From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1791) id 17DEC3858C2D; Tue, 11 Apr 2023 14:18:36 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 17DEC3858C2D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1681222716; bh=i0lMXRB9B9aabHwBE6Zw7RwAvKtudzkpReo2DEKcPQk=; h=From:To:Subject:Date:From; b=TUhxVl8+9+pHXDraOQ148V/elxy5Ua0a1jX0aifGf4Mg4rWMWcTPXtKXJvILiept7 FD7yF9+SU3JSn7pbrQYzHwLNL5kmiLGUmyOP8GiczBDKwI2elC4S7NGw2nsEPrHlLC lyvPrE5KtTKB53EBSY9U9HV+FZylN/zXCV63SEvo= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Adhemerval Zanella To: glibc-cvs@sourceware.org Subject: [glibc/azanella/bz12683] i386: Fix Race conditions in pthread cancellation [BZ#12683] X-Act-Checkin: glibc X-Git-Author: Adhemerval Zanella X-Git-Refname: refs/heads/azanella/bz12683 X-Git-Oldrev: 2139a68f2a0d63b53865779a4d005f1f1aa150a8 X-Git-Newrev: c9c8107f3cda81810e3f1441fdb54695f3a2df90 Message-Id: <20230411141836.17DEC3858C2D@sourceware.org> Date: Tue, 11 Apr 2023 14:18:36 +0000 (GMT) List-Id: https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c9c8107f3cda81810e3f1441fdb54695f3a2df90 commit c9c8107f3cda81810e3f1441fdb54695f3a2df90 Author: Adhemerval Zanella Date: Sun Apr 2 10:28:05 2023 -0300 i386: Fix Race conditions in pthread cancellation [BZ#12683] The syscall bridge uses the old int80 instruction because by using the optimized vDSO symbol the resulting PC value for an interrupted syscall points to an adress outside the expected markers in __syscall_cancel_arch. It has been discussed in LKML [1] on how kernel could help userland to accomplish it, but afaik discussion has stalled. Also, sysenter should not be used directly by libc since its calling convention is set by the kernel depending of the underlying x86 chip (check kernel commit 30bfa7b3488bfb1bb75c9f50a5fcac1832970c60). Checked on i686-linux-gnu. [1] https://lkml.org/lkml/2016/3/8/1105 Diff: --- sysdeps/unix/sysv/linux/i386/syscall_cancel.S | 103 ++++++++++++++++++++++++++ 1 file changed, 103 insertions(+) diff --git a/sysdeps/unix/sysv/linux/i386/syscall_cancel.S b/sysdeps/unix/sysv/linux/i386/syscall_cancel.S new file mode 100644 index 0000000000..7d1560e18f --- /dev/null +++ b/sysdeps/unix/sysv/linux/i386/syscall_cancel.S @@ -0,0 +1,103 @@ +/* Cancellable syscall wrapper. Linux/i686 version. + Copyright (C) 2023 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 +#include + +/* long int [eax] __syscall_cancel_arch (int *cancelhandling [SP], + long int nr [SP+4], + long int arg1 [SP+8], + long int arg2 [SP+12], + long int arg3 [SP+16], + long int arg4 [SP+20], + long int arg5 [SP+24], + long int arg6 [SP+28]) */ + +ENTRY (__syscall_cancel_arch) + pushl %ebp + cfi_def_cfa_offset (8) + cfi_offset (ebp, -8) + pushl %edi + cfi_def_cfa_offset (12) + cfi_offset (edi, -12) + pushl %esi + cfi_def_cfa_offset (16) + cfi_offset (esi, -16) + pushl %ebx + cfi_def_cfa_offset (20) + cfi_offset (ebx, -20) + + .global __syscall_cancel_arch_start +__syscall_cancel_arch_start: + + /* if (*cancelhandling & CANCELED_BITMASK) + __syscall_do_cancel() */ + testb $TCB_CANCELED_BITMASK, (%eax) + jne 1f + + /* Issue a 6 argument syscall, the nr [%eax] being the syscall + number. */ + movl 24(%esp), %eax + movl 28(%esp), %ebx + movl 32(%esp), %ecx + movl 36(%esp), %edx + movl 40(%esp), %esi + movl 44(%esp), %edi + movl 48(%esp), %ebp + + /* We can not use the vDSO helper for syscall (__kernel_vsyscall) + because the returned PC from kernel will point to the vDSO page + instead of the expected __syscall_cancel_arch_{start,end} + marks. */ + int $128 + + .global __syscall_cancel_arch_end +__syscall_cancel_arch_end: + + popl %ebx + cfi_restore (ebx) + cfi_def_cfa_offset (16) + popl %esi + cfi_restore (esi) + cfi_def_cfa_offset (12) + popl %edi + cfi_restore (edi) + cfi_def_cfa_offset (8) + popl %ebp + cfi_restore (ebp) + cfi_def_cfa_offset (4) + ret + +1: + /* Although the __syscall_do_cancel do not return, we need to stack + being set correctly for unwind. */ + popl %ebx + cfi_restore (ebx) + cfi_def_cfa_offset (16) + popl %esi + cfi_restore (esi) + cfi_def_cfa_offset (12) + popl %edi + cfi_restore (edi) + cfi_def_cfa_offset (8) + popl %ebp + cfi_restore (ebp) + cfi_def_cfa_offset (4) + jmp __syscall_do_cancel + +END (__syscall_cancel_arch)