On Sat, Jun 02, 2007 at 12:18:40AM +0100, Russell King wrote: > On Fri, Jun 01, 2007 at 04:10:53PM -0700, Deepak Saxena wrote: > > The -rt patch adds a NR_syscalls symbol to the arm/unistd.h but > > it is not the correct value as there are 348 syscalls on ARM > > and the existing change sets the symbol to 322. > > > > Russell: Why isn't this in mainline? Other arches all seem to have > > this symbol already defined. > > The hint is that it isn't in mainline; it's just plainly not required. > It's also the wrong place to define it; it's not a property that > unistd.h should concern itself with - it's a property of the kernel's > branch table for calling the syscalls, and on ARM we calculate that > number directly from the size of the kernel's branch table. > > It's also not just last_syscall_number+1 since the table is sized to > make the assembly easy - iow, a number divisible by 4. > > So all in all, NR_syscalls in unistd.h is just utterly wrong.
BTW, it should be pointed out that you've found the exact reason why putting it in unistd.h is _wrong_. It's all to easy for it to get out of sync with updates to the place where it really matters - the code which bounds-checks the syscall number (that being the assembly code which indexes the branch table.) -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
