Messages in this thread Patch in this message | | | Date | Fri, 9 Jan 2004 21:29:15 -0600 | From | Matt Mackall <> | Subject | [patch] arch-specific cond_syscall usage issues |
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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:
tiny-mpm/arch/ppc/kernel/syscalls.c | 2 -- tiny-mpm/kernel/sys.c | 3 +++ 2 files changed, 3 insertions(+), 2 deletions(-)
diff -puN arch/ppc/kernel/syscalls.c~ppc_cond_syscall arch/ppc/kernel/syscalls.c --- tiny/arch/ppc/kernel/syscalls.c~ppc_cond_syscall 2004-01-09 21:15:02.000000000 -0600 +++ tiny-mpm/arch/ppc/kernel/syscalls.c 2004-01-09 21:15:08.000000000 -0600 @@ -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 kernel/sys.c --- tiny/kernel/sys.c~ppc_cond_syscall 2004-01-09 21:15:02.000000000 -0600 +++ tiny-mpm/kernel/sys.c 2004-01-09 21:15:02.000000000 -0600 @@ -252,6 +252,9 @@ cond_syscall(sys_epoll_wait) cond_syscall(sys_pciconfig_read) cond_syscall(sys_pciconfig_write) +/* arch-specific weak syscall entries */ +cond_syscall(sys_pciconfig_iobase) + static int set_one_prio(struct task_struct *p, int niceval, int error) { int no_nice; _
-- Matt Mackall : http://www.selenic.com : Linux development and consulting - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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