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fix local vs global symbol names, locals now are local

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This commit is contained in:
Freya Murphy 2024-09-23 10:13:38 -04:00
parent 0eec2bf24d
commit 9d3d75fecb
Signed by: freya
GPG key ID: 744AB800E383AE52
4 changed files with 108 additions and 19 deletions
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29
mld/link.c
View file

@ -44,7 +44,7 @@ static int load_objects(struct linker *linker)
// load obj file
linker->obj_len++;
if (object_load(obj, path))
if (object_load(obj, path, i+1))
return M_ERROR;
skip_obj:
}
@ -55,7 +55,7 @@ skip_obj:
char *path = _STR(PREFIX) "/lib/mips/runtime.o";
struct object *obj = &linker->objects[linker->obj_len++];
if (object_load(obj, path))
if (object_load(obj, path, 0))
return M_ERROR;
#undef _STR
@ -208,7 +208,7 @@ static int relocate_symbol(struct linker *linker, struct object *obj,
new.st_shndx = B16(new_shndx);
new.st_size = 0;
if (symtab_get(&linker->symtab, NULL, name) == M_SUCCESS) {
if (symtab_get(&linker->symtab, NULL, name, obj->index) == M_SUCCESS) {
ERROR("cannot link doubly defiend symbol '%s'", name);
return M_ERROR;
}
@ -216,6 +216,9 @@ static int relocate_symbol(struct linker *linker, struct object *obj,
if (symtab_push(&linker->symtab, &new))
return M_ERROR;
if (symtab_map_push(&linker->symtab_map, obj))
return M_ERROR;
return M_SUCCESS;
}
@ -380,12 +383,12 @@ static int relocate_instruction_rela(struct linker *linker,
/// of this relocation in that segment part
uint32_t off = B32(rel->r_offset);
if (off > seg->size) {
ERROR("relocation in segment '%s' out of bounds", seg->name);
ERROR("invalid relocation in '%s'", seg->obj->name);
return M_ERROR;
}
if (B32(rel->r_info) == 0) {
WARNING("skiping empty relocation entry");
WARNING("skiping empty relocation entry in '%s'", seg->name);
return M_SUCCESS;
}
@ -397,22 +400,21 @@ static int relocate_instruction_rela(struct linker *linker,
/// read the symbol from the relocation
struct symbol_table *symtab = seg->reltab.symtab;
if (idx >= symtab->len) {
ERROR("relocation in segment '%s', symbol index [%d] out of "
"bounds", seg->name, idx);
ERROR("invalid relocation in '%s'", seg->obj->name);
return M_ERROR;
}
Elf32_Sym *sym = &symtab->syms[idx];
char const *sym_name = symtab->strtab->data + B32(sym->st_name);
if (B32(sym->st_name) >= symtab->strtab->len) {
ERROR("relocation symbol name out of bounds");
ERROR("symbol name out of bounds in '%s'", seg->obj->name);
return M_ERROR;
}
// get the new sym for the new vaddr
Elf32_Sym *new_sym = NULL;
if (symtab_get(&linker->symtab, &new_sym, sym_name)) {
ERROR("relocation symbol not found");
if (symtab_get(&linker->symtab, &new_sym, sym_name, seg->obj->index)) {
ERROR("symbol '%s' undefined", sym_name);
return M_ERROR;
}
@ -656,7 +658,7 @@ static int link_executable(struct linker *linker)
ehdr->e_shstrndx = B16(linker->shstrtab_shidx);
Elf32_Sym *entry = NULL;
if (symtab_get(&linker->symtab, &entry, "_start")) {
if (symtab_get(&linker->symtab, &entry, "_start", -1)) {
ERROR("undefined symbol _start");
return M_ERROR;
}
@ -681,6 +683,7 @@ static int linker_init(struct linker *linker, struct linker_arguments *args)
linker->objects = NULL;
linker->segments.size = 0;
linker->symtab.syms = NULL;
linker->symtab_map.meta = NULL;
linker->shstrtab.data = NULL;
linker->strtab.data = NULL;
linker->shdr = NULL;
@ -693,7 +696,10 @@ static int linker_init(struct linker *linker, struct linker_arguments *args)
return M_ERROR;
if (symtab_init(&linker->symtab))
return M_ERROR;
if (symtab_map_init(&linker->symtab_map))
return M_ERROR;
linker->symtab.strtab = &linker->strtab;
linker->symtab.map = &linker->symtab_map;
return M_SUCCESS;
}
@ -712,6 +718,7 @@ static void linker_free(struct linker *linker)
strtab_free(&linker->shstrtab);
strtab_free(&linker->strtab);
symtab_free(&linker->symtab);
symtab_map_free(&linker->symtab_map);
}
int link_files(struct linker_arguments args) {

