fs_shell: Use proper readv/writev functions on Haiku hosts.

Fixes #18269.

src/tools/fs_shell/uio.cpp

@@ -79,7 +79,11 @@ fssh_readv_pos(int fd, fssh_off_t pos, const struct fssh_iovec *vec, int count)
 	if (FSShell::restricted_file_restrict_io(fd, pos, length) < 0)
 		return -1;
 
+#if defined(__HAIKU__)
+	return readv_pos(fd, pos, systemVecs, count);
+#else
 	return _kern_readv(fd, pos, systemVecs, count);
+#endif
 }
 
 
@@ -114,5 +118,9 @@ fssh_writev_pos(int fd, fssh_off_t pos, const struct fssh_iovec *vec, int count)
 	if (FSShell::restricted_file_restrict_io(fd, pos, length) < 0)
 		return -1;
 
+#if defined(__HAIKU__)
+	return writev_pos(fd, pos, systemVecs, count);
+#else
 	return _kern_writev(fd, pos, systemVecs, count);
+#endif
 }

src/tools/fs_shell/unistd.cpp

@@ -390,7 +390,11 @@ fssh_read_pos(int fd, fssh_off_t pos, void *buffer, fssh_size_t count)
 {
 	if (FSShell::restricted_file_restrict_io(fd, pos, count) < 0)
 		return -1;
+#if defined(__HAIKU__)
+	return read_pos(fd, pos, buffer, count);
+#else
 	return _kern_read(fd, pos, buffer, count);
+#endif
 }
 
 
@@ -417,7 +421,11 @@ fssh_write_pos(int fd, fssh_off_t pos, const void *buffer, fssh_size_t count)
 {
 	if (FSShell::restricted_file_restrict_io(fd, pos, count) < 0)
 		return -1;
+#if defined(__HAIKU__)
+	return write_pos(fd, pos, buffer, count);
+#else
 	return _kern_write(fd, pos, buffer, count);
+#endif
 }