[PATCH] i386: Avoid overwriting the current pgd (V4, i386)
kexec: Avoid overwriting the current pgd (V4, i386)
This patch upgrades the i386-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>
diff --git a/arch/i386/kernel/machine_kexec.c b/arch/i386/kernel/machine_kexec.c
index 66c3dc9..91966ba 100644
--- a/arch/i386/kernel/machine_kexec.c
+++ b/arch/i386/kernel/machine_kexec.c
@@ -21,70 +21,13 @@
#include <asm/system.h>
#define PAGE_ALIGNED __attribute__ ((__aligned__(PAGE_SIZE)))
-
-#define L0_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
-#define L1_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
-#define L2_ATTR (_PAGE_PRESENT)
-
-#define LEVEL0_SIZE (1UL << 12UL)
-
-#ifndef CONFIG_X86_PAE
-#define LEVEL1_SIZE (1UL << 22UL)
-static u32 pgtable_level1[1024] PAGE_ALIGNED;
-
-static void identity_map_page(unsigned long address)
-{
- unsigned long level1_index, level2_index;
- u32 *pgtable_level2;
-
- /* Find the current page table */
- pgtable_level2 = __va(read_cr3());
-
- /* Find the indexes of the physical address to identity map */
- level1_index = (address % LEVEL1_SIZE)/LEVEL0_SIZE;
- level2_index = address / LEVEL1_SIZE;
-
- /* Identity map the page table entry */
- pgtable_level1[level1_index] = address | L0_ATTR;
- pgtable_level2[level2_index] = __pa(pgtable_level1) | L1_ATTR;
-
- /* Flush the tlb so the new mapping takes effect.
- * Global tlb entries are not flushed but that is not an issue.
- */
- load_cr3(pgtable_level2);
-}
-
-#else
-#define LEVEL1_SIZE (1UL << 21UL)
-#define LEVEL2_SIZE (1UL << 30UL)
-static u64 pgtable_level1[512] PAGE_ALIGNED;
-static u64 pgtable_level2[512] PAGE_ALIGNED;
-
-static void identity_map_page(unsigned long address)
-{
- unsigned long level1_index, level2_index, level3_index;
- u64 *pgtable_level3;
-
- /* Find the current page table */
- pgtable_level3 = __va(read_cr3());
-
- /* Find the indexes of the physical address to identity map */
- level1_index = (address % LEVEL1_SIZE)/LEVEL0_SIZE;
- level2_index = (address % LEVEL2_SIZE)/LEVEL1_SIZE;
- level3_index = address / LEVEL2_SIZE;
-
- /* Identity map the page table entry */
- pgtable_level1[level1_index] = address | L0_ATTR;
- pgtable_level2[level2_index] = __pa(pgtable_level1) | L1_ATTR;
- set_64bit(&pgtable_level3[level3_index],
- __pa(pgtable_level2) | L2_ATTR);
-
- /* Flush the tlb so the new mapping takes effect.
- * Global tlb entries are not flushed but that is not an issue.
- */
- load_cr3(pgtable_level3);
-}
+static u32 kexec_pgd[1024] PAGE_ALIGNED;
+#ifdef CONFIG_X86_PAE
+static u32 kexec_pmd0[1024] PAGE_ALIGNED;
+static u32 kexec_pmd1[1024] PAGE_ALIGNED;
#endif
+static u32 kexec_pte0[1024] PAGE_ALIGNED;
+static u32 kexec_pte1[1024] PAGE_ALIGNED;
static void set_idt(void *newidt, __u16 limit)
{
@@ -128,16 +71,6 @@
#undef __STR
}
-typedef asmlinkage NORET_TYPE void (*relocate_new_kernel_t)(
- unsigned long indirection_page,
- unsigned long reboot_code_buffer,
- unsigned long start_address,
- unsigned int has_pae) ATTRIB_NORET;
-
-extern const unsigned char relocate_new_kernel[];
-extern void relocate_new_kernel_end(void);
-extern const unsigned int relocate_new_kernel_size;
-
/*
* A architecture hook called to validate the
* proposed image and prepare the control pages
@@ -170,25 +103,29 @@
*/
NORET_TYPE void machine_kexec(struct kimage *image)
{
- unsigned long page_list;
- unsigned long reboot_code_buffer;
-
- relocate_new_kernel_t rnk;
