Commit 4bfaaef0 authored by Magnus Damm's avatar Magnus Damm Committed by Andi Kleen
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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: default avatarMagnus Damm <magnus@valinux.co.jp>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent f5741644
......@@ -15,6 +15,15 @@
#include <asm/mmu_context.h>
#include <asm/io.h>
#define PAGE_ALIGNED __attribute__ ((__aligned__(PAGE_SIZE)))
static u64 kexec_pgd[512] PAGE_ALIGNED;
static u64 kexec_pud0[512] PAGE_ALIGNED;
static u64 kexec_pmd0[512] PAGE_ALIGNED;
static u64 kexec_pte0[512] PAGE_ALIGNED;
static u64 kexec_pud1[512] PAGE_ALIGNED;
static u64 kexec_pmd1[512] PAGE_ALIGNED;
static u64 kexec_pte1[512] PAGE_ALIGNED;
static void init_level2_page(pmd_t *level2p, unsigned long addr)
{
unsigned long end_addr;
......@@ -144,32 +153,19 @@ static void load_segments(void)
);
}
typedef NORET_TYPE void (*relocate_new_kernel_t)(unsigned long indirection_page,
unsigned long control_code_buffer,
unsigned long start_address,
unsigned long pgtable) ATTRIB_NORET;
extern const unsigned char relocate_new_kernel[];
extern const unsigned long relocate_new_kernel_size;
int machine_kexec_prepare(struct kimage *image)
{
unsigned long start_pgtable, control_code_buffer;
unsigned long start_pgtable;
int result;
/* Calculate the offsets */
start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
control_code_buffer = start_pgtable + PAGE_SIZE;
/* Setup the identity mapped 64bit page table */
result = init_pgtable(image, start_pgtable);
if (result)
return result;
/* Place the code in the reboot code buffer */
memcpy(__va(control_code_buffer), relocate_new_kernel,
relocate_new_kernel_size);
return 0;
}
......@@ -184,28 +180,34 @@ void machine_kexec_cleanup(struct kimage *image)
*/
NORET_TYPE void machine_kexec(struct kimage *image)
{
unsigned long page_list;
unsigned long control_code_buffer;
unsigned long start_pgtable;
relocate_new_kernel_t rnk;
unsigned long page_list[PAGES_NR];
void *control_page;
/* Interrupts aren't acceptable while we reboot */
local_irq_disable();
/* Calculate the offsets */
page_list = image->head;
start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
control_code_buffer = start_pgtable + PAGE_SIZE;
/* Set the low half of the page table to my identity mapped
* page table for kexec. Leave the high half pointing at the
* kernel pages. Don't bother to flush the global pages
* as that will happen when I fully switch to my identity mapped
* page table anyway.
*/
memcpy(__va(read_cr3()), __va(start_pgtable), PAGE_SIZE/2);
__flush_tlb();
control_page = page_address(image->control_code_page) + PAGE_SIZE;
memcpy(control_page, relocate_kernel, PAGE_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;
page_list[PA_PUD_0] = __pa(kexec_pud0);
page_list[VA_PUD_0] = (unsigned long)kexec_pud0;
page_list[PA_PMD_0] = __pa(kexec_pmd0);
page_list[VA_PMD_0] = (unsigned long)kexec_pmd0;
page_list[PA_PTE_0] = __pa(kexec_pte0);
page_list[VA_PTE_0] = (unsigned long)kexec_pte0;
page_list[PA_PUD_1] = __pa(kexec_pud1);
page_list[VA_PUD_1] = (unsigned long)kexec_pud1;
page_list[PA_PMD_1] = __pa(kexec_pmd1);
page_list[VA_PMD_1] = (unsigned long)kexec_pmd1;
page_list[PA_PTE_1] = __pa(kexec_pte1);
page_list[VA_PTE_1] = (unsigned long)kexec_pte1;
page_list[PA_TABLE_PAGE] =
(unsigned long)__pa(page_address(image->control_code_page));
/* The segment registers are funny things, they have both a
* visible and an invisible part. Whenever the visible part is
......@@ -222,9 +224,10 @@ NORET_TYPE void machine_kexec(struct kimage *image)
*/
set_gdt(phys_to_virt(0),0);
set_idt(phys_to_virt(0),0);
/* now call it */
rnk = (relocate_new_kernel_t) control_code_buffer;
(*rnk)(page_list, control_code_buffer, image->start, start_pgtable);
relocate_kernel((unsigned long)image->head, (unsigned long)page_list,
image->start);
}
/* crashkernel=size@addr specifies the location to reserve for
......
......@@ -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
#ifndef _X86_64_KEXEC_H
#define _X86_64_KEXEC_H
#define PA_CONTROL_PAGE 0
#define VA_CONTROL_PAGE 1
#define PA_PGD 2
#define VA_PGD 3
#define PA_PUD_0 4
#define VA_PUD_0 5
#define PA_PMD_0 6
#define VA_PMD_0 7
#define PA_PTE_0 8
#define VA_PTE_0 9
#define PA_PUD_1 10
#define VA_PUD_1 11
#define PA_PMD_1 12
#define VA_PMD_1 13
#define PA_PTE_1 14
#define VA_PTE_1 15
#define PA_TABLE_PAGE 16
#define PAGES_NR 17
#ifndef __ASSEMBLY__
#include <linux/string.h>
#include <asm/page.h>
......@@ -64,4 +85,12 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
newregs->rip = (unsigned long)current_text_addr();
}
}
NORET_TYPE void
relocate_kernel(unsigned long indirection_page,
unsigned long page_list,
unsigned long start_address) ATTRIB_NORET;
#endif /* __ASSEMBLY__ */
#endif /* _X86_64_KEXEC_H */
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