x86emul: split off insn decoding

This is a fair chunk of code and data and can easily live separate from
the main emulation function.

Code moved gets slightly adjusted in a few places, e.g. replacing EXC_*
by X86_EXC_* (such that EXC_* don't need to move as well; we want these
to be phased out anyway).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

tools/fuzz/x86_instruction_emulator/Makefile

@@ -33,7 +33,7 @@ GCOV_FLAGS := --coverage
 
 OBJS := fuzz-emul.o x86-emulate.o
 OBJS += x86_emulate/0f01.o x86_emulate/0fae.o x86_emulate/0fc7.o
-OBJS += x86_emulate/fpu.o
+OBJS += x86_emulate/decode.o x86_emulate/fpu.o
 
 x86-emulate.h: x86_emulate/x86_emulate.h
 x86-emulate.o x86-emulate-cov.o: x86-emulate.h x86_emulate/x86_emulate.c x86_emulate/private.h

tools/tests/x86_emulator/Makefile

@@ -252,7 +252,7 @@ endif # 32-bit override
 
 OBJS := x86-emulate.o cpuid.o test_x86_emulator.o evex-disp8.o predicates.o wrappers.o
 OBJS += x86_emulate/0f01.o x86_emulate/0fae.o x86_emulate/0fc7.o
-OBJS += x86_emulate/fpu.o
+OBJS += x86_emulate/decode.o x86_emulate/fpu.o
 
 $(TARGET): $(OBJS)
 	$(HOSTCC) $(HOSTCFLAGS) -o $@ $^

tools/tests/x86_emulator/x86-emulate.c

@@ -3,11 +3,6 @@
 #include <errno.h>
 #include <sys/mman.h>
 
-#define DEFINE_PER_CPU(type, var) type per_cpu_##var
-#define this_cpu(var) per_cpu_##var
-
-#define ERR_PTR(val) NULL
-
 /* See gcc bug 100680, but here don't bother making this version dependent. */
 #define gcc11_wrap(x) ({                  \
     unsigned long x_;                     \

tools/tests/x86_emulator/x86-emulate.h

@@ -48,6 +48,9 @@
 #define ASSERT assert
 #define ASSERT_UNREACHABLE() assert(!__LINE__)
 
+#define DEFINE_PER_CPU(type, var) type per_cpu_##var
+#define this_cpu(var) per_cpu_##var
+
 #define MASK_EXTR(v, m) (((v) & (m)) / ((m) & -(m)))
 #define MASK_INSR(v, m) (((v) * ((m) & -(m))) & (m))
 

xen/arch/x86/x86_emulate.c

@@ -9,7 +9,6 @@
  *    Keir Fraser <keir@xen.org>
  */
 
-#include <xen/err.h>
 #include <xen/event.h>
 
 #include <asm/x86_emulate.h>

xen/arch/x86/x86_emulate/Makefile

@@ -1,4 +1,5 @@
 obj-y += 0f01.o
 obj-y += 0fae.o
 obj-y += 0fc7.o
+obj-y += decode.o
 obj-$(CONFIG_HVM) += fpu.o

xen/arch/x86/x86_emulate/private.h

@@ -39,9 +39,11 @@
 #ifdef __i386__
 # define mode_64bit() false
 # define r(name) e ## name
+# define PTR_POISON NULL /* 32-bit builds are for user-space, so NULL is OK. */
 #else
 # define mode_64bit() (ctxt->addr_size == 64)
 # define r(name) r ## name
+# define PTR_POISON ((void *)0x8086000000008086UL) /* non-canonical */
 #endif
 
 /* Operand sizes: 8-bit operands or specified/overridden size. */
@@ -78,6 +80,23 @@
 
 typedef uint8_t opcode_desc_t;
 
+enum disp8scale {
+    /* Values 0 ... 4 are explicit sizes. */
+    d8s_bw = 5,
+    d8s_dq,
+    /* EVEX.W ignored outside of 64-bit mode */
+    d8s_dq64,
+    /*
+     * All further values must strictly be last and in the order
+     * given so that arithmetic on the values works.
+     */
+    d8s_vl,
+    d8s_vl_by_2,
+    d8s_vl_by_4,
+    d8s_vl_by_8,
+};
+typedef uint8_t disp8scale_t;
+
 /* Type, address-of, and value of an instruction's operand. */
 struct operand {
     enum { OP_REG, OP_MEM, OP_IMM, OP_NONE } type;
@@ -184,6 +203,9 @@ enum vex_pfx {
     vex_f2
 };
 
+#define VEX_PREFIX_DOUBLE_MASK 0x1
+#define VEX_PREFIX_SCALAR_MASK 0x2
+
 union vex {
     uint8_t raw[2];
     struct {             /* SDM names */
@@ -718,6 +740,10 @@ do {                                                            \
     if ( rc ) goto done;                                        \
 } while (0)
 
+int x86emul_decode(struct x86_emulate_state *s,
+                   struct x86_emulate_ctxt *ctxt,
+                   const struct x86_emulate_ops *ops);
+
 int x86emul_fpu(struct x86_emulate_state *s,
                 struct cpu_user_regs *regs,
                 struct operand *dst,
@@ -747,6 +773,13 @@ int x86emul_0fc7(struct x86_emulate_state *s,
                  const struct x86_emulate_ops *ops,
                  mmval_t *mmvalp);
 
+/* Initialise output state in x86_emulate_ctxt */
+static inline void init_context(struct x86_emulate_ctxt *ctxt)
+{
+    ctxt->retire.raw = 0;
+    x86_emul_reset_event(ctxt);
+}
+
 static inline bool is_aligned(enum x86_segment seg, unsigned long offs,
                               unsigned int size, struct x86_emulate_ctxt *ctxt,
                               const struct x86_emulate_ops *ops)