Can't we just add libsys.so to the /usr/lib/libc.so linker script? That would work for everything except static linking?
-Dimitry > On 21 Feb 2024, at 21:00, Brooks Davis <bro...@freebsd.org> wrote: > > TL;DR: you can work around this by adding -lsys to the link line and I > aim to improve the situation soon. > > The sanitizers reach somewhat questionably into libc internals that are > exported to allow rtld to update them. I was unable to find an solution > that didn't break this and I felt that fixing things like closefrom() > using non-deprecated syscalls was more important than avoiding changes > to the sanitizer interface. > > I'm trying to find a way to better solution to the sanitizer. A few > ideas I'm considering: > - Teach clang to add -lsys when linking with sanitizers on sufficently > new systems (con: doesn't fix gcc). > - Make the symbol weak in the sanitizer and complain when it's not > found or call back to using environ. The latter migth have > limitations around direct exec with rtld. > - Relocate __elf_aux_vector to csu so the symbol is always available. > - Adding a new interface to access __elf_aux_vector directly. > > I'll continue to work on this. > > -- Brooks > > On Wed, Feb 21, 2024 at 09:52:23AM +0000, hartmut.bra...@dlr.de wrote: >> Hi, >> >> I updated yesterday and now event a minimal program with >> >> cc -fsanitize=address >> >> produces >> >> ld: error: undefined symbol: __elf_aux_vector >>>>> referenced by sanitizer_linux_libcdep.cpp:950 >>>>> (/usr/src/contrib/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp:950) >>>>> sanitizer_linux_libcdep.o:(__sanitizer::ReExec()) in archive >>>>> /usr/lib/clang/17/lib/freebsd/libclang_rt.asan-x86_64.a >> cc: error: linker command failed with exit code 1 (use -v to see invocation) >> >> I think this is caused by the libsys split. >> >> Cheers, >> Harti >> >> -----Original Message----- >> From: owner-freebsd-curr...@freebsd.org <owner-freebsd-curr...@freebsd.org> >> On Behalf Of Brooks Davis >> Sent: Friday, February 2, 2024 11:32 PM >> To: curr...@freebsd.org >> Subject: libc/libsys split coming soon >> >> 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. >> 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). >> 3. It allows language runtimes to link with libsys for system call >> implementations without requiring libc. >> >> libsys is an auxiliary filter for libc. This means that for any symbol >> defined by both, the libsys version takes precedence at runtime. For system >> call implementations, libc contains empty stubs. For others it contains >> copies of the functions (this could be further refined at a later date). >> The statically linked libc contains the full implementations so linking >> libsys is not required. >> >> Additionally, libthr is now linked with libsys to provide _umtx_op_err(). >> >> The overall implementation follows https://reviews.freebsd.org/D14609, >> but is redone from scratch as multiple commits to facilitate review and >> assist git's rename detection. >> >> Testing: >> - Boot testing on amd64, aarch64, and riscv >> - make tinderbox (prior version, final run in progress) >> - exp-run: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=276391 >> - Kyua tests in poudriere amd64 jails: same 359 failures as with the >> latest freebsdci build >> >> Thanks to Ali Mashtizadeh and Tal Garfinkel for D14609 and many apologies >> for not landing this in a timely manner. Additional thanks to kib@ for many >> rounds of review, markj@ and kib@ for debugging rtld issues exposed by this >> patch, and antoine@ for exp-runs. >> >> Future work: >> - Purely functional interfaces to system calls (no errorno). >> Unfortunately there isn't an obvious way to do this without >> significant (possibly generated) assembly code. >> - Investigate msyscall(2) and pinsyscalls(2). >> - Reduce the size of stubs in libc. I????????ve errored on the >> side of not touching the copies that end up in libc to keep diff >> size down. We might want to generate empty stubs instead. >> >> See also: >> - Solaris Linker and Libraries Guide: >> https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter4-4.html >> >> -- Brooks
