From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACB99C433EF for ; Thu, 23 Jun 2022 14:09:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231661AbiFWOJI (ORCPT ); Thu, 23 Jun 2022 10:09:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44052 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231849AbiFWOJH (ORCPT ); Thu, 23 Jun 2022 10:09:07 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B6646434BD; Thu, 23 Jun 2022 07:09:06 -0700 (PDT) Received: from pwmachine.localnet (lfbn-lyo-1-1062-211.w86-248.abo.wanadoo.fr [86.248.131.211]) by linux.microsoft.com (Postfix) with ESMTPSA id 8565520C7064; Thu, 23 Jun 2022 07:09:03 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 8565520C7064 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1655993346; bh=LRpVeov3fFL6CWYvOD+HQ0kYTCxTXqw7Mo36h8/5pG4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ar+l+hBnYQNHgReiMLu6jgCQm2vfeD5cacocn/0pOQhNSmwoxVnRedCclVbwxxKrJ TDksNaQB7500x4ueuDlDgqOnrcx50e+N8g82ZcYLqFc/fGshsgBbfCoG9cSQc0Kr8z Fp1kXz9TH1IlJg87u5HZCY6DJI9lw45SqGEI7Xos= From: Francis Laniel To: linux-trace-devel@vger.kernel.org Cc: James Morse , Daniel Kiss , Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou , Mark Brown , Peter Collingbourne , Kees Cook , Mark Rutland , Christophe Leroy , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v2 0/1] Remove forget_syscall() from start_thread_common() Date: Thu, 23 Jun 2022 16:09:01 +0200 Message-ID: <2635206.mvXUDI8C0e@pwmachine> Organization: Microsoft In-Reply-To: <20220608162447.666494-1-flaniel@linux.microsoft.com> References: <20220608162447.666494-1-flaniel@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Hi. Le mercredi 8 juin 2022, 18:24:45 CEST Francis Laniel a =E9crit : > Hi. >=20 >=20 > First, I hope you are fine and the same for your relatives. >=20 > With this contribution, I enabled using syscalls:sys_exit_execve and > syscalls:sys_exit_execveat as tracepoints on arm64. > Indeed, before this contribution, the above tracepoint would not print th= eir > information as syscall number was set to -1 by calling forget_syscall(). >=20 > I tested it by compiling a kernel for arm64 and running it within a VM: > # Perf was compiled with linux kernel source. > root@vm-arm64:~# perf record -ag -e 'syscalls:sys_exit_execve' -e > 'syscalls:sys_enter_execve' & [1] 263 > root@vm-arm64:~# ls > perf.data share > root@vm-arm64:~# fg > perf record -ag -e 'syscalls:sys_exit_execve' -e 'syscalls:sys_enter_exec= ve' > ^C[ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.061 MB perf.data (2 samples) ] > root@vm-arm64:~# perf script > bash 264 [000] 66.220187: syscalls:sys_enter_execve: filename: > 0xaaab05d9d ... > # Below line does not appear without this patch. > ls 264 [000] 66.226848: syscalls:sys_exit_execve: 0x0 > ... >=20 > Forgetting the syscall number before starting a new thread was confirmed = to > be a bug [1]. > Particularly, the following architectures do not forget the syscall number > before starting a new thread: > * arm (32 bits) EABI: start_thread() sets r7 to previous r7 for ELF FDPIC= =20 > and to 0 for other binfmts [2]. > * arm (32 bits) OABI: syscall number is set to -1 if > ptrace_report_syscall_entry() failed [3]. > * mips: start_thread() does not modify current_thread_info->syscall which= is > taken directly from v0 [4, 5]. > * riscv: start_thread() does not modify a7 [6]. > * x86_64: start_thread_common() does not touch orig_ax which seems to > contain the syscall number [7]. >=20 > If you see any way to improve this contribution, feel free to share! >=20 > Change since: > v1: > * Remove call to forget_syscall() and store previous syscall number in > regs->syscallno unconditionnaly. >=20 > Francis Laniel (1): > arm64: Do not forget syscall when starting a new thread. >=20 > arch/arm64/include/asm/processor.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) >=20 >=20 > Best regards and thank you in advance. > --- > [1] https://lore.kernel.org/linux-arm-kernel/YoT1iLPEbteRTQGZ@arm.com/ > [2] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/arm/include/as= m/ > processor.h#L52 > [3] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/arm/kernel/ > ptrace.c#L847 > [4] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/mips/kernel/ > process.c#L52 > [5] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/mips/kernel/ > scall64-n64.S#L85 > [6] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/riscv/kernel/ > process.c#L87 > [7] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/x86/kernel/ > process_64.c#L505 Can someone please take a quick look at this patch? Best regards and thank you in advance.