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From: Richard Weinberger <richard@nod.at>
To: Will Deacon <will.deacon@arm.com>
Cc: "Haibo.Xu" <haibo.xu@arm.com>,
	catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, nd@arm.com, jdike@addtoit.com
Subject: Re: [PATCH] arm64/ptrace: add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support
Date: Mon, 03 Sep 2018 18:40:51 +0200	[thread overview]
Message-ID: <102400624.EOB2phcGqB@blindfold> (raw)
In-Reply-To: <20180903163103.GC6954@arm.com>

Am Montag, 3. September 2018, 18:31:03 CEST schrieb Will Deacon:
> On Mon, Sep 03, 2018 at 02:23:17PM +0800, Haibo.Xu wrote:
> > Add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support on ARM64.
> > This copies the x86 semantics for invoking ptrace hooks, and have
> > been verified on ARM64 machine.
> > 
> > Signed-off-by: Haibo.Xu <haibo.xu@arm.com>
> > Signed-off-by: Bin.Lu <bin.lu@arm.com>
> > ---
> >  arch/arm64/include/asm/thread_info.h |  5 ++++-
> >  arch/arm64/include/uapi/asm/ptrace.h |  2 ++
> >  arch/arm64/kernel/ptrace.c           | 17 +++++++++++++++++
> >  3 files changed, 23 insertions(+), 1 deletion(-)
> 
> What is PTRACE_SYSEMU and what is its semantics? Why isn't it done in the
> core ptrace code?

It is an optimization added for UserModeLinux many years ago.
PTRACE_SYSEMU basically allows you to handle system calls in user space
without the kernel seeing them.
Before that UML had to render every system call into a no-op, e.h. getpid().
This was complicated and slow.

The ptrace() manpage has a section on PTRACE_SYSEMU, more documentation on the
semantics is not available.

And yes, I think this should also done in the core. Like many other ptrace() areas
this needs a cleanup. ;-)

I wonder what Haibo Xu want to do with PTRACE_SYSEMU on arm64.
Are you porting UML or gvisor to arm64?

Thanks,
//richard



WARNING: multiple messages have this Message-ID (diff)
From: richard@nod.at (Richard Weinberger)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64/ptrace: add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support
Date: Mon, 03 Sep 2018 18:40:51 +0200	[thread overview]
Message-ID: <102400624.EOB2phcGqB@blindfold> (raw)
In-Reply-To: <20180903163103.GC6954@arm.com>

Am Montag, 3. September 2018, 18:31:03 CEST schrieb Will Deacon:
> On Mon, Sep 03, 2018 at 02:23:17PM +0800, Haibo.Xu wrote:
> > Add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support on ARM64.
> > This copies the x86 semantics for invoking ptrace hooks, and have
> > been verified on ARM64 machine.
> > 
> > Signed-off-by: Haibo.Xu <haibo.xu@arm.com>
> > Signed-off-by: Bin.Lu <bin.lu@arm.com>
> > ---
> >  arch/arm64/include/asm/thread_info.h |  5 ++++-
> >  arch/arm64/include/uapi/asm/ptrace.h |  2 ++
> >  arch/arm64/kernel/ptrace.c           | 17 +++++++++++++++++
> >  3 files changed, 23 insertions(+), 1 deletion(-)
> 
> What is PTRACE_SYSEMU and what is its semantics? Why isn't it done in the
> core ptrace code?

It is an optimization added for UserModeLinux many years ago.
PTRACE_SYSEMU basically allows you to handle system calls in user space
without the kernel seeing them.
Before that UML had to render every system call into a no-op, e.h. getpid().
This was complicated and slow.

The ptrace() manpage has a section on PTRACE_SYSEMU, more documentation on the
semantics is not available.

And yes, I think this should also done in the core. Like many other ptrace() areas
this needs a cleanup. ;-)

I wonder what Haibo Xu want to do with PTRACE_SYSEMU on arm64.
Are you porting UML or gvisor to arm64?

Thanks,
//richard

  reply	other threads:[~2018-09-03 16:40 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-03  6:23 [PATCH] arm64/ptrace: add PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support Haibo.Xu
2018-09-03 16:31 ` Will Deacon
2018-09-03 16:31   ` Will Deacon
2018-09-03 16:40   ` Richard Weinberger [this message]
2018-09-03 16:40     ` Richard Weinberger
2018-09-03 16:57     ` Will Deacon
2018-09-03 16:57       ` Will Deacon
2018-09-04  2:11       ` 答复: " Haibo Xu (Arm Technology China)
2018-09-04  2:11         ` Haibo Xu (Arm Technology China)
2018-09-04 19:45         ` Richard Weinberger
2018-09-04 19:45           ` Richard Weinberger
2018-09-05 10:21           ` 答复: " Haibo Xu (Arm Technology China)
2018-09-05 10:21             ` Haibo Xu (Arm Technology China)
2018-10-16  2:54           ` Haibo Xu (Arm Technology China)
2018-10-16  2:54             ` Haibo Xu (Arm Technology China)

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