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>

1 files changed, 29 insertions, 0 deletions

diff --git a/target/i386/tcg/sysemu/seg_helper.c b/target/i386/tcg/sysemu/seg_helper.c
index e0d7b32b82..82c0856c41 100644
--- a/target/i386/tcg/sysemu/seg_helper.c
+++ b/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);
+    }
+}