linux-kernel - Re: [PATCHv3] x86/boot/KASLR: skip the specified crashkernel region

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Message-ID: <20190402080811.GO7627@MiWiFi-R3L-srv>
Date:   Tue, 2 Apr 2019 16:08:11 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Will Deacon <will.deacon@....com>,
        Nicolas Pitre <nico@...aro.org>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3] x86/boot/KASLR: skip the specified crashkernel region

> +/* handle crashkernel=x@y or =range1:size1[,range2:size2,...]@offset options */
> +static void mem_avoid_specified_crashkernel_region(char *option)
> +{
> +	unsigned long long crash_size, crash_base = 0;
> +	char	*first_colon, *first_space, *cur = option;
> +

Another thing which need be noticed is that you may only need to handle
when '@' is found. Otherwise just let it go. Right?

> +	first_colon = strchr(option, ':');
> +	first_space = strchr(option, ' ');
> +	/* if contain ":" */
> +	if (first_colon && (!first_space || first_colon < first_space)) {
> +		int i;
> +		u64 total_sz = 0;
> +		struct boot_e820_entry *entry;
> +
> +		for (i = 0; i < boot_params->e820_entries; i++) {
> +			entry = &boot_params->e820_table[i];
> +			/* Skip non-RAM entries. */
> +			if (entry->type != E820_TYPE_RAM)
> +				continue;
> +			total_sz += entry->size;
> +		}
> +		handle_crashkernel_mem(option, total_sz, &crash_size,
> +			&crash_base);
> +	} else {
> +		crash_size = memparse(option, &cur);
> +		if (option == cur)
> +			return;
> +		while (*cur && *cur != ' ' && *cur != '@')
> +			cur++;
> +		if (*cur == '@') {
> +			option = cur + 1;
> +			crash_base = memparse(option, &cur);
> +		}
> +	}
> +	if (crash_base) {
> +		mem_avoid[MEM_AVOID_CRASHKERNEL].start = crash_base;
> +		mem_avoid[MEM_AVOID_CRASHKERNEL].size = crash_size;
> +	} else {
> +		/*
> + 		 * Clearing mem_avoid if no offset is given. This is consistent
> + 		 * with kernel, which uses the last crashkernel= option.
> +		 */
> +		mem_avoid[MEM_AVOID_CRASHKERNEL].start = 0;
> +		mem_avoid[MEM_AVOID_CRASHKERNEL].size = 0;
> +	}
> +}