On Mon, Oct 15, 2012 at 05:07:10PM +0100, Catalin Marinas wrote: > On Sun, Oct 14, 2012 at 08:56:11PM +0100, Al Viro wrote: > > On Sun, Oct 14, 2012 at 08:24:03PM +0100, Al Viro wrote: > > > > > Russell, could you recall what those had been about? I'm not sure if that > > > had been oopsable that far back (again, oops scenario is userland stack > > > page getting swapped out before we get to start_thread(), leading to > > > direct read from an absent page in start_thread() by plain ldr, without > > > anything in exception table about that insn), but it looks very odd > > > regardless of that problem. > > > > BTW, arm64 has copied that logics, so it also seems to be unsafe and very > > odd - there we definitely have only ELF to cope with. arm64 folks Cc'd... > > Good point. We don't need this on arm64 and probably neither on arm (at > least since EABI). > > Setting x0 may cause other issues as well. The dynamic loader simply > ignores the startup registers but for static binaries the _start code in > glibc expects r0 to contain a function pointer to be registered with > atexit() in __libc_start_main() or NULL. Since we pass argc in there, > for static binaries the rtld_fini argument to __libc_start_main() is > neither NULL nor something meaningful. The value left there by start_thread() will not reach the userland anyway... -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
