x86, paravirt: prevent gcc from generating the wrong addressing mode
Impact: fix crash on VMI (VMware)
When we generate a call sequence for calling a paravirtualized
function, we presume that the generated code is "call *0xXXXXX",
which is a 6 byte opcode; this is larger than a normal
direct call, and so we can patch a direct call over it.
At the moment, however we give gcc enough rope to hang us by
putting the address in a register and generating a two byte
indirect-via-register call. Prevent this by explicitly
dereferencing the function pointer and passing it into the
asm as a constant.
This prevents crashes in VMI, as it cannot handle unpatchable
callsites.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Alok Kataria <akataria@vmware.com>
LKML-Reference: <49BEEDC2.2070809@goop.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index e299287..0c212d5 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -360,7 +360,7 @@
#define paravirt_type(op) \
[paravirt_typenum] "i" (PARAVIRT_PATCH(op)), \
- [paravirt_opptr] "m" (op)
+ [paravirt_opptr] "i" (&(op))
#define paravirt_clobber(clobber) \
[paravirt_clobber] "i" (clobber)
@@ -412,7 +412,7 @@
* offset into the paravirt_patch_template structure, and can therefore be
* freely converted back into a structure offset.
*/
-#define PARAVIRT_CALL "call *%[paravirt_opptr];"
+#define PARAVIRT_CALL "call *%c[paravirt_opptr];"
/*
* These macros are intended to wrap calls through one of the paravirt