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From: Peter Zijlstra <peterz@infradead.org>
To: Nadav Amit <namit@vmware.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
	x86@kernel.org, Arnd Bergmann <arnd@arndb.de>,
	linux-arch@vger.kernel.org,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Nadav Amit <nadav.amit@gmail.com>, Jiri Kosina <jkosina@suse.cz>,
	Andy Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH v2 1/6] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()"
Date: Thu, 6 Sep 2018 21:40:03 +0200	[thread overview]
Message-ID: <20180906194003.GD4816@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20180902173224.30606-2-namit@vmware.com>

On Sun, Sep 02, 2018 at 10:32:19AM -0700, Nadav Amit wrote:
> text_mutex is expected to be held before text_poke() is called, but we
> cannot add a lockdep assertion since kgdb does not take it, and instead
> *supposedly* ensures the lock is not taken and will not be acquired by
> any other core while text_poke() is running.
> 
> The reason for the "supposedly" comment is that it is not entirely clear
> that this would be the case if gdb_do_roundup is zero.

Argh, that's pretty shit code...

Not only is that text_mutex abuse ugly, so too is the fixmap usage from
IRQ context. I suppose this really does require your alternative mm
patches for text_poke().

  reply	other threads:[~2018-09-06 19:40 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-02 17:32 [PATCH v2 0/6] x86/alternatives: text_poke() fixes Nadav Amit
2018-09-02 17:32 ` Nadav Amit
2018-09-02 17:32 ` [PATCH v2 1/6] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Nadav Amit
2018-09-02 17:32   ` Nadav Amit
2018-09-06 19:40   ` Peter Zijlstra [this message]
2018-09-06 19:42     ` Nadav Amit
2018-09-06 19:53       ` Peter Zijlstra
2018-09-06 19:58         ` Nadav Amit
2018-09-06 20:25           ` Peter Zijlstra
2018-09-06 20:57             ` Nadav Amit
2018-09-06 21:41               ` Peter Zijlstra
2018-09-02 17:32 ` [PATCH v2 2/6] x86/mm: temporary mm struct Nadav Amit
2018-09-02 17:32   ` Nadav Amit
2018-09-02 17:32 ` [PATCH v2 3/6] fork: provide a function for copying init_mm Nadav Amit
2018-09-02 17:32   ` Nadav Amit
2018-09-02 17:32 ` [PATCH v2 4/6] x86/alternatives: initializing temporary mm for patching Nadav Amit
2018-09-02 17:32   ` Nadav Amit
2018-09-06  9:01   ` Peter Zijlstra
2018-09-07 20:52     ` Nadav Amit
2018-09-02 17:32 ` [PATCH v2 5/6] x86/alternatives: use temporary mm for text poking Nadav Amit
2018-09-02 17:32   ` Nadav Amit
2018-09-02 17:32 ` [PATCH v2 6/6] x86/alternatives: remove text_poke() return value Nadav Amit
2018-09-02 17:32   ` Nadav Amit
2018-09-05 18:56 ` [PATCH v2 0/6] x86/alternatives: text_poke() fixes Peter Zijlstra
2018-09-05 19:02   ` Nadav Amit
2018-09-05 19:10     ` Nadav Amit
2018-09-06  8:13       ` Peter Zijlstra
2018-09-06  8:42         ` Peter Zijlstra
2018-09-06  9:18         ` Peter Zijlstra
2018-09-06 10:16         ` Peter Zijlstra
2018-09-06 17:01           ` Nadav Amit
2018-09-06 17:17             ` Peter Zijlstra
2018-09-06 17:58               ` Nadav Amit
2018-09-06 18:09                 ` Andy Lutomirski
2018-09-06 18:31                   ` Peter Zijlstra
2018-09-06 18:38                     ` Nadav Amit
2018-09-06 19:19                       ` Peter Zijlstra
2018-09-06 17:23             ` Peter Zijlstra

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