Re: libc/libsys split coming soon

On 02/02/2024 23:31, Brooks Davis wrote:
> TL;DR: The implementation of system calls is moving to a seperate
> library (libsys).  No changes are required to existing software (except
> to ensure that libsys is present when building custom disk images).
>
> Code:https://github.com/freebsd/freebsd-src/pull/908
>
> After nearly a decade of intermittent work, I'm about to land a series
> of patches which moves system calls, vdso support, and libc's parsing of
> the ELF auxiliary argument vector into a separate library (libsys).  I
> plan to do this early next week (February 5th).
>
> This change serves three primary purposes:
>    1. It's easier to completely replace system call implementations for
>       tracing or compartmentalization purposes.

Will that affect code that makes syscalls without currently linking to libc?

>    2. It simplifies the implementation of restrictions on system calls such
>       as those implemented by OpenBSD's msyscall(2)
>       (https://man.openbsd.org/msyscall.2).

That's one to ignore for tools that make syscalls outside of the libc 
memory mapping.

>    3. It allows language runtimes to link with libsys for system call
>       implementations without requiring libc.

I see that pagesize is on the list of functions that are moving. There 
are a couple of other functions that might cause me problems if libc 
isn't linked.

Could you do a quick test with an exe linked to libsys but not libc 
running under Valgrind memcheck, please?

A+

Paul