[PATCH] kdump: Routines for copying dump pages

This patch provides the interfaces necessary to read the dump contents,
treating it as a high memory device.

Signed off by Hariprasad Nellitheertha <[email protected]>
Signed-off-by: Eric Biederman <[email protected]>
Signed-off-by: Vivek Goyal <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

arch/i386/mm/highmem.c

@@ -75,6 +75,24 @@ void kunmap_atomic(void *kvaddr, enum km_type type)
 	preempt_check_resched();
 }
 
+/* This is the same as kmap_atomic() but can map memory that doesn't
+ * have a struct page associated with it.
+ */
+void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
+{
+	enum fixed_addresses idx;
+	unsigned long vaddr;
+
+	inc_preempt_count();
+
+	idx = type + KM_TYPE_NR*smp_processor_id();
+	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+	set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
+	__flush_tlb_one(vaddr);
+
+	return (void*) vaddr;
+}
+
 struct page *kmap_atomic_to_page(void *ptr)
 {
 	unsigned long idx, vaddr = (unsigned long)ptr;

include/asm-i386/highmem.h

@@ -70,6 +70,7 @@ void *kmap(struct page *page);
 void kunmap(struct page *page);
 void *kmap_atomic(struct page *page, enum km_type type);
 void kunmap_atomic(void *kvaddr, enum km_type type);
+void *kmap_atomic_pfn(unsigned long pfn, enum km_type type);
 struct page *kmap_atomic_to_page(void *ptr);
 
 #define flush_cache_kmaps()	do { } while (0)

include/linux/crash_dump.h

@@ -0,0 +1,13 @@
+#ifndef LINUX_CRASH_DUMP_H
+#define LINUX_CRASH_DUMP_H
+
+#ifdef CONFIG_CRASH_DUMP
+#include <linux/kexec.h>
+#include <linux/smp_lock.h>
+#include <linux/device.h>
+#include <linux/proc_fs.h>
+
+extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
+						unsigned long, int);
+#endif /* CONFIG_CRASH_DUMP */
+#endif /* LINUX_CRASHDUMP_H */

include/linux/highmem.h

@@ -28,6 +28,7 @@ static inline void *kmap(struct page *page)
 
 #define kmap_atomic(page, idx)		page_address(page)
 #define kunmap_atomic(addr, idx)	do { } while (0)
+#define kmap_atomic_pfn(pfn, idx)	page_address(pfn_to_page(pfn))
 #define kmap_atomic_to_page(ptr)	virt_to_page(ptr)
 
 #endif /* CONFIG_HIGHMEM */

kernel/Makefile

@@ -28,6 +28,7 @@ obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
 obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
+obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_SECCOMP) += seccomp.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)

kernel/crash_dump.c

@@ -0,0 +1,49 @@
+/*
+ *	kernel/crash_dump.c - Memory preserving reboot related code.
+ *
+ *	Created by: Hariprasad Nellitheertha ([email protected])
+ *	Copyright (C) IBM Corporation, 2004. All rights reserved
+ */
+
+#include <linux/smp_lock.h>
+#include <linux/errno.h>
+#include <linux/proc_fs.h>
+#include <linux/bootmem.h>
+#include <linux/highmem.h>
+#include <linux/crash_dump.h>
+
+#include <asm/io.h>
+#include <asm/uaccess.h>
+
+/*
+ * Copy a page from "oldmem". For this page, there is no pte mapped
+ * in the current kernel. We stitch up a pte, similar to kmap_atomic.
+ */
+ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
+				size_t csize, unsigned long offset, int userbuf)
+{
+	void *page, *vaddr;
+
+	if (!csize)
+		return 0;
+
+	page = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
+	copy_page(page, vaddr);
+	kunmap_atomic(vaddr, KM_PTE0);
+
+	if (userbuf) {
+		if (copy_to_user(buf, (page + offset), csize)) {
+			kfree(page);
+			return -EFAULT;
+		}
+	} else {
+		memcpy(buf, (page + offset), csize);
+	}
+
+	kfree(page);
+	return csize;
+}