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struct symbol_table_mapping;
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struct glboff_table;
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///
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/// relocation table
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@ -220,6 +224,10 @@ struct object {
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// program table
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Elf32_Phdr *phdr;
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size_t phdr_len;
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bool phdr_local; // if phdr was created though malloc
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// phdr <=> shdr mappings
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uint32_t *phdr_to_shdr_mapping;
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// object meta
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const char *name;
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105
mld/obj.c
105
mld/obj.c
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@ -49,10 +49,10 @@ static int load_ehdr(struct object *object)
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EHDR_ASSERT(type, sizeof(Elf32_Half));
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EHDR_ASSERT(machine, sizeof(Elf32_Half));
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EHDR_ASSERT(version, sizeof(Elf32_Word));
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EHDR_ASSERT(flags, sizeof(Elf32_Word));
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// EHDR_ASSERT(flags, sizeof(Elf32_Word));
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EHDR_ASSERT(ehsize, sizeof(Elf32_Half));
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EHDR_ASSERT(phentsize, sizeof(Elf32_Half));
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EHDR_ASSERT(shentsize, sizeof(Elf32_Half));
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// EHDR_ASSERT(phentsize, sizeof(Elf32_Half));
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// EHDR_ASSERT(shentsize, sizeof(Elf32_Half));
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#undef EHDR_ASSERT
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@ -81,23 +81,94 @@ static int load_shdr(struct object *object)
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return M_SUCCESS;
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}
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/**
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* Create the phdr
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*/
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static int create_phdr(struct object *object)
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{
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uint32_t entries = 0;
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for (uint32_t i = 0; i < object->shdr_len; i++) {
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Elf32_Shdr *hdr = &object->shdr[i];
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uint32_t type = B32(hdr->sh_type);
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if (type != SHT_PROGBITS && type != SHT_NOBITS)
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continue;
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entries += 1;
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}
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Elf32_Phdr *phdr = malloc(entries * sizeof(Elf32_Phdr));
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if (phdr == NULL) {
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PERROR("cannot alloc");
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return M_ERROR;
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}
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object->phdr = phdr;
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object->phdr_len = entries;
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object->phdr_local = true;
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uint32_t *mapping = malloc(entries * sizeof(uint32_t));
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if (mapping == NULL) {
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PERROR("cannot alloc");
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return M_ERROR;
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}
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object->phdr_to_shdr_mapping = mapping;
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uint32_t index = 0;
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for (uint32_t i = 0; i < object->shdr_len; i++) {
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Elf32_Shdr *hdr = &object->shdr[i];
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uint32_t type = B32(hdr->sh_type);
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if (type != SHT_PROGBITS && type != SHT_NOBITS)
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continue;
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mapping[index] = i;
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phdr[index++] = (Elf32_Phdr) {
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.p_type = B32(PT_LOAD),
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.p_flags = B32(
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// execute
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((B32(hdr->sh_flags) & SHF_EXECINSTR)
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? PF_X : 0) |
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// write
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((B32(hdr->sh_flags) & SHF_WRITE)
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? PF_W : 0) |
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// read
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((B32(hdr->sh_flags) & SHF_ALLOC)
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? PF_R : 0)
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),
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.p_offset = hdr->sh_offset,
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.p_vaddr = hdr->sh_addr,
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.p_paddr = hdr->sh_addr,
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.p_filesz = hdr->sh_size,
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.p_memsz = hdr->sh_size,
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.p_align = B32(SEC_ALIGN),
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};
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}
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return M_SUCCESS;
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}
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/**
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* Map the phdr
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*/
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static int load_phdr(struct object *object)
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{
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size_t phdr_len = B16(object->ehdr->e_phentsize) *
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B16(object->ehdr->e_phnum);
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size_t phdr_off = B32(object->ehdr->e_phoff);
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object->phdr = (Elf32_Phdr *) (object->mapped + phdr_off);
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object->phdr_len = B16(object->ehdr->e_phnum);
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//size_t phdr_len = B16(object->ehdr->e_phentsize) *
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// B16(object->ehdr->e_phnum);
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if (BOUND_CHK(object, phdr_len, phdr_off)) {
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ERROR("cannot read phdr");
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return M_ERROR;
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}
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//if (phdr_len < 1)
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return create_phdr(object);
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return M_SUCCESS;
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//size_t phdr_off = B32(object->ehdr->e_phoff);
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//object->phdr = (Elf32_Phdr *) (object->mapped + phdr_off);
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//object->phdr_len = B16(object->ehdr->e_phnum);
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//if (BOUND_CHK(object, phdr_len, phdr_off)) {
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// ERROR("cannot read phdr");
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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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@ -231,7 +302,7 @@ static int load_shstrtab(struct object *object)
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*/
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static int load_segments(struct object *object)
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{
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object->segment_len = B16(object->ehdr->e_phnum);
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object->segment_len = object->phdr_len;
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object->segments = malloc(sizeof(struct segment) *
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object->segment_len);
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@ -287,6 +358,8 @@ int object_load(struct object *object, char *path, uint32_t index)
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object->mapped = NULL;
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object->name = path;
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object->index = index;
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object->phdr_local = false;
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object->phdr_to_shdr_mapping = NULL;
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/** load the file */
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if (map_file(object, path))
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@ -331,6 +404,10 @@ void object_free(struct object *obj)
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free(obj->strtabs);
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if (obj->segments != NULL)
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free(obj->segments);
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if (obj->phdr_local)
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free(obj->phdr);
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if (obj->phdr_to_shdr_mapping)
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free(obj->phdr_to_shdr_mapping);
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if (obj->fd > 0)
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close(obj->fd);
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if (obj->mapped != NULL && obj->mapped != MAP_FAILED)
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20
mld/seg.c
20
mld/seg.c
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@ -25,14 +25,8 @@ static int load_phdr(struct object *obj, struct segment *seg, size_t index)
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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 (!PHDR_SHDR_MATCH(seg->phdr, hdr))
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continue;
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uint32_t shndx = obj->phdr_to_shdr_mapping[index];
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Elf32_Shdr *hdr = &obj->shdr[shndx];
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// get name
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uint32_t name = B32(hdr->sh_name);
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@ -52,16 +46,8 @@ static int load_shdr(struct object *obj, struct segment *seg, size_t 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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seg->shdr_idx = shndx;
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return M_SUCCESS;
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}
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@ -56,6 +56,10 @@ int symtab_get(struct symbol_table *symtab, Elf32_Sym **res, const char *name,
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if (strcmp(name, symname) != 0)
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continue;
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// ignore absolute symbols
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if (B16(sym->st_shndx) == SHN_ABS)
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continue;
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// only allow retrevial of local variables from the
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// same object
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if (sym->st_info >> 4 != STB_GLOBAL && symtab->map != NULL &&
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