kboot: Implement getpid(2)

Add host_getpid() so we can know if we're running as init(8) or not.  If
we are, we may chose to do early system setup / sanity operations.

Sponsored by:		Netflix

stand/kboot/arch/amd64/syscall_nr.h

@@ -1,5 +1,6 @@
 #define SYS_close		  3
 #define SYS_getdents		 78
+#define	SYS_getpid		 39
 #define SYS_gettimeofday	 96
 #define SYS_kexec_load		246
 #define SYS_lseek		  8

stand/kboot/arch/powerpc64/syscall_nr.h

@@ -1,6 +1,7 @@
 #define SYS_close		  6
 #define SYS_fstat		108
 #define SYS_getdents		141
+#define	SYS_getpid		 20
 #define SYS_gettimeofday	 78
 #define SYS_kexec_load		268
 #define SYS_llseek		140

stand/kboot/host_syscall.h

@@ -92,6 +92,7 @@ struct host_timeval {
 int host_close(int fd);
 int host_fstat(int fd, struct host_kstat *sb);
 int host_getdents(int fd, void *dirp, int count);
+int host_getpid(void);
 int host_gettimeofday(struct host_timeval *a, void *b);
 int host_kexec_load(uint32_t start, int nsegs, uint32_t segs, uint32_t flags);
 ssize_t host_llseek(int fd, int32_t offset_high, int32_t offset_lo, uint64_t *result, int whence);

stand/kboot/host_syscalls.c

@@ -25,6 +25,12 @@ host_getdents(int fd, void *dirp, int count)
 	return host_syscall(SYS_getdents, fd, (uintptr_t)dirp, count);
 }
 
+int
+host_getpid(void)
+{
+	return host_syscall(SYS_getpid);
+}
+
 int
 host_gettimeofday(struct host_timeval *a, void *b)
 {