Kernel+Userland: Replace the beep syscall with the new /dev/beep device

There's no need to have separate syscall for this kind of functionality,
as we can just have a device node in /dev, called "beep", that allows
writing tone generation packets to emulate the same behavior.

In addition to that, we remove LibC sysbeep function, as this function
was never being used by any C program nor it was standardized in any
way.
Instead, we move the userspace implementation to LibCore.

Userland/DevTools/UserspaceEmulator/Emulator.h

@@ -145,7 +145,6 @@ private:
     int virt$accept4(FlatPtr);
     u32 virt$allocate_tls(FlatPtr, size_t);
     int virt$anon_create(size_t, int);
-    int virt$beep();
     int virt$bind(int sockfd, FlatPtr address, socklen_t address_length);
     u32 virt$bindmount(u32 params_addr);
     int virt$chdir(FlatPtr, size_t);

Userland/DevTools/UserspaceEmulator/Emulator_syscalls.cpp

@@ -47,8 +47,6 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
         return virt$anon_create(arg1, arg2);
     case SC_annotate_mapping:
         return virt$annotate_mapping(arg1);
-    case SC_beep:
-        return virt$beep();
     case SC_bind:
         return virt$bind(arg1, arg2, arg3);
     case SC_bindmount:
@@ -1606,11 +1604,6 @@ u32 Emulator::virt$allocate_tls(FlatPtr initial_data, size_t size)
     return tls_base;
 }
 
-int Emulator::virt$beep()
-{
-    return syscall(SC_beep);
-}
-
 u32 Emulator::virt$sysconf(u32 name)
 {
     return syscall(SC_sysconf, name);

Userland/Libraries/LibC/unistd.cpp

@@ -925,12 +925,6 @@ int gettid()
     return cached_tid;
 }
 
-int sysbeep(int tone)
-{
-    int rc = syscall(SC_beep, tone);
-    __RETURN_WITH_ERRNO(rc, rc, -1);
-}
-
 // https://pubs.opengroup.org/onlinepubs/9699919799/functions/fsync.html
 int fsync(int fd)
 {

Userland/Libraries/LibC/unistd.h

@@ -36,7 +36,6 @@ int get_process_name(char* buffer, int buffer_size);
 int set_process_name(char const* name, size_t name_length);
 void dump_backtrace(void);
 int fsync(int fd);
-int sysbeep(int tone);
 int gettid(void);
 int getpagesize(void);
 pid_t fork(void);

Userland/Libraries/LibCore/System.cpp

@@ -9,10 +9,12 @@
 
 #include <AK/DeprecatedString.h>
 #include <AK/FixedArray.h>
+#include <AK/ScopeGuard.h>
 #include <AK/ScopedValueRollback.h>
 #include <AK/StdLibExtras.h>
 #include <AK/String.h>
 #include <AK/Vector.h>
+#include <Kernel/API/BeepInstruction.h>
 #include <LibCore/SessionManagement.h>
 #include <LibCore/System.h>
 #include <limits.h>
@@ -147,11 +149,13 @@ namespace Core::System {
 
 #ifdef AK_OS_SERENITY
 
-ErrorOr<void> beep(Optional<size_t> tone)
+ErrorOr<void> beep(u16 tone)
 {
-    auto rc = ::sysbeep(tone.value_or(440));
-    if (rc < 0)
-        return Error::from_syscall("beep"sv, -errno);
+    static Optional<int> beep_fd;
+    if (!beep_fd.has_value())
+        beep_fd = TRY(Core::System::open("/dev/beep"sv, O_RDWR));
+    BeepInstruction instruction { tone };
+    TRY(Core::System::write(beep_fd.value(), Span<u8 const>(&instruction, sizeof(BeepInstruction))));
     return {};
 }
 

Userland/Libraries/LibCore/System.h

@@ -51,7 +51,7 @@
 namespace Core::System {
 
 #ifdef AK_OS_SERENITY
-ErrorOr<void> beep(Optional<size_t> tone);
+ErrorOr<void> beep(u16 tone = 440);
 ErrorOr<void> pledge(StringView promises, StringView execpromises = {});
 ErrorOr<void> unveil(StringView path, StringView permissions);
 ErrorOr<void> unveil_after_exec(StringView path, StringView permissions);

Userland/Libraries/LibVT/TerminalWidget.cpp

@@ -1069,7 +1069,7 @@ void TerminalWidget::beep()
         return;
     }
     if (m_bell_mode == BellMode::AudibleBeep) {
-        sysbeep(440);
+        [[maybe_unused]] auto ret_val = Core::System::beep();
         return;
     }
     m_visual_beep_timer->restart(200);

Userland/Services/DeviceMapper/DeviceEventLoop.cpp

@@ -194,6 +194,7 @@ struct PluggableOnceCharacterDeviceNodeMatch {
 };
 
 static constexpr PluggableOnceCharacterDeviceNodeMatch s_simple_matchers[] = {
+    { "/dev/beep"sv, 0666, 1, 10 },
     { "/dev/kcov"sv, 0666, 30, 0 },
 };
 

Userland/Utilities/beep.cpp

@@ -14,6 +14,6 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     Core::ArgsParser args_parser;
     args_parser.add_option(tone, "Beep tone", "beep-tone", 'f', "Beep tone (frequency in Hz)");
     args_parser.parse(arguments);
-    TRY(Core::System::beep(tone));
+    TRY(Core::System::beep(tone.value_or(440)));
     return 0;
 }