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Postings from July 2012
On Thu Jul 05 02:15:16 2012, oleg@redhat.com wrote:
> Father,
>
> I do not know if it is OK to reply to perlbug-followup@perl.org,
> so I CC'ed you explicitly.
>
> On 07/04, Father Chrysostomos via RT wrote:
> >
> > I don’t supposed it’s possible to
> > write an automated test for this, is it?
>
> Well, please see below. Not sure it is the best...
>
> So. The test-case assumes 64-bit linux, otherwise it won't work.
>
> It exploits the fact that vdso is mmapped at "high" address which
> can't fit in I32.
>
> It does mremap(vdso_addr, 1, 1, 0) which is "nop" but should return
> the original address.
>
> Btw, "-w" complains:
>
> Hexadecimal number > 0xffffffff non-portable at ...
>
> a bit annoying on 64-bit systems... Not sure why Perl_grok_hex()
> thinks this is not portable.
>
> Oleg.
>
> -------------------------------------------------------------------
> #!/usr/bin/perl -w
> use strict;
>
> sub find_vdso()
> {
> open my $maps, '<', '/proc/self/maps' or die;
> /^(.*?)-.*\[vdso\]$/ and return hex $1 for <$maps>;
> }
>
> my $vdso_addr = find_vdso || die 'not 64-bit linux?';
>
> my $ret = syscall 25, # __NR_mremap
> $vdso_addr, # old_addr
> 1, # old_len
> 1, # new_len
> 0, # flags
> 0; # new_addr (unused)
>
> $ret == $vdso_addr or die "FAILED\n";
>
Thank you. I’ll have to adjust this a bit to turn it into a test. Does
$^O give you ‘linux’?
There is a possibility that another OS might have a plain file called
/proc/self/maps whose contents just happen to match the regular
expression, resulting in an invalid syscall, and perhaps a crash.
So we should skip early if $^O is not appropriate.
--
Father Chrysostomos
---
via perlbug: queue: perl5 status: resolved
https://rt.perl.org:443/rt3/Ticket/Display.html?id=113980
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