Messages in this thread | | | Date | Mon, 24 Aug 2009 10:42:28 -0400 | From | Jason Baron <> | Subject | Re: [PATCH 05/12] update FTRACE_SYSCALL_MAX |
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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?
No, you are right. When I changed the FTRACE_SYSCALL_MAX to 299, and 337, there was no reflinkat syscall in the tree. So, it was equivalent to NR_syscalls at that point in time. So that's where the confusion is.
Clearly, all the more reason to drop FTRACE_SYSCALL_MAX and change to NR_syscalls...
thanks,
-Jason
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