From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754047AbaK0Fxp (ORCPT ); Thu, 27 Nov 2014 00:53:45 -0500 Received: from mail-pa0-f43.google.com ([209.85.220.43]:52141 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751040AbaK0Fxn (ORCPT ); Thu, 27 Nov 2014 00:53:43 -0500 Message-ID: <5476BC60.6060005@linaro.org> Date: Thu, 27 Nov 2014 14:53:36 +0900 From: AKASHI Takahiro User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Will Deacon CC: "keescook@chromium.org" , Catalin Marinas , "dsaxena@linaro.org" , "arndb@arndb.de" , "linux-arm-kernel@lists.infradead.org" , "linaro-kernel@lists.linaro.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v9 1/6] arm64: ptrace: add NT_ARM_SYSTEM_CALL regset References: <1416977391-24231-1-git-send-email-takahiro.akashi@linaro.org> <1416977391-24231-2-git-send-email-takahiro.akashi@linaro.org> <20141126124128.GH14866@arm.com> In-Reply-To: <20141126124128.GH14866@arm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/26/2014 09:41 PM, Will Deacon wrote: > Hi Akashi, > > On Wed, Nov 26, 2014 at 04:49:46AM +0000, AKASHI Takahiro wrote: >> This regeset is intended to be used to get and set a system call number >> while tracing. >> There was some discussion about possible approaches to do so: >> >> (1) modify x8 register with ptrace(PTRACE_SETREGSET) indirectly, >> and update regs->syscallno later on in syscall_trace_enter(), or >> (2) define a dedicated regset for this purpose as on s390, or >> (3) support ptrace(PTRACE_SET_SYSCALL) as on arch/arm >> >> Thinking of the fact that user_pt_regs doesn't expose 'syscallno' to >> tracer as well as that secure_computing() expects a changed syscall number, >> especially case of -1, to be visible before this function returns in >> syscall_trace_enter(), (1) doesn't work well. >> We will take (2) since it looks much cleaner. >> >> Signed-off-by: AKASHI Takahiro >> --- >> arch/arm64/kernel/ptrace.c | 35 +++++++++++++++++++++++++++++++++++ >> include/uapi/linux/elf.h | 1 + >> 2 files changed, 36 insertions(+) >> >> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c >> index 8a4ae8e..8b98781 100644 >> --- a/arch/arm64/kernel/ptrace.c >> +++ b/arch/arm64/kernel/ptrace.c >> @@ -551,6 +551,32 @@ static int tls_set(struct task_struct *target, const struct user_regset *regset, >> return ret; >> } >> >> +static int system_call_get(struct task_struct *target, >> + const struct user_regset *regset, >> + unsigned int pos, unsigned int count, >> + void *kbuf, void __user *ubuf) >> +{ >> + struct pt_regs *regs = task_pt_regs(target); >> + >> + return user_regset_copyout(&pos, &count, &kbuf, &ubuf, >> + ®s->syscallno, 0, -1); > > Does this work for big-endian machines? regs->syscallno is a u64, but the > regset defines it as an int. I think you need to copy to a temporary > register first. Right. I will fix it. Do you prefer to use s32, instead of int, like other regsets? Thanks, -Takahiro AKASHI > Will >