From: Matt Mackall Experimenting with trying to use cond_syscall for a few arch-specific syscalls, I discovered that it can't actually be used outside the file in which sys_ni_syscall is declared because the assembler doesn't feel obliged to output the symbol in that case: weak.c: #define cond_syscall(x) asm(".weak\t" #x "\n\t.set\t" #x ",sys_ni_syscall"); cond_syscall(sys_foo); $ nm weak.o U sys_ni_syscall One arch (PPC) is apparently trying to use cond_syscall this way anyway, though it's probably never been actually tested as the above test was done on a PPC. After trying a bunch of tricks to get it to work nicely, I decided there are basically two alternatives: make weak versions of sys_ni_syscall wherever they're wanted or put the arch-specific cond_syscalls in kernel/sys.c where sys_ni_syscall is defined. The former approach is a bit crufty and doesn't actually do the right thing in practice as you'll get multiple copies of sys_ni_syscall in your final image. The latter introduces some slight arch-pollution in sys.c, but as arch-specific cond_syscalls aren't all that frequent, it should be pretty minor. So here's a patch to move the current offender to sys.c: --- arch/ppc/kernel/syscalls.c | 2 -- kernel/sys.c | 3 +++ 2 files changed, 3 insertions(+), 2 deletions(-) diff -puN arch/ppc/kernel/syscalls.c~ppc-cond_syscall-fix arch/ppc/kernel/syscalls.c --- 25/arch/ppc/kernel/syscalls.c~ppc-cond_syscall-fix 2004-01-14 12:07:42.000000000 -0800 +++ 25-akpm/arch/ppc/kernel/syscalls.c 2004-01-14 12:07:42.000000000 -0800 @@ -271,5 +271,3 @@ long ppc_fadvise64_64(int fd, int advice { return sys_fadvise64_64(fd, offset, len, advice); } - -cond_syscall(sys_pciconfig_iobase); diff -puN kernel/sys.c~ppc-cond_syscall-fix kernel/sys.c --- 25/kernel/sys.c~ppc-cond_syscall-fix 2004-01-14 12:07:42.000000000 -0800 +++ 25-akpm/kernel/sys.c 2004-01-14 12:08:20.000000000 -0800 @@ -249,8 +249,11 @@ cond_syscall(compat_sys_futex) cond_syscall(sys_epoll_create) cond_syscall(sys_epoll_ctl) cond_syscall(sys_epoll_wait) + +/* arch-specific weak syscall entries */ cond_syscall(sys_pciconfig_read) cond_syscall(sys_pciconfig_write) +cond_syscall(sys_pciconfig_iobase) static int set_one_prio(struct task_struct *p, int niceval, int error) { _