Re: sed not working on /proc files

[David Woodhouse <David.Woodhouse@mvhi.com>]

alan@lxorguk.ukuu.org.uk said:
>  So fix the buggy libc. Relying on mmap() being available is broken

It only assumes that mmap is available if the mmap() call returns success. 
That's not _too_ unreasonable an assumption.

mmap.c has an optimisation - if it's a zero-length map that's requested, 
return success immediately.

Perhaps if we checked that the filedescriptor has mmap() capability _first_, 
rather than later, the desired effect would be achieved...


Index: mmap.c
===================================================================
RCS file: /cvs/linux/mm/mmap.c,v
retrieving revision 1.2
diff -u -w -r1.2 mmap.c
--- mmap.c      1999/04/20 11:03:16     1.2
+++ mmap.c      1999/05/04 14:57:43
@@ -176,6 +176,9 @@
        struct vm_area_struct * vma;
        int error;

+       if (file && (!file->f_op || !file->f_op->mmap))
+               return -ENODEV;
+
        if ((len = PAGE_ALIGN(len)) == 0)
                return addr;

@@ -244,8 +247,6 @@
         * specific mapper. the address has already been validated, but
         * not unmapped, but the maps are removed from the list.
         */
-       if (file && (!file->f_op || !file->f_op->mmap))
-               return -ENODEV;

        vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
        if (!vma)



----                                 ----                                 ----
David Woodhouse        David.Woodhouse@mvhi.com       Office: (+44) 1223 810302
 Project Leader,     Process Information Systems      Mobile: (+44) 976 658355
    Axiom (Cambridge) Ltd., Swaffham Bulbeck, Cambridge, CB5 0NA, UK.
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