[RFC PATCH v1 3/3] vmcore: read vmcore through direct mapping region

HATAYAMA Daisuke
2013-01-17T01:04:17Z

Now regions represented by vmcore are mapped through direct mapping
region. We reads requested memory through direct mapping region
instead of using ioremap.

Notice that we still keep read_from_oldmem that uses ioremap because
we need to use it when reading elf headers to make vmcore_list in
vmcore initialization.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
---

fs/proc/vmcore.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 44 insertions(+), 1 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index aa14570..1c6259e 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -123,6 +123,49 @@ static ssize_t read_from_oldmem(char *buf, size_t count,
return read;
}

+/* Reads a page from the oldmem device from given offset. */
+static ssize_t read_from_oldmem_noioremap(char *buf, size_t count,
+ u64 *ppos, int userbuf)
+{
+ unsigned long pfn, offset;
+ size_t nr_bytes;
+ ssize_t read = 0;
+
+ if (!count)
+ return 0;
+
+ offset = (unsigned long)(*ppos % PAGE_SIZE);
+ pfn = (unsigned long)(*ppos / PAGE_SIZE);
+
+ do {
+ if (count > (PAGE_SIZE - offset))
+ nr_bytes = PAGE_SIZE - offset;
+ else
+ nr_bytes = count;
+
+ /* If pfn is not ram, return zeros for sparse dump files */
+ if (pfn_is_ram(pfn) == 0)
+ memset(buf, 0, nr_bytes);
+ else {
+ void *vaddr = pfn_to_kaddr(pfn);
+
+ if (userbuf) {
+ if (copy_to_user(buf, vaddr + offset, nr_bytes))
+ return -EFAULT;
+ } else
+ memcpy(buf, vaddr + offset, nr_bytes);
+ }
+ *ppos += nr_bytes;
+ count -= nr_bytes;
+ buf += nr_bytes;
+ read += nr_bytes;
+ ++pfn;
+ offset = 0;
+ } while (count);
+
+ return read;
+}
+
/* Maps vmcore file offset to respective physical address in memroy. */
static u64 map_offset_to_paddr(loff_t offset, struct list_head *vc_list,
struct vmcore **m_ptr)
@@ -553,7 +596,7 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
tsz = nr_bytes;

while (buflen) {
- tmp = read_from_oldmem(buffer, tsz, &start, 1);
+ tmp = read_from_oldmem_noioremap(buffer, tsz, &start, 1);
if (tmp < 0)
return tmp;
buflen -= tsz;