Commit efe067fa authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds

[PATCH] ppc cond_syscall fix

From: Matt Mackall <mpm@selenic.com>

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:
parent 2d0630e0
...@@ -271,5 +271,3 @@ long ppc_fadvise64_64(int fd, int advice, loff_t offset, loff_t len) ...@@ -271,5 +271,3 @@ long ppc_fadvise64_64(int fd, int advice, loff_t offset, loff_t len)
{ {
return sys_fadvise64_64(fd, offset, len, advice); return sys_fadvise64_64(fd, offset, len, advice);
} }
cond_syscall(sys_pciconfig_iobase);
...@@ -249,8 +249,11 @@ cond_syscall(compat_sys_futex) ...@@ -249,8 +249,11 @@ cond_syscall(compat_sys_futex)
cond_syscall(sys_epoll_create) cond_syscall(sys_epoll_create)
cond_syscall(sys_epoll_ctl) cond_syscall(sys_epoll_ctl)
cond_syscall(sys_epoll_wait) cond_syscall(sys_epoll_wait)
/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read) cond_syscall(sys_pciconfig_read)
cond_syscall(sys_pciconfig_write) cond_syscall(sys_pciconfig_write)
cond_syscall(sys_pciconfig_iobase)
static int set_one_prio(struct task_struct *p, int niceval, int error) static int set_one_prio(struct task_struct *p, int niceval, int error)
{ {
......
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