[Xen-devel] [PATCH v3 4/9] Clear AC bit in RFLAGS to protect Xen itself by SMAP

[Feng Wu <feng.wu@xxxxxxxxx>]

Clear AC bit in RFLAGS at the beginning of exception, interrupt, hypercall,
so Xen itself can be protected by SMAP mechanism.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
 xen/arch/x86/x86_64/compat/entry.S | 1 +
 xen/arch/x86/x86_64/entry.S        | 8 ++++++++
 xen/arch/x86/x86_64/traps.c        | 4 ++--
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/x86_64/compat/entry.S 
b/xen/arch/x86/x86_64/compat/entry.S
index 32b3bcc..ac594c9 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -13,6 +13,7 @@
 #include <irq_vectors.h>
 
 ENTRY(compat_hypercall)
+        ASM_CLAC
         pushq $0
         SAVE_VOLATILE type=TRAP_syscall compat=1
 
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 1c81852..5f46803 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -273,6 +273,7 @@ ENTRY(sysenter_entry)
         pushq $0
         pushfq
 GLOBAL(sysenter_eflags_saved)
+        ASM_CLAC
         pushq $3 /* ring 3 null cs */
         pushq $0 /* null rip */
         pushq $0
@@ -309,6 +310,7 @@ UNLIKELY_END(sysenter_gpf)
         jmp   .Lbounce_exception
 
 ENTRY(int80_direct_trap)
+        ASM_CLAC
         pushq $0
         SAVE_VOLATILE 0x80
 
@@ -466,6 +468,7 @@ ENTRY(dom_crash_sync_extable)
         jmp   asm_domain_crash_synchronous /* Does not return */
 
 ENTRY(common_interrupt)
+        ASM_CLAC
         SAVE_ALL
         movq %rsp,%rdi
         callq do_IRQ
@@ -485,6 +488,7 @@ ENTRY(page_fault)
         movl  $TRAP_page_fault,4(%rsp)
 /* No special register assumptions. */
 GLOBAL(handle_exception)
+        ASM_CLAC
         SAVE_ALL
 handle_exception_saved:
         testb $X86_EFLAGS_IF>>8,UREGS_eflags+1(%rsp)
@@ -613,6 +617,7 @@ ENTRY(spurious_interrupt_bug)
         jmp   handle_exception
 
 ENTRY(double_fault)
+        ASM_CLAC
         movl  $TRAP_double_fault,4(%rsp)
         SAVE_ALL
         movq  %rsp,%rdi
@@ -628,6 +633,7 @@ ENTRY(early_page_fault)
         .popsection
 
 ENTRY(nmi)
+        ASM_CLAC
         pushq $0
         movl  $TRAP_nmi,4(%rsp)
 handle_ist_exception:
@@ -665,6 +671,7 @@ handle_ist_exception:
         jmp   compat_restore_all_guest
 
 ENTRY(nmi_crash)
+        ASM_CLAC
         pushq $0
         movl $TRAP_nmi,4(%rsp)
         SAVE_ALL
@@ -673,6 +680,7 @@ ENTRY(nmi_crash)
         ud2
 
 ENTRY(machine_check)
+        ASM_CLAC
         pushq $0
         movl  $TRAP_machine_check,4(%rsp)
         jmp   handle_ist_exception
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index 90072c1..466b2f2 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -437,8 +437,8 @@ void __devinit subarch_percpu_traps_init(void)
     /* Common SYSCALL parameters. */
     wrmsr(MSR_STAR, 0, (FLAT_RING3_CS32<<16) | __HYPERVISOR_CS);
     wrmsr(MSR_SYSCALL_MASK,
-          X86_EFLAGS_VM|X86_EFLAGS_RF|X86_EFLAGS_NT|
-          X86_EFLAGS_DF|X86_EFLAGS_IF|X86_EFLAGS_TF,
+          X86_EFLAGS_VM|X86_EFLAGS_RF|X86_EFLAGS_NT|X86_EFLAGS_DF|
+          X86_EFLAGS_IF|X86_EFLAGS_TF|X86_EFLAGS_AC,
           0U);
 }
 
-- 
1.8.3.1


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