Re: [LTP] [PATCH] mmap04: Make sure the scanf address format is at least 8 hex chars

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> > > The addresses in /proc/self/maps are at least 8 hex chars. Zeros are
> > > added to the front of the address when shorted (both on 32bit and
> > > 64bit systems.
> > > 
> > > Under valgrind the mmaps used in kernel/syscalls/mmap/mmap04.c come
> > > out very low in the address space and might be shorter than 8 hex
> > > chars. This causes the scanf to fail:
> > > mmap04.c:62: TBROK: Expected 1 conversions got 0 FILE '/proc/self/maps'
> > 
> > I guess I do not understand the problem here. The PRIxPTR translates to
> > "x", "lx", or "llx" depending on architecture and as far as I can tell
> > the %x modifier handles leading zeroes just fine.
> 
> The problem is that we want to match (scanf) an absolute address
> (addr2) at the start of the line. It is this absolute/literal address
> that doesn't match (because it might not have leading zeros).
> 
> e.g. We might want to match the address 403a000 and want to match
> against: 0403a000-04048000 rw-p
> 
> When creating the fmt which we want to use for scanf we currently
> generate: "403a000-%*x %s" Which doesn't match because it is missing
> the leading zero (the "-%*x %s" would match the rest, except that the
> start of the line doesn't). So with the "%08" fix we would generate:
> "0403a000-%*x %s" which does match because it has the same number of
> leading zeros.

Ah right, I'm blind, we generate the fmt on the fly. In that case
padding to eight zeroes will match what kernel does.

Reviewed-by: Cyril Hrubis <chrubis@suse.cz>


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Cyril Hrubis
chrubis@suse.cz

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