tss: block userspace access to all I/O ports.

A userspace process (CPL=3) can access an i/o port if the bit corresponding to
the port is set to 0 in the I/O permission bitmap.

Configure the I/O permission bitmap address beyond the last valid byte in the
TSS so access to all i/o ports is blocked.

Signed-off-by: Liu Hua <sdu.liu@huawei.com>
Change-Id: I3df76980c3735491db768f7210e71703f86bb989
PiperOrigin-RevId: 257336518

1 files changed, 34 insertions, 0 deletions

diff --git a/test/syscalls/linux/exceptions.cc b/test/syscalls/linux/exceptions.cc
index 0da4c817d..370e85166 100644
--- a/test/syscalls/linux/exceptions.cc
+++ b/test/syscalls/linux/exceptions.cc
@@ -56,6 +56,26 @@ void inline Int3Normal() { asm(".byte 0xcd, 0x03\r\n"); }
 
 void inline Int3Compact() { asm(".byte 0xcc\r\n"); }
 
+void InIOHelper(int width, int value) {
+  EXPECT_EXIT(
+      {
+        switch (width) {
+          case 1:
+            asm volatile("inb %%dx, %%al" ::"d"(value) : "%eax");
+            break;
+          case 2:
+            asm volatile("inw %%dx, %%ax" ::"d"(value) : "%eax");
+            break;
+          case 4:
+            asm volatile("inl %%dx, %%eax" ::"d"(value) : "%eax");
+            break;
+          default:
+            FAIL() << "invalid input width, only 1, 2 or 4 is allowed";
+        }
+      },
+      ::testing::KilledBySignal(SIGSEGV), "");
+}
+
 TEST(ExceptionTest, Halt) {
   // In order to prevent the regular handler from messing with things (and
   // perhaps refaulting until some other signal occurs), we reset the handler to
@@ -87,6 +107,20 @@ TEST(ExceptionTest, DivideByZero) {
       ::testing::KilledBySignal(SIGFPE), "");
 }
 
+TEST(ExceptionTest, IOAccessFault) {
+  // See above.
+  struct sigaction sa = {};
+  sa.sa_handler = SIG_DFL;
+  auto const cleanup = ASSERT_NO_ERRNO_AND_VALUE(ScopedSigaction(SIGSEGV, sa));
+
+  InIOHelper(1, 0x0);
+  InIOHelper(2, 0x7);
+  InIOHelper(4, 0x6);
+  InIOHelper(1, 0xffff);
+  InIOHelper(2, 0xffff);
+  InIOHelper(4, 0xfffd);
+}
+
 TEST(ExceptionTest, Alignment) {
   SetAlignmentCheck();
   ClearAlignmentCheck();