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i386: Make patching more robust, fix paravirt issue

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Commit 19d36ccdc3 "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: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andi Kleen
2007-08-10 22:31:03 +02:00
committed by Linus Torvalds
parent d3f3c93469
commit ab144f5ec6
6 changed files with 90 additions and 67 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/lguest/lguest.c
View File

@ -936,23 +936,24 @@ static const struct lguest_insns
/* Now our patch routine is fairly simple (based on the native one in
* paravirt.c). If we have a replacement, we copy it in and return how much of
* the available space we used. */
static unsigned lguest_patch(u8 type, u16 clobber, void *insns, unsigned len)
static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
unsigned long addr, unsigned len)
{
unsigned int insn_len;
/* Don't do anything special if we don't have a replacement */
if (type >= ARRAY_SIZE(lguest_insns) || !lguest_insns[type].start)
return paravirt_patch_default(type, clobber, insns, len);
return paravirt_patch_default(type, clobber, ibuf, addr, len);
insn_len = lguest_insns[type].end - lguest_insns[type].start;
/* Similarly if we can't fit replacement (shouldn't happen, but let's
* be thorough). */
if (len < insn_len)
return paravirt_patch_default(type, clobber, insns, len);
return paravirt_patch_default(type, clobber, ibuf, addr, len);
/* Copy in our instructions. */
memcpy(insns, lguest_insns[type].start, insn_len);
memcpy(ibuf, lguest_insns[type].start, insn_len);
return insn_len;
}