target/i386: Move helper_check_io to sysemu

The we never allow i/o from user-only, and the tss check
that helper_check_io does will always fail.  Use an ifdef
within gen_check_io and return false, indicating that an
exception is known to be raised.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210514151342.384376-50-richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/i386/helper.h

@@ -86,7 +86,6 @@ DEF_HELPER_1(rdtsc, void, env)
 DEF_HELPER_1(rdtscp, void, env)
 DEF_HELPER_FLAGS_1(rdpmc, TCG_CALL_NO_WG, noreturn, env)
 
-DEF_HELPER_FLAGS_3(check_io, TCG_CALL_NO_WG, void, env, i32, i32)
 DEF_HELPER_3(outb, void, env, i32, i32)
 DEF_HELPER_2(inb, tl, env, i32)
 DEF_HELPER_3(outw, void, env, i32, i32)
@@ -95,6 +94,7 @@ DEF_HELPER_3(outl, void, env, i32, i32)
 DEF_HELPER_2(inl, tl, env, i32)
 
 #ifndef CONFIG_USER_ONLY
+DEF_HELPER_FLAGS_3(check_io, TCG_CALL_NO_WG, void, env, i32, i32)
 DEF_HELPER_FLAGS_4(bpt_io, TCG_CALL_NO_WG, void, env, i32, i32, tl)
 DEF_HELPER_2(svm_check_intercept, void, env, i32)
 DEF_HELPER_4(svm_check_io, void, env, i32, i32, i32)

target/i386/tcg/seg_helper.c

@@ -2416,31 +2416,3 @@ void helper_verw(CPUX86State *env, target_ulong selector1)
     }
     CC_SRC = eflags | CC_Z;
 }
-
-/* check if Port I/O is allowed in TSS */
-void helper_check_io(CPUX86State *env, uint32_t addr, uint32_t size)
-{
-    uintptr_t retaddr = GETPC();
-    uint32_t io_offset, val, mask;
-
-    /* TSS must be a valid 32 bit one */
-    if (!(env->tr.flags & DESC_P_MASK) ||
-        ((env->tr.flags >> DESC_TYPE_SHIFT) & 0xf) != 9 ||
-        env->tr.limit < 103) {
-        goto fail;
-    }
-    io_offset = cpu_lduw_kernel_ra(env, env->tr.base + 0x66, retaddr);
-    io_offset += (addr >> 3);
-    /* Note: the check needs two bytes */
-    if ((io_offset + 1) > env->tr.limit) {
-        goto fail;
-    }
-    val = cpu_lduw_kernel_ra(env, env->tr.base + io_offset, retaddr);
-    val >>= (addr & 7);
-    mask = (1 << size) - 1;
-    /* all bits must be zero to allow the I/O */
-    if ((val & mask) != 0) {
-    fail:
-        raise_exception_err_ra(env, EXCP0D_GPF, 0, retaddr);
-    }
-}

target/i386/tcg/sysemu/seg_helper.c

@@ -23,6 +23,7 @@
 #include "exec/helper-proto.h"
 #include "exec/cpu_ldst.h"
 #include "tcg/helper-tcg.h"
+#include "../seg_helper.h"
 
 #ifdef TARGET_X86_64
 void helper_syscall(CPUX86State *env, int next_eip_addend)
@@ -123,3 +124,31 @@ void x86_cpu_do_interrupt(CPUState *cs)
         env->old_exception = -1;
     }
 }
+
+/* check if Port I/O is allowed in TSS */
+void helper_check_io(CPUX86State *env, uint32_t addr, uint32_t size)
+{
+    uintptr_t retaddr = GETPC();
+    uint32_t io_offset, val, mask;
+
+    /* TSS must be a valid 32 bit one */
+    if (!(env->tr.flags & DESC_P_MASK) ||
+        ((env->tr.flags >> DESC_TYPE_SHIFT) & 0xf) != 9 ||
+        env->tr.limit < 103) {
+        goto fail;
+    }
+    io_offset = cpu_lduw_kernel_ra(env, env->tr.base + 0x66, retaddr);
+    io_offset += (addr >> 3);
+    /* Note: the check needs two bytes */
+    if ((io_offset + 1) > env->tr.limit) {
+        goto fail;
+    }
+    val = cpu_lduw_kernel_ra(env, env->tr.base + io_offset, retaddr);
+    val >>= (addr & 7);
+    mask = (1 << size) - 1;
+    /* all bits must be zero to allow the I/O */
+    if ((val & mask) != 0) {
+    fail:
+        raise_exception_err_ra(env, EXCP0D_GPF, 0, retaddr);
+    }
+}

target/i386/tcg/translate.c

@@ -203,7 +203,6 @@ STUB_HELPER(read_crN, TCGv ret, TCGv_env env, TCGv_i32 reg)
 STUB_HELPER(set_dr, TCGv_env env, TCGv_i32 reg, TCGv val)
 STUB_HELPER(stgi, TCGv_env env)
 STUB_HELPER(svm_check_intercept, TCGv_env env, TCGv_i32 type)
-STUB_HELPER(svm_check_io, TCGv_env env, TCGv_i32 port, TCGv_i32 p, TCGv_i32 a)
 STUB_HELPER(vmload, TCGv_env env, TCGv_i32 aflag)
 STUB_HELPER(vmmcall, TCGv_env env)
 STUB_HELPER(vmrun, TCGv_env env, TCGv_i32 aflag, TCGv_i32 pc_ofs)
@@ -217,6 +216,7 @@ static void gen_jr(DisasContext *s, TCGv dest);
 static void gen_jmp(DisasContext *s, target_ulong eip);
 static void gen_jmp_tb(DisasContext *s, target_ulong eip, int tb_num);
 static void gen_op(DisasContext *s1, int op, MemOp ot, int d);
+static void gen_exception_gpf(DisasContext *s);
 
 /* i386 arith/logic operations */
 enum {
@@ -681,6 +681,14 @@ static void gen_helper_out_func(MemOp ot, TCGv_i32 v, TCGv_i32 n)
 static bool gen_check_io(DisasContext *s, MemOp ot, TCGv_i32 port,
                          uint32_t svm_flags)
 {
+#ifdef CONFIG_USER_ONLY
+    /*
+     * We do not implement the ioperm(2) syscall, so the TSS check
+     * will always fail.
+     */
+    gen_exception_gpf(s);
+    return false;
+#else
     if (PE(s) && (CPL(s) > IOPL(s) || VM86(s))) {
         gen_helper_check_io(cpu_env, port, tcg_constant_i32(1 << ot));
     }
@@ -699,6 +707,7 @@ static bool gen_check_io(DisasContext *s, MemOp ot, TCGv_i32 port,
                                 tcg_constant_i32(next_eip - cur_eip));
     }
     return true;
+#endif
 }
 
 static inline void gen_movs(DisasContext *s, MemOp ot)