kernel, libc: Add an usleep() system call and use that to implement usleep() and sleep() in libc

kernel/CMakeLists.txt

@@ -22,6 +22,7 @@ set(SOURCES
     src/sys/console_write.cpp
     src/sys/clock_gettime.cpp
     src/sys/allocate_memory.cpp
+    src/sys/usleep.cpp
     src/InitRD.cpp
     src/ELF.cpp
 )

kernel/src/sys/usleep.cpp

@@ -0,0 +1,12 @@
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+#include <sys/types.h>
+
+Result<u64> sys_usleep(Registers*, SyscallArgs args)
+{
+    useconds_t us = (useconds_t)args[0];
+
+    kernel_sleep(us / 1000);
+
+    return 0;
+}

libc/CMakeLists.txt

@@ -1,4 +1,4 @@
-file(GLOB HEADERS include/*.h)
+file(GLOB_RECURSE HEADERS include/*.h)
 
 set(SOURCES
     ${HEADERS}

libc/include/sys/types.h

@@ -11,5 +11,6 @@
 typedef int pid_t;
 typedef __i64_t time_t;
 typedef __u16_t mode_t;
+typedef __u64_t useconds_t;
 
 #endif

libc/include/unistd.h

@@ -24,6 +24,12 @@ extern "C"
     /* Calls the operating system kernel for a specific service. */
     long syscall(long num, ...);
 
+    /* Sleeps for X microseconds. */
+    int usleep(useconds_t us);
+
+    /* Sleeps for X seconds. */
+    unsigned long sleep(unsigned long seconds);
+
 #ifdef __cplusplus
 }
 #endif

libc/src/unistd.cpp

@@ -1,5 +1,7 @@
+#include <bits/errno-return.h>
 #include <stdarg.h>
 #include <stdint.h>
+#include <sys/syscall.h>
 #include <unistd.h>
 
 extern "C" long arch_invoke_syscall(long, uintptr_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t);
@@ -23,4 +25,16 @@ extern "C"
 
         return rc;
     }
+
+    int usleep(useconds_t us)
+    {
+        long rc = syscall(SYS_usleep, us);
+        __errno_return(rc, int);
+    }
+
+    unsigned long sleep(unsigned long seconds)
+    {
+        syscall(SYS_usleep, seconds * 1000000);
+        return 0;
+    }
 }

luna/include/luna/Syscall.h

@@ -1,6 +1,7 @@
 #pragma once
 
-#define enumerate_syscalls(_e) _e(exit) _e(console_write) _e(clock_gettime) _e(allocate_memory) _e(deallocate_memory)
+#define enumerate_syscalls(_e)                                                                                         \
+    _e(exit) _e(console_write) _e(clock_gettime) _e(allocate_memory) _e(deallocate_memory) _e(usleep)
 
 enum Syscalls
 {