Commit 42854dc0 authored Mar 16, 2009 by Jeremy Fitzhardinge Committed by H. Peter Anvin Mar 16, 2009

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>

parent 895791da

arch/x86/include/asm/paravirt.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -360,7 +360,7 @@ extern struct pv_lock_ops pv_lock_ops;

		#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 @@ int paravirt_disable_iospace(void);
		* 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