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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>
This commit is contained in:
Magnus Damm
Andi Kleen
parent
f574164491
commit
4bfaaef01a
@ -15,6 +15,15 @@
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#include <asm/mmu_context.h>
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#include <asm/io.h>
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#define PAGE_ALIGNED __attribute__ ((__aligned__(PAGE_SIZE)))
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static u64 kexec_pgd[512] PAGE_ALIGNED;
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static u64 kexec_pud0[512] PAGE_ALIGNED;
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static u64 kexec_pmd0[512] PAGE_ALIGNED;
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static u64 kexec_pte0[512] PAGE_ALIGNED;
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static u64 kexec_pud1[512] PAGE_ALIGNED;
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static u64 kexec_pmd1[512] PAGE_ALIGNED;
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static u64 kexec_pte1[512] PAGE_ALIGNED;
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static void init_level2_page(pmd_t *level2p, unsigned long addr)
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{
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unsigned long end_addr;
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@ -144,32 +153,19 @@ static void load_segments(void)
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);
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}
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typedef NORET_TYPE void (*relocate_new_kernel_t)(unsigned long indirection_page,
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unsigned long control_code_buffer,
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unsigned long start_address,
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unsigned long pgtable) ATTRIB_NORET;
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extern const unsigned char relocate_new_kernel[];
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extern const unsigned long relocate_new_kernel_size;
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int machine_kexec_prepare(struct kimage *image)
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{
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unsigned long start_pgtable, control_code_buffer;
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unsigned long start_pgtable;
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int result;
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/* Calculate the offsets */
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start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
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control_code_buffer = start_pgtable + PAGE_SIZE;
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/* Setup the identity mapped 64bit page table */
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result = init_pgtable(image, start_pgtable);
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if (result)
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return result;
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/* Place the code in the reboot code buffer */
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memcpy(__va(control_code_buffer), relocate_new_kernel,
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relocate_new_kernel_size);
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return 0;
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}
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@ -184,28 +180,34 @@ void machine_kexec_cleanup(struct kimage *image)
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*/
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NORET_TYPE void machine_kexec(struct kimage *image)
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{
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unsigned long page_list;
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unsigned long control_code_buffer;
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unsigned long start_pgtable;
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relocate_new_kernel_t rnk;
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unsigned long page_list[PAGES_NR];
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void *control_page;
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/* Interrupts aren't acceptable while we reboot */
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local_irq_disable();
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/* Calculate the offsets */
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page_list = image->head;
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start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
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control_code_buffer = start_pgtable + PAGE_SIZE;
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control_page = page_address(image->control_code_page) + PAGE_SIZE;
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memcpy(control_page, relocate_kernel, PAGE_SIZE);
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/* Set the low half of the page table to my identity mapped
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* page table for kexec. Leave the high half pointing at the
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* kernel pages. Don't bother to flush the global pages
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* as that will happen when I fully switch to my identity mapped
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* page table anyway.
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*/
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memcpy(__va(read_cr3()), __va(start_pgtable), PAGE_SIZE/2);
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__flush_tlb();
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page_list[PA_CONTROL_PAGE] = __pa(control_page);
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page_list[VA_CONTROL_PAGE] = (unsigned long)relocate_kernel;
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page_list[PA_PGD] = __pa(kexec_pgd);
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page_list[VA_PGD] = (unsigned long)kexec_pgd;
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page_list[PA_PUD_0] = __pa(kexec_pud0);
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page_list[VA_PUD_0] = (unsigned long)kexec_pud0;
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page_list[PA_PMD_0] = __pa(kexec_pmd0);
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page_list[VA_PMD_0] = (unsigned long)kexec_pmd0;
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page_list[PA_PTE_0] = __pa(kexec_pte0);
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page_list[VA_PTE_0] = (unsigned long)kexec_pte0;
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page_list[PA_PUD_1] = __pa(kexec_pud1);
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page_list[VA_PUD_1] = (unsigned long)kexec_pud1;
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page_list[PA_PMD_1] = __pa(kexec_pmd1);
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page_list[VA_PMD_1] = (unsigned long)kexec_pmd1;
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page_list[PA_PTE_1] = __pa(kexec_pte1);
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page_list[VA_PTE_1] = (unsigned long)kexec_pte1;
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page_list[PA_TABLE_PAGE] =
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(unsigned long)__pa(page_address(image->control_code_page));
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/* The segment registers are funny things, they have both a
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* visible and an invisible part. Whenever the visible part is
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@ -222,9 +224,10 @@ NORET_TYPE void machine_kexec(struct kimage *image)
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*/
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set_gdt(phys_to_virt(0),0);
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set_idt(phys_to_virt(0),0);
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/* now call it */
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rnk = (relocate_new_kernel_t) control_code_buffer;
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(*rnk)(page_list, control_code_buffer, image->start, start_pgtable);
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relocate_kernel((unsigned long)image->head, (unsigned long)page_list,
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image->start);
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}
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/* crashkernel=size@addr specifies the location to reserve for
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@ -7,31 +7,169 @@
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*/
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#include <linux/linkage.h>
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#include <asm/page.h>
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#include <asm/kexec.h>
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/*
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* Must be relocatable PIC code callable as a C function, that once
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* it starts can not use the previous processes stack.
