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Commit 19a76608 authored by Alessandro Di Federico's avatar Alessandro Di Federico
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Added debug information and safety checks

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with 67 additions and 29 deletions
loader.c
+ 67
− 29
View file @ 19a76608
......@@ -85,7 +85,8 @@ typedef uint32_t Elf_MemSz;
typedef unsigned char mem_t;
// Proof that macros lead to bad stuffs
#define DBG_MSG(format, ...) printf(format "\n", ##__VA_ARGS__ )
#define DBG_MSG(format, ...) printf("[%s:%d] " format "\n", __FILE__, __LINE__, \
##__VA_ARGS__ )
#define CHECK_ARGS_RET(condition, ret) \
do { \
if (!(condition)) { \
......@@ -165,16 +166,22 @@ typedef struct elf_object {
typedef unsigned long elf_hash_t;
// Linker generated symbols
extern Elf_Dyn _DYNAMIC;
// Declarations
static int eld_elf_object_handle_dyn(elf_object_t *this);
elf_hash_t eld_elf_hash(char *cursor) {
elf_hash_t result;
while (*cursor) {
elf_hash_t tmp;
result = (result << 4) + *cursor++;
if ((tmp = result & 0xf0000000))
result ^= tmp >> 24;
result &= ~tmp;
}
return result;
elf_hash_t result;
while (*cursor) {
elf_hash_t tmp;
result = (result << 4) + *cursor++;
if ((tmp = result & 0xf0000000))
result ^= tmp >> 24;
result &= ~tmp;
}
return result;
}
/**
......@@ -207,10 +214,15 @@ static void eld_elf_object_destroy(elf_object_t *this) {
* Initialize ELF object list
*/
int eld_init() {
int result = SUCCESS;
DBG_MSG("Initializing ELD dynamic loader");
SLIST_INIT(&elves);
elf_object_t *main_elf = eld_elf_object_new(STR_PAR("main"));
RETURN_ON_NULL(main_elf);
main_elf->dynamic_info_section = &_DYNAMIC;
RETURN_ON_ERROR(eld_elf_object_handle_dyn(main_elf));
SLIST_INSERT_HEAD(&elves, main_elf, next);
return SUCCESS;
......@@ -237,7 +249,8 @@ static int eld_elf_object_get_symbol(elf_object_t *this, char *target_name,
Elf_Sym **target_symbol,
Elf_Sym **weak_symbol,
elf_object_t **weak_elf) {
CHECK_ARGS(this && target_name && target_symbol && weak_symbol && weak_elf);
CHECK_ARGS(this && target_name && target_symbol && weak_symbol && weak_elf &&
this->dynamic_info.hash_buckets && this->dynamic_info.hash_chains);
// TODO: lookup cache
// TOOD: gnu hash
......@@ -299,31 +312,49 @@ static int eld_elf_object_find_symbol(elf_object_t *this, char *name,
Elf_Sym *weak_match = NULL;
elf_object_t *weak_match_elf = NULL;
if (eld_elf_object_get_symbol(this, name, hash, match,
&weak_match, &weak_match_elf) == SUCCESS) {
int result = SUCCESS;
DBG_MSG("Looking for symbol \"%s\" in the library \"%s\" itself", name,
this->soname);
if ((result =
eld_elf_object_get_symbol(this, name, hash, match,
&weak_match, &weak_match_elf)) == SUCCESS) {
*match_elf = this;
DBG_MSG("Symbol \"%s\" found in the library \"%s\" itself", name,
this->soname);
} else {
if (result != ERROR_SYMBOL_NOT_FOUND && result != ERROR_WEAK_RESULT) {
return result;
}
elf_object_t *loaded_elf = NULL;
SLIST_FOREACH(loaded_elf, &elves, next) {
if (eld_elf_object_get_symbol(loaded_elf, name, hash, match,
&weak_match,
&weak_match_elf) == SUCCESS) {
DBG_MSG("Looking for symbol \"%s\" in the \"%s\" library", name,
loaded_elf->soname);
if ((result = eld_elf_object_get_symbol(loaded_elf, name, hash, match,
&weak_match,
&weak_match_elf)) == SUCCESS) {
*match_elf = loaded_elf;
DBG_MSG("Symbol \"%s\" found in the \"%s\" library", name,
loaded_elf->soname);
break;
} else if (result != ERROR_SYMBOL_NOT_FOUND &&
result != ERROR_WEAK_RESULT) {
return result;
}
}
}
if (!*match && weak_match) {
DBG_MSG("Symbol \"%s\" has a weak match in \"%s\" library", name,
weak_match_elf->soname);
*match = weak_match;
*match_elf = weak_match_elf;
}
if (!match) {
DBG_MSG("Symbol \"%s\" not found", name);
}
return match ? SUCCESS : ERROR_SYMBOL_NOT_FOUND;
}
