Andi Kleen wrote:
On Sunday 12 August 2007 10:12, Petr Vandrovec wrote:
Hello,
after I upgraded kernel on my box to current git, only thing it did
was rebooting in a loop. After some digging I found that it is silly
to apply alternative to memcpy by using that every same memcpy...
Sorry if it is known bug, I do not see it reported in my LKML mailbox...
Ok Linus already applied your patch. Even though it's a really
bad fragile hack, not better than the old bug.
Petr are you double sure you really tested with
ab144f5ec64c42218a555ec1dbde6b60cf2982d6
already applied? I bet not -- it is the symptom exactly fixed by this patch
I'm quite sure that this patch is in my tree, as I have that "u8 *instr
= a->instr;" in apply_alternatives, and it seems that this one was added
by checkin you mention... My tree was synced up to:
Commit: 3dab307e527f2a9bbb4f9d00240374bb93d1945f
Author: Chuck Ebbert <[EMAIL PROTECTED]> Fri, 10 Aug 2007 22:31:11 +0200
which as far as I can tell really *is* after your fix. I'm quite sure
that I did not hit any BUG_ON() or anything like that - when patching
got to memcpy alternative, it entered text_poke(), and instead of
returning to caller it returned to BIOS :-(
(although
Linus, I would prefer if you reverted
b8d3f2448b8f4ba24f301e23585547ba1acc1f04
again -- it should really not be needed with
ab144f5ec64c42218a555ec1dbde6b60cf2982d6
And I really dislike Petr's patch because while it might work
today (I'm not 100% sure it actually works to only replace
2 bytes) if we change memcpy ever it'll likely cause strange
problems again.
It does not actually change two bytes - it changes two bytes now because
alternative is two bytes long - it makes no sense to replace whole
function with NOPs - it is necessary when you fall through that
function, but for this (and other x86-64 alternatives) it makes no sense
to replace whole function with nops if first instruction in alternative
is jump - then you need to only put that jump in place.
Petr
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