[RFC,v3,08/27] x86/CPU: Adapt assembly for PIE support

Commit Message

Thomas Garnier Oct. 4, 2017, 9:19 p.m. UTC

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 <[e-mail]>
---
 arch/x86/include/asm/processor.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Patch

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
 }