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 C8680C43334 for ; Wed, 8 Jun 2022 16:25:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238327AbiFHQZL (ORCPT ); Wed, 8 Jun 2022 12:25:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43732 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245412AbiFHQZJ (ORCPT ); Wed, 8 Jun 2022 12:25:09 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0404C1DF860; Wed, 8 Jun 2022 09:25:06 -0700 (PDT) Received: from pwmachine.home (154.pool92-186-13.dynamic.orange.es [92.186.13.154]) by linux.microsoft.com (Postfix) with ESMTPSA id CF4D620BE61B; Wed, 8 Jun 2022 09:25:01 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com CF4D620BE61B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1654705506; bh=ew5GzO4FE+U+0SWUgqG4Xavp3v72gNEOJF0LnOkp+rw=; h=From:To:Cc:Subject:Date:From; b=Fd3VFGu9AwImhcqGxwixF/Ih8YO5xFjwkPRdgo/nzbzT+c7gxHGAWKvdcoG68zMBf R8LQMhgA/iStrvVoqt+B3eafaBIS4wMAhU23QY++PkFhMBGge194PNWzfgRjaXQKgZ SqfNtFkJ8k9ZfBwctAkBG/1sB6uqewzgB3RIi1yM= From: Francis Laniel To: linux-trace-devel@vger.kernel.org Cc: James Morse , Daniel Kiss , Francis Laniel , 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: [PATCH v2 0/1] Remove forget_syscall() from start_thread_common() Date: Wed, 8 Jun 2022 17:24:45 +0100 Message-Id: <20220608162447.666494-1-flaniel@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Hi. First, I hope you are fine and the same for your relatives. 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 their information as syscall number was set to -1 by calling forget_syscall(). 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_execve' ^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 ... 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 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]. If you see any way to improve this contribution, feel free to share! Change since: v1: * Remove call to forget_syscall() and store previous syscall number in regs->syscallno unconditionnaly. Francis Laniel (1): arm64: Do not forget syscall when starting a new thread. arch/arm64/include/asm/processor.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) 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/asm/ 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 -- 2.25.1