[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
