linux-kernel - Re: [PATCHv2] x86/boot/KASLR: skip the specified crashkernel reserved region

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Date:   Thu, 21 Mar 2019 14:37:40 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.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>, Baoquan He <bhe@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Nicolas Pitre <nico@...aro.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2] x86/boot/KASLR: skip the specified crashkernel
 reserved region

On Wed, Mar 13, 2019 at 12:19:31PM +0800, Pingfan Liu wrote:

I tested it in Qemu test with 12G memory, and set crashkernel=6G@6G.
Without this PATCH, it successed to reserve memory just 4 times(total
10 times).
With this PATCH, it successed to reserve memory 15 times(total 15
times).

So I think if you post new version, you can add:

Tested-by: Chao Fan <fanc.fnst@...fujitsu.com>

Thanks,
Chao Fan

>crashkernel=x@y option may fail to reserve the required memory region if
>KASLR puts kernel into the region. To avoid this uncertainty, making KASLR
>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: Pingfan Liu <kernelfans@...il.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: linux-kernel@...r.kernel.org
>---
>v1 -> v2: fix some trival format
>
> arch/x86/boot/compressed/kaslr.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
>diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>index 9ed9709..e185318 100644
>--- a/arch/x86/boot/compressed/kaslr.c
>+++ b/arch/x86/boot/compressed/kaslr.c
>@@ -109,6 +109,7 @@ 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,
> };
> 
>@@ -240,6 +241,25 @@ static void parse_gb_huge_pages(char *param, char *val)
> 	}
> }
> 
>+/* parse crashkernel=x@y option */
>+static void mem_avoid_crashkernel_simple(char *option)
>+{
>+	unsigned long long crash_size, crash_base;
>+	char *cur = option;
>+
>+	crash_size = memparse(option, &cur);
>+	if (option == cur)
>+		return;
>+
>+	if (*cur == '@') {
>+		option = cur + 1;
>+		crash_base = memparse(option, &cur);
>+		if (option == cur)
>+			return;
>+		mem_avoid[MEM_AVOID_CRASHKERNEL].start = crash_base;
>+		mem_avoid[MEM_AVOID_CRASHKERNEL].size = crash_size;
>+	}
>+}
> 
> static void handle_mem_options(void)
> {
>@@ -250,7 +270,7 @@ static void handle_mem_options(void)
> 	u64 mem_size;
> 
> 	if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
>-		!strstr(args, "hugepages"))
>+		!strstr(args, "hugepages") && !strstr(args, "crashkernel="))
> 		return;
> 
> 	tmp_cmdline = malloc(len + 1);
>@@ -286,6 +306,8 @@ static void handle_mem_options(void)
> 				goto out;
> 
> 			mem_limit = mem_size;
>+		} else if (strstr(param, "crashkernel")) {
>+			mem_avoid_crashkernel_simple(val);
> 		}
> 	}
> 
>@@ -414,7 +436,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
> 
> 	/* We don't need to set a mapping for setup_data. */
> 
>-	/* Mark the memmap regions we need to avoid */
>+	/* Mark the regions we need to avoid */
> 	handle_mem_options();
> 
> #ifdef CONFIG_X86_VERBOSE_BOOTUP
>-- 
>2.7.4
>
>
>