linux-kernel - Re: [PATCH v4 2/2] x86/boot/KASLR: skip the specified crashkernel region

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Date:   Tue, 16 Apr 2019 21:01:28 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Baoquan He <bhe@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Nicolas Pitre <nico@...aro.org>,
        Vivek Goyal <vgoyal@...hat.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] x86/boot/KASLR: skip the specified crashkernel
 region

On Mon, Apr 08, 2019 at 01:58:35PM +0800, Pingfan Liu wrote:
> crashkernel=x@y or or =range1:size1[,range2:size2,...]@offset option may
> fail to reserve the required memory region if KASLR puts kernel into the
> region. To avoid this uncertainty, asking KASLR to skip the required
> region.
> 
> Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Baoquan He <bhe@...hat.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Nicolas Pitre <nico@...aro.org>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: Chao Fan <fanc.fnst@...fujitsu.com>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> CC: Hari Bathini <hbathini@...ux.vnet.ibm.com>
> Cc: linux-kernel@...r.kernel.org
> ---
>  arch/x86/boot/compressed/kaslr.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 2e53c05..765a593 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -107,6 +107,7 @@ enum mem_avoid_index {
>  	MEM_AVOID_BOOTPARAMS,
>  	MEM_AVOID_MEMMAP_BEGIN,
>  	MEM_AVOID_MEMMAP_END = MEM_AVOID_MEMMAP_BEGIN + MAX_MEMMAP_REGIONS - 1,
> +	MEM_AVOID_CRASHKERNEL,
>  	MEM_AVOID_MAX,
>  };
>  
> @@ -131,6 +132,11 @@ char *skip_spaces(const char *str)
>  }
>  #include "../../../../lib/ctype.c"
>  #include "../../../../lib/cmdline.c"
> +#ifdef CONFIG_CRASH_CORE
> +#define printk
> +#define _BOOT_KASLR
> +#include "../../../../lib/parse_crashkernel.c"
> +#endif
>  
>  static int
>  parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> @@ -292,6 +298,39 @@ static void handle_mem_options(void)
>  	return;
>  }
>  
> +static u64 mem_ram_size(void)
> +{
> +	struct boot_e820_entry *entry;
> +	u64 total_sz = 0;
> +	int i;
> +
> +	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;
> +	}
> +	return total_sz;
> +}
> +
> +/*
> + * For crashkernel=size@...set or =range1:size1[,range2:size2,...]@offset
> + * options, recording mem_avoid for them.
> + */
> +static void handle_crashkernel_options(void)
> +{
> +	unsigned long long crash_size, crash_base = 0;
> +	char *cmdline = (char *)get_cmd_line_ptr();
> +	u64 total_sz = mem_ram_size();
> +
> +	parse_crashkernel(cmdline, total_sz, &crash_size, &crash_base);

That function has a return value which you could test. And then you
don't need to set crash_base to 0 above.

-- 
Regards/Gruss,
    Boris.

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