target: Provide errno definitions and fallback for unimplemented syscalls.

src/include/target.h

@@ -36,6 +36,28 @@ int jtag_scan(const uint8_t *lrlens);
 bool target_foreach(void (*cb)(int i, target *t, void *context), void *context);
 void target_list_free(void);
 
+enum target_errno {
+	TARGET_EPERM = 1,
+	TARGET_ENOENT = 2,
+	TARGET_EINTR = 4,
+	TARGET_EBADF = 9,
+	TARGET_EACCES = 13,
+	TARGET_EFAULT = 14,
+	TARGET_EBUSY = 16,
+	TARGET_EEXIST = 17,
+	TARGET_ENODEV = 19,
+	TARGET_ENOTDIR = 20,
+	TARGET_EISDIR = 21,
+	TARGET_EINVAL = 22,
+	TARGET_EMFILE = 24,
+	TARGET_ENFILE = 23,
+	TARGET_EFBIG = 27,
+	TARGET_ENOSPC = 28,
+	TARGET_ESPIPE = 29,
+	TARGET_EROFS = 30,
+	TARGET_ENAMETOOLONG = 36,
+};
+
 enum target_open_flags {
 	TARGET_O_RDONLY = 0,
 	TARGET_O_WRONLY = 1,
@@ -79,7 +101,7 @@ struct target_controller {
 	int (*isatty)(struct target_controller *, int fd);
 	int (*system)(struct target_controller *,
 	              target_addr cmd, unsigned cmd_len);
-	int errno_;
+	enum target_errno errno_;
 	bool interrupted;
 };
 

src/target/target.c

@@ -427,62 +427,100 @@ void tc_printf(target *t, const char *fmt, ...)
 int tc_open(target *t, target_addr path, unsigned plen,
             enum target_open_flags flags, mode_t mode)
 {
+	if (t->tc->open == NULL) {
+		t->tc->errno_ = TARGET_ENFILE;
+		return -1;
+	}
 	return t->tc->open(t->tc, path, plen, flags, mode);
 }
 
 int tc_close(target *t, int fd)
 {
+	if (t->tc->close == NULL) {
+		t->tc->errno_ = TARGET_EBADF;
+		return -1;
+	}
 	return t->tc->close(t->tc, fd);
 }
 
 int tc_read(target *t, int fd, target_addr buf, unsigned int count)
 {
+	if (t->tc->read == NULL)
+		return 0;
 	return t->tc->read(t->tc, fd, buf, count);
 }
 
 int tc_write(target *t, int fd, target_addr buf, unsigned int count)
 {
+	if (t->tc->write == NULL)
+		return 0;
 	return t->tc->write(t->tc, fd, buf, count);
 }
 
 long tc_lseek(target *t, int fd, long offset, enum target_seek_flag flag)
 {
+	if (t->tc->lseek == NULL)
+		return 0;
 	return t->tc->lseek(t->tc, fd, offset, flag);
 }
 
 int tc_rename(target *t, target_addr oldpath, unsigned oldlen,
                          target_addr newpath, unsigned newlen)
 {
+	if (t->tc->rename == NULL) {
+		t->tc->errno_ = TARGET_ENOENT;
+		return -1;
+	}
 	return t->tc->rename(t->tc, oldpath, oldlen, newpath, newlen);
 }
 
 int tc_unlink(target *t, target_addr path, unsigned plen)
 {
+	if (t->tc->unlink == NULL) {
+		t->tc->errno_ = TARGET_ENOENT;
+		return -1;
+	}
 	return t->tc->unlink(t->tc, path, plen);
 }
 
 int tc_stat(target *t, target_addr path, unsigned plen, target_addr buf)
 {
+	if (t->tc->stat == NULL) {
+		t->tc->errno_ = TARGET_ENOENT;
+		return -1;
+	}
 	return t->tc->stat(t->tc, path, plen, buf);
 }
 
 int tc_fstat(target *t, int fd, target_addr buf)
 {
+	if (t->tc->fstat == NULL) {
+		return 0;
+	}
 	return t->tc->fstat(t->tc, fd, buf);
 }
 
 int tc_gettimeofday(target *t, target_addr tv, target_addr tz)
 {
+	if (t->tc->gettimeofday == NULL) {
+		return -1;
+	}
 	return t->tc->gettimeofday(t->tc, tv, tz);
 }
 
 int tc_isatty(target *t, int fd)
 {
+	if (t->tc->isatty == NULL) {
+		return 1;
+	}
 	return t->tc->isatty(t->tc, fd);
 }
 
 int tc_system(target *t, target_addr cmd, unsigned cmdlen)
 {
+	if (t->tc->system == NULL) {
+		return -1;
+	}
 	return t->tc->system(t->tc, cmd, cmdlen);
 }