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Add drgn_error_catch() - take 2 #456

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merged 2 commits into from
Dec 18, 2024
Merged

Add drgn_error_catch() - take 2 #456

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60273c4
libdrgn: add drgn_error_catch()
brenns10 Dec 16, 2024
7406ff8
linux_kernel_helpers: use drgn_error_catch()
brenns10 Dec 17, 2024
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18 changes: 18 additions & 0 deletions libdrgn/error.h
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Original file line number Diff line number Diff line change
Expand Up @@ -155,6 +155,24 @@ static inline void drgn_recursion_guard_cleanup(int **guard)
__attribute__((__cleanup__(drgn_recursion_guard_cleanup), __unused__)) \
int *PP_UNIQUE(recursion_count_ptr) = &unique_recursion_count

/**
* Catch a certain kind of @ref drgn_error and free it
*
* If @a errp points to a non-@c NULL error whose code matches @a code, then the
* free the error (if necessary), replace the pointer value with @c NULL, and
* return @c true. Otherwise, return @c false, and @a err is not modified.
*/
static inline bool drgn_error_catch(struct drgn_error **errp,
enum drgn_error_code code)
{
if (*errp && (*errp)->code == code) {
drgn_error_destroy(*errp);
*errp = NULL;
return true;
}
return false;
}

/** @} */

#endif /* DRGN_ERROR_H */
29 changes: 9 additions & 20 deletions libdrgn/linux_kernel_helpers.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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");
}
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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
Expand Down
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