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From: Oleg Nesterov <oleg@redhat.com>
To: Gregory Price <gregory.price@memverge.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Gregory Price <gourry.memverge@gmail.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Linux-Arch <linux-arch@vger.kernel.org>,
	avagin@gmail.com, Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	krisman@collabora.com, Thomas Gleixner <tglx@linutronix.de>,
	Jonathan Corbet <corbet@lwn.net>, shuah <shuah@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	tongtiangen@huawei.com, Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok
Date: Thu, 30 Mar 2023 01:54:43 +0200	[thread overview]
Message-ID: <20230329235442.GA10790@redhat.com> (raw)
In-Reply-To: <ZCQMsWNfkMJ0xHSy@memverge.com>

On 03/29, Gregory Price wrote:
>
> Last note on this before I push up another patch set.
>
> The change from __get_user to get_user also introduces a call to
> might_fault() which adds a larger callstack for every syscall /
> dispatch.  This turns into a might_sleep and might_reschedule, which
> represent a very different pattern of execution from before.

might_fault() is nop unless CONFIG_PROVE_LOCKING || DEBUG_ATOMIC_SLEEP.

Again, I won't really argue with task_access_ok(). Just I am not sure
2/4 gives enough justification for this new helper with unclear semantics
(until we ensure that access_ok() doesn't depend on current).

Oleg.


WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Gregory Price <gregory.price@memverge.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Gregory Price <gourry.memverge@gmail.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Linux-Arch <linux-arch@vger.kernel.org>,
	avagin@gmail.com, Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	krisman@collabora.com, Thomas Gleixner <tglx@linutronix.de>,
	Jonathan Corbet <corbet@lwn.net>, shuah <shuah@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	tongtiangen@huawei.com, Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok
Date: Thu, 30 Mar 2023 01:54:43 +0200	[thread overview]
Message-ID: <20230329235442.GA10790@redhat.com> (raw)
In-Reply-To: <ZCQMsWNfkMJ0xHSy@memverge.com>

On 03/29, Gregory Price wrote:
>
> Last note on this before I push up another patch set.
>
> The change from __get_user to get_user also introduces a call to
> might_fault() which adds a larger callstack for every syscall /
> dispatch.  This turns into a might_sleep and might_reschedule, which
> represent a very different pattern of execution from before.

might_fault() is nop unless CONFIG_PROVE_LOCKING || DEBUG_ATOMIC_SLEEP.

Again, I won't really argue with task_access_ok(). Just I am not sure
2/4 gives enough justification for this new helper with unclear semantics
(until we ensure that access_ok() doesn't depend on current).

Oleg.


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  reply	other threads:[~2023-03-29 23:55 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-28 16:48 [PATCH v14 0/4] Checkpoint Support for Syscall User Dispatch Gregory Price
2023-03-28 16:48 ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok Gregory Price
2023-03-28 16:48   ` Gregory Price
2023-03-28 18:46   ` Arnd Bergmann
2023-03-28 18:46     ` Arnd Bergmann
2023-03-29 15:15   ` Oleg Nesterov
2023-03-29 15:15     ` Oleg Nesterov
2023-03-29 15:41     ` Arnd Bergmann
2023-03-29 15:41       ` Arnd Bergmann
2023-03-29 16:03       ` Oleg Nesterov
2023-03-29 16:03         ` Oleg Nesterov
2023-03-29  3:56         ` Gregory Price
2023-03-29  3:56           ` Gregory Price
2023-03-29 17:13           ` Oleg Nesterov
2023-03-29 17:13             ` Oleg Nesterov
2023-03-29  5:37             ` Gregory Price
2023-03-29  5:37               ` Gregory Price
2023-03-29 17:58               ` Oleg Nesterov
2023-03-29 17:58                 ` Oleg Nesterov
2023-03-29  5:54                 ` Gregory Price
2023-03-29  5:54                   ` Gregory Price
2023-03-29 18:13                   ` Oleg Nesterov
2023-03-29 18:13                     ` Oleg Nesterov
2023-03-29 10:02                 ` Gregory Price
2023-03-29 10:02                   ` Gregory Price
2023-03-29 23:54                   ` Oleg Nesterov [this message]
2023-03-29 23:54                     ` Oleg Nesterov
2023-03-29 18:29         ` Arnd Bergmann
2023-03-29 18:29           ` Arnd Bergmann
2023-03-29 16:22   ` Catalin Marinas
2023-03-29 16:22     ` Catalin Marinas
2023-03-29  4:34     ` Gregory Price
2023-03-29  4:34       ` Gregory Price
2023-03-30 14:05       ` Catalin Marinas
2023-03-30 14:05         ` Catalin Marinas
2023-03-30  4:18         ` Gregory Price
2023-03-30  4:18           ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 2/4] syscall_user_dispatch: helper function to operate on given task Gregory Price
2023-03-28 16:48   ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 3/4] ptrace,syscall_user_dispatch: checkpoint/restore support for SUD Gregory Price
2023-03-28 16:48   ` Gregory Price
2023-03-28 16:48 ` [PATCH v14 4/4] selftest,ptrace: Add selftest for syscall user dispatch config api Gregory Price
2023-03-28 16:48   ` Gregory Price

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