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Subject[PATCH -v2 3/8] kexec jump: check code size in control page
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Date
Kexec/Kexec-jump require code size in control page is less than
PAGE_SIZE/2. This patch add link-time checking for this.

ASSERT() of ld link script is used as the link-time checking
mechanism.

Signed-off-by: Huang Ying <ying.huang@intel.com>

---
arch/x86/kernel/machine_kexec_32.c | 2 +-
arch/x86/kernel/relocate_kernel_32.S | 10 +++++++---
arch/x86/kernel/vmlinux_32.lds.S | 2 ++
arch/x86/kernel/vmlinux_check_32.lds.S | 7 +++++++
include/asm-x86/kexec.h | 4 ++++
5 files changed, 21 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -138,7 +138,7 @@ void machine_kexec(struct kimage *image)
}

control_page = page_address(image->control_code_page);
- memcpy(control_page, relocate_kernel, PAGE_SIZE/2);
+ memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);

relocate_kernel_ptr = control_page;
page_list[PA_CONTROL_PAGE] = __pa(control_page);
--- a/arch/x86/kernel/relocate_kernel_32.S
+++ b/arch/x86/kernel/relocate_kernel_32.S
@@ -20,10 +20,11 @@
#define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
#define PAE_PGD_ATTR (_PAGE_PRESENT)

-/* control_page + PAGE_SIZE/2 ~ control_page + PAGE_SIZE * 3/4 are
- * used to save some data for jumping back
+/* control_page + KEXEC_CONTROL_CODE_MAX_SIZE
+ * ~ control_page + PAGE_SIZE * 3/4 are used to save some data for
+ * jumping back
*/
-#define DATA(offset) (PAGE_SIZE/2+(offset))
+#define DATA(offset) (KEXEC_CONTROL_CODE_MAX_SIZE+(offset))

/* Minimal CPU state */
#define ESP DATA(0x0)
@@ -376,3 +377,6 @@ swap_pages:
popl %ebx
popl %ebp
ret
+
+ .globl kexec_control_code_size
+.set kexec_control_code_size, . - relocate_kernel
--- a/include/asm-x86/kexec.h
+++ b/include/asm-x86/kexec.h
@@ -41,6 +41,10 @@
# define PAGES_NR 17
#endif

+#ifdef CONFIG_X86_32
+# define KEXEC_CONTROL_CODE_MAX_SIZE 2048
+#endif
+
#ifndef __ASSEMBLY__

#include <linux/string.h>
--- a/arch/x86/kernel/vmlinux_32.lds.S
+++ b/arch/x86/kernel/vmlinux_32.lds.S
@@ -209,3 +209,5 @@ SECTIONS

DWARF_DEBUG
}
+
+#include "vmlinux_check_32.lds.S"
--- /dev/null
+++ b/arch/x86/kernel/vmlinux_check_32.lds.S
@@ -0,0 +1,7 @@
+/*
+ * Link time checks
+ */
+
+#include <asm/kexec.h>
+
+ASSERT(kexec_control_code_size <= KEXEC_CONTROL_CODE_MAX_SIZE, "kexec control code size is too big")



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