......@@ -338,6 +369,7 @@ static int eld_elf_object_find_symbol(elf_object_t *this, char *name,
static int eld_elf_object_relocate(elf_object_t *this,
int reloc_index, int reloc_size_index) {
CHECK_ARGS(this);
int result = SUCCESS;
// We only support relocation with addend
int reloc_count =
......@@ -347,6 +379,8 @@ static int eld_elf_object_relocate(elf_object_t *this,
Elf_Rela *first_reloc =
(Elf_Rela *) this->dynamic_info.basic[reloc_index].d_ptr;
DBG_MSG("Relocating section %d (size: %d)", reloc_index, reloc_count);
int i = 0;
Elf_Rela *reloc = first_reloc;
Elf_Addr *patch_location = NULL;
......@@ -376,11 +410,8 @@ static int eld_elf_object_relocate(elf_object_t *this,
Elf_Sym *match = NULL;
elf_object_t *match_elf = NULL;
if (eld_elf_object_find_symbol(this, name, hash, &match,
&match_elf) != SUCCESS) {
DBG_MSG("Couldn't find symbol \"%s\".", name);
return ERROR_SYMBOL_NOT_FOUND;
}
RETURN_ON_ERROR(eld_elf_object_find_symbol(this, name, hash, &match,
&match_elf));
Elf_Addr symbol_address = match->st_value;
......@@ -495,13 +526,16 @@ static int eld_elf_object_load(elf_object_t *this) {
Elf_MemSz to_allocate = max_address - min_address;
this->load_address = malloc(to_allocate);
this->elf_offset = this->load_address - min_address;
if (!this->load_address) {
DBG_MSG("Cannot allocate the necessary memory (0x%x bytes)", to_allocate);
return ERROR_OUT_OF_MEMORY;
} else {
DBG_MSG("The library has been loaded at %p", this->load_address);
}
this->elf_offset = this->load_address - min_address;
// Load from file
for (Elf_Phdr *program_header = program_header_begin;
program_header < program_header_end; program_header++) {
......@@ -524,6 +558,10 @@ static int eld_elf_object_load(elf_object_t *this) {
}
}
// Update pointers
this->dynamic_info_section = (Elf_Dyn *) (this->elf_offset +
(Elf_Addr) this->dynamic_info_section);
return SUCCESS;
}
......@@ -539,6 +577,8 @@ static int eld_elf_object_load(elf_object_t *this) {
static int eld_elf_object_handle_dyn(elf_object_t *this) {
CHECK_ARGS(this && this->dynamic_info_section);
int result = SUCCESS;
// First pass over the dynamic entries
for (Elf_Dyn *dynamic_info_entry = this->dynamic_info_section;
dynamic_info_entry->d_tag != DT_NULL;
......@@ -562,8 +602,6 @@ static int eld_elf_object_handle_dyn(elf_object_t *this) {
if (this->dynamic_info.basic[to_rebase[counter]].d_ptr) {
this->dynamic_info.basic[to_rebase[counter]].d_ptr +=
(Elf_Addr) this->elf_offset;
DBG_MSG("%d @ 0x%x", to_rebase[counter],
this->dynamic_info.basic[to_rebase[counter]].d_ptr);
}
}
......@@ -574,8 +612,7 @@ static int eld_elf_object_handle_dyn(elf_object_t *this) {
if (this->dynamic_info.basic[DT_SONAME].d_ptr) {
this->dynamic_info.basic[DT_SONAME].d_ptr += (Elf_Addr) this->strtab;
this->soname = (char *) this->dynamic_info.basic[DT_SONAME].d_ptr;
DBG_MSG("%d @ 0x%p: %s", DT_SONAME, this->soname,
(char *) this->soname);
DBG_MSG("Loading \"%s\"", (char *) this->soname);
}
if (this->dynamic_info.basic[DT_RPATH].d_ptr) {
......@@ -631,10 +668,10 @@ static int eld_elf_object_handle_dyn(elf_object_t *this) {
}
// TODO: handle errors
eld_elf_object_relocate(this, DT_REL, DT_RELSZ);
eld_elf_object_relocate(this, DT_RELA, DT_RELASZ);
RETURN_ON_ERROR(eld_elf_object_relocate(this, DT_REL, DT_RELSZ));
RETURN_ON_ERROR(eld_elf_object_relocate(this, DT_RELA, DT_RELASZ));
// TODO: implement lazy loading (see _dl_md_reloc_got)
eld_elf_object_relocate(this, DT_JMPREL, DT_PLTRELSZ);
RETURN_ON_ERROR(eld_elf_object_relocate(this, DT_JMPREL, DT_PLTRELSZ));
t_init_function init_function =
(t_init_function) this->dynamic_info.basic[DT_INIT].d_ptr;
......@@ -693,6 +730,7 @@ fail:
}
void *dlopen(mem_t *filename, int flag) {
DBG_MSG("dlopen(%p, %x)", filename, flag);
CHECK_ARGS_RET(filename, NULL);
// TODO: flags
......
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