[PATCH] kdump: read previous kernel's memory
- Moving the crash_dump.c file to arch dependent part as kmap_atomic_pfn is
specific to i386 and highmem may not exist in other archs.
- Use ioremap for x86_64 to map the previous kernel memory.
- In copy_oldmem_page(), we now directly copy to the user/kernel buffer and
avoid the unneccesary copy to a kmalloc'd page.
Signed-off-by: Rachita Kothiyal <rachita@in.ibm.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/kernel/crash_dump.c b/arch/i386/kernel/crash_dump.c
new file mode 100644
index 0000000..3f532df
--- /dev/null
+++ b/arch/i386/kernel/crash_dump.c
@@ -0,0 +1,74 @@
+/*
+ * kernel/crash_dump.c - Memory preserving reboot related code.
+ *
+ * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
+ * Copyright (C) IBM Corporation, 2004. All rights reserved
+ */
+
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/crash_dump.h>
+
+#include <asm/uaccess.h>
+
+static void *kdump_buf_page;
+
+/**
+ * copy_oldmem_page - copy one page from "oldmem"
+ * @pfn: page frame number to be copied
+ * @buf: target memory address for the copy; this can be in kernel address
+ * space or user address space (see @userbuf)
+ * @csize: number of bytes to copy
+ * @offset: offset in bytes into the page (based on pfn) to begin the copy
+ * @userbuf: if set, @buf is in user address space, use copy_to_user(),
+ * otherwise @buf is in kernel address space, use memcpy().
+ *
+ * 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.
+ *
+ * Calling copy_to_user() in atomic context is not desirable. Hence first
+ * copying the data to a pre-allocated kernel page and then copying to user
+ * space in non-atomic context.
+ */
+ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
+ size_t csize, unsigned long offset, int userbuf)
+{
+ void *vaddr;
+
+ if (!csize)
+ return 0;
+
+ vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
+
+ if (!userbuf) {
+ memcpy(buf, (vaddr + offset), csize);
+ kunmap_atomic(vaddr, KM_PTE0);
+ } else {
+ if (!kdump_buf_page) {
+ printk(KERN_WARNING "Kdump: Kdump buffer page not"
+ " allocated\n");
+ return -EFAULT;
+ }
+ copy_page(kdump_buf_page, vaddr);
+ kunmap_atomic(vaddr, KM_PTE0);
+ if (copy_to_user(buf, (kdump_buf_page + offset), csize))
+ return -EFAULT;
+ }
+
+ return csize;
+}
+
+static int __init kdump_buf_page_init(void)
+{
+ int ret = 0;
+
+ kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!kdump_buf_page) {
+ printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
+ " page\n");
+ ret = -ENOMEM;
+ }
+
+ return ret;
+}
+arch_initcall(kdump_buf_page_init);