[Xen-devel] [RFC 14/22] x86/paravirt: Adapt assembly for PIE support

[Thomas Garnier <thgarnie@xxxxxxxxxx>]

if PIE is enabled, switch the paravirt assembly constraints to be
compatible. The %c/i constrains generate smaller code so is kept by
default.

Position Independent Executable (PIE) support will allow to extended the
KASLR randomization range below the -2G memory limit.

Signed-off-by: Thomas Garnier <thgarnie@xxxxxxxxxx>
---
 arch/x86/include/asm/paravirt_types.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/paravirt_types.h 
b/arch/x86/include/asm/paravirt_types.h
index 9ffc36bfe4cd..6f67c10672ec 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -347,9 +347,17 @@ extern struct pv_lock_ops pv_lock_ops;
 #define PARAVIRT_PATCH(x)                                      \
        (offsetof(struct paravirt_patch_template, x) / sizeof(void *))
 
+#ifdef CONFIG_X86_PIE
+#define paravirt_opptr_call "a"
+#define paravirt_opptr_type "p"
+#else
+#define paravirt_opptr_call "c"
+#define paravirt_opptr_type "i"
+#endif
+
 #define paravirt_type(op)                              \
        [paravirt_typenum] "i" (PARAVIRT_PATCH(op)),    \
-       [paravirt_opptr] "i" (&(op))
+       [paravirt_opptr] paravirt_opptr_type (&(op))
 #define paravirt_clobber(clobber)              \
        [paravirt_clobber] "i" (clobber)
 
@@ -403,7 +411,7 @@ 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 *%c[paravirt_opptr];"
+#define PARAVIRT_CALL  "call *%" paravirt_opptr_call "[paravirt_opptr];"
 
 /*
  * These macros are intended to wrap calls through one of the paravirt
-- 
2.13.2.932.g7449e964c-goog


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