On Tue, Jun 9, 2015 at 12:03 PM, Denys Vlasenko <[email protected]> wrote: > On 06/09/2015 09:01 PM, Andy Lutomirski wrote: >> On Tue, Jun 9, 2015 at 11:54 AM, Denys Vlasenko <[email protected]> wrote: >>> This doesn't change much, but this uses shorter 32-bit insns: >>> >>> -48 8b 74 24 68 mov 0x68(%rsp),%rsi >>> -48 8b 7c 24 70 mov 0x70(%rsp),%rdi >>> -48 8b 54 24 60 mov 0x60(%rsp),%rdx >>> +8b 74 24 68 mov 0x68(%rsp),%esi >>> +8b 7c 24 70 mov 0x70(%rsp),%edi >>> +8b 54 24 60 mov 0x60(%rsp),%edx >>> >>> Since these are the only uses of RESTORE_RSI_RDI[_RDX], drop these macros. >>> >> >> It probably doesn't matter for these fast paths, but, for the full >> slow path return, we really do need to restore the full pt_regs. >> After all, the syscall we're returning from might be sigreturn. > > This is compat 32-bit syscall handling code. > IIUC we do not restore high half of any registers for 32-bit tasks. > > Am I missing something?
Yes -- 64-bit tasks can call 32-bit compat syscalls. In fact, we should really excise the entire concept of "64-bit tasks" and "32-bit tasks" from the kernel. The things that have bitness are the current syscall (TS_COMPAT), CS, the mm, and the signal context. The task should be agnostic. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
