[Xen-devel] [PATCH v3 08/27] x86/CPU: Adapt assembly for PIE support

[Thomas Garnier <thgarnie@xxxxxxxxxx>]

Change the assembly code to use only relative references of symbols for the
kernel to be PIE compatible. Use the new _ASM_MOVABS macro instead of
the 'mov $symbol, %dst' construct.

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/processor.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index c119d423eacb..81ae6877df29 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -50,7 +50,7 @@ static inline void *current_text_addr(void)
 {
        void *pc;
 
-       asm volatile("mov $1f, %0; 1:":"=r" (pc));
+       asm volatile(_ASM_MOVABS " $1f, %0; 1:":"=r" (pc));
 
        return pc;
 }
@@ -718,6 +718,7 @@ static inline void sync_core(void)
                : ASM_CALL_CONSTRAINT : : "memory");
 #else
        unsigned int tmp;
+       unsigned long tmp2;
 
        asm volatile (
                UNWIND_HINT_SAVE
@@ -728,11 +729,13 @@ static inline void sync_core(void)
                "pushfq\n\t"
                "mov %%cs, %0\n\t"
                "pushq %q0\n\t"
-               "pushq $1f\n\t"
+               "leaq 1f(%%rip), %1\n\t"
+               "pushq %1\n\t"
                "iretq\n\t"
                UNWIND_HINT_RESTORE
                "1:"
-               : "=&r" (tmp), ASM_CALL_CONSTRAINT : : "cc", "memory");
+               : "=&r" (tmp), "=&r" (tmp2), ASM_CALL_CONSTRAINT
+               : : "cc", "memory");
 #endif
 }
 
-- 
2.17.0.441.gb46fe60e1d-goog


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