x86/emul: Provide a wrapper to x86_emulate() to ASSERT() certain behaviour

In debug builds, confirm that some properties of x86_emulate()'s behaviour
actually hold.  The first property, fixed in a previous change, is that retire
flags are only ever set in the X86EMUL_OKAY case.

While adjusting the userspace test harness to cope with ASSERT() in
x86_emulate.h, fix a build problem introduced in c/s 122dd9575c7 "x86emul:
in_longmode() should not ignore ->read_msr() errors" by providing an
implementation of likely()/unlikely().

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/tools/tests/x86_emulator/test_x86_emulator.c b/tools/tests/x86_emulator/test_x86_emulator.c
index f255fef3e30c478b7dd50a82b41fd83d8647524e..b54fd11fe053cbff4d6fb696fee8e794976e4e6e 100644 (file)
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <errno.h>
 #include <limits.h>
 #include <stdbool.h>

diff --git a/tools/tests/x86_emulator/x86_emulate.c b/tools/tests/x86_emulator/x86_emulate.c
index c46b7fcc7dee0719a35c7cad3c44f35964774aba..897b9ab299b1c0009f56d72ced355973c55149e2 100644 (file)
--- a/tools/tests/x86_emulator/x86_emulate.c
+++ b/tools/tests/x86_emulator/x86_emulate.c
@@ -16,7 +16,6 @@ typedef bool bool_t;
 #define EFER_LMA       (1 << 10)
 
 #define BUG() abort()
-#define ASSERT assert
 #define ASSERT_UNREACHABLE() assert(!__LINE__)
 
 #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
@@ -50,4 +49,7 @@ typedef bool bool_t;
 #define __init
 #define __maybe_unused __attribute__((__unused__))
 
+#define likely(x)     __builtin_expect(!!(x), true)
+#define unlikely(x)   __builtin_expect(!!(x), false)
+
 #include "x86_emulate/x86_emulate.c"

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index bfcc05dff3ed8a2223536c7bb20a8b05ee8eaa58..3e602da34a5900e16e8ecb5451463c0ca6bd2f7d 100644 (file)
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2404,6 +2404,9 @@ x86_decode(
 #undef insn_fetch_bytes
 #undef insn_fetch_type
 
+/* Undo DEBUG wrapper. */
+#undef x86_emulate
+
 int
 x86_emulate(
     struct x86_emulate_ctxt *ctxt,

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h b/xen/arch/x86/x86_emulate/x86_emulate.h
index ef39601c47b7a7ec7d8c91baf3e790be95e27e20..60f9105663ea4b2daa0a599cc06889bce25a3f21 100644 (file)
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -23,6 +23,10 @@
 #ifndef __X86_EMULATE_H__
 #define __X86_EMULATE_H__
 
+#if !defined(__XEN__) && !defined(ASSERT)
+#define ASSERT assert
+#endif
+
 #define MAX_INST_LEN 15
 
 struct x86_emulate_ctxt;
@@ -546,13 +550,34 @@ struct x86_emulate_stub {
 
 /*
  * x86_emulate: Emulate an instruction.
- * Returns -1 on failure, 0 on success.
+ * Returns X86EMUL_* constants.
  */
 int
 x86_emulate(
     struct x86_emulate_ctxt *ctxt,
     const struct x86_emulate_ops *ops);
 
+#ifndef NDEBUG
+/*
+ * In debug builds, wrap x86_emulate() with some assertions about its expected
+ * behaviour.
+ */
+static inline int x86_emulate_wrapper(
+    struct x86_emulate_ctxt *ctxt,
+    const struct x86_emulate_ops *ops)
+{
+    int rc = x86_emulate(ctxt, ops);
+
+    /* Retire flags should only be set for successful instruction emulation. */
+    if ( rc != X86EMUL_OKAY )
+        ASSERT(ctxt->retire.raw == 0);
+
+    return rc;
+}
+
+#define x86_emulate x86_emulate_wrapper
+#endif
+
 /*
  * Given the 'reg' portion of a ModRM byte, and a register block, return a
  * pointer into the block that addresses the relevant register.