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*/
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.globl relocate_new_kernel
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/*
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* Must be relocatable PIC code callable as a C function
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*/
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#define PTR(x) (x << 3)
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#define PAGE_ALIGNED (1 << PAGE_SHIFT)
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#define PAGE_ATTR 0x63 /* _PAGE_PRESENT|_PAGE_RW|_PAGE_ACCESSED|_PAGE_DIRTY */
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.text
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.align PAGE_ALIGNED
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.code64
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relocate_new_kernel:
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/* %rdi page_list
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* %rsi reboot_code_buffer
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.globl relocate_kernel
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relocate_kernel:
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/* %rdi indirection_page
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* %rsi page_list
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* %rdx start address
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*/
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/* map the control page at its virtual address */
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movq $0x0000ff8000000000, %r10 /* mask */
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mov $(39 - 3), %cl /* bits to shift */
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movq PTR(VA_CONTROL_PAGE)(%rsi), %r11 /* address to map */
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PGD)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_PUD_0)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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shrq $9, %r10
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sub $9, %cl
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PUD_0)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_PMD_0)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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shrq $9, %r10
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sub $9, %cl
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PMD_0)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_PTE_0)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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shrq $9, %r10
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sub $9, %cl
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PTE_0)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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/* identity map the control page at its physical address */
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movq $0x0000ff8000000000, %r10 /* mask */
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mov $(39 - 3), %cl /* bits to shift */
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movq PTR(PA_CONTROL_PAGE)(%rsi), %r11 /* address to map */
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PGD)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_PUD_1)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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shrq $9, %r10
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sub $9, %cl
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PUD_1)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_PMD_1)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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shrq $9, %r10
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sub $9, %cl
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PMD_1)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_PTE_1)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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shrq $9, %r10
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sub $9, %cl
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movq %r11, %r9
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andq %r10, %r9
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shrq %cl, %r9
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movq PTR(VA_PTE_1)(%rsi), %r8
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addq %r8, %r9
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movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
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orq $PAGE_ATTR, %r8
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movq %r8, (%r9)
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relocate_new_kernel:
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/* %rdi indirection_page
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* %rsi page_list
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* %rdx start address
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* %rcx page_table
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* %r8 arg5
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* %r9 arg6
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*/
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/* zero out flags, and disable interrupts */
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pushq $0
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popfq
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/* set a new stack at the bottom of our page... */
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lea 4096(%rsi), %rsp
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/* get physical address of control page now */
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/* this is impossible after page table switch */
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movq PTR(PA_CONTROL_PAGE)(%rsi), %r8
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/* store the parameters back on the stack */
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pushq %rdx /* store the start address */
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/* get physical address of page table now too */
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movq PTR(PA_TABLE_PAGE)(%rsi), %rcx
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/* switch to new set of page tables */
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movq PTR(PA_PGD)(%rsi), %r9
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movq %r9, %cr3
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/* setup a new stack at the end of the physical control page */
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lea 4096(%r8), %rsp
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/* jump to identity mapped page */
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addq $(identity_mapped - relocate_kernel), %r8
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pushq %r8
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ret
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identity_mapped:
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/* store the start address on the stack */
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pushq %rdx
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/* Set cr0 to a known state:
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* 31 1 == Paging enabled
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@ -136,8 +274,3 @@ relocate_new_kernel:
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xorq %r15, %r15
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ret
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relocate_new_kernel_end:
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.globl relocate_new_kernel_size
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relocate_new_kernel_size:
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.quad relocate_new_kernel_end - relocate_new_kernel
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@ -1,6 +1,27 @@
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#ifndef _X86_64_KEXEC_H
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#define _X86_64_KEXEC_H
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#define PA_CONTROL_PAGE 0
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#define VA_CONTROL_PAGE 1
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#define PA_PGD 2
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#define VA_PGD 3
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#define PA_PUD_0 4
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#define VA_PUD_0 5
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#define PA_PMD_0 6
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#define VA_PMD_0 7
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#define PA_PTE_0 8
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#define VA_PTE_0 9
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#define PA_PUD_1 10
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#define VA_PUD_1 11
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#define PA_PMD_1 12
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#define VA_PMD_1 13
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#define PA_PTE_1 14
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#define VA_PTE_1 15
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#define PA_TABLE_PAGE 16
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#define PAGES_NR 17
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#ifndef __ASSEMBLY__
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#include <linux/string.h>
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#include <asm/page.h>
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@ -64,4 +85,12 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
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newregs->rip = (unsigned long)current_text_addr();
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}
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}
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NORET_TYPE void
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relocate_kernel(unsigned long indirection_page,
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unsigned long page_list,
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unsigned long start_address) ATTRIB_NORET;
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#endif /* __ASSEMBLY__ */
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#endif /* _X86_64_KEXEC_H */
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