[Kernel] Persist loaded ELF string and symbol tables

codyd51 · Dec 26, 2022 · 8dc7990 · 8dc7990
1 parent b12a3c6
commit 8dc7990
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Showing 3 changed files with 25 additions and 7 deletions.
diff --git a/kernel/kernel/assert.c b/kernel/kernel/assert.c
@@ -97,14 +97,15 @@ bool append(char** buf_head, int32_t* buf_size, const char* format, ...) {
 }
 
 bool symbolicate_and_append__user_mode_frame(int frame_idx, uintptr_t* frame_addr, char** buf_head, int32_t* buf_size) {
-    // If we've traversed to the NULL page, we're probably out of stack frames
     return symbolicate_and_append(frame_idx, frame_addr, buf_head, buf_size);
 }
 
 bool symbolicate_and_append(int frame_idx, uintptr_t* frame_addr, char** buf_head, int32_t* buf_size) {
-    printf("symbolicate(%d, 0x%x)\n", frame_idx, frame_addr);
+    printf("symbolicate(%d, 0x%x) = ", frame_idx, frame_addr);
 
     if (frame_addr < PAGE_SIZE) {
+        // If we've traversed to the NULL page, we're probably out of stack frames
+        printf("NULL\n");
         return false;
     }
 
@@ -134,6 +135,7 @@ bool symbolicate_and_append(int frame_idx, uintptr_t* frame_addr, char** buf_hea
         */
     }
 
+    printf("[%02d] 0x%p %s\n", frame_idx, (uintptr_t)frame_addr, symbol);
     bool can_append_more = append(buf_head, buf_size, "[%02d] 0x%p %s\n", frame_idx, (uintptr_t)frame_addr, symbol);
     if (!can_append_more || found_program_start) {
         return false;

diff --git a/kernel/kernel/multitasking/tasks/task_small.c b/kernel/kernel/multitasking/tasks/task_small.c
@@ -116,7 +116,12 @@ void _thread_destroy(task_small_t* thread) {
 
     // Free kernel stack
     //printf("Free kernel stack 0x%p\n", thread->kernel_stack_malloc_head);
-    kfree(thread->kernel_stack_malloc_head);
+    kfree((void*)thread->kernel_stack_malloc_head);
+
+    // Free the string table and symbol table that were copied to the heap
+    // TODO(PT): These are only heap copies when the underlying program was loaded from an ELF
+    kfree((void*)thread->elf_symbol_table.strtab);
+    kfree((void*)thread->elf_symbol_table.symtab);
 
     if (!thread->is_thread) {
         // Free AMC service if there is one

diff --git a/kernel/kernel/util/elf/elf.c b/kernel/kernel/util/elf/elf.c
@@ -154,7 +154,7 @@ static void _record_elf_symbol_table(void* buf, elf_t* elf) {
 			elf->strtabsz = shdr->size;
 		}
 		if (!strcmp(name, ".symtab")) {
-			elf->symtab = (const char*)((uint8_t*)buf + shdr->offset);
+			elf->symtab = (elf_symbol_t *)((uint8_t *) buf + shdr->offset);
 			elf->symtabsz = shdr->size;
 		}
 	}
@@ -171,9 +171,20 @@ void elf_load_buffer(char* program_name, char** argv, uint8_t* buf, uint32_t buf
 	task_assert(elf_validate_header(hdr), "ELF header validation failed", NULL);
 
 	task_small_t* current_task = tasking_get_task_with_pid(getpid());
-
-	char* string_table = elf_get_string_table(hdr, buf_size);
-	_record_elf_symbol_table(buf, &current_task->elf_symbol_table);
+    char* string_table = elf_get_string_table(hdr, buf_size);
+
+    // Copy the strings/symbols data to the heap, since we're freeing the underlying ELF buffer later on
+    elf_t symbols_data;
+	_record_elf_symbol_table(buf, &symbols_data);
+    void* string_table_copy = kmalloc(symbols_data.strtabsz);
+    memcpy(string_table_copy, symbols_data.strtab, symbols_data.strtabsz);
+    current_task->elf_symbol_table.strtabsz = symbols_data.strtabsz;
+    current_task->elf_symbol_table.strtab = string_table_copy;
+
+    void* symbol_table_copy = kmalloc(symbols_data.symtabsz);
+    memcpy(symbol_table_copy, symbols_data.symtab, symbols_data.symtabsz);
+    current_task->elf_symbol_table.symtabsz = symbols_data.symtabsz;
+    current_task->elf_symbol_table.symtab = symbol_table_copy;
 
 	uintptr_t prog_break = 0;
 	uintptr_t bss_loc = 0;