30
mld/link.h
View file

@ -39,6 +39,9 @@
struct linker;
struct object;
struct segment;
struct string_table;
struct symbol_table;
struct symbol_table_mapping;
///
/// relocation table
@ -79,13 +82,35 @@ struct symbol_table {
Elf32_Sym *syms;
size_t len;
size_t size;
// mapping for global symbol table
// can be null
// (metadata for each symbol)
struct symbol_table_mapping *map;
};
///
/// symbol table map
/// (metadata for each symbol)
///
int symtab_init(struct symbol_table *symtab);
void symtab_free(struct symbol_table *symtab);
int symtab_push(struct symbol_table *symtab, const Elf32_Sym *sym);
int symtab_get(struct symbol_table *symtab, Elf32_Sym **sym, const char *name);
int symtab_get(struct symbol_table *symtab, Elf32_Sym **sym, const char *name,
int32_t obj_idx);
struct symbol_table_mapping {
uint32_t len;
uint32_t size;
struct object **meta;
};
int symtab_map_push(struct symbol_table_mapping *symtabm, struct object *seg);
int symtab_map_init(struct symbol_table_mapping *symtabm);
void symtab_map_free(struct symbol_table_mapping *symtabm);
///
/// segment
@ -211,7 +236,7 @@ struct object {
struct symbol_table *symtabs;
};
int object_load(struct object *object, char *path);
int object_load(struct object *object, char *path, uint32_t index);
void object_free(struct object *object);
@ -235,6 +260,7 @@ struct linker {
struct string_table shstrtab;
struct string_table strtab;
struct symbol_table symtab;
struct symbol_table_mapping symtab_map;
// output elf
Elf32_Ehdr ehdr;

3
mld/obj.c
View file

@ -276,7 +276,7 @@ static int map_file(struct object *obj, char *path)
return M_SUCCESS;
}
int object_load(struct object *object, char *path)
int object_load(struct object *object, char *path, uint32_t index)
{
current_file = path;
@ -286,6 +286,7 @@ int object_load(struct object *object, char *path)
object->strtabs = NULL;
object->mapped = NULL;
object->name = path;
object->index = index;
/** load the file */
if (map_file(object, path))

61
mld/symtab.c
View file

@ -1,5 +1,6 @@
#include <elf.h>
#include <merror.h>
#include <stdio.h>
#include <stdlib.h>
#include <melf.h>
@ -19,6 +20,7 @@ int symtab_init(struct symbol_table *symtab)
}
symtab->syms[0] = (Elf32_Sym){0};
symtab->map = NULL;
return M_SUCCESS;
}
@ -45,16 +47,69 @@ int symtab_push(struct symbol_table *symtab, const Elf32_Sym *sym)
return M_SUCCESS;
}
int symtab_get(struct symbol_table *symtab, Elf32_Sym **res, const char *name)
int symtab_get(struct symbol_table *symtab, Elf32_Sym **res, const char *name,
int32_t obj_idx)
{
for (size_t i = 0; i < symtab->len; i++) {
Elf32_Sym *sym = &symtab->syms[i];
const char *symname = symtab->strtab->data + B32(sym->st_name);
if (strcmp(name, symname) == 0) {
if (strcmp(name, symname) != 0)
continue;
// only allow retrevial of local variables from the
// same object
if (sym->st_info >> 4 != STB_GLOBAL && symtab->map != NULL &&
obj_idx >= 0) {
struct object *obj = symtab->map->meta[i];
if (obj->index != (uint32_t)obj_idx)
continue;
} else if (obj_idx < 0 && sym->st_info >> 4 != STB_GLOBAL) {
// when obj_idx is -1, we only want to reutrn
// global symbols
continue;
}
if (res != NULL)
*res = sym;
return M_SUCCESS;
}
}
return M_ERROR;
}
int symtab_map_push(struct symbol_table_mapping *symtabm, struct object *meta)
{
if (symtabm->len >= symtabm->size) {
uint32_t size = symtabm->size * 2;
void *new = realloc(symtabm->meta,
sizeof(struct object *) * size);
if (new == NULL) {
PERROR("cannot realloc");
return M_ERROR;
}
symtabm->size = size;
symtabm->meta = new;
}
symtabm->meta[symtabm->len++] = meta;
return M_SUCCESS;
}
int symtab_map_init(struct symbol_table_mapping *symtabm)
{
symtabm->len = 0;
symtabm->size = SYMTAB_INIT_LEN;
symtabm->meta = malloc(sizeof(struct object *) * symtabm->size);
if (symtabm->meta == NULL) {
PERROR("cannot alloc");
return M_ERROR;
}
return M_SUCCESS;
}
void symtab_map_free(struct symbol_table_mapping *symtabm)
{
free(symtabm->meta);
}