[Xen-devel] [RFC 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_GET_PTR macro instead of
the 'mov $symbol, %dst' construct to not have an absolute reference.

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 b446c5a082ad..b09bd50b06c7 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -49,7 +49,7 @@ static inline void *current_text_addr(void)
 {
        void *pc;
 
-       asm volatile("mov $1f, %0; 1:":"=r" (pc));
+       asm volatile(_ASM_GET_PTR(1f, %0) "; 1:":"=r" (pc));
 
        return pc;
 }
@@ -695,6 +695,7 @@ static inline void sync_core(void)
                : ASM_CALL_CONSTRAINT : : "memory");
 #else
        unsigned int tmp;
+       unsigned long tmp2;
 
        asm volatile (
                UNWIND_HINT_SAVE
@@ -705,11 +706,13 @@ 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
 }
 
-- 
2.14.2.920.gcf0c67979c-goog


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