From: Hariprasad Nellitheertha <hari@in.ibm.com>

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

Signed off by Hariprasad Nellitheertha <hari@in.ibm.com>

Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 25-akpm/arch/i386/mm/highmem.c     |   18 ++++++++++++++++++
 25-akpm/include/asm-i386/highmem.h |    1 +
 25-akpm/include/linux/highmem.h    |    1 +
 25-akpm/kernel/crash.c             |   31 +++++++++++++++++++++++++++++++
 4 files changed, 51 insertions(+)

diff -puN arch/i386/mm/highmem.c~crashdump-routines-for-copying-dump-pages arch/i386/mm/highmem.c
--- 25/arch/i386/mm/highmem.c~crashdump-routines-for-copying-dump-pages	2004-11-30 01:23:56.704146768 -0800
+++ 25-akpm/arch/i386/mm/highmem.c	2004-11-30 01:23:56.712145552 -0800
@@ -74,6 +74,24 @@ void kunmap_atomic(char *kaddr, enum km_
 	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(char *ptr)
 {
 	unsigned long idx, vaddr = (unsigned long)ptr;
diff -puN include/asm-i386/highmem.h~crashdump-routines-for-copying-dump-pages include/asm-i386/highmem.h
--- 25/include/asm-i386/highmem.h~crashdump-routines-for-copying-dump-pages	2004-11-30 01:23:56.706146464 -0800
+++ 25-akpm/include/asm-i386/highmem.h	2004-11-30 01:23:56.713145400 -0800
@@ -72,6 +72,7 @@ void *kmap(struct page *page);
 void kunmap(struct page *page);
 char *kmap_atomic(struct page *page, enum km_type type);
 void kunmap_atomic(char *kvaddr, enum km_type type);
+void *kmap_atomic_pfn(unsigned long pfn, enum km_type type);
 struct page *kmap_atomic_to_page(char *ptr);
 
 #define flush_cache_kmaps()	do { } while (0)
diff -puN include/linux/highmem.h~crashdump-routines-for-copying-dump-pages include/linux/highmem.h
--- 25/include/linux/highmem.h~crashdump-routines-for-copying-dump-pages	2004-11-30 01:23:56.707146312 -0800
+++ 25-akpm/include/linux/highmem.h	2004-11-30 01:23:56.713145400 -0800
@@ -28,6 +28,7 @@ static inline void *kmap(struct page *pa
 
 #define kmap_atomic(page, idx)	 ((char *)page_address(page))
 #define kunmap_atomic(addr, idx) do { char *p = addr; (void)p; } 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 */
diff -puN kernel/crash.c~crashdump-routines-for-copying-dump-pages kernel/crash.c
--- 25/kernel/crash.c~crashdump-routines-for-copying-dump-pages	2004-11-30 01:23:56.708146160 -0800
+++ 25-akpm/kernel/crash.c	2004-11-30 01:23:56.713145400 -0800
@@ -11,6 +11,7 @@
 #include <linux/proc_fs.h>
 #include <asm/io.h>
 #include <asm/uaccess.h>
+#include <asm/highmem.h>
 
 /*
  * Enable kexec reboot upon panic; for dumping
@@ -54,3 +55,33 @@ void __crash_machine_kexec(void)
 		printk(KERN_EMERG "kexec: No kernel image loaded!\n");
 	}
 }
+
+/*
+ * 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, int userbuf)
+{
+	void *page, *vaddr;
+
+	if (!csize)
+		return 0;
+
+	page = kmalloc(PAGE_SIZE, GFP_KERNEL);
+
+	vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
+	copy_page(page, vaddr);
+	kunmap_atomic(vaddr, KM_PTE0);
+
+	if (userbuf) {
+		if (copy_to_user(buf, page, csize)) {
+			kfree(page);
+			return -EFAULT;
+		}
+	} else
+		memcpy(buf, page, csize);
+	kfree(page);
+
+	return 0;
+}
_