Re: [PATCH 3/9] kernel/api: add debugfs interface for kernel API specifications

Sasha Levin
2026-03-13T16:27:34Z

On Fri, Mar 13, 2026 at 04:32:23PM +0100, Greg Kroah-Hartman wrote:
>On Fri, Mar 13, 2026 at 11:09:13AM -0400, Sasha Levin wrote:
>> Add a debugfs interface to expose kernel API specifications at runtime.
>> This allows tools and users to query the complete API specifications
>> through the debugfs filesystem.
>>
>> The interface provides:
>> - /sys/kernel/debug/kapi/list - lists all available API specifications
>> - /sys/kernel/debug/kapi/specs/<name> - detailed info for each API
>>
>> Each specification file includes:
>> - Function name, version, and descriptions
>> - Execution context requirements and flags
>> - Parameter details with types, flags, and constraints
>> - Return value specifications and success conditions
>> - Error codes with descriptions and conditions
>> - Locking requirements and constraints
>> - Signal handling specifications
>> - Examples, notes, and deprecation status
>>
>> This enables runtime introspection of kernel APIs for documentation
>> tools, static analyzers, and debugging purposes.
>>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>> Documentation/dev-tools/kernel-api-spec.rst | 88 ++--
>
>You are removing stuff from the file you created earlier in this patch
>series, is that ok?

Sorry, just a rebasing artifact from shuffling patches around. I'll fix it.

>> --- /dev/null
>> +++ b/kernel/api/kapi_debugfs.c
>> @@ -0,0 +1,503 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Kernel API specification debugfs interface
>> + *
>> + * This provides a debugfs interface to expose kernel API specifications
>> + * at runtime, allowing tools and users to query the complete API specs.
>> + */
>
>No copyright line? :)

I'll add one.

>And this is, a totally and crazy interface with debugfs, I love it!

Thanks :)

>Two minor minor nits:
>
>> +static int __init kapi_debugfs_init(void)
>> +{
>> + struct kernel_api_spec *spec;
>> + struct dentry *spec_dir;
>> +
>> + /* Create main directory */
>> + kapi_debugfs_root = debugfs_create_dir("kapi", NULL);
>> +
>> + /* Create list file */
>> + debugfs_create_file("list", 0444, kapi_debugfs_root, NULL, &kapi_list_fops);
>> +
>> + /* Create specs subdirectory */
>> + spec_dir = debugfs_create_dir("specs", kapi_debugfs_root);
>> +
>> + /* Create a file for each API spec */
>> + for (spec = __start_kapi_specs; spec < __stop_kapi_specs; spec++) {
>> + debugfs_create_file(spec->name, 0444, spec_dir, spec, &kapi_spec_fops);
>> + }
>
>No need for { }

ack

>> +
>> + pr_info("Kernel API debugfs interface initialized\n");
>
>When code is working properly, it should be quiet, no need for this as
>initializing this can not fail.

ack

--
Thanks,
Sasha