[kvm-unit-tests PATCH v2 3/4] x86/access: Forced emulation support

[Mathias Krause <minipli@grsecurity.net>]

Add support to enforce access tests to be handled by the emulator, if
supported by KVM. Exclude it from the ac_test_exec() test, though, to
not slow it down too much.

Signed-off-by: Mathias Krause <minipli@grsecurity.net>
---
 x86/access.c | 37 ++++++++++++++++++++++++++++++++-----
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/x86/access.c b/x86/access.c
index d1ec99b4fa73..ae5e7d8e8892 100644
--- a/x86/access.c
+++ b/x86/access.c
@@ -82,6 +82,13 @@ enum {
 	AC_CPU_CR4_SMEP_BIT,
 	AC_CPU_CR4_PKE_BIT,
 
+	NR_AC_TEST_FLAGS,
+
+	/*
+	 *  synthetic flags follow, won't be exercised by ac_test_exec().
+	 */
+	AC_FEP_BIT,
+
 	NR_AC_FLAGS
 };
 
@@ -121,6 +128,8 @@ enum {
 #define AC_CPU_CR4_SMEP_MASK  (1 << AC_CPU_CR4_SMEP_BIT)
 #define AC_CPU_CR4_PKE_MASK   (1 << AC_CPU_CR4_PKE_BIT)
 
+#define AC_FEP_MASK           (1 << AC_FEP_BIT)
+
 const char *ac_names[] = {
 	[AC_PTE_PRESENT_BIT] = "pte.p",
 	[AC_PTE_ACCESSED_BIT] = "pte.a",
@@ -152,6 +161,7 @@ const char *ac_names[] = {
 	[AC_CPU_CR0_WP_BIT] = "cr0.wp",
 	[AC_CPU_CR4_SMEP_BIT] = "cr4.smep",
 	[AC_CPU_CR4_PKE_BIT] = "cr4.pke",
+	[AC_FEP_BIT] = "fep",
 };
 
 static inline void *va(pt_element_t phys)
@@ -190,6 +200,7 @@ typedef struct {
 
 static void ac_test_show(ac_test_t *at);
 
+static bool fep_available;
 static unsigned long shadow_cr0;
 static unsigned long shadow_cr3;
 static unsigned long shadow_cr4;
@@ -396,7 +407,7 @@ static void ac_test_init(ac_test_t *at, unsigned long virt, ac_pt_env_t *pt_env)
 static int ac_test_bump_one(ac_test_t *at)
 {
 	at->flags = ((at->flags | invalid_mask) + 1) & ~invalid_mask;
-	return at->flags < (1 << NR_AC_FLAGS);
+	return at->flags < (1 << NR_AC_TEST_FLAGS);
 }
 
 #define F(x)  ((flags & x##_MASK) != 0)
@@ -799,10 +810,13 @@ static int ac_test_do_access(ac_test_t *at)
 
 	if (F(AC_ACCESS_TWICE)) {
 		asm volatile ("mov $fixed2, %%rsi \n\t"
-			      "mov (%[addr]), %[reg] \n\t"
+			      "cmp $0, %[fep] \n\t"
+			      "jz 1f \n\t"
+			      KVM_FEP
+			      "1: mov (%[addr]), %[reg] \n\t"
 			      "fixed2:"
 			      : [reg]"=r"(r), [fault]"=a"(fault), "=b"(e)
-			      : [addr]"r"(at->virt)
+			      : [addr]"r"(at->virt), [fep]"r"(F(AC_FEP))
 			      : "rsi");
 		fault = 0;
 	}
@@ -823,9 +837,15 @@ static int ac_test_do_access(ac_test_t *at)
 		      "jnz 2f \n\t"
 		      "cmp $0, %[write] \n\t"
 		      "jnz 1f \n\t"
-		      "mov (%[addr]), %[reg] \n\t"
+		      "cmp $0, %[fep] \n\t"
+		      "jz 0f \n\t"
+		      KVM_FEP
+		      "0: mov (%[addr]), %[reg] \n\t"
 		      "jmp done \n\t"
-		      "1: mov %[reg], (%[addr]) \n\t"
+		      "1: cmp $0, %[fep] \n\t"
+		      "jz 0f \n\t"
+		      KVM_FEP
+		      "0: mov %[reg], (%[addr]) \n\t"
 		      "jmp done \n\t"
 		      "2: call *%[addr] \n\t"
 		      "done: \n"
@@ -843,6 +863,7 @@ static int ac_test_do_access(ac_test_t *at)
 			[write]"r"(F(AC_ACCESS_WRITE)),
 			[user]"r"(F(AC_ACCESS_USER)),
 			[fetch]"r"(F(AC_ACCESS_FETCH)),
+			[fep]"r"(F(AC_FEP)),
 			[user_ds]"i"(USER_DS),
 			[user_cs]"i"(USER_CS),
 			[user_stack_top]"r"(user_stack + sizeof user_stack),
@@ -1228,6 +1249,12 @@ int ac_test_run(int pt_levels)
 		invalid_mask |= AC_PTE_BIT36_MASK;
 	}
 
+	fep_available = is_fep_available();
+	if (!fep_available) {
+		printf("FEP not available, skipping emulation tests\n");
+		invalid_mask |= AC_FEP_MASK;
+	}
+
 	ac_env_int(&pt_env, pt_levels);
 	ac_test_init(&at, 0xffff923400000000ul, &pt_env);
 
-- 
2.39.2