i386: Make patching more robust, fix paravirt issue
Commit 19d36ccdc34f5ed444f8a6af0cbfdb6790eb1177 "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>
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index ea962c0..739cfb2 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -69,7 +69,8 @@
DEF_NATIVE(ud2a, "ud2a");
-static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len)
+static unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
+ unsigned long addr, unsigned len)
{
const unsigned char *start, *end;
unsigned ret;
@@ -90,7 +91,7 @@
#undef SITE
patch_site:
- ret = paravirt_patch_insns(insns, len, start, end);
+ ret = paravirt_patch_insns(ibuf, len, start, end);
break;
case PARAVIRT_PATCH(make_pgd):
@@ -107,7 +108,7 @@
break;
default:
- ret = paravirt_patch_default(type, clobbers, insns, len);
+ ret = paravirt_patch_default(type, clobbers, ibuf, addr, len);
break;
}
@@ -129,68 +130,67 @@
u32 delta;
} __attribute__((packed));
-unsigned paravirt_patch_call(void *target, u16 tgt_clobbers,
- void *site, u16 site_clobbers,
+unsigned paravirt_patch_call(void *insnbuf,
+ const void *target, u16 tgt_clobbers,
+ unsigned long addr, u16 site_clobbers,
unsigned len)
{
- unsigned char *call = site;
- unsigned long delta = (unsigned long)target - (unsigned long)(call+5);
- struct branch b;
+ struct branch *b = insnbuf;
+ unsigned long delta = (unsigned long)target - (addr+5);
if (tgt_clobbers & ~site_clobbers)
return len; /* target would clobber too much for this site */
if (len < 5)
return len; /* call too long for patch site */
- b.opcode = 0xe8; /* call */
- b.delta = delta;
- BUILD_BUG_ON(sizeof(b) != 5);
- text_poke(call, (unsigned char *)&b, 5);
+ b->opcode = 0xe8; /* call */
+ b->delta = delta;
+ BUILD_BUG_ON(sizeof(*b) != 5);
return 5;
}
-unsigned paravirt_patch_jmp(void *target, void *site, unsigned len)
+unsigned paravirt_patch_jmp(const void *target, void *insnbuf,
+ unsigned long addr, unsigned len)
{
- unsigned char *jmp = site;
- unsigned long delta = (unsigned long)target - (unsigned long)(jmp+5);
- struct branch b;
+ struct branch *b = insnbuf;
+ unsigned long delta = (unsigned long)target - (addr+5);
if (len < 5)
return len; /* call too long for patch site */
- b.opcode = 0xe9; /* jmp */
- b.delta = delta;
- text_poke(jmp, (unsigned char *)&b, 5);
+ b->opcode = 0xe9; /* jmp */
+ b->delta = delta;
return 5;
}
-unsigned paravirt_patch_default(u8 type, u16 clobbers, void *site, unsigned len)
+unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
+ unsigned long addr, unsigned len)
{
void *opfunc = *((void **)¶virt_ops + type);
unsigned ret;
if (opfunc == NULL)
/* If there's no function, patch it with a ud2a (BUG) */
- ret = paravirt_patch_insns(site, len, start_ud2a, end_ud2a);
+ ret = paravirt_patch_insns(insnbuf, len, start_ud2a, end_ud2a);
else if (opfunc == paravirt_nop)
/* If the operation is a nop, then nop the callsite */
ret = paravirt_patch_nop();
else if (type == PARAVIRT_PATCH(iret) ||
type == PARAVIRT_PATCH(irq_enable_sysexit))
/* If operation requires a jmp, then jmp */
- ret = paravirt_patch_jmp(opfunc, site, len);
+ ret = paravirt_patch_jmp(opfunc, insnbuf, addr, len);
else
/* Otherwise call the function; assume target could
clobber any caller-save reg */
- ret = paravirt_patch_call(opfunc, CLBR_ANY,
- site, clobbers, len);
+ ret = paravirt_patch_call(insnbuf, opfunc, CLBR_ANY,
+ addr, clobbers, len);
return ret;
}
-unsigned paravirt_patch_insns(void *site, unsigned len,
+unsigned paravirt_patch_insns(void *insnbuf, unsigned len,
const char *start, const char *end)
{
unsigned insn_len = end - start;
@@ -198,7 +198,7 @@
if (insn_len > len || start == NULL)
insn_len = len;
else
- memcpy(site, start, insn_len);
+ memcpy(insnbuf, start, insn_len);
return insn_len;
}