This patch adds writing support for /dev/oldmem. This is used to
restore the memory contents of hibernated system.

Signed-off-by: Huang Ying

---
arch/x86/kernel/crash_dump_32.c | 27 +++++++++++++++++++++++++++
drivers/char/mem.c | 32 ++++++++++++++++++++++++++++++++
include/linux/crash_dump.h | 2 ++
3 files changed, 61 insertions(+)

--- a/arch/x86/kernel/crash_dump_32.c
+++ b/arch/x86/kernel/crash_dump_32.c
@@ -59,6 +59,33 @@ ssize_t copy_oldmem_page(unsigned long p
return csize;
}

+ssize_t write_oldmem_page(unsigned long pfn, const char *buf,
+ size_t csize, unsigned long offset, int userbuf)
+{
+ void *vaddr;
+
+ if (!csize)
+ return 0;
+
+ if (!userbuf) {
+ vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
+ memcpy(vaddr + offset, buf, csize);
+ } else {
+ if (!kdump_buf_page) {
+ printk(KERN_WARNING "Kdump: Kdump buffer page not"
+ " allocated\n");
+ return -EFAULT;
+ }
+ if (copy_from_user(kdump_buf_page, buf, csize))
+ return -EFAULT;
+ vaddr = kmap_atomic_pfn(pfn, KM_PTE0);
+ memcpy(vaddr + offset, kdump_buf_page, csize);
+ }
+ kunmap_atomic(vaddr, KM_PTE0);
+
+ return csize;
+}
+
static int __init kdump_buf_page_init(void)
{
int ret = 0;
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -11,6 +11,8 @@
extern unsigned long long elfcorehdr_addr;
extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
unsigned long, int);
+extern ssize_t write_oldmem_page(unsigned long, const char *, size_t,
+ unsigned long, int);
extern const struct file_operations proc_vmcore_operations;
extern struct proc_dir_entry *proc_vmcore;

--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -348,6 +348,37 @@ static ssize_t read_oldmem(struct file *
}
return read;
}
+
+/*
+ * Write memory corresponding to the old kernel.
+ */
+static ssize_t write_oldmem(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ unsigned long pfn, offset;
+ size_t write = 0, csize;
+ int rc = 0;
+
+ while (count) {
+ pfn = *ppos / PAGE_SIZE;
+ if (pfn > saved_max_pfn)
+ return write;
+
+ offset = (unsigned long)(*ppos % PAGE_SIZE);
+ if (count > PAGE_SIZE - offset)
+ csize = PAGE_SIZE - offset;
+ else
+ csize = count;
+ rc = write_oldmem_page(pfn, buf, csize, offset, 1);
+ if (rc < 0)
+ return rc;
+ buf += csize;
+ *ppos += csize;
+ write += csize;
+ count -= csize;
+ }
+ return write;
+}
#endif

extern long vread(char *buf, char *addr, unsigned long count);
@@ -783,6 +814,7 @@ static const struct file_operations full
#ifdef CONFIG_CRASH_DUMP
static const struct file_operations oldmem_fops = {
.read = read_oldmem,
+ .write = write_oldmem,
.open = open_oldmem,
};
#endif
-
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