[klibc] [PATCH] Add syscall wrappers required by libkeyutils

[hpa at zytor.com]

On July 27, 2020 2:43:36 AM PDT, Christian Eggers <ceggers at arri.de> wrote:
>On Saturday, 25 July 2020, 23:36:33 CEST, Ben Hutchings wrote:
>> On Wed, 2020-07-08 at 08:37 +0200, Christian Eggers wrote:
>> > ...
>> > libkeyutils usually invokes syscall() directly. As syscall() is not
>> > provided by klibc, libkeyutils has to be slightly modified for
>using the
>> > klibc wrappers.
>>
>> Wouldn't it be more useful for klibc to implement syscall() then?
>
>I hope that somebody else could respond to this question as I am likely
>not
>skilled enough to answer this.
>
>For me it looks like there are currently two cases of using syscalls in
>klibc:
>1. Exporting stubs directly: For many syscalls, automatically generated
>stubs
>are directly exported as symbols for use by the linker. Examples:
>setpgid()/
>getpgid()
>
>2. Using stubs internally for implementing public function. The auto
>generated
>stub is used as base for implementing a C library function. Example:
>exit()
>
>For both cases, the code for the individual stubs is auto generated
>using a
>perl script (with an arch specific "plugin"). All generated stubs call
>common
>arch specific assembly code (__syscall_common).
>
>The lack of the syscall function itself lead me to the (probably wrong)
>conclusion that this is "by design". Should all syscalls use the
>generated
>stubs?
>
>There are some syscalls which are traditionally not implemented by C
>libraries
>(like keyctl, add_key and request_key). These functions are required
>for
>mounting encrypted / authenticated (root) file systems. Programs using
>this
>functionality call syscall() directly. Providing a syscall function in
>klibc
>would avoid klibc specific modifications of such software.
>
>Are there reasons for NOT providing the syscall() function in klibc?
>Who is
>able to implement syscall() for klibc?
>
>regards
>Christian
>
>
>
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syscall(3) is not implemented by design, because it is silently broken on many architectures (mainly 32-bit ones.)
-- 
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