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authorMagnus Damm <magnus@valinux.co.jp>2006-09-26 10:52:38 +0200
committerAndi Kleen <andi@basil.nowhere.org>2006-09-26 10:52:38 +0200
commit4bfaaef01a1badb9e8ffb0c0a37cd2379008d21f (patch)
tree652effe9d02c80d93357512233f4ee962320ac3b /arch/x86_64/kernel/relocate_kernel.S
parentf574164491d00d28b727d713685fb5edc9138200 (diff)
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[PATCH] Avoid overwriting the current pgd (V4, x86_64)
kexec: Avoid overwriting the current pgd (V4, x86_64) This patch upgrades the x86_64-specific kexec code to avoid overwriting the current pgd. Overwriting the current pgd is bad when CONFIG_CRASH_DUMP is used to start a secondary kernel that dumps the memory of the previous kernel. The code introduces a new set of page tables. These tables are used to provide an executable identity mapping without overwriting the current pgd. Signed-off-by: Magnus Damm <magnus@valinux.co.jp> Signed-off-by: Andi Kleen <ak@suse.de>
Diffstat (limited to 'arch/x86_64/kernel/relocate_kernel.S')
-rw-r--r--arch/x86_64/kernel/relocate_kernel.S171
1 files changed, 152 insertions, 19 deletions
diff --git a/arch/x86_64/kernel/relocate_kernel.S b/arch/x86_64/kernel/relocate_kernel.S
index d24fa9b..14e9587 100644
--- a/arch/x86_64/kernel/relocate_kernel.S
+++ b/arch/x86_64/kernel/relocate_kernel.S
@@ -7,31 +7,169 @@
*/
#include <linux/linkage.h>
+#include <asm/page.h>
+#include <asm/kexec.h>
- /*
- * Must be relocatable PIC code callable as a C function, that once
- * it starts can not use the previous processes stack.
- */
- .globl relocate_new_kernel
+/*
+ * Must be relocatable PIC code callable as a C function
+ */
+
+#define PTR(x) (x << 3)
+#define PAGE_ALIGNED (1 << PAGE_SHIFT)
+#define PAGE_ATTR 0x63 /* _PAGE_PRESENT|_PAGE_RW|_PAGE_ACCESSED|_PAGE_DIRTY */
+
+ .text
+ .align PAGE_ALIGNED
.code64
+ .globl relocate_kernel
+relocate_kernel:
+ /* %rdi indirection_page
+ * %rsi page_list
+ * %rdx start address
+ */
+
+ /* map the control page at its virtual address */
+
+ movq $0x0000ff8000000000, %r10 /* mask */
+ mov $(39 - 3), %cl /* bits to shift */
+ movq PTR(VA_CONTROL_PAGE)(%rsi), %r11 /* address to map */
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PGD)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_PUD_0)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
+ shrq $9, %r10
+ sub $9, %cl
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PUD_0)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_PMD_0)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
+ shrq $9, %r10
+ sub $9, %cl
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PMD_0)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_PTE_0)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
+ shrq $9, %r10
+ sub $9, %cl
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PTE_0)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
+ /* identity map the control page at its physical address */
+
+ movq $0x0000ff8000000000, %r10 /* mask */
+ mov $(39 - 3), %cl /* bits to shift */
+ movq PTR(PA_CONTROL_PAGE)(%rsi), %r11 /* address to map */
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PGD)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_PUD_1)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
+ shrq $9, %r10
+ sub $9, %cl
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PUD_1)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_PMD_1)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
+ shrq $9, %r10
+ sub $9, %cl
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PMD_1)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_PTE_1)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
+ shrq $9, %r10
+ sub $9, %cl
+
+ movq %r11, %r9
+ andq %r10, %r9
+ shrq %cl, %r9
+
+ movq PTR(VA_PTE_1)(%rsi), %r8
+ addq %r8, %r9
+ movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
+ orq $PAGE_ATTR, %r8
+ movq %r8, (%r9)
+
relocate_new_kernel:
- /* %rdi page_list
- * %rsi reboot_code_buffer
+ /* %rdi indirection_page
+ * %rsi page_list
* %rdx start address
- * %rcx page_table
- * %r8 arg5
- * %r9 arg6
*/
/* zero out flags, and disable interrupts */
pushq $0
popfq
- /* set a new stack at the bottom of our page... */
- lea 4096(%rsi), %rsp
+ /* get physical address of control page now */
+ /* this is impossible after page table switch */
+ movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
+
+ /* get physical address of page table now too */
+ movq PTR(PA_TABLE_PAGE)(%rsi), %rcx
- /* store the parameters back on the stack */
- pushq %rdx /* store the start address */
+ /* switch to new set of page tables */
+ movq PTR(PA_PGD)(%rsi), %r9
+ movq %r9, %cr3
+
+ /* setup a new stack at the end of the physical control page */
+ lea 4096(%r8), %rsp
+
+ /* jump to identity mapped page */
+ addq $(identity_mapped - relocate_kernel), %r8
+ pushq %r8
+ ret
+
+identity_mapped:
+ /* store the start address on the stack */
+ pushq %rdx
/* Set cr0 to a known state:
* 31 1 == Paging enabled
@@ -136,8 +274,3 @@ relocate_new_kernel:
xorq %r15, %r15
ret
-relocate_new_kernel_end:
-
- .globl relocate_new_kernel_size
-relocate_new_kernel_size:
- .quad relocate_new_kernel_end - relocate_new_kernel