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-rw-r--r--elf/elf_module.c139
-rw-r--r--elf/elf_module.h5
-rw-r--r--elf/elftest.c19
3 files changed, 143 insertions, 20 deletions
diff --git a/elf/elf_module.c b/elf/elf_module.c
index 0cf77452..24137402 100644
--- a/elf/elf_module.c
+++ b/elf/elf_module.c
@@ -95,7 +95,10 @@ error:
static int image_unload(struct elf_module *module) {
- fclose(module->_file);
+ if (module->_file != NULL) {
+ fclose(module->_file);
+ module->_file = NULL;
+ }
module->_cr_offset = 0;
return 0;
@@ -155,11 +158,36 @@ struct elf_module *module_alloc(const char *name) {
memset(result, 0, sizeof(struct elf_module));
+ INIT_LIST_HEAD(&result->list);
+ INIT_LIST_HEAD(&result->required);
+ INIT_LIST_HEAD(&result->dependants);
+
strncpy(result->name, name, MODULE_NAME_SIZE);
return result;
}
+static struct module_dep *module_dep_alloc(struct elf_module *module) {
+ struct module_dep *result = malloc(sizeof(struct module_dep));
+
+ INIT_LIST_HEAD (&result->list);
+
+ result->module = module;
+
+ return result;
+}
+
+struct elf_module *module_find(const char *name) {
+ struct elf_module *cr_module;
+
+ list_for_each_entry(cr_module, &modules, list) {
+ if (strcmp(cr_module->name, name) == 0)
+ return cr_module;
+ }
+
+ return NULL;
+}
+
// Performs verifications on ELF header to assure that the open file is a
// valid SYSLINUX ELF module.
static int check_header(Elf32_Ehdr *elf_hdr) {
@@ -261,12 +289,12 @@ static int load_segments(struct elf_module *module, Elf32_Ehdr *elf_hdr) {
if (max_addr - min_addr == 0) {
// No loadable segments
fprintf(stderr, "No loadable segments found\n");
- return -1;
+ goto out;
}
if (dyn_addr == 0) {
fprintf(stderr, "No dynamic information segment found\n");
- return -1;
+ goto out;
}
// The minimum address that should be allocated
@@ -283,7 +311,7 @@ static int load_segments(struct elf_module *module, Elf32_Ehdr *elf_hdr) {
max_alloc-min_alloc) != 0) {
fprintf(stderr, "Could not allocate segments\n");
- return -1;
+ goto out;
}
module->base_addr = (Elf32_Addr)(module->module_addr) - min_alloc;
@@ -337,7 +365,8 @@ static int load_segments(struct elf_module *module, Elf32_Ehdr *elf_hdr) {
out:
// Free up allocated memory
- free(pht);
+ if (pht != NULL)
+ free(pht);
return res;
}
@@ -384,6 +413,59 @@ static int prepare_dynlinking(struct elf_module *module) {
return 0;
}
+static int enforce_dependency(struct elf_module *req, struct elf_module *dep) {
+ struct module_dep *crt_dep;
+ struct module_dep *new_dep;
+
+ list_for_each_entry(crt_dep, &req->dependants, list) {
+ if (crt_dep->module == dep) {
+ // The dependency is already enforced
+ return 0;
+ }
+ }
+
+ new_dep = module_dep_alloc(req);
+ list_add(&new_dep->list, &dep->required);
+
+ new_dep = module_dep_alloc(dep);
+ list_add(&new_dep->list, &req->dependants);
+
+ return 0;
+}
+
+static int clear_dependency(struct elf_module *req, struct elf_module *dep) {
+ struct module_dep *crt_dep = NULL;
+ int found = 0;
+
+ list_for_each_entry(crt_dep, &req->dependants, list) {
+ if (crt_dep->module == dep) {
+ found = 1;
+ break;
+ }
+ }
+
+ if (found) {
+ list_del(&crt_dep->list);
+ free(crt_dep);
+ }
+
+ found = 0;
+
+ list_for_each_entry(crt_dep, &dep->required, list) {
+ if (crt_dep->module == req) {
+ found = 1;
+ break;
+ }
+ }
+
+ if (found) {
+ list_del(&crt_dep->list);
+ free(crt_dep);
+ }
+
+ return 0;
+}
+
static int perform_relocation(struct elf_module *module, Elf32_Rel *rel) {
Elf32_Word *dest = module_get_absolute(rel->r_offset, module);
@@ -409,14 +491,20 @@ static int perform_relocation(struct elf_module *module, Elf32_Rel *rel) {
&sym_module);
if (sym_def == NULL) {
- fprintf(stderr, "Cannot perform relocation for symbol %s\n",
+ // This should never happen
+ fprintf(stderr, "Warning: Cannot perform relocation for symbol %s\n",
module->str_table + sym_ref->st_name);
+ // TODO: Return an error
return 0;
}
// Compute the absolute symbol virtual address
sym_addr = (Elf32_Addr)module_get_absolute(sym_def->st_value, sym_module);
+ if (sym_module != module) {
