On 03/11/2015 11:13 AM, Benjamin Herrenschmidt wrote: > 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.
Yeah right, replacing SYSCALL(switch_endian) with PPC_SYS(switch_endian) in systbl.h does the trick and the test passes again. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
