linux_kernel_helpers: use drgn_error_catch()

As an example of the functionality, refactor the lookup error handling here to use drgn_error_catch(). Signed-off-by: Stephen Brennan <[email protected]>
osandov · Dec 18, 2024 · 7ad4022 · 7ad4022
1 parent 034e20e
commit 7ad4022
Showing 1 changed file with 9 additions and 20 deletions.
diff --git a/libdrgn/linux_kernel_helpers.c b/libdrgn/linux_kernel_helpers.c
@@ -95,10 +95,9 @@ struct drgn_error *linux_helper_direct_mapping_offset(struct drgn_program *prog,
 	uint64_t virt_addr;
 	if (!err) {
 		err = drgn_object_read_unsigned(&tmp, &virt_addr);
-	} else if (err->code == DRGN_ERROR_LOOKUP) {
+	} else if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		// Avoid a confusing error message with our arbitrary variable
 		// name.
-		drgn_error_destroy(err);
 		err = drgn_error_create(DRGN_ERROR_OTHER,
 					"could not find variable in direct mapping");
 	}
@@ -248,8 +247,7 @@ struct drgn_error *linux_helper_per_cpu_ptr(struct drgn_object *res,
 						drgn_object_qualified_type(ptr),
 						ptr_value + per_cpu_offset.uvalue,
 						0);
-	} else if (err->code == DRGN_ERROR_LOOKUP) {
-		drgn_error_destroy(err);
+	} else if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		return drgn_object_copy(res, ptr);
 	} else {
 		return err;
@@ -299,9 +297,8 @@ struct drgn_error *linux_helper_task_thread_info(struct drgn_object *res,
 	if (!err) {
 		// CONFIG_THREAD_INFO_IN_TASK=y
 		return drgn_object_address_of(res, &tmp);
-	} else if (err->code == DRGN_ERROR_LOOKUP) {
+	} else if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		// CONFIG_THREAD_INFO_IN_TASK=n
-		drgn_error_destroy(err);
 		err = drgn_object_member_dereference(&tmp, task, "stack");
 		if (err)
 			return err;
@@ -340,20 +337,17 @@ struct drgn_error *linux_helper_task_cpu(const struct drgn_object *task,
 	if (err)
 		return err;
 	err = drgn_object_member_dereference(&tmp, &tmp, "cpu");
-	if (err && err->code == DRGN_ERROR_LOOKUP) {
-		drgn_error_destroy(err);
+	if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		err = drgn_object_member_dereference(&tmp, task, "cpu");
 	}
 	if (!err) {
 		union drgn_value value;
 		err = drgn_object_read_integer(&tmp, &value);
 		if (!err)
 			*ret = value.uvalue;
-	} else if (err->code == DRGN_ERROR_LOOKUP) {
+	} else if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		// CONFIG_SMP=n
-		drgn_error_destroy(err);
 		*ret = 0;
-		err = NULL;
 	}
 	return err;
 }
@@ -387,8 +381,7 @@ linux_helper_xa_load(struct drgn_object *res,
 			return err;
 		internal_flag = 2;
 		node_min = 4097;
-	} else if (err->code == DRGN_ERROR_LOOKUP) {
-		drgn_error_destroy(err);
+	} else if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		// entry = (void *)xa->rnode
 		err = drgn_object_member_dereference(&entry, xa, "rnode");
 		if (err)
@@ -587,10 +580,8 @@ struct drgn_error *linux_helper_idr_find(struct drgn_object *res,
 		if (err)
 			return err;
 		id -= idr_base.uvalue;
-	} else if (err->code == DRGN_ERROR_LOOKUP) {
+	} else if (!drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		/* idr_base was added in v4.16. */
-		drgn_error_destroy(err);
-	} else {
 		return err;
 	}
 
@@ -787,8 +778,7 @@ struct drgn_error *linux_helper_find_pid(struct drgn_object *res,
 		if (err)
 			return err;
 		return drgn_object_cast(res, qualified_type, &tmp);
-	} else if (err->code == DRGN_ERROR_LOOKUP) {
-		drgn_error_destroy(err);
+	} else if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		err = drgn_program_find_object(drgn_object_program(res),
 					       "pid_hash", NULL,
 					       DRGN_FIND_OBJECT_ANY, &tmp);
@@ -851,8 +841,7 @@ struct drgn_error *linux_helper_pid_task(struct drgn_object *res,
 		    + 1];
 	snprintf(member, sizeof(member), PID_LINKS_FORMAT, pid_type);
 	err = drgn_object_container_of(res, &first, task_struct_type, member);
-	if (err && err->code == DRGN_ERROR_LOOKUP) {
-		drgn_error_destroy(err);
+	if (drgn_error_catch(&err, DRGN_ERROR_LOOKUP)) {
 		/* container_of(first, struct task_struct, pids[pid_type].node) */
 		snprintf(member, sizeof(member), PIDS_NODE_FORMAT, pid_type);
 #undef PID_LINKS_FORMAT