[PATCH 08/10] hw/9pfs: Allow using hw/9pfs with emscripten

[Kohei Tokunaga]

Emscripten's fiber does not support submitting coroutines to other
threads. So this commit modifies hw/9pfs/coth.h to disable this behavior
when compiled with Emscripten.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
---
 fsdev/file-op-9p.h     |  3 +++
 fsdev/meson.build      |  2 +-
 hw/9pfs/9p-util-stub.c | 43 ++++++++++++++++++++++++++++++++++++++++++
 hw/9pfs/9p-util.h      | 18 ++++++++++++++++++
 hw/9pfs/9p.c           |  3 +++
 hw/9pfs/coth.h         | 12 ++++++++++++
 hw/9pfs/meson.build    |  2 ++
 meson.build            |  6 +++---
 8 files changed, 85 insertions(+), 4 deletions(-)
 create mode 100644 hw/9pfs/9p-util-stub.c

diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
index 4997677460..b7ca2640ce 100644
--- a/fsdev/file-op-9p.h
+++ b/fsdev/file-op-9p.h
@@ -26,6 +26,9 @@
 # include <sys/param.h>
 # include <sys/mount.h>
 #endif
+#ifdef EMSCRIPTEN
+#include <sys/vfs.h>
+#endif
 
 #define SM_LOCAL_MODE_BITS    0600
 #define SM_LOCAL_DIR_MODE_BITS    0700
diff --git a/fsdev/meson.build b/fsdev/meson.build
index c751d8cb62..c3e92a29d7 100644
--- a/fsdev/meson.build
+++ b/fsdev/meson.build
@@ -5,6 +5,6 @@ fsdev_ss.add(when: ['CONFIG_FSDEV_9P'], if_true: files(
   '9p-marshal.c',
   'qemu-fsdev.c',
 ), if_false: files('qemu-fsdev-dummy.c'))
-if host_os in ['linux', 'darwin']
+if host_os in ['linux', 'darwin', 'emscripten']
   system_ss.add_all(fsdev_ss)
 endif
diff --git a/hw/9pfs/9p-util-stub.c b/hw/9pfs/9p-util-stub.c
new file mode 100644
index 0000000000..57c89902ab
--- /dev/null
+++ b/hw/9pfs/9p-util-stub.c
@@ -0,0 +1,43 @@
+/*
+ * 9p utilities stub functions
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "9p-util.h"
+
+ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name,
+                             void *value, size_t size)
+{
+    return -1;
+}
+
+ssize_t flistxattrat_nofollow(int dirfd, const char *filename,
+                              char *list, size_t size)
+{
+    return -1;
+}
+
+ssize_t fremovexattrat_nofollow(int dirfd, const char *filename,
+                                const char *name)
+{
+    return -1;
+}
+
+int fsetxattrat_nofollow(int dirfd, const char *path, const char *name,
+                         void *value, size_t size, int flags)
+{
+    return -1;
+
+}
+
+int qemu_mknodat(int dirfd, const char *filename, mode_t mode, dev_t dev)
+{
+    return -1;
+}
+
+ssize_t fgetxattr(int fd, const char *name, void *value, size_t size)
+{
+    return -1;
+}
diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h
index 7bc4ec8e85..8c5006fcdc 100644
--- a/hw/9pfs/9p-util.h
+++ b/hw/9pfs/9p-util.h
@@ -84,6 +84,24 @@ static inline int errno_to_dotl(int err) {
     } else if (err == EOPNOTSUPP) {
         err = 95; /* ==EOPNOTSUPP on Linux */
     }
+#elif defined(EMSCRIPTEN)
+    /*
+     * FIXME: Only most important errnos translated here yet, this should be
+     * extended to as many errnos being translated as possible in future.
+     */
+    if (err == ENAMETOOLONG) {
+        err = 36; /* ==ENAMETOOLONG on Linux */
+    } else if (err == ENOTEMPTY) {
+        err = 39; /* ==ENOTEMPTY on Linux */
+    } else if (err == ELOOP) {
+        err = 40; /* ==ELOOP on Linux */
+    } else if (err == ENODATA) {
+        err = 61; /* ==ENODATA on Linux */
+    } else if (err == ENOTSUP) {
+        err = 95; /* ==EOPNOTSUPP on Linux */
+    } else if (err == EOPNOTSUPP) {
+        err = 95; /* ==EOPNOTSUPP on Linux */
+    }
 #else
 #error Missing errno translation to Linux for this host system
 #endif
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 7cad2bce62..4f45f0edd3 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -4013,6 +4013,9 @@ out_nofid:
  * Linux guests.
  */
 #define P9_XATTR_SIZE_MAX 65536
+#elif defined(EMSCRIPTEN)
+/* No support for xattr */
+#define P9_XATTR_SIZE_MAX 0
 #else
 #error Missing definition for P9_XATTR_SIZE_MAX for this host system
 #endif
diff --git a/hw/9pfs/coth.h b/hw/9pfs/coth.h
index 2c54249b35..7b0d05ba1b 100644
--- a/hw/9pfs/coth.h
+++ b/hw/9pfs/coth.h
@@ -19,6 +19,7 @@
 #include "qemu/coroutine-core.h"
 #include "9p.h"
 
