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/vmi.c b/arch/i386/kernel/vmi.c
index 72042bb..18673e0 100644
--- a/arch/i386/kernel/vmi.c
+++ b/arch/i386/kernel/vmi.c
@@ -87,12 +87,14 @@
#define IRQ_PATCH_INT_MASK 0
#define IRQ_PATCH_DISABLE 5
-static inline void patch_offset(unsigned char *eip, unsigned char *dest)
+static inline void patch_offset(void *insnbuf,
+ unsigned long eip, unsigned long dest)
{
- *(unsigned long *)(eip+1) = dest-eip-5;
+ *(unsigned long *)(insnbuf+1) = dest-eip-5;
}
-static unsigned patch_internal(int call, unsigned len, void *insns)
+static unsigned patch_internal(int call, unsigned len, void *insnbuf,
+ unsigned long eip)
{
u64 reloc;
struct vmi_relocation_info *const rel = (struct vmi_relocation_info *)&reloc;
@@ -100,14 +102,14 @@
switch(rel->type) {
case VMI_RELOCATION_CALL_REL:
BUG_ON(len < 5);
- *(char *)insns = MNEM_CALL;
- patch_offset(insns, rel->eip);
+ *(char *)insnbuf = MNEM_CALL;
+ patch_offset(insnbuf, eip, (unsigned long)rel->eip);
return 5;
case VMI_RELOCATION_JUMP_REL:
BUG_ON(len < 5);
- *(char *)insns = MNEM_JMP;
- patch_offset(insns, rel->eip);
+ *(char *)insnbuf = MNEM_JMP;
+ patch_offset(insnbuf, eip, (unsigned long)rel->eip);
return 5;
case VMI_RELOCATION_NOP:
@@ -128,21 +130,26 @@
* Apply patch if appropriate, return length of new instruction
* sequence. The callee does nop padding for us.
*/
-static unsigned vmi_patch(u8 type, u16 clobbers, void *insns, unsigned len)
+static unsigned vmi_patch(u8 type, u16 clobbers, void *insns,
+ unsigned long eip, unsigned len)
{
switch (type) {
case PARAVIRT_PATCH(irq_disable):
- return patch_internal(VMI_CALL_DisableInterrupts, len, insns);
+ return patch_internal(VMI_CALL_DisableInterrupts, len,
+ insns, eip);
case PARAVIRT_PATCH(irq_enable):
- return patch_internal(VMI_CALL_EnableInterrupts, len, insns);
+ return patch_internal(VMI_CALL_EnableInterrupts, len,
+ insns, eip);
case PARAVIRT_PATCH(restore_fl):
- return patch_internal(VMI_CALL_SetInterruptMask, len, insns);
+ return patch_internal(VMI_CALL_SetInterruptMask, len,
+ insns, eip);
case PARAVIRT_PATCH(save_fl):
- return patch_internal(VMI_CALL_GetInterruptMask, len, insns);
+ return patch_internal(VMI_CALL_GetInterruptMask, len,
+ insns, eip);
case PARAVIRT_PATCH(iret):
- return patch_internal(VMI_CALL_IRET, len, insns);
+ return patch_internal(VMI_CALL_IRET, len, insns, eip);
case PARAVIRT_PATCH(irq_enable_sysexit):
- return patch_internal(VMI_CALL_SYSEXIT, len, insns);
+ return patch_internal(VMI_CALL_SYSEXIT, len, insns, eip);
default:
break;
}