lkml.org 
[lkml]   [2010]   [Jan]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 2/8] jump label v4 - x86: Introduce generic jump patching without stop_machine
On Thu, Jan 14, 2010 at 11:23:35AM -0500, Masami Hiramatsu wrote:
> > * Steven Rostedt (rostedt@goodmis.org) wrote:
> >> On Tue, 2010-01-12 at 11:26 -0500, Jason Baron wrote:
> >>
> >>> +/**
> >>> + * text_poke_fixup() -- cross-modifying kernel text with fixup address.
> >>> + * @addr: Modifying address.
> >>> + * @opcode: New instruction.
> >>> + * @len: length of modifying bytes.
> >>> + * @fixup: Fixup address.
> >>> + *
> >>> + * Note: You must backup replaced instructions before calling this,
> >>> + * if you need to recover it.
> >>> + * Note: Must be called under text_mutex.
> >>> + */
> >>> +void *__kprobes text_poke_fixup(void *addr, const void *opcode, size_t len,
> >>> + void *fixup)
> >>> +{
> >>> + static const unsigned char int3_insn = BREAKPOINT_INSTRUCTION;
> >>> + static const int int3_size = sizeof(int3_insn);
> >>> +
> >>> + /* Replacing 1 byte can be done atomically. */
> >>> + if (unlikely(len <= 1))
> >>> + return text_poke(addr, opcode, len);
> >>
> >> This part bothers me. The text_poke just writes over the text directly
> >> (using a separate mapping). But if that memory is in the pipeline of
> >> another CPU, I think this could cause a GPF.
> >
> > It looks like we are thinking along the same lines.
> >
> > I'm under the impression that I pointed out this exact same issue in the
> > previous round of review a few weeks ago. Does this submission reflect
> > the up-to-date state of this patch ?
>
> No, the latest patch just skips step 3 if len == 1.
> (Jason, could you update your repository?)
> I thought I sent it the end of the last year ... :)
>
> http://lkml.org/lkml/2009/12/18/312
>
> Thank you,
>

sorry about that...i've updated to the latest.

thanks,

-Jason


\
 
 \ /
  Last update: 2010-01-14 17:45    [W:0.075 / U:0.940 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site