On Wed, 2015-03-11 at 11:08 +0530, Anshuman Khandual wrote: > On 03/10/2015 04:25 PM, Michael Ellerman wrote: > > On Tue, 2015-03-10 at 20:34 +1100, Benjamin Herrenschmidt wrote: > >> On Tue, 2015-03-10 at 18:36 +1100, Michael Ellerman wrote: > >>> We currently have a "special" syscall for switching endianness. This is > >>> syscall number 0x1ebe, which is handled explicitly in the 64-bit syscall > >>> exception entry. > >>> > >>> That has a few problems, firstly the syscall number is outside of the > >>> usual range, which confuses various tools. For example strace doesn't > >>> recognise the syscalls at all. > >>> > >>> Secondly it's handled explicitly as a special case in the syscall > >>> exception entry, which is complicated enough without it. > >>> > >>> As a first step toward removing the special syscall, we need to add a > >>> regular syscall that implements the same functionality. > >>> > >>> The logic is simple, it simply toggles the MSR_LE bit in the userspace > >>> MSR. This is the same as the special syscall, with the caveat that the > >>> special syscall clobbers fewer registers. > >> > >> You can set _TIF_RESTOREALL to force a restore of all the registers on > >> the way back which should do the job. > > > > Right, I'd forgotten we talked about that. > > > > I'll try that tomorrow. > > The test fails when we add set_thread_flag(TIF_RESTOREALL) after the MSR flip. > Though the test passes with the original patch.
We also need to wrap the syscall like we do for fork() etc... to save_nvgpr's. Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
