has_int128_type is set to false on emscripten as of now to avoid errors by
libffi. Tests are disabled on emscripten because they rely on host
features that aren't supported by emscripten (e.g. fork and unix
socket).

Signed-off-by: Kohei Tokunaga <ktokunaga.m...@gmail.com>
---
 MAINTAINERS                   |  1 +
 configs/meson/emscripten.txt  |  8 ++++++++
 configure                     |  7 +++++++
 meson.build                   | 29 ++++++++++++++++++++++++-----
 meson_options.txt             |  2 +-
 scripts/meson-buildoptions.sh |  2 +-
 6 files changed, 42 insertions(+), 7 deletions(-)
 create mode 100644 configs/meson/emscripten.txt

diff --git a/MAINTAINERS b/MAINTAINERS
index 750afd44c5..dd5a97ac36 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -634,6 +634,7 @@ S: Maintained
 F: include/system/os-wasm.h
 F: os-wasm.c
 F: util/coroutine-wasm.c
+F: configs/meson/emscripten.txt
 
 Alpha Machines
 --------------
diff --git a/configs/meson/emscripten.txt b/configs/meson/emscripten.txt
new file mode 100644
index 0000000000..4230e88005
--- /dev/null
+++ b/configs/meson/emscripten.txt
@@ -0,0 +1,8 @@
+[built-in options]
+c_args = ['-pthread']
+cpp_args = ['-pthread']
+objc_args = ['-pthread']
+# -sPROXY_TO_PTHREAD link time flag always requires -pthread even during
+# configuration so explicitly add the flag here.
+c_link_args = 
['-pthread','-sASYNCIFY=1','-sPROXY_TO_PTHREAD=1','-sFORCE_FILESYSTEM','-sALLOW_TABLE_GROWTH','-sTOTAL_MEMORY=2GB','-sWASM_BIGINT','-sEXPORT_ES6=1','-sASYNCIFY_IMPORTS=ffi_call_js','-sEXPORTED_RUNTIME_METHODS=addFunction,removeFunction,TTY,FS']
+cpp_link_args = 
['-pthread','-sASYNCIFY=1','-sPROXY_TO_PTHREAD=1','-sFORCE_FILESYSTEM','-sALLOW_TABLE_GROWTH','-sTOTAL_MEMORY=2GB','-sWASM_BIGINT','-sEXPORT_ES6=1','-sASYNCIFY_IMPORTS=ffi_call_js','-sEXPORTED_RUNTIME_METHODS=addFunction,removeFunction,TTY,FS']
diff --git a/configure b/configure
index 000309cf61..de12241c62 100755
--- a/configure
+++ b/configure
@@ -360,6 +360,10 @@ elif check_define __NetBSD__; then
   host_os=netbsd
 elif check_define __APPLE__; then
   host_os=darwin
+elif check_define EMSCRIPTEN ; then
+  host_os=emscripten
+  cpu=wasm32
+  cross_compile="yes"
 else
   # This is a fatal error, but don't report it yet, because we
   # might be going to just print the --help text, or it might
@@ -526,6 +530,9 @@ case "$cpu" in
     linux_arch=x86
     CPU_CFLAGS="-m64"
     ;;
+  wasm32)
+    CPU_CFLAGS="-m32"
+    ;;
 esac
 
 if test -n "$host_arch" && {
diff --git a/meson.build b/meson.build
index bcb9d39a38..fc38b02cee 100644
--- a/meson.build
+++ b/meson.build
@@ -50,9 +50,9 @@ genh = []
 qapi_trace_events = []
 
 bsd_oses = ['gnu/kfreebsd', 'freebsd', 'netbsd', 'openbsd', 'dragonfly', 
'darwin']
-supported_oses = ['windows', 'freebsd', 'netbsd', 'openbsd', 'darwin', 
'sunos', 'linux']
+supported_oses = ['windows', 'freebsd', 'netbsd', 'openbsd', 'darwin', 
'sunos', 'linux', 'emscripten']
 supported_cpus = ['ppc', 'ppc64', 's390x', 'riscv32', 'riscv64', 'x86', 
'x86_64',
-  'arm', 'aarch64', 'loongarch64', 'mips', 'mips64', 'sparc64']
+  'arm', 'aarch64', 'loongarch64', 'mips', 'mips64', 'sparc64', 'wasm32']
 
 cpu = host_machine.cpu_family()
 
