On Wed, May 15, 2013 at 06:06:26PM +0900, HATAYAMA Daisuke wrote:
> This patch introduces mmap_vmcore().
>
> Don't permit writable nor executable mapping even with mprotect()
> because this mmap() is aimed at reading crash dump memory.
> Non-writable mapping is also requirement of remap_pfn_range() when
> mapping linear pages on non-consecutive physical pages; see
> is_cow_mapping().
>
> Set VM_MIXEDMAP flag to remap memory by remap_pfn_range and by
> remap_vmalloc_range_pertial at the same time for a single
> vma. do_munmap() can correctly clean partially remapped vma with two
> functions in abnormal case. See zap_pte_range(), vm_normal_page() and
> their comments for details.
>
> 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 at jp.fujitsu.com>
> ---
This one looks fine to me assuming vm folks like
remap_vmalloc_range_partial().
Acked-by: Vivek Goyal <vgoyal at redhat.com>
Thanks
Vivek
>
> fs/proc/vmcore.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 86 insertions(+), 0 deletions(-)
>
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index 7f2041c..2c72487 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -20,6 +20,7 @@
> #include <linux/init.h>
> #include <linux/crash_dump.h>
> #include <linux/list.h>
> +#include <linux/vmalloc.h>
> #include <asm/uaccess.h>
> #include <asm/io.h>
> #include "internal.h"
> @@ -200,9 +201,94 @@ 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;
> +
> + 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);
> + vma->vm_flags |= VM_MIXEDMAP;
> +
> + 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;
> + }
> +
> + if (start < elfcorebuf_sz + elfnotes_sz) {
> + void *kaddr;
> +
> + tsz = elfcorebuf_sz + elfnotes_sz - start;
> + if (size < tsz)
> + tsz = size;
> + kaddr = elfnotes_buf + start - elfcorebuf_sz;
> + if (remap_vmalloc_range_partial(vma, vma->vm_start + len,
> + kaddr, tsz)) {
> + do_munmap(vma->vm_mm, vma->vm_start, len);
> + 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 paddr = 0;
> +
> + tsz = m->offset + m->size - start;
> + if (size < tsz)
> + tsz = size;
> + paddr = m->paddr + start - m->offset;
> + if (remap_pfn_range(vma, vma->vm_start + len,
> + paddr >> PAGE_SHIFT, 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)
