[Xen-devel] [PATCH v6 05/10] 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 | 3 ++-
 xen/arch/x86/x86_64/entry.S        | 7 +++++--
 xen/arch/x86/x86_64/traps.c        | 2 +-
 xen/include/asm-x86/asm_defns.h    | 5 ++++-
 4 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/x86_64/compat/entry.S 
b/xen/arch/x86/x86_64/compat/entry.S
index 32b3bcc..00dd0f3 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
 
@@ -178,7 +179,7 @@ ENTRY(compat_restore_all_guest)
 
 .section .fixup,"ax"
 .Lfx0:  sti
-        SAVE_ALL
+        SAVE_ALL 0
         movq  UREGS_error_code(%rsp),%rsi
         movq  %rsp,%rax
         andq  $~0xf,%rsp
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 1c81852..205251d 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -68,7 +68,7 @@ iret_exit_to_guest:
 
 .section .fixup,"ax"
 .Lfx0:  sti
-        SAVE_ALL
+        SAVE_ALL 0
         movq  UREGS_error_code(%rsp),%rsi
         movq  %rsp,%rax
         andq  $~0xf,%rsp
@@ -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
 
@@ -621,7 +623,7 @@ ENTRY(double_fault)
 
         .pushsection .init.text, "ax", @progbits
 ENTRY(early_page_fault)
-        SAVE_ALL
+        SAVE_ALL 0
         movq  %rsp,%rdi
         call  do_early_page_fault
         jmp   restore_all_xen
@@ -673,6 +675,7 @@ 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..b87b33e 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -437,7 +437,7 @@ 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_AC|X86_EFLAGS_VM|X86_EFLAGS_RF|X86_EFLAGS_NT|
           X86_EFLAGS_DF|X86_EFLAGS_IF|X86_EFLAGS_TF,
           0U);
 }
diff --git a/xen/include/asm-x86/asm_defns.h b/xen/include/asm-x86/asm_defns.h
index 0302836..9aa3657 100644
--- a/xen/include/asm-x86/asm_defns.h
+++ b/xen/include/asm-x86/asm_defns.h
@@ -190,7 +190,10 @@ static inline void stac(void)
 #endif
 
 #ifdef __ASSEMBLY__
-.macro SAVE_ALL
+.macro SAVE_ALL clear_ac=1
+.if \clear_ac
+        ASM_CLAC
+.endif
         addq  $-(UREGS_error_code-UREGS_r15), %rsp
         cld
         movq  %rdi,UREGS_rdi(%rsp)
-- 
1.8.3.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel