• Andi Kleen's avatar
    i386: Make patching more robust, fix paravirt issue · ab144f5e
    Andi Kleen authored
    Commit 19d36ccd "x86: Fix alternatives
    and kprobes to remap write-protected kernel text" uses code which is
    being patched for patching.
    
    In particular, paravirt_ops does patching in two stages: first it
    calls paravirt_ops.patch, then it fills any remaining instructions
    with nop_out().  nop_out calls text_poke() which calls
    lookup_address() which calls pgd_val() (aka paravirt_ops.pgd_val):
    that call site is one of the places we patch.
    
    If we always do patching as one single call to text_poke(), we only
    need make sure we're not patching the memcpy in text_poke itself.
    This means the prototype to paravirt_ops.patch needs to change, to
    marshal the new code into a buffer rather than patching in place as it
    does now.  It also means all patching goes through text_poke(), which
    is known to be safe (apply_alternatives is also changed to make a
    single patch).
    
    AK: fix compilation on x86-64 (bad rusty!)
    AK: fix boot on x86-64 (sigh)
    AK: merged with other patches
    Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: default avatarAndi Kleen <ak@suse.de>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    ab144f5e
alternative.c 10.8 KB