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

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Date:   Mon, 25 Feb 2019 15:59:56 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     x86@...nel.org
Cc:     Pingfan Liu <kernelfans@...il.com>,
        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>,
        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: [PATCH] x86/boot/KASLR: skip the specified crashkernel reserved region

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
---
 arch/x86/boot/compressed/kaslr.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 9ed9709..728bc4b 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 +241,27 @@ static void parse_gb_huge_pages(char *param, char *val)
 	}
 }
 
+/* parse crashkernel=x@y option */
+static int mem_avoid_crashkernel_simple(char *option)
+{
+	char *cur = option;
+	unsigned long long crash_size, crash_base;
+
+	crash_size = memparse(option, &cur);
+	if (option == cur)
+		return -EINVAL;
+
+	if (*cur == '@') {
+		option = cur + 1;
+		crash_base = memparse(option, &cur);
+		if (option == cur)
+			return -EINVAL;
+		mem_avoid[MEM_AVOID_CRASHKERNEL].start = crash_base;
+		mem_avoid[MEM_AVOID_CRASHKERNEL].size = crash_size;
+	}
+
+	return 0;
+}
 
 static void handle_mem_options(void)
 {
@@ -250,7 +272,7 @@ 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 +308,8 @@ static void handle_mem_options(void)
 				goto out;
 
 			mem_limit = mem_size;
+		} else if (strstr(param, "crashkernel")) {
+			mem_avoid_crashkernel_simple(val);
 		}
 	}
 
-- 
2.7.4