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Subject[PATCH 13/13] vmcore: introduce mmap_vmcore()
Date
This patch introduces mmap_vmcore().

If vmcore object has VMCORE_OLD_MEMORY type, remaped is a page on old
memory. If vmcore object has VMCORE_2ND_KERNEL type, remaped is buffer
on 2nd kernel.

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

On ELF32 mmap() is not suppoted, returning -ENODEV, since then dump
file size must be less than 4GB; exiting read() interface is enough.

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>
---

fs/proc/vmcore.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 76 insertions(+), 0 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 99f5673..f521480 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -186,9 +186,85 @@ 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)
+{
+ unsigned char *e_ident = (unsigned char *)elfcorebuf;
+ size_t size = vma->vm_end - vma->vm_start;
+ u64 start, end, len, tsz;
+ struct vmcore *m;
+
+ if (e_ident[EI_CLASS] == ELFCLASS32)
+ 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;
+ switch (m->type) {
+ case VMCORE_OLD_MEMORY:
+ pfn = (m->paddr + (start - m->offset))
+ >> PAGE_SHIFT;
+ break;
+ case VMCORE_2ND_KERNEL:
+ pfn = __pa(m->buf + start - m->offset)
+ >> PAGE_SHIFT;
+ break;
+ }
+ 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)


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