+ // Create a dependency
+ enforce_dependency(sym_module, module);
+ }
}
switch (type) {
@@ -443,8 +531,8 @@ static int perform_relocation(struct elf_module *module, Elf32_Rel *rel) {
*dest += module->base_addr;
break;
default:
- fprintf(stderr, "Relocation type %d not supported\n", type);
- return -1;
+ fprintf(stderr, "Warning: Relocation type %d not supported\n", type);
+ break;
}
return 0;
@@ -569,6 +657,7 @@ static int check_symbols(struct elf_module *module) {
// We have an undefined symbol
if (strong_count == 0 && weak_count == 0) {
fprintf(stderr, "Symbol %s is undefined\n", crt_name);
+ // TODO: Return an error
//return -1;
}
} else {
@@ -587,11 +676,6 @@ int module_load(struct elf_module *module) {
int res;
Elf32_Ehdr elf_hdr;
-
- INIT_LIST_HEAD(&module->list);
- INIT_LIST_HEAD(&module->deps);
-
-
// Get a mapping/copy of the ELF file in memory
res = image_load(module);
@@ -622,15 +706,23 @@ int module_load(struct elf_module *module) {
list_add(&module->list, &modules);
// Perform the relocations
- CHECKED(res, resolve_symbols(module), error);
+ resolve_symbols(module);
// The file image is no longer needed
- CHECKED(res, image_unload(module), error);
+ image_unload(module);
return 0;
error:
+ // Remove the module from the module list (if applicable)
+ list_del_init(&module->list);
+
+ if (module->module_addr != NULL) {
+ free(module->module_addr);
+ module->module_addr = NULL;
+ }
+
image_unload(module);
return res;
@@ -638,7 +730,24 @@ error:
// Unloads the module from the system and releases all the associated memory
int module_unload(struct elf_module *module) {
+ struct module_dep *crt_dep, *tmp;
+ // Make sure nobody needs us
+ if (!list_empty(&module->dependants)) {
+ fprintf(stderr, "Module is required by other modules.\n");
+ return -1;
+ }
+
+ // Remove any dependency information
+ list_for_each_entry_safe(crt_dep, tmp, &module->required, list) {
+ clear_dependency(crt_dep->module, module);
+ }
+
+ // Remove the module from the module list
+ list_del_init(&module->list);
+ // Release the loaded segments
+ free(module->module_addr);
+ // Release the module structure
free(module);
return 0;
diff --git a/elf/elf_module.h b/elf/elf_module.h
index 856717f7..1454ee71 100644
--- a/elf/elf_module.h
+++ b/elf/elf_module.h
@@ -23,7 +23,8 @@ typedef void (*module_exit_func)();
struct elf_module {
char name[MODULE_NAME_SIZE]; // The module name
- struct list_head deps; // Head of module dependency list
+ struct list_head required; // Head of the required modules list
+ struct list_head dependants; // Head of module dependants list
struct list_head list; // The list entry in the module list
module_init_func init_func; // The initialization entry point
@@ -71,6 +72,8 @@ extern int module_load(struct elf_module *module);
// Unloads the module from the system and releases all the associated memory
extern int module_unload(struct elf_module *module);
+extern struct elf_module *module_find(const char *name);
+
extern Elf32_Sym *module_find_symbol(const char *name, struct elf_module *module);
extern Elf32_Sym *global_find_symbol(const char *name, struct elf_module **module);
diff --git a/elf/elftest.c b/elf/elftest.c
index 7013938e..0a38bbe6 100644
--- a/elf/elftest.c
+++ b/elf/elftest.c
@@ -37,6 +37,7 @@ void test_hello() {
int main(int argc, char **argv) {
int res;
+ int i;
struct elf_module *module;
const char *module_name = NULL;
@@ -56,8 +57,8 @@ int main(int argc, char **argv) {
exit(1);
}
- while (argc > 0) {
- module_name = argv[0];
+ for (i=0; i < argc; i++){
+ module_name = argv[i];
module = module_alloc(module_name);
@@ -73,12 +74,22 @@ int main(int argc, char **argv) {
goto error;
}
- argc--;
- argv++;
}
test_hello();
+ for (i=argc-1; i >= 0; i--) {
+ module_name = argv[i];
+ module = module_find(module_name);
+
+ res = module_unload(module);
+
+ if (res < 0) {
+ fprintf(stderr, "Could not unload the module\n");
+ goto error;
+ }
+ }
+
modules_term();
return 0;
generated by cgit v1.2.3 (git 2.25.1) at 2021-03-08 02:33:39 +0000