FreeBSD source tree https://cgit-dev.freebsd.org/src-test2/atom?h=master 2020-02-09T12:22:43Z 2020-02-09T12:22:43Z Konstantin Belousov kib@FreeBSD.org 2020-02-09T12:22:43Z urn:sha1:aef199e56393cbe7df59c27733d41c6add7b560b This allows for rtld to not issue two sigprocmask(2) syscalls for each symbol binding operation in single-threaded processes. Rtld needs to block signals as part of locking to ensure signal safety of the bind process, because signal handlers might need to lazily resolve symbol references. As result, number of syscalls issued on startup by simple programs not using libthr, is typically reduced 2x. For instance, for hello world, I see: non-sigfastblock # (truss ./hello > /dev/null) |& wc -l 63 sigfastblock # (truss ./hello > /dev/null) |& wc -l 37 Tested by: pho Disscussed with: cem, emaste, jilles Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D12773 2019-06-30T11:49:58Z Alex Richardson arichardson@FreeBSD.org 2019-06-30T11:49:58Z urn:sha1:b54a59f3ba244b76a34488090653df687527e53c Currently RTLD is linked against libc_nossp_pic which means that any libc symbol used in rtld can pull in a lot of depedencies. This was causing symbol such as __libc_interposing and all the pthread stubs to be included in RTLD even though they are not required. It turns out most of these dependencies can easily be avoided by providing overrides inside of rtld. This change is motivated by CHERI, where we have an experimental ABI that requires additional relocation processing to allow the use of function pointers inside of rtld. Instead of adding this self-relocation code to RTLD I attempted to remove most function pointers from RTLD and discovered that most of them came from the libc dependencies instead of being actually used inside rtld. A nice side-effect of this change is that rtld is now 22% smaller on amd64. text data bss dec hex filename 0x21eb6 0xce0 0xe60 145910 239f6 /home/alr48/ld-elf-x86.before.so.1 0x1a6ed 0x728 0xdd8 113645 1bbed /home/alr48/ld-elf-x86.after.so.1 The number of R_X86_64_RELATIVE relocations that need to be processed on startup has also gone down from 368 to 187 (almost 50% less). Reviewed By: kib Differential Revision: https://reviews.freebsd.org/D20663 2018-10-29T21:08:28Z Alex Richardson arichardson@FreeBSD.org 2018-10-29T21:08:28Z urn:sha1:3ab5b6bd979c53e17056ed91f6fe6f0358ed72c9 Reviewed By: kib Approved By: brooks (mentor) Differential Revision: https://reviews.freebsd.org/D17154 2017-11-27T15:25:02Z Pedro F. Giffuni pfg@FreeBSD.org 2017-11-27T15:25:02Z urn:sha1:e6209940dee96d8deed5ee7c2b2663512dd55db9 Mainly focus on files that use BSD 2-Clause license, however the tool I was using misidentified many licenses so this was mostly a manual - error prone - task. The Software Package Data Exchange (SPDX) group provides a specification to make it easier for automated tools to detect and summarize well known opensource licenses. We are gradually adopting the specification, noting that the tags are considered only advisory and do not, in any way, superceed or replace the license texts. No functional change intended. 2017-01-10T19:26:55Z Konstantin Belousov kib@FreeBSD.org 2017-01-10T19:26:55Z urn:sha1:b88a8d3d1d04a73764b09d94065ff4678cde6ce3 Obtaining compat rtld lock in write mode sets process signal mask to block all signals. Previous mask is stored in the global variable oldsigmask. If a lock is write-locked while another lock is already write-locked, oldsigmask is overwritten by the total mask and on the last unlock, all signals except traps appear to be blocked. Fix this by counting the write-lock nested level, and only storing to oldsigmask/restoring from it at the outermost level. Masking signals disables involuntary preemption for libc_r, and there could be no voluntary context switches in the locked code (dl_iterate_phdr(3) keeps a lock around user callback, but it was added long after libc_r was renounced). Due to this, remembering the level in the global variable after the lock is obtained should be safe, because no two libc_r threads can acquire different write locks in parallel. PR: 215826 Reported by: kami Tested by: yamagi@yamagi.org (previous version) To be reviewed by: kan Sponsored by: The FreeBSD Foundation MFC after: 2 weeks 2017-01-10T17:05:34Z Konstantin Belousov kib@FreeBSD.org 2017-01-10T17:05:34Z urn:sha1:e7bfd34bdf8fd0f38f652234801f6639692a7c64 Sponsored by: The FreeBSD Foundation MFC after: 1 week 2015-03-29T18:53:21Z Konstantin Belousov kib@FreeBSD.org 2015-03-29T18:53:21Z urn:sha1:0c4f9ecde30ac34f0f849a31244158bd149bdac0 rtld on x86 to be hidden. This is a micro-optimization, which allows intrinsic references inside rtld to be handled without indirection through PLT. The visibility of rtld symbols for other objects in the symbol namespace is controlled by a version script. Reviewed by: kan, jilles Sponsored by: The FreeBSD Foundation MFC after: 2 weeks 2014-05-24T10:23:06Z Konstantin Belousov kib@FreeBSD.org 2014-05-24T10:23:06Z urn:sha1:1c70d00733741b90a62c44b0a5cea6a1971b65b6 mode. This allows the binder to be functional in the child after the fork (assuming no lazy loading of a filter is needed), but other rtld services which require write lock on rtld_bind_lock cause deadlock, if called by child. Change the _rtld_atfork() to lock the bind lock in write mode, making the rtld fully functional after the fork. Pre-resolve the symbols which are called by the libthr' fork() interposer, since dynamic resolution causes deadlock due to the rtld_bind_lock already owned in the write mode. Reported and tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 2 weeks 2011-08-24T20:05:13Z Konstantin Belousov kib@FreeBSD.org 2011-08-24T20:05:13Z urn:sha1:0e9a2605200b721fdfcf32d2c95f79a81fc84352 C runtime services, like printf(). Unfortunately, the multithread-safeness measures in the libc do not work in rtld environment. Rip the kernel printf() implementation and use it in the rtld instead of libc version. This printf does not require any shared global data and thus is mt-safe. Systematically use rtld_printf() and related functions, remove the calls to err(3). Note that stdio is still pulled from libc due to libmap implementaion using fopen(). This is safe but unoptimal, and can be changed later. Reported and tested by: pgj Diagnosed and reviewed by: kan (previous version) Approved by: re (bz) 2011-02-09T09:20:27Z Konstantin Belousov kib@FreeBSD.org 2011-02-09T09:20:27Z urn:sha1:a7bc470a84ecda53b360df72d35434bef1658131 lock upgrade in rtld. There is no need to care about the mask, which causes a lot of unneeded sigprocmask(2) calls during each symbol lookup.