+ unsigned long page_list[PAGES_NR];
+ void *control_page;
/* Interrupts aren't acceptable while we reboot */
local_irq_disable();
- /* Compute some offsets */
- reboot_code_buffer = page_to_pfn(image->control_code_page)
- << PAGE_SHIFT;
- page_list = image->head;
+ control_page = page_address(image->control_code_page);
+ memcpy(control_page, relocate_kernel, PAGE_SIZE);
- /* Set up an identity mapping for the reboot_code_buffer */
- identity_map_page(reboot_code_buffer);
-
- /* copy it out */
- memcpy((void *)reboot_code_buffer, relocate_new_kernel,
- relocate_new_kernel_size);
+ page_list[PA_CONTROL_PAGE] = __pa(control_page);
+ page_list[VA_CONTROL_PAGE] = (unsigned long)relocate_kernel;
+ page_list[PA_PGD] = __pa(kexec_pgd);
+ page_list[VA_PGD] = (unsigned long)kexec_pgd;
+#ifdef CONFIG_X86_PAE
+ page_list[PA_PMD_0] = __pa(kexec_pmd0);
+ page_list[VA_PMD_0] = (unsigned long)kexec_pmd0;
+ page_list[PA_PMD_1] = __pa(kexec_pmd1);
+ page_list[VA_PMD_1] = (unsigned long)kexec_pmd1;
+#endif
+ page_list[PA_PTE_0] = __pa(kexec_pte0);
+ page_list[VA_PTE_0] = (unsigned long)kexec_pte0;
+ page_list[PA_PTE_1] = __pa(kexec_pte1);
+ page_list[VA_PTE_1] = (unsigned long)kexec_pte1;
/* The segment registers are funny things, they have both a
* visible and an invisible part. Whenever the visible part is
@@ -207,8 +144,8 @@
set_idt(phys_to_virt(0),0);
/* now call it */
- rnk = (relocate_new_kernel_t) reboot_code_buffer;
- (*rnk)(page_list, reboot_code_buffer, image->start, cpu_has_pae);
+ relocate_kernel((unsigned long)image->head, (unsigned long)page_list,
+ image->start, cpu_has_pae);
}
/* crashkernel=size@addr specifies the location to reserve for
diff --git a/arch/i386/kernel/relocate_kernel.S b/arch/i386/kernel/relocate_kernel.S
index d312616..f151d6f 100644
--- a/arch/i386/kernel/relocate_kernel.S
+++ b/arch/i386/kernel/relocate_kernel.S
@@ -7,16 +7,138 @@
*/
#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 << 2)
+#define PAGE_ALIGNED (1 << PAGE_SHIFT)
+#define PAGE_ATTR 0x63 /* _PAGE_PRESENT|_PAGE_RW|_PAGE_ACCESSED|_PAGE_DIRTY */
+#define PAE_PGD_ATTR 0x01 /* _PAGE_PRESENT */
+
+ .text
+ .align PAGE_ALIGNED
+ .globl relocate_kernel
+relocate_kernel:
+ movl 8(%esp), %ebp /* list of pages */
+
+#ifdef CONFIG_X86_PAE
+ /* map the control page at its virtual address */
+
+ movl PTR(VA_PGD)(%ebp), %edi
+ movl PTR(VA_CONTROL_PAGE)(%ebp), %eax
+ andl $0xc0000000, %eax
+ shrl $27, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_PMD_0)(%ebp), %edx
+ orl $PAE_PGD_ATTR, %edx
+ movl %edx, (%eax)
+
+ movl PTR(VA_PMD_0)(%ebp), %edi
+ movl PTR(VA_CONTROL_PAGE)(%ebp), %eax
+ andl $0x3fe00000, %eax
+ shrl $18, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_PTE_0)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+
+ movl PTR(VA_PTE_0)(%ebp), %edi
+ movl PTR(VA_CONTROL_PAGE)(%ebp), %eax
+ andl $0x001ff000, %eax
+ shrl $9, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+
+ /* identity map the control page at its physical address */
+
+ movl PTR(VA_PGD)(%ebp), %edi
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %eax
+ andl $0xc0000000, %eax
+ shrl $27, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_PMD_1)(%ebp), %edx
+ orl $PAE_PGD_ATTR, %edx
+ movl %edx, (%eax)
+
+ movl PTR(VA_PMD_1)(%ebp), %edi
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %eax
+ andl $0x3fe00000, %eax
+ shrl $18, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_PTE_1)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+
