Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751095AbWEAJtS (ORCPT ); Mon, 1 May 2006 05:49:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751098AbWEAJtS (ORCPT ); Mon, 1 May 2006 05:49:18 -0400 Received: from sv1.valinux.co.jp ([210.128.90.2]:34701 "EHLO sv1.valinux.co.jp") by vger.kernel.org with ESMTP id S1751095AbWEAJtR (ORCPT ); Mon, 1 May 2006 05:49:17 -0400 From: Magnus Damm To: fastboot@lists.osdl.org, linux-kernel@vger.kernel.org Cc: Magnus Damm , ebiederm@xmission.com Message-Id: <20060501095041.16897.49541.sendpatchset@cherry.local> Subject: [PATCH] kexec: Avoid overwriting the current pgd (i386) Date: Mon, 1 May 2006 18:49:16 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9888 Lines: 327 kexec: Avoid overwriting the current pgd (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 called "page_table_a". These tables are used to provide an executable identity mapping without overwriting the current pgd. Signed-off-by: Magnus Damm --- The patch has been tested with regular kexec and CONFIG_CRASH_DUMP. Both PAE and non-PAE configurations work well. Apply on top of 2.6.17-rc3. arch/i386/kernel/machine_kexec.c | 174 +++++++++++++++++++----------------- arch/i386/kernel/relocate_kernel.S | 19 +++ include/linux/kexec.h | 11 ++ 3 files changed, 121 insertions(+), 83 deletions(-) --- 0001/arch/i386/kernel/machine_kexec.c +++ work/arch/i386/kernel/machine_kexec.c 2006-05-01 11:38:13.000000000 +0900 @@ -2,6 +2,9 @@ * machine_kexec.c - handle transition of Linux booting another kernel * Copyright (C) 2002-2005 Eric Biederman * + * 2006-04-27 Magnus Damm : + * - rewrote identity map code to avoid overwriting current pgd + * * This source code is licensed under the GNU General Public License, * Version 2. See the file COPYING for more details. */ @@ -19,72 +22,6 @@ #include #include -#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); -} -#endif - static void set_idt(void *newidt, __u16 limit) { struct Xgt_desc_struct curidt; @@ -96,7 +33,6 @@ static void set_idt(void *newidt, __u16 load_idt(&curidt); }; - static void set_gdt(void *newgdt, __u16 limit) { struct Xgt_desc_struct curgdt; @@ -131,12 +67,66 @@ typedef asmlinkage NORET_TYPE void (*rel unsigned long indirection_page, unsigned long reboot_code_buffer, unsigned long start_address, - unsigned int has_pae) ATTRIB_NORET; + unsigned long page_table_a, + unsigned long has_pae) ATTRIB_NORET; const extern unsigned char relocate_new_kernel[]; extern void relocate_new_kernel_end(void); const extern unsigned int relocate_new_kernel_size; +static int allocate_page_table_a(struct kimage *image) +{ + struct page *page; + int k = sizeof(image->page_table_a) / sizeof(image->page_table_a[0]); + + for (; k > 0; k--) { + page = kimage_alloc_control_pages(image, 0); + if (!page) + return -ENOMEM; + + clear_page(page_address(page)); + image->page_table_a[k - 1] = page; + } + + return 0; +} + +/* workaround for include/asm-i386/pgtable-3level.h */ + +#ifdef CONFIG_X86_PAE +#undef pud_present +#define pud_present(pud) (pud_val(pud) & _PAGE_PRESENT) +#endif + +#define pa_page(page) __pa(page_address(page)) + +static int create_mapping(struct page *root, struct page **pages, + unsigned long va, unsigned long pa) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + int k = 0; + + pgd = (pgd_t *)page_address(root) + pgd_index(va); + if (!pgd_present(*pgd)) + set_pgd(pgd, __pgd(pa_page(pages[k++]) | _KERNPG_TABLE)); + + pud = pud_offset(pgd, va); + if (!pud_present(*pud)) + set_pud(pud, __pud(pa_page(pages[k++]) | _KERNPG_TABLE)); + + pmd = pmd_offset(pud, va); + if (!pmd_present(*pmd)) + set_pmd(pmd, __pmd(pa_page(pages[k++]) | _KERNPG_TABLE)); + + pte = (pte_t *)page_address(pmd_page(*pmd)) + pte_index(va); + set_pte(pte, __pte(pa | _PAGE_KERNEL_EXEC)); + + return k; +} + /* * A architecture hook called to validate the * proposed image and prepare the control pages @@ -152,6 +142,33 @@ const extern unsigned int relocate_new_k */ int machine_kexec_prepare(struct kimage *image) { + void *control_page; + unsigned long pa; + int k; + + k = allocate_page_table_a(image); + if (k) + return k; + + /* fill in control_page with assembly code */ + + control_page = page_address(image->control_code_page); + memcpy(control_page, relocate_new_kernel, relocate_new_kernel_size); + + /* map the control_page at the virtual address of relocate_kernel.S */ + + pa = __pa(control_page); + + k = create_mapping(image->page_table_a[0], + &image->page_table_a[1], + (unsigned long)relocate_new_kernel, pa); + + /* identity map the control_page */ + + create_mapping(image->page_table_a[0], + &image->page_table_a[k + 1], + pa, pa); + return 0; } @@ -170,24 +187,16 @@ void machine_kexec_cleanup(struct kimage NORET_TYPE void machine_kexec(struct kimage *image) { unsigned long page_list; - unsigned long reboot_code_buffer; - + unsigned long control_code; + unsigned long page_table_a; relocate_new_kernel_t rnk; /* 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; - - /* 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); + control_code = __pa(page_address(image->control_code_page)); + page_table_a = __pa(page_address(image->page_table_a[0])); /* The segment registers are funny things, they are * automatically loaded from a table, in memory wherever you @@ -209,6 +218,7 @@ NORET_TYPE void machine_kexec(struct kim 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); + rnk = (relocate_new_kernel_t) relocate_new_kernel; + (*rnk)(page_list, control_code, image->start, + page_table_a, (unsigned long)cpu_has_pae); } --- 0001/arch/i386/kernel/relocate_kernel.S +++ work/arch/i386/kernel/relocate_kernel.S 2006-05-01 11:13:14.000000000 +0900 @@ -7,7 +7,11 @@ */ #include +#include +.text +.align (1 << PAGE_SHIFT) + /* * Must be relocatable PIC code callable as a C function, that once * it starts can not use the previous processes stack. @@ -18,18 +22,31 @@ relocate_new_kernel: movl 4(%esp), %ebx /* page_list */ movl 8(%esp), %ebp /* reboot_code_buffer */ movl 12(%esp), %edx /* start address */ - movl 16(%esp), %ecx /* cpu_has_pae */ + movl 16(%esp), %edi /* page_table_a */ + movl 20(%esp), %ecx /* cpu_has_pae */ /* zero out flags, and disable interrupts */ pushl $0 popfl + /* switch to page_table_a */ + movl %edi, %eax + movl %eax, %cr3 + /* set a new stack at the bottom of our page... */ lea 4096(%ebp), %esp /* store the parameters back on the stack */ pushl %edx /* store the start address */ + /* jump to identity mapped page */ + movl %ebp, %eax + addl $(identity_mapped - relocate_new_kernel), %eax + pushl %eax + ret + +identity_mapped: + /* Set cr0 to a known state: * 31 0 == Paging disabled * 18 0 == Alignment check disabled --- 0001/include/linux/kexec.h +++ work/include/linux/kexec.h 2006-05-01 11:13:14.000000000 +0900 @@ -69,6 +69,17 @@ struct kimage { unsigned long start; struct page *control_code_page; + /* page_table_a[] holds enough pages to create a new page table + * that maps the control page twice.. + */ + +#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE) + struct page *page_table_a[3]; /* (2 * pte) + pgd */ +#endif +#if defined(CONFIG_X86_32) && defined(CONFIG_X86_PAE) + struct page *page_table_a[5]; /* (2 * pte) + (2 * pmd) + pgd */ +#endif + unsigned long nr_segments; struct kexec_segment segment[KEXEC_SEGMENT_MAX]; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/