Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 25 Jun 2018 10:14:29 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Pavel Tatashin <pasha.tatashin@oracle.com>
Cc:     steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
        linux@armlinux.org.uk, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, john.stultz@linaro.org,
        sboyd@codeaurora.org, x86@kernel.org, linux-kernel@vger.kernel.org,
        mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com,
        douly.fnst@cn.fujitsu.com, prarit@redhat.com, feng.tang@intel.com,
        pmladek@suse.com, gnomes@lxorguk.ukuu.org.uk,
        linux-s390@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v12 01/11] x86: text_poke() may access uninitialized
 struct pages
Message-ID: <20180625081429.GS2494@hirez.programming.kicks-ass.net>
References: <20180621212518.19914-1-pasha.tatashin@oracle.com>
 <20180621212518.19914-2-pasha.tatashin@oracle.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20180621212518.19914-2-pasha.tatashin@oracle.com>
User-Agent: Mutt/1.10.0 (2018-05-17)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Jun 21, 2018 at 05:25:08PM -0400, Pavel Tatashin wrote:
> ---
>  arch/x86/include/asm/text-patching.h |  1 +
>  arch/x86/kernel/alternative.c        | 10 +++++++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
> index 2ecd34e2d46c..e85ff65c43c3 100644
> --- a/arch/x86/include/asm/text-patching.h
> +++ b/arch/x86/include/asm/text-patching.h
> @@ -37,5 +37,6 @@ extern void *text_poke_early(void *addr, const void *opcode, size_t len);
>  extern void *text_poke(void *addr, const void *opcode, size_t len);
>  extern int poke_int3_handler(struct pt_regs *regs);
>  extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);
> +extern int after_bootmem;
>  
>  #endif /* _ASM_X86_TEXT_PATCHING_H */
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index a481763a3776..0230dbc3c599 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -686,13 +686,21 @@ void *__init_or_module text_poke_early(void *addr, const void *opcode,
>   *
>   * Note: Must be called under text_mutex.
>   */
> -void *text_poke(void *addr, const void *opcode, size_t len)
> +void __ref *text_poke(void *addr, const void *opcode, size_t len)
>  {
>  	unsigned long flags;
>  	char *vaddr;
>  	struct page *pages[2];
>  	int i;
>  
> +	/* While boot memory allocator is runnig we cannot use struct

Broken comment style..

> +	 * pages as they are not yet initialized. However, we also know
> +	 * that this is early in boot, and it is safe to fallback to
> +	 * text_poke_early.
> +	 */
> +	if (unlikely(!after_bootmem))
> +		return text_poke_early(addr, opcode, len);

I'm not entirely sure this is right.. Because not only do we need the
whole fixmap stuff working, we also need #DB and the IPI handlers set-up
and working.

Also, why do this here and not override @poker in
__jump_label_transform() ?

And I added a sync_core() in text_poke_early(), which I think we need
for this.

>  	if (!core_kernel_text((unsigned long)addr)) {
>  		pages[0] = vmalloc_to_page(addr);
>  		pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
> -- 
> 2.17.1
>