Messages in this thread | | | Subject | Re: [PATCH 3/4] kmod: Return directly if module name is empty in request_module() | From | Tiezhu Yang <> | Date | Mon, 20 Apr 2020 12:08:46 +0800 |
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On 04/18/2020 03:19 PM, Luis Chamberlain wrote: > On Sat, Apr 18, 2020 at 01:58:45PM +0800, Tiezhu Yang wrote: >> On 04/18/2020 01:48 PM, Luis Chamberlain wrote: >>> On Fri, Apr 17, 2020 at 11:45 PM Luis Chamberlain <mcgrof@kernel.org> wrote: >>>> On Sat, Apr 18, 2020 at 01:19:59PM +0800, Tiezhu Yang wrote: >>>>> If module name is empty, it is better to return directly at the beginning >>>>> of request_module() without doing the needless call_modprobe() operation. >>>>> >>>>> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> >>>>> --- >>>>> kernel/kmod.c | 5 +++++ >>>>> 1 file changed, 5 insertions(+) >>>>> >>>>> diff --git a/kernel/kmod.c b/kernel/kmod.c >>>>> index 3cd075c..5851444 100644 >>>>> --- a/kernel/kmod.c >>>>> +++ b/kernel/kmod.c >>>>> @@ -28,6 +28,8 @@ >>>>> >>>>> #include <trace/events/module.h> >>>>> >>>>> +#define MODULE_NOT_FOUND 256 >>>>> + >>>>> /* >>>>> * Assuming: >>>>> * >>>>> @@ -144,6 +146,9 @@ int __request_module(bool wait, const char *fmt, ...) >>>>> if (ret >= MODULE_NAME_LEN) >>>>> return -ENAMETOOLONG; >>>>> >>>>> + if (strlen(module_name) == 0) >>>>> + return MODULE_NOT_FOUND; >>>> I'd rather we just use something standard like -EINVAL. >>>> What do we return if its not found? Then use that value. >>> Also, are we testing for this condition yet? If not can we add one? >> Yes, kmod_test_0001_driver() in tools/testing/selftests/kmod/kmod.sh tests >> this case and expects result MODULE_NOT_FOUND which is 256. > OK I see now I had put: > > errno_name_to_val() > { > case "$1" in > # kmod calls modprobe and upon of a module not found > # modprobe returns just 1... However in the > # kernel we *sometimes* see 256... > MODULE_NOT_FOUND) > echo 256;; > > I found that through testing, however there was nothing set in stone, > nothing documented. While you are at it, can you find the places where > this is returned in the kernel code? We should clear this up and > se things straight. We cannot change what we gave userspace already > though.
Call Trace:
__request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL);
__request_module() returns the exist status of child process, if module name is empty or non-exist, sub_info->retval is 256 after call kernel_wait4().
Should I add this analysis to the commit message?
Thanks, Tiezhu Yang
> > Luis
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