From patchwork Wed Oct 16 15:46:17 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Liebler X-Patchwork-Id: 35048 Received: (qmail 5374 invoked by alias); 16 Oct 2019 15:46:28 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 5364 invoked by uid 89); 16 Oct 2019 15:46:27 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-23.1 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_SHORT, RCVD_IN_DNSWL_LOW, SPF_PASS autolearn=ham version=3.3.1 spammy= X-HELO: mx0a-001b2d01.pphosted.com Subject: Re: [PATCH v3 18/21] nptl: s390: Fix Race conditions in pthread cancellation (BZ#12683) To: libc-alpha@sourceware.org References: <20191014205656.29834-1-adhemerval.zanella@linaro.org> <20191014205656.29834-19-adhemerval.zanella@linaro.org> From: Stefan Liebler Date: Wed, 16 Oct 2019 17:46:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191014205656.29834-19-adhemerval.zanella@linaro.org> x-cbid: 19101615-0008-0000-0000-000003229EF4 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19101615-0009-0000-0000-00004A41B97F Message-Id: <7092d7c2-71fb-b130-9923-d80a9786c6b9@linux.ibm.com> Hi Adhemerval, I've added some notes below to the s390-64 file, but the same applies also for s390-32. I've also attached a diff. I've also recognized that a call starting from e.g. write () involves various shuffling of the argument registers at each level: write (ARGS in r2-r4) -> __syscall_cancel (r2=nr, ARGS in r3-r6 and two stack-slots) --> __syscall_cancel_arch (r2=*ch, r3=nr, ARGS in r4-r6 and three stack-slots) ---> "syscall-instruction" (ARGS in r2-r7) Just as a quick idea (I don't know if there are other limitations), those shuffling instructions could perhaps be omitted if the nr / ch arguments of the __syscall_cancel / __syscall_cancel_arch functions would be the last arguments instead of the first ones. I assume that also other archs could benefit from such an ordering. Bye, Stefan On 10/14/19 10:56 PM, Adhemerval Zanella wrote: > This patch adds the s390 modifications required for the BZ#12683 fix > by adding the arch-specific cancellation syscall bridge. > > Checked on s390-linux-gnu and s390x-linux-gnu. > --- > .../sysv/linux/s390/s390-32/syscall_cancel.S | 83 +++++++++++++++++++ > .../sysv/linux/s390/s390-64/syscall_cancel.S | 83 +++++++++++++++++++ > 2 files changed, 166 insertions(+) > create mode 100644 sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S > create mode 100644 sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S > > diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S b/sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S > new file mode 100644 > index 0000000000..3c934addbd > --- /dev/null > +++ b/sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S > @@ -0,0 +1,83 @@ > +/* Cancellable syscall wrapper. Linux/s390 version. > + Copyright (C) 2019 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#include > + > +/* long int __syscall_cancel_arch (int *cancelhandling, > + __syscall_arg_t nr, > + __syscall_arg_t arg1, > + __syscall_arg_t arg2, > + __syscall_arg_t arg3, > + __syscall_arg_t arg4, > + __syscall_arg_t arg5, > + __syscall_arg_t arg6) */ > + > +ENTRY (__syscall_cancel_arch) > + stm %r6,%r15,24(%r15) > + cfi_offset (6, -72) > + cfi_offset (7, -68) > + cfi_offset (8, -64) > + cfi_offset (9, -60) > + cfi_offset (10, -56) > + cfi_offset (11, -52) > + cfi_offset (12, -48) > + cfi_offset (13, -44) > + cfi_offset (14, -40) > + cfi_offset (15, -36) > + ahi %r15, -96 > + cfi_def_cfa_offset (192) > + > + .globl __syscall_cancel_arch_start > + .type __syscall_cancel_arch_start,@function > +__syscall_cancel_arch_start: > + l %r0, 0(%r2) > + tml %r0, 4 > + jne 1f > + lr %r1, %r3 > + lr %r2, %r4 > + lr %r3, %r5 > + lr %r4, %r6 > + l %r5, 192(%r15) > + l %r6, 196(%r15) > + l %r7, 200(%r15) > + svc 0 > + > + .globl __syscall_cancel_arch_end > + .type __syscall_cancel_arch_end,@function > +__syscall_cancel_arch_end: > + l %r4, 152(%r15) > + lm %r6, %r15, 120(%r15) > + cfi_remember_state > + cfi_restore (15) > + cfi_restore (14) > + cfi_restore (13) > + cfi_restore (12) > + cfi_restore (11) > + cfi_restore (10) > + cfi_restore (9) > + cfi_restore (8) > + cfi_restore (7) > + cfi_restore (6) > + cfi_def_cfa_offset (96) > + br %r4 > + > +1: > + cfi_restore_state > + brasl %r14, __syscall_do_cancel > +END (__syscall_cancel_arch) > +libc_hidden_def (__syscall_cancel_arch) > diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S b/sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S > new file mode 100644 > index 0000000000..3480020fbb > --- /dev/null > +++ b/sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S > @@ -0,0 +1,83 @@ > +/* Cancellable syscall wrapper. Linux/s390x version. > + Copyright (C) 2019 Free Software Foundation, Inc. > + This file is part of the GNU C Library. > + > + The GNU C Library is free software; you can redistribute it and/or > + modify it under the terms of the GNU Lesser General Public > + License as published by the Free Software Foundation; either > + version 2.1 of the License, or (at your option) any later version. > + > + The GNU C Library is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + Lesser General Public License for more details. > + > + You should have received a copy of the GNU Lesser General Public > + License along with the GNU C Library; if not, see > + . */ > + > +#include > + > +/* long int __syscall_cancel_arch (int *cancelhandling, > + __syscall_arg_t nr, > + __syscall_arg_t arg1, > + __syscall_arg_t arg2, > + __syscall_arg_t arg3, > + __syscall_arg_t arg4, > + __syscall_arg_t arg5, > + __syscall_arg_t arg6) */ > + > +ENTRY (__syscall_cancel_arch) > + stmg %r6, %r15, 48(%r15) Please omit the spaces between the operands to have the same style as below (the same applies to multiple instructions in the s390-32 file. > + cfi_offset (6, -112) Please use e.g. %r6 instead of just 6 for the cfi statements here and below for cfi_restore. > + cfi_offset (7, -104) > + cfi_offset (8, -96) > + cfi_offset (9, -88) > + cfi_offset (10, -80) > + cfi_offset (11, -72) > + cfi_offset (12, -64) > + cfi_offset (13, -56) > + cfi_offset (14, -48) > + cfi_offset (15, -40) > + aghi %r15,-160 > + cfi_def_cfa_offset (320) I think the new stack frame is not needed at all. The kernel does not clobber any registers and also does not need an own stack frame. (I've recognized that syscall.S also contains an extra frame and I will work on a patch) Then r8-r15 are not clobbered here and we just have to store and restore r6 and r7. > + > + .globl __syscall_cancel_arch_start > + .type __syscall_cancel_arch_start,@function > +__syscall_cancel_arch_start: Could you add the comments like e.g. done in the x86_64 patch? /* if (*cancelhandling & CANCELED_BITMASK) __syscall_do_cancel() */ > + l %r0,0(%r2) > + tmll %r0,4 We can combine l and tmll here: tm 3(%r2),4 > + jne 1f /* Issue a 6 argument syscall, the nr [%r1] being the syscall number. */ > + lgr %r1,%r3 > + lgr %r2,%r4 > + lgr %r3,%r5 > + lgr %r4,%r6 > + lg %r5,320(%r15) > + lg %r6,328(%r15) > + lg %r7,336(%r15) We can use lmg in order to load r5-r7. > + svc 0 > + > + .globl __syscall_cancel_arch_end > + .type __syscall_cancel_arch_end,@function > +__syscall_cancel_arch_end: > + lg %r4,272(%r15) > + lmg %r6,%r15,208(%r15) > + cfi_remember_state > + cfi_restore (15) > + cfi_restore (14) > + cfi_restore (13) > + cfi_restore (12) > + cfi_restore (11) > + cfi_restore (10) > + cfi_restore (9) > + cfi_restore (8) > + cfi_restore (7) > + cfi_restore (6) > + cfi_def_cfa_offset (160) > + br %r4 > + > +1: > + cfi_restore_state > + brasl %r14, __syscall_do_cancel We can just use jg __syscall_do_cancel for this