From c0a7f6776f0cf99eb8c7948770403ef5b90fb27e Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 11 Mar 2023 22:19:58 +0100
Subject: [PATCH] kernel+libc: Add getpid()

---
 apps/app.c                     | 2 +-
 initrd/etc/motd                | 2 +-
 kernel/CMakeLists.txt          | 1 +
 kernel/src/sys/id.cpp          | 7 +++++++
 libc/include/unistd.h          | 4 +++-
 libc/src/unistd.cpp            | 5 +++++
 libluna/include/luna/Syscall.h | 2 +-
 7 files changed, 19 insertions(+), 4 deletions(-)
 create mode 100644 kernel/src/sys/id.cpp

diff --git a/apps/app.c b/apps/app.c
index eeaaadfc..ea977091 100644
--- a/apps/app.c
+++ b/apps/app.c
@@ -12,7 +12,7 @@ void bye()
 int main()
 {
     atexit(bye);
-    printf("Welcome to %s from userspace!\n", "Luna");
+    printf("Welcome to %s from userspace (pid %d)!\n", "Luna", getpid());
 
     int fd = open("/etc/motd", 0);
     if (fd < 0)
diff --git a/initrd/etc/motd b/initrd/etc/motd
index f222d343..af5626b4 100644
--- a/initrd/etc/motd
+++ b/initrd/etc/motd
@@ -1 +1 @@
-G'day mate!
+Hello, world!
diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index 6c53ecb3..ffc1b5fe 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -28,6 +28,7 @@ set(SOURCES
     src/sys/usleep.cpp
     src/sys/open.cpp
     src/sys/file.cpp
+    src/sys/id.cpp
     src/fs/VFS.cpp
     src/fs/tmpfs/FileSystem.cpp
     src/InitRD.cpp
diff --git a/kernel/src/sys/id.cpp b/kernel/src/sys/id.cpp
new file mode 100644
index 00000000..43dccdca
--- /dev/null
+++ b/kernel/src/sys/id.cpp
@@ -0,0 +1,7 @@
+#include "sys/Syscall.h"
+#include "thread/Scheduler.h"
+
+Result<u64> sys_getpid(Registers*, SyscallArgs)
+{
+    return Scheduler::current()->id;
+}
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 6bef9cf3..c35d7030 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -15,7 +15,9 @@ extern "C"
 #endif
 
     pid_t fork();
-    pid_t getpid();
+
+    /* Returns the current process' process ID. */
+    pid_t getpid(void);
 
     int execv(const char*, char* const*);
     int execve(const char*, char* const*, char* const*);
diff --git a/libc/src/unistd.cpp b/libc/src/unistd.cpp
index 02374238..220d429b 100644
--- a/libc/src/unistd.cpp
+++ b/libc/src/unistd.cpp
@@ -8,6 +8,11 @@ extern "C" long arch_invoke_syscall(long, uintptr_t, uintptr_t, uintptr_t, uintp
 
 extern "C"
 {
+    pid_t getpid(void)
+    {
+        return (pid_t)syscall(SYS_getpid);
+    }
+
     long syscall(long num, ...)
     {
         va_list ap;
diff --git a/libluna/include/luna/Syscall.h b/libluna/include/luna/Syscall.h
index 1797b548..f6516ecc 100644
--- a/libluna/include/luna/Syscall.h
+++ b/libluna/include/luna/Syscall.h
@@ -2,7 +2,7 @@
 
 #define enumerate_syscalls(_e)                                                                                         \
     _e(exit) _e(console_write) _e(clock_gettime) _e(allocate_memory) _e(deallocate_memory) _e(usleep) _e(open)         \
-        _e(close) _e(read)
+        _e(close) _e(read) _e(getpid)
 
 enum Syscalls
 {