@@ -353,6 +353,8 @@ foreach lang : all_languages
       # endif
       #endif''')
     # ok
+  elif compiler.get_id() == 'emscripten'
+    # ok
   else
     error('You either need GCC v7.4 or Clang v10.0 (or XCode Clang v15.0) to 
compile QEMU')
   endif
@@ -470,7 +472,10 @@ endif
 # instead, we can't add -no-pie because it overrides -shared: the linker then
 # tries to build an executable instead of a shared library and fails.  So
 # don't add -no-pie anywhere and cross fingers. :(
-if not get_option('b_pie')
+#
+# Emscripten doesn't support -no-pie but meson can't catch the compiler
+# warning. So explicitly omit the flag for Emscripten.
+if not get_option('b_pie') and host_os != 'emscripten'
   qemu_common_flags += cc.get_supported_arguments('-fno-pie', '-no-pie')
 endif
 
@@ -514,6 +519,8 @@ ucontext_probe = '''
 supported_backends = []
 if host_os == 'windows'
   supported_backends += ['windows']
+elif host_os == 'emscripten'
+  supported_backends += ['wasm']
 else
   if host_os != 'darwin' and cc.links(ucontext_probe)
     supported_backends += ['ucontext']
@@ -902,6 +909,10 @@ if get_option('tcg').allowed()
     if not get_option('tcg_interpreter')
       error('Unsupported CPU @0@, try --enable-tcg-interpreter'.format(cpu))
     endif
+  elif host_arch == 'wasm32'
+    if not get_option('tcg_interpreter')
+      error('WebAssembly host requires --enable-tcg-interpreter')
+    endif
   elif get_option('tcg_interpreter')
     warning('Use of the TCG interpreter is not recommended on this host')
     warning('architecture. There is a native TCG execution backend available')
@@ -2962,7 +2973,9 @@ config_host_data.set('CONFIG_ATOMIC64', cc.links('''
     return 0;
   }''', args: qemu_isa_flags))
 
-has_int128_type = cc.compiles('''
+# has_int128_type is set to false on Emscripten to avoid errors by libffi
+# during runtime.
+has_int128_type = host_os != 'emscripten' and cc.compiles('''
   __int128_t a;
   __uint128_t b;
   int main(void) { b = a; }''')
@@ -3777,6 +3790,8 @@ if have_block
   # os-win32.c does not
   if host_os == 'windows'
     system_ss.add(files('os-win32.c'))
+  elif host_os == 'emscripten'
+    blockdev_ss.add(files('os-wasm.c'))
   else
     blockdev_ss.add(files('os-posix.c'))
   endif
@@ -4515,7 +4530,11 @@ subdir('scripts')
 subdir('tools')
 subdir('pc-bios')
 subdir('docs')
-subdir('tests')
+# Tests are disabled on emscripten because they rely on host features that 
aren't
+# supported by emscripten (e.g. fork and unix socket).
+if host_os != 'emscripten'
+  subdir('tests')
+endif
 if gtk.found()
   subdir('po')
 endif
diff --git a/meson_options.txt b/meson_options.txt
index 59d973bca0..45772484cc 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -34,7 +34,7 @@ option('fuzzing_engine', type : 'string', value : '',
 option('trace_file', type: 'string', value: 'trace',
        description: 'Trace file prefix for simple backend')
 option('coroutine_backend', type: 'combo',
-       choices: ['ucontext', 'sigaltstack', 'windows', 'auto'],
+       choices: ['ucontext', 'sigaltstack', 'windows', 'wasm', 'auto'],
        value: 'auto', description: 'coroutine backend to use')
 
 # Everything else can be set via --enable/--disable-* option
diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index 3e8e00852b..0568385f00 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -80,7 +80,7 @@ meson_options_help() {
   printf "%s\n" '  --tls-priority=VALUE     Default TLS protocol/cipher 
priority string'
   printf "%s\n" '                           [NORMAL]'
   printf "%s\n" '  --with-coroutine=CHOICE  coroutine backend to use (choices:'
-  printf "%s\n" '                           auto/sigaltstack/ucontext/windows)'
+  printf "%s\n" '                           
auto/sigaltstack/ucontext/windows/wasm)'
   printf "%s\n" '  --with-pkgversion=VALUE  use specified string as 
sub-version of the'
   printf "%s\n" '                           package'
   printf "%s\n" '  --with-suffix=VALUE      Suffix for QEMU 
data/modules/config directories'
-- 
2.43.0


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