not-returning-tail-call. (For the s390-32 part: Both instructions are z900 instructions, but as gcc has removed support for g5 and g6, this is okay at this point of time) > +END (__syscall_cancel_arch) > +libc_hidden_def (__syscall_cancel_arch) > diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S b/sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S index 3c934addbd..faa32b3e99 100644 --- a/sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S +++ b/sysdeps/unix/sysv/linux/s390/s390-32/syscall_cancel.S @@ -28,56 +28,38 @@ __syscall_arg_t arg6) */ ENTRY (__syscall_cancel_arch) - stm %r6,%r15,24(%r15) - cfi_offset (6, -72) - cfi_offset (7, -68) - cfi_offset (8, -64) - cfi_offset (9, -60) - cfi_offset (10, -56) - cfi_offset (11, -52) - cfi_offset (12, -48) - cfi_offset (13, -44) - cfi_offset (14, -40) - cfi_offset (15, -36) - ahi %r15, -96 - cfi_def_cfa_offset (192) + stm %r6,%r7,24(%r15) + cfi_offset (%r6, -72) + cfi_offset (%r7, -68) .globl __syscall_cancel_arch_start .type __syscall_cancel_arch_start,@function __syscall_cancel_arch_start: - l %r0, 0(%r2) - tml %r0, 4 + /* if (*cancelhandling & CANCELED_BITMASK) + __syscall_do_cancel() */ + tm 3(%r2),4 jne 1f - lr %r1, %r3 - lr %r2, %r4 - lr %r3, %r5 - lr %r4, %r6 - l %r5, 192(%r15) - l %r6, 196(%r15) - l %r7, 200(%r15) + + /* Issue a 6 argument syscall, the nr [%r1] being the syscall + number. */ + lr %r1,%r3 + lr %r2,%r4 + lr %r3,%r5 + lr %r4,%r6 + lm %r5,%r7,96(%r15) svc 0 .globl __syscall_cancel_arch_end .type __syscall_cancel_arch_end,@function __syscall_cancel_arch_end: - l %r4, 152(%r15) - lm %r6, %r15, 120(%r15) + lm %r6,%r7,24(%r15) cfi_remember_state - cfi_restore (15) - cfi_restore (14) - cfi_restore (13) - cfi_restore (12) - cfi_restore (11) - cfi_restore (10) - cfi_restore (9) - cfi_restore (8) - cfi_restore (7) - cfi_restore (6) - cfi_def_cfa_offset (96) - br %r4 + cfi_restore (%r7) + cfi_restore (%r6) + br %r14 1: cfi_restore_state - brasl %r14, __syscall_do_cancel + jg __syscall_do_cancel END (__syscall_cancel_arch) libc_hidden_def (__syscall_cancel_arch) diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S b/sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S index 3480020fbb..7ea6bf48be 100644 --- a/sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S +++ b/sysdeps/unix/sysv/linux/s390/s390-64/syscall_cancel.S @@ -28,56 +28,38 @@ __syscall_arg_t arg6) */ ENTRY (__syscall_cancel_arch) - stmg %r6, %r15, 48(%r15) - cfi_offset (6, -112) - cfi_offset (7, -104) - cfi_offset (8, -96) - cfi_offset (9, -88) - cfi_offset (10, -80) - cfi_offset (11, -72) - cfi_offset (12, -64) - cfi_offset (13, -56) - cfi_offset (14, -48) - cfi_offset (15, -40) - aghi %r15,-160 - cfi_def_cfa_offset (320) + stmg %r6,%r7,48(%r15) + cfi_offset (%r6, -112) + cfi_offset (%r7, -104) .globl __syscall_cancel_arch_start .type __syscall_cancel_arch_start,@function __syscall_cancel_arch_start: - l %r0,0(%r2) - tmll %r0,4 + /* if (*cancelhandling & CANCELED_BITMASK) + __syscall_do_cancel() */ + tm 3(%r2),4 jne 1f + + /* Issue a 6 argument syscall, the nr [%r1] being the syscall + number. */ lgr %r1,%r3 lgr %r2,%r4 lgr %r3,%r5 lgr %r4,%r6 - lg %r5,320(%r15) - lg %r6,328(%r15) - lg %r7,336(%r15) + lmg %r5,%r7,160(%r15) svc 0 .globl __syscall_cancel_arch_end .type __syscall_cancel_arch_end,@function __syscall_cancel_arch_end: - lg %r4,272(%r15) - lmg %r6,%r15,208(%r15) + lmg %r6,%r7,48(%r15) cfi_remember_state - cfi_restore (15) - cfi_restore (14) - cfi_restore (13) - cfi_restore (12) - cfi_restore (11) - cfi_restore (10) - cfi_restore (9) - cfi_restore (8) - cfi_restore (7) - cfi_restore (6) - cfi_def_cfa_offset (160) - br %r4 + cfi_restore (%r7) + cfi_restore (%r6) + br %r14 1: cfi_restore_state - brasl %r14, __syscall_do_cancel + jg __syscall_do_cancel END (__syscall_cancel_arch) libc_hidden_def (__syscall_cancel_arch)