vmcore: introduce mmap_vmcore()

This patch introduces mmap_vmcore().

If flag MEM_TYPE_CURRENT_KERNEL is set, remapped is the buffer on the 2nd
kernel.  If not set, remapped is some area in old memory.

Neither writable nor executable mapping is permitted even with mprotect().
 Non-writable mapping is also requirement of remap_pfn_range() when
mapping linear pages on non-consequtive physical pages; see
is_cow_mapping().

On x86-32 PAE kernels, mmap() supports at most 16TB memory only.  This
limitation comes from the fact that the third argument of
remap_pfn_range(), pfn, is of 32-bit length on x86-32: unsigned long.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index dd1d601da8bd9b1bbc5b2cf2146b096342129083..bc4848cc44abd03c01c8c85f370ef8774ef8d583 100644 (file)
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -185,9 +185,81 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
        return acc;
 }
 
+static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
+{
+       size_t size = vma->vm_end - vma->vm_start;
+       u64 start, end, len, tsz;
+       struct vmcore *m;
+
+       if (!support_mmap_vmcore)
+               return -ENODEV;
+
+       start = (u64)vma->vm_pgoff << PAGE_SHIFT;
+       end = start + size;
+
+       if (size > vmcore_size || end > vmcore_size)
+               return -EINVAL;
+
+       if (vma->vm_flags & (VM_WRITE | VM_EXEC))
+               return -EPERM;
+
+       vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC);
+
+       len = 0;
+
+       if (start < elfcorebuf_sz) {
+               u64 pfn;
+
+               tsz = elfcorebuf_sz - start;
+               if (size < tsz)
+                       tsz = size;
+               pfn = __pa(elfcorebuf + start) >> PAGE_SHIFT;
+               if (remap_pfn_range(vma, vma->vm_start, pfn, tsz,
+                                   vma->vm_page_prot))
+                       return -EAGAIN;
+               size -= tsz;
+               start += tsz;
+               len += tsz;
+
+               if (size == 0)
+                       return 0;
+       }
+
+       list_for_each_entry(m, &vmcore_list, list) {
+               if (start < m->offset + m->size) {
+                       u64 pfn = 0;
+
+                       tsz = m->offset + m->size - start;
+                       if (size < tsz)
+                               tsz = size;
+                       if (m->flag & MEM_TYPE_CURRENT_KERNEL) {
+                               pfn = __pa(m->buf + start - m->offset)
+                                       >> PAGE_SHIFT;
+                       } else {
+                               pfn = (m->paddr + (start - m->offset))
+                                       >> PAGE_SHIFT;
+                       }
+                       if (remap_pfn_range(vma, vma->vm_start + len, pfn, tsz,
+                                           vma->vm_page_prot)) {
+                               do_munmap(vma->vm_mm, vma->vm_start, len);
+                               return -EAGAIN;
+                       }
+                       size -= tsz;
+                       start += tsz;
+                       len += tsz;
+
+                       if (size == 0)
+                               return 0;
+               }
+       }
+
+       return 0;
+}
+
 static const struct file_operations proc_vmcore_operations = {
        .read           = read_vmcore,
        .llseek         = default_llseek,
+       .mmap           = mmap_vmcore,
 };
 
 static struct vmcore* __init get_new_element(void)