Re: [PATCH] MIPS: use 32-bit wrapper for compat_sys_futex
From: Ralf Baechle <hidden>
Date: 2011-08-18 20:19:24
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On Wed, Aug 17, 2011 at 10:17:52AM -0700, David Daney wrote:
quoted
diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S index 46c4763..f48b18e 100644 --- a/arch/mips/kernel/scall64-o32.S +++ b/arch/mips/kernel/scall64-o32.S@@ -441,7 +441,7 @@ sys_call_table: PTR sys_fremovexattr /* 4235 */ PTR sys_tkill PTR sys_sendfile64 - PTR compat_sys_futex + PTR sys_32_futexThis change is redundant, scall64-o32.S already does the right thing so additional zero extending is not needed and is just extra instructions to execute for no reason.
Compat_sys_futex is a syscall entry point and for some configurations such as CONFIG_FTRACE_SYSCALLS SYSCALL_DEFINE*() will do additional work beyond cleaning up the arguments. The 3 unnecessary shifts are the overhead we just gotta live with.
quoted
PTR compat_sys_sched_setaffinity PTR compat_sys_sched_getaffinity /* 4240 */ PTR compat_sys_io_setupBut really I think this patch fixes things at the wrong level. Each architecture potentially needs a similar patch. What would happen if we did something like:
quoted hunk ↗ jump to hunk
+++ b/kernel/futex_compat.c@@ -180,9 +180,9 @@ err_unlock: return ret; } -asmlinkage long compat_sys_futex(u32 __user *uaddr, int op, u32 val, - struct compat_timespec __user *utime, u32 __user *uaddr2, - u32 val3) +SYSCALL_DEFINE6(compat_sys_futex, u32 __user *, uaddr, int , op, u32, val, + struct compat_timespec __user *, utime, u32 __user *, uaddr2, + u32, val3) { struct timespec ts; ktime_t t, *tp = NULL;Obviously the function name is wrong, but a varient of SYSCALL_DEFINE*() could be created so the proper function names are produced.
Right now none of the the generic compat_ functions is wrapped in SYSCALL_DEFINE* because for some architectures a further wrapper function is needed. It seems some architectures call compat_ calls directly without SYSCALL_DEFINE* which with CONFIG_FTRACE_SYSCALLS is a bug ... Ralf