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Message-ID: <dadac419-acda-7ba5-b7bb-4bc5b6fee92d@huawei.com>
Date:   Fri, 18 Nov 2022 09:41:03 +0800
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Subject: Re: [PATCH v4 2/8] riscv/kprobe: Allocate detour buffer from module
 area
To:     Steven Rostedt <rostedt@goodmis.org>,
        Chen Guokai <chenguokai17@mails.ucas.ac.cn>
CC:     <paul.walmsley@sifive.com>, <palmer@dabbelt.com>,
        <aou@eecs.berkeley.edu>, <mingo@redhat.com>,
        <sfr@canb.auug.org.au>, <linux-riscv@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
References: <20221106100316.2803176-1-chenguokai17@mails.ucas.ac.cn>
 <20221106100316.2803176-3-chenguokai17@mails.ucas.ac.cn>
 <20221116202521.6c528955@gandalf.local.home>
From:   "liaochang (A)" <liaochang1@huawei.com>
In-Reply-To: <20221116202521.6c528955@gandalf.local.home>
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在 2022/11/17 9:25, Steven Rostedt 写道:
> On Sun,  6 Nov 2022 18:03:10 +0800
> Chen Guokai <chenguokai17@mails.ucas.ac.cn> wrote:
> 
>> @@ -84,6 +85,30 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>>  }
>>  
>>  #ifdef CONFIG_MMU
>> +#if defined(CONFIG_OPTPROBES) && defined(CONFIG_64BIT)
>> +void *alloc_optinsn_page(void)
>> +{
>> +	void *page;
>> +
>> +	page = __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR,
>> +				    MODULES_END, GFP_KERNEL,
>> +				    PAGE_KERNEL, 0, NUMA_NO_NODE,
>> +				    __builtin_return_address(0));
>> +	if (!page)
>> +		return NULL;
>> +
>> +	set_vm_flush_reset_perms(page);
>> +	/*
>> +	 * First make the page read-only, and only then make it executable to
>> +	 * prevent it from being W+X in between.
>> +	 */
>> +	set_memory_ro((unsigned long)page, 1);
>> +	set_memory_x((unsigned long)page, 1);
> 
> FYI, the above combination is going to be going away:
> 
>   https://lore.kernel.org/all/Y10OyLCLAAS6rsZv@hirez.programming.kicks-ass.net/

Thanks for reminding, i will use this API in next revision.
> -- Steve
> 
> 
>> +
>> +	return page;
>> +}
>> +#endif
>> +
> 

-- 
BR,
Liao, Chang