• Michael Ellerman's avatar
    powerpc: Add a proper syscall for switching endianness · 529d235a
    Michael Ellerman authored
    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 syscall 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.
    
    This version clobbers r9-r12, XER, CTR, and CR0-1,5-7.
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    529d235a
systbl.h 8.78 KB