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x86, paravirt: prevent gcc from generating the wrong addressing mode

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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>
This commit is contained in:
Jeremy Fitzhardinge 2009-03-16 17:24:34 -07:00 committed by H. Peter Anvin
parent 895791dac6
commit 42854dc0a6
1 changed files with 2 additions and 2 deletions
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4
arch/x86/include/asm/paravirt.h
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@ -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