+#ifndef EMSCRIPTEN
 /*
  * we want to use bottom half because we want to make sure the below
  * sequence of events.
@@ -57,6 +58,17 @@
         /* re-enter back to qemu thread */                              \
         qemu_coroutine_yield();                                         \
     } while (0)
+#else
+/*
+ * FIXME: implement this on emscripten but emscripten's coroutine
+ * implementation (fiber) doesn't support submitting a coroutine to other
+ * threads.
+ */
+#define v9fs_co_run_in_worker(code_block)                               \
+    do {                                                                \
+        code_block;                                                     \
+    } while (0)
+#endif
 
 void co_run_in_worker_bh(void *);
 int coroutine_fn v9fs_co_readlink(V9fsPDU *, V9fsPath *, V9fsString *);
diff --git a/hw/9pfs/meson.build b/hw/9pfs/meson.build
index d35d4f44ff..04f85fb9e9 100644
--- a/hw/9pfs/meson.build
+++ b/hw/9pfs/meson.build
@@ -17,6 +17,8 @@ if host_os == 'darwin'
   fs_ss.add(files('9p-util-darwin.c'))
 elif host_os == 'linux'
   fs_ss.add(files('9p-util-linux.c'))
+elif host_os == 'emscripten'
+  fs_ss.add(files('9p-util-stub.c'))
 endif
 fs_ss.add(when: 'CONFIG_XEN_BUS', if_true: files('xen-9p-backend.c'))
 system_ss.add_all(when: 'CONFIG_FSDEV_9P', if_true: fs_ss)
diff --git a/meson.build b/meson.build
index ab84820bc5..a3aadf8b59 100644
--- a/meson.build
+++ b/meson.build
@@ -2356,11 +2356,11 @@ dbus_display = get_option('dbus_display') \
   .allowed()
 
 have_virtfs = get_option('virtfs') \
-    .require(host_os == 'linux' or host_os == 'darwin',
+    .require(host_os == 'linux' or host_os == 'darwin' or host_os == 
'emscripten',
              error_message: 'virtio-9p (virtfs) requires Linux or macOS') \
-    .require(host_os == 'linux' or cc.has_function('pthread_fchdir_np'),
+    .require(host_os == 'linux' or host_os == 'emscripten' or 
cc.has_function('pthread_fchdir_np'),
              error_message: 'virtio-9p (virtfs) on macOS requires the presence 
of pthread_fchdir_np') \
-    .require(host_os == 'darwin' or libattr.found(),
+    .require(host_os == 'darwin' or host_os == 'emscripten' or libattr.found(),
              error_message: 'virtio-9p (virtfs) on Linux requires 
libattr-devel') \
     .disable_auto_if(not have_tools and not have_system) \
     .allowed()
-- 
2.25.1