[kernel-hardening] [RFC v3 18/27] kvm: Adapt assembly for PIE support

[Thomas Garnier <thgarnie@google.com>]

Change the assembly code to use only relative references of symbols for the
kernel to be PIE compatible. The new __ASM_GET_PTR_PRE macro is used to
get the address of a symbol on both 32 and 64-bit with PIE support.

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

Signed-off-by: Thomas Garnier <thgarnie@google.com>
---
 arch/x86/include/asm/kvm_host.h | 6 ++++--
 arch/x86/kernel/kvm.c           | 6 ++++--
 arch/x86/kvm/svm.c              | 4 ++--
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9d7d856b2d89..14073fda75fb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1342,9 +1342,11 @@ asmlinkage void kvm_spurious_fault(void);
 	".pushsection .fixup, \"ax\" \n" \
 	"667: \n\t" \
 	cleanup_insn "\n\t"		      \
-	"cmpb $0, kvm_rebooting \n\t"	      \
+	"cmpb $0, kvm_rebooting" __ASM_SEL(,(%%rip)) " \n\t" \
 	"jne 668b \n\t"      		      \
-	__ASM_SIZE(push) " $666b \n\t"	      \
+	__ASM_SIZE(push) "%%" _ASM_AX " \n\t"		\
+	__ASM_GET_PTR_PRE(666b) "%%" _ASM_AX "\n\t"	\
+	"xchg %%" _ASM_AX ", (%%" _ASM_SP ") \n\t"	\
 	"call kvm_spurious_fault \n\t"	      \
 	".popsection \n\t" \
 	_ASM_EXTABLE(666b, 667b)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index aa60a08b65b1..07176bfc188b 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -620,8 +620,10 @@ asm(
 ".global __raw_callee_save___kvm_vcpu_is_preempted;"
 ".type __raw_callee_save___kvm_vcpu_is_preempted, @function;"
 "__raw_callee_save___kvm_vcpu_is_preempted:"
-"movq	__per_cpu_offset(,%rdi,8), %rax;"
-"cmpb	$0, " __stringify(KVM_STEAL_TIME_preempted) "+steal_time(%rax);"
+"leaq	__per_cpu_offset(%rip), %rax;"
+"movq	(%rax,%rdi,8), %rax;"
+"addq	" __stringify(KVM_STEAL_TIME_preempted) "+steal_time(%rip), %rax;"
+"cmpb	$0, (%rax);"
 "setne	%al;"
 "ret;"
 ".popsection");
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0e68f0b3cbf7..364536080438 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -568,12 +568,12 @@ static u32 svm_msrpm_offset(u32 msr)
 
 static inline void clgi(void)
 {
-	asm volatile (__ex(SVM_CLGI));
+	asm volatile (__ex(SVM_CLGI) : :);
 }
 
 static inline void stgi(void)
 {
-	asm volatile (__ex(SVM_STGI));
+	asm volatile (__ex(SVM_STGI) : :);
 }
 
 static inline void invlpga(unsigned long addr, u32 asid)
-- 
2.14.2.920.gcf0c67979c-goog