On 07/11/2016 03:07 AM, Peter Lieven wrote: > the allocated stack will be adjusted to the minimum supported stack size > by the OS and rounded up to be a multiple of the system pagesize. > Additionally an architecture dependent guard page is added to the stack > to catch stack overflows. > > Signed-off-by: Peter Lieven <p...@kamp.de> > --- > include/sysemu/os-posix.h | 23 +++++++++++++++++++++++ > util/oslib-posix.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 67 insertions(+) >
> +
> +static size_t adjust_stack_size(size_t sz)
> +{
> + /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
> + sz = MAX(sz, sysconf(_SC_THREAD_STACK_MIN));
sz is unsigned, but sysconf() is signed. Furthermore, sysconf() is
permitted to return -1 if there is no such minimum. MAX() would then
operate on the common integral promotion between the two arguments,
which may treat (unsigned)(-1) as the larger of the two values, and give
you the wrong results.
I think it is theoretical (all platforms that we compile on have a
working sysconf(_SC_THREAD_STACK_MIN), right?), but still may be worth
being sure that sysconf() returned a positive value before computing MAX().
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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