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From: Oleg Nesterov <oleg@redhat.com>
To: tip-bot for Marcin Nowakowski <tipbot@zytor.com>
Cc: linux-tip-commits@vger.kernel.org, linux-kernel@vger.kernel.org,
	peterz@infradead.org, alexander.shishkin@linux.intel.com,
	acme@kernel.org, marcin.nowakowski@imgtec.com, acme@redhat.com,
	mingo@kernel.org, victor.kamensky@linaro.org, jolsa@redhat.com,
	hpa@zytor.com, torvalds@linux-foundation.org, tglx@linutronix.de
Subject: Re: [tip:perf/urgent] uprobes: Fix uprobes on MIPS, allow for a cache flush after ixol breakpoint creation
Date: Tue, 20 Dec 2016 14:08:20 +0100	[thread overview]
Message-ID: <20161220130820.GA24822@redhat.com> (raw)
In-Reply-To: <tip-297e765e390a2ac996000b5f7228cbd84d995174@git.kernel.org>

On 12/19, tip-bot for Marcin Nowakowski wrote:
>
> uprobes: Fix uprobes on MIPS, allow for a cache flush after ixol breakpoint creation
>
> Commit:
>
>   72e6ae285a1d ('ARM: 8043/1: uprobes need icache flush after xol write'
>
> ... has introduced an arch-specific method to ensure all caches are
> flushed appropriately after an instruction is written to an XOL page.

when this page is already mmaped,

> However, when the XOL area is created and the out-of-line breakpoint
> instruction is copied, caches are not flushed at all and stale data may
> be found in icache.

but in this case the page is not mmaped yet, the probed application will
take a page fault if it tries to execute this insn,

> Replace a simple copy_to_page() with arch_uprobe_copy_ixol() to allow
> the arch to ensure all caches are updated accordingly.
>
> This change fixes uprobes on MIPS InterAptiv (tested on Creator Ci40).

OK, I know nothing about MIPS, but could you help me understand this change?

See above. If we really need flush_icache_range() here then perhaps we should
modify install_special_mapping() and/or __do_fault/special_mapping_fault paths
instead?

Oleg.

  reply	other threads:[~2016-12-20 13:08 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-13 10:40 [PATCH] uprobes: " Marcin Nowakowski
2016-12-20  7:58 ` [tip:perf/urgent] uprobes: Fix uprobes on MIPS, " tip-bot for Marcin Nowakowski
2016-12-20 13:08   ` Oleg Nesterov [this message]
2016-12-20 15:21     ` Marcin Nowakowski
2016-12-20 17:50       ` Oleg Nesterov
2016-12-21 11:24         ` Ralf Baechle

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