Date: Mon, 5 Feb 2024 16:02:19 +0000 From: Brooks Davis <brooks@freebsd.org> To: Paul Floyd <paulf2718@gmail.com> Cc: freebsd-current@freebsd.org Subject: Re: libc/libsys split coming soon Message-ID: <ZcEGixWOv98DKw6y@spindle.one-eyed-alien.net> In-Reply-To: <8a34573d-4a6c-4d5d-a771-b39279059547@gmail.com> References: <Zb1tTz5LXuVQ5Caj@spindle.one-eyed-alien.net> <8a34573d-4a6c-4d5d-a771-b39279059547@gmail.com>
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On Sat, Feb 03, 2024 at 05:11:42PM +0100, Paul Floyd wrote: > > 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? Such programs might be broken in these environments but it would depend a lot on the details of both the program and the replacement syscall layer. > > 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. Should someone implement msyscall(2) there will certainly be an opt out mechanism along the usual lines that uses elfctl and procctl. > > 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? Could you suggest a more concrete example? -- Brooks
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