From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 26 Nov 2014 12:41:28 +0000 Subject: [PATCH v9 1/6] arm64: ptrace: add NT_ARM_SYSTEM_CALL regset In-Reply-To: <1416977391-24231-2-git-send-email-takahiro.akashi@linaro.org> References: <1416977391-24231-1-git-send-email-takahiro.akashi@linaro.org> <1416977391-24231-2-git-send-email-takahiro.akashi@linaro.org> Message-ID: <20141126124128.GH14866@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Will From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751144AbaKZMle (ORCPT ); Wed, 26 Nov 2014 07:41:34 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:39698 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750770AbaKZMld (ORCPT ); Wed, 26 Nov 2014 07:41:33 -0500 Date: Wed, 26 Nov 2014 12:41:28 +0000 From: Will Deacon To: AKASHI Takahiro 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 Message-ID: <20141126124128.GH14866@arm.com> References: <1416977391-24231-1-git-send-email-takahiro.akashi@linaro.org> <1416977391-24231-2-git-send-email-takahiro.akashi@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1416977391-24231-2-git-send-email-takahiro.akashi@linaro.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Will