Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 76 insertions, 0 deletions

diff --git a/linux-user/semihost.c b/linux-user/semihost.c
new file mode 100644
index 000000000..17f074ac5
--- /dev/null
+++ b/linux-user/semihost.c
@@ -0,0 +1,76 @@
+/*
+ * ARM Compatible Semihosting Console Support.
+ *
+ * Copyright (c) 2019 Linaro Ltd
+ *
+ * Currently ARM and RISC-V are unique in having support for
+ * semihosting support in linux-user. So for now we implement the
+ * common console API but just for arm and risc-v linux-user.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "semihosting/console.h"
+#include "qemu.h"
+#include "user-internals.h"
+#include <termios.h>
+
+int qemu_semihosting_console_outs(CPUArchState *env, target_ulong addr)
+{
+    int len = target_strlen(addr);
+    void *s;
+    if (len < 0){
+       qemu_log_mask(LOG_GUEST_ERROR,
+                     "%s: passed inaccessible address " TARGET_FMT_lx,
+                     __func__, addr);
+       return 0;
+    }
+    s = lock_user(VERIFY_READ, addr, (long)(len + 1), 1);
+    g_assert(s);  /* target_strlen has already verified this will work */
+    len = write(STDERR_FILENO, s, len);
+    unlock_user(s, addr, 0);
+    return len;
+}
+
+void qemu_semihosting_console_outc(CPUArchState *env, target_ulong addr)
+{
+    char c;
+
+    if (get_user_u8(c, addr)) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: passed inaccessible address " TARGET_FMT_lx,
+                      __func__, addr);
+    } else {
+        if (write(STDERR_FILENO, &c, 1) != 1) {
+            qemu_log_mask(LOG_UNIMP, "%s: unexpected write to stdout failure",
+                          __func__);
+        }
+    }
+}
+
+/*
+ * For linux-user we can safely block. However as we want to return as
+ * soon as a character is read we need to tweak the termio to disable
+ * line buffering. We restore the old mode afterwards in case the
+ * program is expecting more normal behaviour. This is slow but
+ * nothing using semihosting console reading is expecting to be fast.
+ */
+target_ulong qemu_semihosting_console_inc(CPUArchState *env)
+{
+    uint8_t c;
+    struct termios old_tio, new_tio;
+
+    /* Disable line-buffering and echo */
+    tcgetattr(STDIN_FILENO, &old_tio);
+    new_tio = old_tio;
+    new_tio.c_lflag &= (~ICANON & ~ECHO);
+    tcsetattr(STDIN_FILENO, TCSANOW, &new_tio);
+
+    c = getchar();
+
+    /* restore config */
+    tcsetattr(STDIN_FILENO, TCSANOW, &old_tio);
+
+    return (target_ulong) c;
+}