Kernel: Added the ability to set the hostname via new syscall

Userland/hostname: Now takes parameter to set the hostname
LibC/unistd: Added sethostname function

Kernel/Process.cpp

@@ -712,6 +712,18 @@ int Process::sys$gethostname(char* buffer, ssize_t size)
     return 0;
 }
 
+int Process::sys$sethostname(const char* hostname, ssize_t length)
+{
+    REQUIRE_PROMISE(stdio);
+    if (length < 0)
+        return -EINVAL;
+    LOCKER(*s_hostname_lock, Lock::Mode::Shared);
+    if (length > 64)
+        return -ENAMETOOLONG;
+    *s_hostname = validate_and_copy_string_from_user(hostname, length);
+    return 0;
+}
+
 pid_t Process::sys$fork(RegisterState& regs)
 {
     REQUIRE_PROMISE(proc);

Kernel/Process.h

@@ -223,6 +223,7 @@ public:
     int sys$clock_settime(clockid_t, timespec*);
     int sys$clock_nanosleep(const Syscall::SC_clock_nanosleep_params*);
     int sys$gethostname(char*, ssize_t);
+    int sys$sethostname(const char*, ssize_t);
     int sys$uname(utsname*);
     int sys$readlink(const Syscall::SC_readlink_params*);
     int sys$ttyname_r(int fd, char*, ssize_t);

Kernel/Syscall.h

@@ -63,6 +63,7 @@ namespace Kernel {
     __ENUMERATE_SYSCALL(getcwd)               \
     __ENUMERATE_SYSCALL(gettimeofday)         \
     __ENUMERATE_SYSCALL(gethostname)          \
+    __ENUMERATE_SYSCALL(sethostname)          \
     __ENUMERATE_SYSCALL(chdir)                \
     __ENUMERATE_SYSCALL(uname)                \
     __ENUMERATE_SYSCALL(set_mmap_name)        \

Libraries/LibC/unistd.cpp

@@ -352,6 +352,12 @@ int gethostname(char* buffer, size_t size)
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
+int sethostname(const char* hostname, ssize_t size)
+{
+    int rc = syscall(SC_sethostname, hostname, size);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
 ssize_t readlink(const char* path, char* buffer, size_t size)
 {
     Syscall::SC_readlink_params params { { path, strlen(path) }, { buffer, size } };

Libraries/LibC/unistd.h

@@ -104,6 +104,7 @@ int stat(const char* path, struct stat* statbuf);
 int sleep(unsigned seconds);
 int usleep(useconds_t);
 int gethostname(char*, size_t);
+int sethostname(const char*, ssize_t);
 ssize_t readlink(const char* path, char* buffer, size_t);
 char* ttyname(int fd);
 int ttyname_r(int fd, char* buffer, size_t);

Shell/GlobalState.h

@@ -36,7 +36,7 @@ struct GlobalState {
     String username;
     String home;
     char ttyname[32];
-    char hostname[32];
+    char hostname[64];
     uid_t uid;
     struct termios termios;
     struct termios default_termios;

Userland/hostname.cpp

@@ -36,14 +36,24 @@ int main(int argc, char** argv)
         return 1;
     }
 
-    (void)argc;
-    (void)argv;
-    char buffer[HOST_NAME_MAX];
-    int rc = gethostname(buffer, sizeof(buffer));
-    if (rc < 0) {
-        printf("gethostname() error: %s\n", strerror(errno));
+    if (argc == 1) {
+      char buffer[HOST_NAME_MAX];
+      int rc = gethostname(buffer, sizeof(buffer));
+      if (rc < 0) {
+          printf("gethostname() error: %s\n", strerror(errno));
+          return 1;
+      }
+      printf("%s\n", buffer);
+    }
+    else if (argc == 2) {
+      if (strlen(argv[1]) >= HOST_NAME_MAX) {
+        printf("hostname must be less than %i characters\n", HOST_NAME_MAX);
         return 1;
+      }
+      else {
+        sethostname(argv[1], strlen(argv[1]));
+      }
     }
-    printf("%s\n", buffer);
+
     return 0;
 }