On 26/05/16 15:20, Catalin Marinas wrote: > While writing the above, I realised the current ILP32 patches still miss > on converting pointers passed from user space (unless I got myself > confused in macros). The new __SC_WRAP() and COMPAT_SYSCALL_WRAPx() > macros take care of zero or sign extension via __SC_COMPAT_CAST(). > However, we have two more existing cases which I don't see covered: > > a) Native syscalls taking a pointer argument and invoked directly from > ILP32. For example, sys_read() takes a pointer but I don't see any > __SC_WRAP added by patch 5 > > b) Current compat syscalls taking a pointer argument. For example, > compat_sys_vmsplice() gets the iov32 pointer and the compiler assumes > it is a 64-bit variable. I don't see where the upper half is zeroed > on x32 sign/zero extension is currently left to userspace, which is difficult to deal with, (long long)arg does the wrong thing for pointer args. > We can solve (a) by adding more __SC_WRAP annotations in the generic > unistd.h. For (b), we would need an __SC_DELOUSE with a bit of penalty > on AArch32/compat support where it isn't needed. So maybe davem has a > point on the overall impact of always zeroing the upper half of the > arguments ;) (both from a performance and maintainability perspective). > I guess this part of the ABI is still up for discussion. > -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
