On Thu, Jan 30, 2014 at 09:38:59PM +0400, Kostya Serebryany wrote: > On Thu, Jan 30, 2014 at 8:54 PM, Rich Felker <[email protected]> wrote: > > On Thu, Jan 30, 2014 at 12:49:03AM -0500, Carlos O'Donell wrote: > >> On 01/30/2014 12:33 AM, Kostya Serebryany wrote: > >> > On Thu, Jan 30, 2014 at 9:23 AM, Carlos O'Donell <[email protected]> > >> > wrote: > >> >> > >> >> On 01/29/2014 04:48 AM, Kostya Serebryany wrote: > >> >>> [text only] > >> >>> > >> >>>> Indeed so, thanks! > >> >>>> So, exporting __signal_safe_memalign&co will allow us to extend the > >> >>>> existing hack to 2.19. > >> >>>> If this simple change can not be done for 2.19, can *anything* be > >> >>>> done at all? > >> >>>> (Long term we'd still prefer something less hackish) > >> >>> > >> >>> FTR, I've implemented an even-uglier-then-before hack that deals with > >> >>> dynamic TLS in both <=2.18 and 2.19. > >> >>> So, we will survive the 2.19 release. > >> >>> But I would appreciate if we can resolve > >> >>> https://sourceware.org/bugzilla/show_bug.cgi?id=16291 > >> >>> before the next one (2.20). > >> >> > >> >> Can you please describe the hack? > >> > > >> > intercept __tls_get_addr and __libc_memalign. > >> > if __libc_memalign is called while we are inside __tls_get_addr, we > >> > know we are in <= 2.18 mode and we know what to do. > > > > Or a signal handler happened to interrupt __tls_get_addr and something > > from the signal handler caused __libc_memalign to get called. Is this > > case handled? > > Is __libc_memalign AS-safe? I guess not. > AddressSanitizer's implementation is certainly not. > So, if __libc_memalign is called in a signal handler it is a problem by > itself. > That's what forced the the change in 2.19 in the first place.
It's legal to call anything (even non AS-safe functions) from a signal handler if the signal handler did not interrupt a non-AS-safe function. This is easy to guarantee if the only threads where the signal is unblocked are only using AS-safe functions (a trivial example would be a thread doing for (;;) pause();). Rich -- You received this message because you are subscribed to the Google Groups "address-sanitizer" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
