libc+kernel: Add alarm() and getpagesize()

kernel/CMakeLists.txt

@@ -44,6 +44,7 @@ set(SOURCES
     src/sys/signal.cpp
     src/sys/socket.cpp
     src/sys/poll.cpp
+    src/sys/alarm.cpp
     src/fs/VFS.cpp
     src/fs/Pipe.cpp
     src/fs/Mount.cpp

kernel/src/sys/alarm.cpp

@@ -0,0 +1,15 @@
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+
+Result<u64> sys_alarm(Registers*, SyscallArgs args)
+{
+    unsigned int seconds = (unsigned int)args[0];
+
+    auto* current = Scheduler::current();
+
+    u64 time_left = current->alarm_ticks_left;
+
+    current->alarm_ticks_left = seconds * 1000;
+
+    return time_left * 1000;
+}

kernel/src/thread/Scheduler.cpp

@@ -282,6 +282,8 @@ namespace Scheduler
             {
                 if (thread->sleep_ticks_left == 0 || --thread->sleep_ticks_left == 0) thread->wake_up();
             }
+
+            if (thread->alarm_ticks_left && --thread->alarm_ticks_left == 0) thread->send_signal(SIGALRM);
         }
 
         if (!g_current->ticks_left) switch_task(regs);

kernel/src/thread/Thread.h

@@ -87,6 +87,7 @@ struct Thread : public LinkedListNode<Thread>
 
     u64 ticks_left;
     u64 sleep_ticks_left;
+    u64 alarm_ticks_left { 0 };
 
     Stack stack;
     Stack kernel_stack;

libc/include/unistd.h

@@ -190,6 +190,12 @@ extern "C"
     /* Truncate a file to a specific length. */
     int ftruncate(int fd, size_t size);
 
+    /* Return the system page size. */
+    int getpagesize(void);
+
+    /* Schedule an alarm signal. */
+    unsigned int alarm(unsigned int seconds);
+
 #ifdef __cplusplus
 }
 #endif

libc/src/unistd.cpp

@@ -8,6 +8,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/ioctl.h>
+#include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/utsname.h>
@@ -510,4 +511,14 @@ extern "C"
         long rc = syscall(SYS_ftruncate, fd, size);
         __errno_return(rc, int);
     }
+
+    int getpagesize(void)
+    {
+        return PAGE_SIZE;
+    }
+
+    unsigned int alarm(unsigned int seconds)
+    {
+        return (unsigned int)syscall(SYS_alarm, seconds);
+    }
 }