* Mathieu Desnoyers via Libc-alpha: > Register rseq TLS for each thread (including main), and unregister for > each thread (excluding main). "rseq" stands for Restartable Sequences. > > See the rseq(2) man page proposed here: > https://lkml.org/lkml/2018/9/19/647 > > Those are based on glibc master branch commit 3ee1e0ec5c. > The rseq system call was merged into Linux 4.18. > > The TLS_STATIC_SURPLUS define is increased to leave additional room for > dlopen'd initial-exec TLS, which keeps elf/tst-auditmany working. > > The increase (76 bytes) is larger than 32 bytes because it has not been > increased in quite a while. The cost in terms of additional TLS storage > is quite significant, but it will also obscure some initial-exec-related > dlopen failures. We need another change to get this working on most non-x86 architectures: diff --git a/elf/dl-tls.c b/elf/dl-tls.c index 817bcbbf59..ca13778ca9 100644 --- a/elf/dl-tls.c +++ b/elf/dl-tls.c @@ -134,6 +134,12 @@ void _dl_determine_tlsoffset (void) { size_t max_align = TLS_TCB_ALIGN; + /* libc.so with rseq has TLS with 32-byte alignment. Since TLS is + initialized before audit modules are loaded and slotinfo + information is available, this is not taken into account below in + the audit case. */ + max_align = MAX (max_align, 32U); + size_t freetop = 0; size_t freebottom = 0; This isn't visible on x86-64 because TLS_TCB_ALIGN is already 64 there. I plan to re-test with this fix and push the series. Carlos, is it okay if I fold in the dl-tls.c change if testing looks good? Thanks, Florian
