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SubjectRe: [PATCH 05/12] update FTRACE_SYSCALL_MAX
On Mon, Aug 24, 2009 at 11:15:39PM +0900, Paul Mundt wrote:
> On Mon, Aug 24, 2009 at 10:06:29AM -0400, Jason Baron wrote:
> > On Mon, Aug 24, 2009 at 10:41:52PM +0900, Paul Mundt wrote:
> > > I hope you can clarify what the meaning of this is supposed to be
> > > exactly. Is this number supposed to be the last usable syscall, or is it
> > > supposed to be the equivalent of NR_syscalls?
> > >
> >
> > I am using as the equivalent of NR_syscalls.
> >
> NR_syscalls has always been the total number of system calls, not the
> last one.
>
> > > Presently on SH we have this as NR_syscalls - 1, while on s390 I see it
> > > is treated as NR_syscalls directly. s390 opencodes the NR_syscalls
> > > directly and so presently blows up in -next due to a missing
> > > FTRACE_SYSCALL_MAX definition:
> > >
> > > http://kisskb.ellerman.id.au/kisskb/buildresult/1120523/
> > >
> > > I was in the process of fixing that up when I noticed this difference.
> > > x86 seems to also treat this as NR_syscalls - 1, but that looks to me
> > > like there is an off-by-1 in arch_init_ftrace_syscalls() causing the last
> > > syscall to be skipped?
> >
> > I don't see how its used as 'NR_syscalls - 1' on x86,
> > arch_init_ftrace_syscalls() does:
> >
> > for (i = 0; i < FTRACE_SYSCALL_MAX; i++) {
> > meta = find_syscall_meta(psys_syscall_table[i]);
> > syscalls_metadata[i] = meta;
> > }
> >
> > So the last syscall should not be skipped.
> >
>
> In today's -next:
>
> #ifdef CONFIG_X86_64
> # define FTRACE_SYSCALL_MAX 299
> #else
> # define FTRACE_SYSCALL_MAX 337
> #endif
>
> unistd_32.h:
>
> #define __NR_reflinkat 337
>
> unistd_64.h:
>
> #define __NR_reflinkat 299
>
> The first syscall starts at 0, but I don't see how this last syscall is
> handled. If there were a __NR_syscalls 300 and 338 respectively, that
> would seem to do the right thing. Or am I missing something?


Yeah, I guess what we need here is NR_syscalls + 1.



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