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From: Dave Martin <Dave.Martin@arm.com>
To: Keno Fischer <keno@juliacomputing.com>
Cc: Kyle Huey <khuey@pernos.co>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: arm64: Register modification during syscall entry/exit stop
Date: Mon, 1 Jun 2020 10:23:29 +0100	[thread overview]
Message-ID: <20200601092329.GX5031@arm.com> (raw)
In-Reply-To: <CABV8kRwhsPhhqUXS46Rwh-xDEDY2q=KSd-xz1W-pu4Gy4KVp8Q@mail.gmail.com>

On Sun, May 31, 2020 at 12:20:51PM -0400, Keno Fischer wrote:
> > Can't PTRACE_SYSEMU be emulated by using PTRACE_SYSCALL, cancelling the
> > syscall at the syscall enter stop, then modifying the regs at the
> > syscall exit stop?
> 
> Yes, it can. The idea behind SYSEMU is to be able to save half the
> ptrace traps that would require, in theory making the ptracer
> a decent amount faster. That said, the x7 issue is orthogonal to
> SYSEMU, you'd have the same issues if you used PTRACE_SYSCALL.

Right, I just wondered whether there was some deeper difference between
the two approaches.

Cheers
---Dave

WARNING: multiple messages have this Message-ID (diff)
From: Dave Martin <Dave.Martin@arm.com>
To: Keno Fischer <keno@juliacomputing.com>
Cc: Kyle Huey <khuey@pernos.co>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: arm64: Register modification during syscall entry/exit stop
Date: Mon, 1 Jun 2020 10:23:29 +0100	[thread overview]
Message-ID: <20200601092329.GX5031@arm.com> (raw)
In-Reply-To: <CABV8kRwhsPhhqUXS46Rwh-xDEDY2q=KSd-xz1W-pu4Gy4KVp8Q@mail.gmail.com>

On Sun, May 31, 2020 at 12:20:51PM -0400, Keno Fischer wrote:
> > Can't PTRACE_SYSEMU be emulated by using PTRACE_SYSCALL, cancelling the
> > syscall at the syscall enter stop, then modifying the regs at the
> > syscall exit stop?
> 
> Yes, it can. The idea behind SYSEMU is to be able to save half the
> ptrace traps that would require, in theory making the ptracer
> a decent amount faster. That said, the x7 issue is orthogonal to
> SYSEMU, you'd have the same issues if you used PTRACE_SYSCALL.

Right, I just wondered whether there was some deeper difference between
the two approaches.

Cheers
---Dave

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-06-01  9:23 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19  1:05 arm64: Register modification during syscall entry/exit stop Keno Fischer
2020-05-19  1:05 ` Keno Fischer
2020-05-19  8:15 ` Will Deacon
2020-05-19  8:15   ` Will Deacon
2020-05-19  8:37   ` Keno Fischer
2020-05-19  8:37     ` Keno Fischer
2020-05-20 17:41     ` Will Deacon
2020-05-20 17:41       ` Will Deacon
2020-05-23  5:35       ` Keno Fischer
2020-05-23  5:35         ` Keno Fischer
2020-05-24  6:56         ` Keno Fischer
2020-05-24  6:56           ` Keno Fischer
2020-05-27  9:55           ` Will Deacon
2020-05-27  9:55             ` Will Deacon
2020-05-27 10:19             ` Dave Martin
2020-05-27 10:19               ` Dave Martin
2020-05-31  9:33               ` Will Deacon
2020-05-31  9:33                 ` Will Deacon
2020-05-31 16:13                 ` Keno Fischer
2020-05-31 16:13                   ` Keno Fischer
2020-06-01  9:14                   ` Dave Martin
2020-06-01  9:14                     ` Dave Martin
2020-06-01  9:23                     ` Keno Fischer
2020-06-01  9:23                       ` Keno Fischer
2020-06-01  9:52                       ` Dave Martin
2020-06-01  9:52                         ` Dave Martin
2020-05-31 16:20               ` Keno Fischer
2020-05-31 16:20                 ` Keno Fischer
2020-06-01  9:23                 ` Dave Martin [this message]
2020-06-01  9:23                   ` Dave Martin
2020-06-01  9:40                   ` Keno Fischer
2020-06-01  9:40                     ` Keno Fischer
2020-06-01  9:59                     ` Dave Martin
2020-06-01  9:59                       ` Dave Martin

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