Re: 1352 NUL bytes at the end of a page?

[Steven Cole]

On May 17, 2004, at 9:37 AM, viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
wrote:

> On Mon, May 17, 2004 at 08:22:10AM -0700, Linus Torvalds wrote:
> > On Mon, 17 May 2004, Theodore Ts'o wrote:
> > > Note though that the stdio library uses a writeable mmap to implement
> > > fwrite.
> >
> > It does? Whee. Then I'll have to agree with Andrew - if there is a 
> > path
> > that is more likely to have bugs, it's trying to do writes with mmap 
> > and
> > ftruncate.
> >
> > Who came up with that braindead idea? Is it some crazed Mach developer
> > that infiltrated the glibc development group?
>
> IIRC, that idiocy had been disabled by default (note that it's 
> inherently
> broken, since truncate() between your mmap() and memcpy() will lead to
> a coredump, which is not something fwrite() is allowed to do in such
> situation).
>
> strace should show if there such mmap calls are made, anyway.  Did they
> show up in the traces?

These calls show up in an strace which I did from a non-failing system,
but which has the same glibc as the failing system:

mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 
0) = 0x40018000
old_mmap(NULL, 19184, PROT_READ, MAP_PRIVATE, 3, 0) = 0x40018000

The command was the following, with the result "Nothing to pull".
strace bk pull bk://linux.bkbits.net/linux-2.5

There were 52 instances of mmap2 or old_mmap in the saved script log.

	Steven

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