Add getppid(2)

arch/amd64/syscall.c

@@ -82,6 +82,7 @@ void *syscall_table[256] = {
     [SYSCALL_NR_GETPGID] =          sys_getpgid,
     [SYSCALL_NR_SETPGID] =          sys_setpgid,
     [SYSCALL_NR_SIGALTSTACK] =      sys_sigaltstack,
+    [SYSCALL_NR_GETPPID] =          sys_getppid,
 
     // System
     [SYSCALL_NR_SYNC] =             sys_sync,

include/sys/sys_proc.h

@@ -10,6 +10,7 @@ void sys_sigreturn(void);
 int sys_clone(int (*entry) (void *), void *stack, int flags, void *arg);
 int sys_execve(const char *path, const char **argp, const char **envp);
 pid_t sys_getpid(void);
+pid_t sys_getppid(void);
 
 uid_t sys_getuid(void);
 gid_t sys_getgid(void);

include/user/syscall.h

@@ -51,6 +51,7 @@
 #define SYSCALL_NR_SETUID           105
 #define SYSCALL_NR_SETGID           106
 #define SYSCALL_NR_SETPGID          109
+#define SYSCALL_NR_GETPPID          110
 #define SYSCALL_NR_GETPGID          121
 #define SYSCALL_NR_SIGALTSTACK      131
 #define SYSCALL_NRX_WAITPID         247

sys/execve.c

@@ -218,6 +218,7 @@ int sys_execve(const char *path, const char **argv, const char **envp) {
         }
         proc->first_child = NULL;
         proc->next_child = NULL;
+        // TODO: automatically parent all subsequent processes to init (1)
         proc->parent = NULL;
         proc->sigq = 0;
 

sys/thread.c

@@ -875,6 +875,17 @@ pid_t sys_getpid(void) {
     return thread_self->proc->pid;
 }
 
+pid_t sys_getppid(void) {
+    _assert(thread_self && thread_self->proc);
+    struct process *proc = thread_self->proc;
+    if (!proc->parent) {
+        _assert(proc->pid == 1);
+        return 1;
+    } else {
+        return proc->parent->pid;
+    }
+}
+
 pid_t sys_getpgid(pid_t pid) {
     struct process *proc;