eepro100: Don't allow guests to fail assertions

The idea of using assert() for input validation is rather questionable.
Let's remove it from eepro100, so that guests need to find more interesting
ways if they want to crash qemu.

This patch replaces asserts that are directly dependent on guest-accessible
data by other means of error handling.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/eepro100.c

@@ -73,7 +73,7 @@
 
 #define TRACE(flag, command) ((flag) ? (command) : (void)0)
 
-#define missing(text)       assert(!"feature is missing in this emulation: " text)
+#define missing(text) fprintf(stderr, "eepro100: feature is missing in this emulation: " text "\n")
 
 #define MAX_ETH_FRAME_SIZE 1514
 
@@ -672,6 +672,7 @@ static void eepro100_cu_command(EEPRO100State * s, uint8_t val)
         bool bit_s = ((command & 0x4000) != 0);
         bool bit_i = ((command & 0x2000) != 0);
         bool bit_nc = ((command & 0x0010) != 0);
+        bool success = true;
         //~ bool bit_sf = ((command & 0x0008) != 0);
         uint16_t cmd = command & 0x0007;
         s->cu_offset = le32_to_cpu(tx.link);
@@ -698,9 +699,17 @@ static void eepro100_cu_command(EEPRO100State * s, uint8_t val)
             TRACE(RXTX, logout
                 ("transmit, TBD array address 0x%08x, TCB byte count 0x%04x, TBD count %u\n",
                  tbd_array, tcb_bytes, tx.tbd_count));
-            assert(!bit_nc);
+
+            if (bit_nc) {
+                missing("CmdTx: NC = 0");
+                success = false;
+                break;
+            }
             //~ assert(!bit_sf);
-            assert(tcb_bytes <= 2600);
+            if (tcb_bytes > 2600) {
+                logout("TCB byte count too large, using 2600\n");
+                tcb_bytes = 2600;
+            }
             /* Next assertion fails for local configuration. */
             //~ assert((tcb_bytes > 0) || (tbd_array != 0xffffffff));
             if (!((tcb_bytes > 0) || (tbd_array != 0xffffffff))) {
@@ -732,7 +741,6 @@ static void eepro100_cu_command(EEPRO100State * s, uint8_t val)
                 uint8_t tbd_count = 0;
                 if (device_supports_eTxCB(s) && !(s->configuration[6] & BIT(4))) {
                     /* Extended Flexible TCB. */
-                    assert(tcb_bytes == 0);
                     for (; tbd_count < 2; tbd_count++) {
                         uint32_t tx_buffer_address = ldl_phys(tbd_address);
                         uint16_t tx_buffer_size = lduw_phys(tbd_address + 4);
@@ -782,9 +790,11 @@ static void eepro100_cu_command(EEPRO100State * s, uint8_t val)
             break;
         default:
             missing("undefined command");
+            success = false;
+            break;
         }
-        /* Write new status (success). */
-        stw_phys(cb_address, status | 0x8000 | 0x2000);
+        /* Write new status. */
+        stw_phys(cb_address, status | 0x8000 | (success ? 0x2000 : 0));
         if (bit_i) {
             /* CU completed action. */
             eepro100_cx_interrupt(s);
@@ -1492,7 +1502,10 @@ static ssize_t nic_receive(VLANClientState *vc, const uint8_t * buf, size_t size
         { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
 
     /* TODO: check multiple IA bit. */
-    assert(!(s->configuration[20] & BIT(6)));
+    if (s->configuration[20] & BIT(6)) {
+        missing("Multiple IA bit");
+        return -1;
+    }
 
     if (s->configuration[8] & 0x80) {
         /* CSMA is disabled. */
@@ -1521,7 +1534,9 @@ static ssize_t nic_receive(VLANClientState *vc, const uint8_t * buf, size_t size
         /* Multicast frame. */
         TRACE(RXTX, logout("%p received multicast, len=%zu\n", s, size));
         /* TODO: check multicast all bit. */
-        assert(!(s->configuration[21] & BIT(3)));
+        if (s->configuration[21] & BIT(3)) {
+            missing("Multicast All bit");
+        }
         int mcast_idx = compute_mcast_idx(buf);
         if (!(s->mult[mcast_idx >> 3] & (1 << (mcast_idx & 7)))) {
             return size;
@@ -1551,7 +1566,12 @@ static ssize_t nic_receive(VLANClientState *vc, const uint8_t * buf, size_t size
                              offsetof(eepro100_rx_t, packet));
     uint16_t rfd_command = le16_to_cpu(rx.command);
     uint16_t rfd_size = le16_to_cpu(rx.size);
-    assert(size <= rfd_size);
+
+    if (size > rfd_size) {
+        logout("Receive buffer (%" PRId16 " bytes) too small for data "
+            "(%zu bytes); data truncated\n", rfd_size, size);
+        size = rfd_size;
+    }
     if (size < 64) {
         rfd_status |= 0x0080;
     }
@@ -1563,7 +1583,10 @@ static ssize_t nic_receive(VLANClientState *vc, const uint8_t * buf, size_t size
     /* Early receive interrupt not supported. */
     //~ eepro100_er_interrupt(s);
     /* Receive CRC Transfer not supported. */
-    assert(!(s->configuration[18] & 4));
+    if (s->configuration[18] & 4) {
+        missing("Receive CRC Transfer");
+        return -1;
+    }
     /* TODO: check stripping enable bit. */
     //~ assert(!(s->configuration[17] & 1));
     cpu_physical_memory_write(s->ru_base + s->ru_offset +
@@ -1573,7 +1596,8 @@ static ssize_t nic_receive(VLANClientState *vc, const uint8_t * buf, size_t size
     s->ru_offset = le32_to_cpu(rx.link);
     if (rfd_command & 0x8000) {
         /* EL bit is set, so this was the last frame. */
-        assert(0);
+        logout("receive: Running out of frames\n");
+        set_ru_state(s, ru_suspended);
     }
     if (rfd_command & 0x4000) {
         /* S bit is set. */