[Xen-devel] [RFC 06/22] kvm: 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. 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@xxxxxxxxxx>
---
 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 87ac4fba6d8e..3041201a3aeb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1352,9 +1352,11 @@ 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 71c17a5be983..53b8ad162589 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -618,8 +618,10 @@ 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 4d8141e533c3..8b718c6d6729 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -554,12 +554,12 @@ 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)
-- 
2.13.2.932.g7449e964c-goog


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