On Thu, May 12, 2016 at 11:45:53AM +0800, Zhangjian (Bamvor) wrote:
[...]
> >Hmm, that is indeed tricky. I think COMPAT_SYSCALL_WRAP4 rightfully
> >refuses the loff_t argument here, as the common case is that this is
> >not possible.
> It works if I apply the following patch, I defined the wrong `__TYPE_IS_xxx`
> yesterday. Should we merge this into ILP32 series or send the compat.h
> and syscalls.h individually? The current series of ILP32 is a little bit
> long and hard to review.
> diff --git a/include/linux/compat.h b/include/linux/compat.h
> index ba6ebe0..22a9565 100644
> --- a/include/linux/compat.h
> +++ b/include/linux/compat.h
> @@ -747,7 +747,8 @@ asmlinkage long compat_sys_fanotify_mark(int, unsigned int, __u32, __u32,
> #ifndef __SC_COMPAT_CAST
> #define __SC_COMPAT_CAST(t, a) ({ \
> BUILD_BUG_ON((sizeof(t) > 4) && !__TYPE_IS_L(t) && \
> - !__TYPE_IS_UL(t) && !__TYPE_IS_PTR(t)); \
> + !__TYPE_IS_UL(t) && !__TYPE_IS_PTR(t) && \
> + !__TYPE_IS_LOFFT(t)); \
I think it's wrong, as loff_t is 64-bit in 32-bit userspace, and this
will clear meaningful data in top halve.
> ((t) ((t)(-1) < 0 ? (s64)(s32)(a) : (u64)(u32)(a))); \
> })
> #endif
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 6e57d9c..66eb85d 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -47,6 +47,7 @@
> #define __TYPE_IS_L(t) (__same_type((t)0, 0L))
> #define __TYPE_IS_UL(t) (__same_type((t)0, 0UL))
> #define __TYPE_IS_LL(t) (__same_type((t)0, 0LL) || __same_type((t)0, 0ULL))
> +#define __TYPE_IS_LOFFT(t) (__same_type((t)0, (loff_t)0))
> #define __SC_LONG(t, a) __typeof(__builtin_choose_expr(__TYPE_IS_LL(t), 0LL, 0L)) a
> #define __SC_CAST(t, a) (t) a
> #define __SC_ARGS(t, a) a
> diff --git a/kernel/compat_wrapper.c b/kernel/compat_wrapper.c
> index 98b68b8..28f02d0 100644
> --- a/kernel/compat_wrapper.c
> +++ b/kernel/compat_wrapper.c
> @@ -304,3 +304,7 @@ COMPAT_SYSCALL_WRAP3(getpeername, int, fd, struct sockaddr __user *, usockaddr,
> COMPAT_SYSCALL_WRAP6(sendto, int, fd, void __user *, buff, size_t, len,
> unsigned int, flags, struct sockaddr __user *, addr,
> int, addr_len);
> +COMPAT_SYSCALL_WRAP4(pread64, unsigned int, fd, char __user *, buf,
> + size_t, count, loff_t, pos);
> +COMPAT_SYSCALL_WRAP4(pwrite64, unsigned int, fd, const char __user *, buf,
> + size_t, count, loff_t, pos);
For cases like this I think we should write wrappers by hands. In
unistd.h we can use __SC_WRAP, so they will work like wrappers
generated by COMPAT_SYSCALL_WRAPx()
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