On Wed, Apr 23, 2014 at 12:27 PM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Fri, Apr 11, 2014 at 01:45:02PM +0100, Russell King - ARM Linux wrote: >> On Fri, Apr 11, 2014 at 02:02:32PM +0200, Miklos Szeredi wrote: >> > On Fri, Apr 11, 2014 at 1:54 PM, Russell King - ARM Linux >> > <linux@xxxxxxxxxxxxxxxx> wrote: >> > > On Fri, Apr 11, 2014 at 01:50:50PM +0200, Miklos Szeredi wrote: >> > >> Yes, and the padding will be of wrong length if NR_syscalls is >> > >> incorrect (which may be Oopsable?). At least that is my impression >> > >> from a casual glance. >> > > >> > > Please explain. >> > >> > Look at ending lines of arch/arm/kernel/calls.S: if NR_syscalls is a >> > multiple of 4, then syscalls_padding will be zero. I.e. no padding >> > despite the fact that there is in fact only 382 system calls in table >> > and there should be 2 sys_ni_syscall pads. >> >> Hmm, it looks like you're right... this used to work fine until... >> >> commit 1f66e06fb6414732bef7bf4a071ef76a837badec >> Author: Wade Farnsworth <wade_farnsworth@xxxxxxxxxx> >> Date: Fri Sep 7 18:18:25 2012 +0100 >> >> ARM: 7524/1: support syscall tracing >> >> because the tracing code wanted to know the number of syscalls. I don't >> know what the answer is here, because the current solution is IMHO far >> to fragile. > > Actually, no, you're wrong. Look closely at the definitions. __NR_syscalls > is not the same as NR_syscalls. > > __NR_syscalls is the statically defined size of the syscall table for > *probes purposes. > > NR_syscalls is the assembly-counted number of CALL() macros in > arch/arm/kernel/calls.S. All I can say is: UGGGGH. But I've not had close encounters with arch code, so this may be acceptable to you. Whatever... Thanks, Miklos -- 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