+ movl PTR(VA_PTE_1)(%ebp), %edi
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %eax
+ andl $0x001ff000, %eax
+ shrl $9, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+#else
+ /* map the control page at its virtual address */
+
+ movl PTR(VA_PGD)(%ebp), %edi
+ movl PTR(VA_CONTROL_PAGE)(%ebp), %eax
+ andl $0xffc00000, %eax
+ shrl $20, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_PTE_0)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+
+ movl PTR(VA_PTE_0)(%ebp), %edi
+ movl PTR(VA_CONTROL_PAGE)(%ebp), %eax
+ andl $0x003ff000, %eax
+ shrl $10, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+
+ /* identity map the control page at its physical address */
+
+ movl PTR(VA_PGD)(%ebp), %edi
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %eax
+ andl $0xffc00000, %eax
+ shrl $20, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_PTE_1)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+
+ movl PTR(VA_PTE_1)(%ebp), %edi
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %eax
+ andl $0x003ff000, %eax
+ shrl $10, %eax
+ addl %edi, %eax
+
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %edx
+ orl $PAGE_ATTR, %edx
+ movl %edx, (%eax)
+#endif
+
relocate_new_kernel:
/* read the arguments and say goodbye to the stack */
movl 4(%esp), %ebx /* page_list */
- movl 8(%esp), %ebp /* reboot_code_buffer */
+ movl 8(%esp), %ebp /* list of pages */
movl 12(%esp), %edx /* start address */
movl 16(%esp), %ecx /* cpu_has_pae */
@@ -24,11 +146,26 @@
pushl $0
popfl
- /* set a new stack at the bottom of our page... */
- lea 4096(%ebp), %esp
+ /* get physical address of control page now */
+ /* this is impossible after page table switch */
+ movl PTR(PA_CONTROL_PAGE)(%ebp), %edi
- /* store the parameters back on the stack */
- pushl %edx /* store the start address */
+ /* switch to new set of page tables */
+ movl PTR(PA_PGD)(%ebp), %eax
+ movl %eax, %cr3
+
+ /* setup a new stack at the end of the physical control page */
+ lea 4096(%edi), %esp
+
+ /* jump to identity mapped page */
+ movl %edi, %eax
+ addl $(identity_mapped - relocate_kernel), %eax
+ pushl %eax
+ ret
+
+identity_mapped:
+ /* store the start address on the stack */
+ pushl %edx
/* Set cr0 to a known state:
* 31 0 == Paging disabled
@@ -113,8 +250,3 @@
xorl %edi, %edi
xorl %ebp, %ebp
ret
-relocate_new_kernel_end:
-
- .globl relocate_new_kernel_size
-relocate_new_kernel_size:
- .long relocate_new_kernel_end - relocate_new_kernel
diff --git a/include/asm-i386/kexec.h b/include/asm-i386/kexec.h
index 53f0e06..4dfc9f5 100644
--- a/include/asm-i386/kexec.h
+++ b/include/asm-i386/kexec.h
@@ -1,6 +1,26 @@
#ifndef _I386_KEXEC_H
#define _I386_KEXEC_H
+#define PA_CONTROL_PAGE 0
+#define VA_CONTROL_PAGE 1
+#define PA_PGD 2
+#define VA_PGD 3
+#define PA_PTE_0 4
+#define VA_PTE_0 5
+#define PA_PTE_1 6
+#define VA_PTE_1 7
+#ifdef CONFIG_X86_PAE
+#define PA_PMD_0 8
+#define VA_PMD_0 9
+#define PA_PMD_1 10
+#define VA_PMD_1 11
+#define PAGES_NR 12
+#else
+#define PAGES_NR 8
+#endif
+
+#ifndef __ASSEMBLY__
+
#include <asm/fixmap.h>
#include <asm/ptrace.h>
#include <asm/string.h>
@@ -72,5 +92,12 @@
newregs->eip = (unsigned long)current_text_addr();
}
}
+asmlinkage NORET_TYPE void
+relocate_kernel(unsigned long indirection_page,
+ unsigned long control_page,
+ unsigned long start_address,
+ unsigned int has_pae) ATTRIB_NORET;
+
+#endif /* __ASSEMBLY__ */
#endif /* _I386_KEXEC_H */