[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>

6 files changed, 88 insertions, 27 deletions

diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index be1880bb75b4..60c3f76dfca4 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o nmi.o
 obj-$(CONFIG_X86_IO_APIC)       += io_apic.o
 obj-$(CONFIG_X86_REBOOTFIXUPS)  += reboot_fixups.o
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o crash.o
+obj-$(CONFIG_CRASH_DUMP)        += crash_dump.o
 obj-$(CONFIG_X86_NUMAQ)         += numaq.o
 obj-$(CONFIG_X86_SUMMIT_NUMA)   += summit.o
 obj-$(CONFIG_KPROBES)           += kprobes.o
diff --git a/arch/i386/kernel/crash_dump.c b/arch/i386/kernel/crash_dump.c
new file mode 100644
index 000000000000..3f532df488bc
--- /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);
diff --git a/arch/x86_64/kernel/Makefile b/arch/x86_64/kernel/Makefile
index fe4cbd1c4b2f..12bc54005e2f 100644
--- a/arch/x86_64/kernel/Makefile
+++ b/arch/x86_64/kernel/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o  nmi.o
 obj-$(CONFIG_X86_IO_APIC)       += io_apic.o mpparse.o \
                 genapic.o genapic_cluster.o genapic_flat.o
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o crash.o
+obj-$(CONFIG_CRASH_DUMP)        += crash_dump.o
 obj-$(CONFIG_PM)                += suspend.o
 obj-$(CONFIG_SOFTWARE_SUSPEND)  += suspend_asm.o
 obj-$(CONFIG_CPU_FREQ)          += cpufreq/
diff --git a/kernel/crash_dump.c b/arch/x86_64/kernel/crash_dump.c
index fccb27dbc623..942deac4d43a 100644
--- a/kernel/crash_dump.c
+++ b/arch/x86_64/kernel/crash_dump.c
@@ -5,21 +5,12 @@
  *      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>
-#include <asm/kexec.h>
-
-/* Stores the physical address of elf header of crash image. */
-unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
+#include <asm/io.h>
 
-#ifndef HAVE_ARCH_COPY_OLDMEM_PAGE
 /**
  * copy_oldmem_page - copy one page from "oldmem"
  * @pfn: page frame number to be copied
@@ -34,31 +25,23 @@ unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
  * 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)
+                               size_t csize, unsigned long offset, int userbuf)
 {
-        void *page, *vaddr;
+        void  *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);
+        vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
 
         if (userbuf) {
-                if (copy_to_user(buf, (page + offset), csize)) {
-                        kfree(page);
+                if (copy_to_user(buf, (vaddr + offset), csize)) {
+                        iounmap(vaddr);
                         return -EFAULT;
                 }
-        } else {
-                memcpy(buf, (page + offset), csize);
-        }
+        } else
+        memcpy(buf, (vaddr + offset), csize);
 
-        kfree(page);
+        iounmap(vaddr);
         return csize;
 }
-#endif
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 3b2e7b69e63a..5378d7c78419 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -35,6 +35,9 @@ static size_t elfcorebuf_sz;
 /* Total size of vmcore file. */
 static u64 vmcore_size;
 
+/* Stores the physical address of elf header of crash image. */
+unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
+
 struct proc_dir_entry *proc_vmcore = NULL;
 
 /* Reads a page from the oldmem device from given offset. */
diff --git a/kernel/Makefile b/kernel/Makefile
index a940bac02837..1e039700c0ad 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -30,7 +30,6 @@ obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_SECCOMP) += seccomp.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o