linux-kernel - Re: [PATCH v2 4/6] x86/alternatives: initializing temporary mm for patching

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Date:   Fri, 7 Sep 2018 20:52:04 +0000
From:   Nadav Amit <namit@...are.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arch <linux-arch@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH v2 4/6] x86/alternatives: initializing temporary mm for
 patching

at 2:01 AM, Peter Zijlstra <peterz@...radead.org> wrote:

> On Sun, Sep 02, 2018 at 10:32:22AM -0700, Nadav Amit wrote:
>> +void __init poking_init(void)
>> +{
>> +	unsigned long poking_addr;
>> +
>> +	poking_mm = copy_init_mm();
>> +	if (!poking_mm) {
>> +		pr_err("x86/mm: error setting a separate poking address space");
>> +		return;
>> +	}
>> +
>> +	/*
>> +	 * Randomize the poking address, but make sure that the following page
>> +	 * will be mapped at the same PMD. We need 2 pages, so find space for 3,
>> +	 * and adjust the address if the PMD ends after the first one.
>> +	 */
>> +	poking_addr = TASK_UNMAPPED_BASE +
>> +		(kaslr_get_random_long("Poking") & PAGE_MASK) %
>> +		(TASK_SIZE - TASK_UNMAPPED_BASE - 3 * PAGE_SIZE);
>> +
>> +	if (((poking_addr + PAGE_SIZE) & ~PMD_MASK) == 0)
>> +		poking_addr += PAGE_SIZE;
>> +}
> 
> This fails to compile for me.. I don't have kaslr_get_random_long().

Will be fixed in v3. Thanks.