Re: [PATCH v3 0/4] kstrtox: introduce memparse_safe()

Qu Wenruo
2024-01-14T20:01:14Z

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On 2024/1/15 00:12, Andy Shevchenko wrote:
> On Sun, Jan 07, 2024 at 07:28:27AM +1030, Qu Wenruo wrote:
>> On 2024/1/7 01:04, Andy Shevchenko wrote:
>>> On Thu, Jan 04, 2024 at 09:57:47AM +1030, Qu Wenruo wrote:
>
> ...
>
>>> Having test cases is quite good, thanks!
>>> But as I understood what Alexey wanted, is not using the kstrtox files for this.
>>> You can introduce it in the cmdline.c, correct? Just include local "kstrtox.h".
>>
>> Not really possible, all the needed parsing helpers are internal inside
>> kstrtox.c.
>
> I'm not sure I follow. The functions are available to other library (built-in)
> modules.

Did I miss something?

Firstly neither _parse_integer_fixup_radix() nor _parse_integer_limit()
is exported to modules. (No EXPORT_SYMBOL() call on them).

Secondly _parse_integer_fixup_radix() and _parse_integer_limit have "_"
prefix, and is only declared in "lib/kstrtox.h", which means they are
designed only for internal usage.
If putting memparse_safe() into cmdline.c, at least we would need to
include local header "kstrtox.h", and I'm not sure if this is any better
than putting memparse_safe() into kstrtox.[ch].

Finally, I just tried putting memparse_safe() into cmdline.c, and it
failed at linkage stage, even if that offending file has no call to
memparse_safe():

ld: arch/x86/boot/compressed/kaslr.o: in function `memparse_safe':
kaslr.c:(.text+0xbb1): undefined reference to `_parse_integer_fixup_radix'
ld: kaslr.c:(.text+0xbc5): undefined reference to `_parse_integer'
ld: arch/x86/boot/compressed/vmlinux: hidden symbol `_parse_integer'
isn't defined

I can try again but I'm not sure if it's possible to move
memparse_safe() to cmdline.[ch].

>
>> Furthermore, this also means memparse() can not be enhanced due to:
>>
>> - Lack of ways to return errors
>
> What does this mean?

If you want to keep the prototype of memparse() (aka, a drop-in
enhancement), then there is no good way to indicate the errors like
overflow at all.

>
>> - Unable to call the parsing helpers inside cmdline.c
>
> ??? (see above)
>
See above.

Thanks,
Qu

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