linux-kernel - Re: [PATCH bpf 3/3] selftest/bpf: Test the read of vsyscall page under x86-64

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Date: Mon, 22 Jan 2024 16:25:58 -0800
From: Sohil Mehta <sohil.mehta@...el.com>
To: Hou Tao <houtao@...weicloud.com>, <x86@...nel.org>, <bpf@...r.kernel.org>
CC: Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski
	<luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>,
	<linux-kernel@...r.kernel.org>, xingwei lee <xrivendell7@...il.com>, "Jann
 Horn" <jannh@...gle.com>, <houtao1@...wei.com>
Subject: Re: [PATCH bpf 3/3] selftest/bpf: Test the read of vsyscall page
 under x86-64

On 1/18/2024 11:30 PM, Hou Tao wrote:

> vsyscall page could be disabled by CONFIG_LEGACY_VSYSCALL_NONE or
> vsyscall=none boot cmd-line, but it doesn't affect the reproduce of the
> problem and the returned error codes.
> 

With vsyscall=emulate a direct read of the vsyscall address from
userspace is expected to go through. This is mode deprecated so maybe it
wouldn't matter much. Without the fix in patch 2/3, do you see the same
behavior with vsyscall=emulate set in the cmdline?

Sohil