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2023-12-09 b22da3d8526a935aa31e086e63f60ff3246cb61c 
 kernel/drivers/tty/n_tty.c
....@@ -50,8 +50,10 @@
5050 #include <linux/ratelimit.h>
5151 #include <linux/vmalloc.h>
5252 
53
-
54
-/* number of characters left in xmit buffer before select has we have room */
53
+/*
54
+ * Until this number of characters is queued in the xmit buffer, select will
55
+ * return "we have room for writes".
56
+ */
5557 #define WAKEUP_CHARS 256
5658 
5759 /*
....@@ -82,7 +84,7 @@
8284 #ifdef N_TTY_TRACE
8385 # define n_tty_trace(f, args...)	trace_printk(f, ##args)
8486 #else
85
-# define n_tty_trace(f, args...)
87
+# define n_tty_trace(f, args...)	no_printk(f, ##args)
8688 #endif
8789 
8890 struct n_tty_data {
....@@ -162,29 +164,24 @@
162164 		memset(buffer, 0x00, size);
163165 }
164166 
165
-static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
166
-			    size_t tail, size_t n)
167
+static void tty_copy(struct tty_struct *tty, void *to, size_t tail, size_t n)
167168 {
168169 	struct n_tty_data *ldata = tty->disc_data;
169170 	size_t size = N_TTY_BUF_SIZE - tail;
170171 	void *from = read_buf_addr(ldata, tail);
171
-	int uncopied;
172172 
173173 	if (n > size) {
174174 		tty_audit_add_data(tty, from, size);
175
-		uncopied = copy_to_user(to, from, size);
176
-		zero_buffer(tty, from, size - uncopied);
177
-		if (uncopied)
178
-			return uncopied;
175
+		memcpy(to, from, size);
176
+		zero_buffer(tty, from, size);
179177 		to += size;
180178 		n -= size;
181179 		from = ldata->read_buf;
182180 	}
183181 
184182 	tty_audit_add_data(tty, from, n);
185
-	uncopied = copy_to_user(to, from, n);
186
-	zero_buffer(tty, from, n - uncopied);
187
-	return uncopied;
183
+	memcpy(to, from, n);
184
+	zero_buffer(tty, from, n);
188185 }
189186 
190187 /**
....@@ -320,7 +317,7 @@
320317 
321318 /**
322319  *	reset_buffer_flags	-	reset buffer state
323
- *	@tty: terminal to reset
320
+ *	@ldata: line disc data to reset
324321  *
325322  *	Reset the read buffer counters and clear the flags.
326323  *	Called from n_tty_open() and n_tty_flush_buffer().
....@@ -548,9 +545,9 @@
548545 	mutex_lock(&ldata->output_lock);
549546 
550547 	space = tty_write_room(tty);
551
-	if (!space) {
548
+	if (space <= 0) {
552549 		mutex_unlock(&ldata->output_lock);
553
-		return 0;
550
+		return space;
554551 	}
555552 	if (nr > space)
556553 		nr = space;
....@@ -652,9 +649,9 @@
652649 			op = echo_buf(ldata, tail + 1);
653650 
654651 			switch (op) {
652
+			case ECHO_OP_ERASE_TAB: {
655653 				unsigned int num_chars, num_bs;
656654 
657
-			case ECHO_OP_ERASE_TAB:
658655 				if (MASK(ldata->echo_commit) == MASK(tail + 2))
659656 					goto not_yet_stored;
660657 				num_chars = echo_buf(ldata, tail + 2);
....@@ -685,7 +682,7 @@
685682 				}
686683 				tail += 3;
687684 				break;
688
-
685
+			}
689686 			case ECHO_OP_SET_CANON_COL:
690687 				ldata->canon_column = ldata->column;
691688 				tail += 2;
....@@ -904,7 +901,7 @@
904901 /**
905902  *	echo_char_raw	-	echo a character raw
906903  *	@c: unicode byte to echo
907
- *	@tty: terminal device
904
+ *	@ldata: line disc data
908905  *
909906  *	Echo user input back onto the screen. This must be called only when
910907  *	L_ECHO(tty) is true. Called from the driver receive_buf path.
....@@ -1940,42 +1937,38 @@
19401937 /**
19411938  *	copy_from_read_buf	-	copy read data directly
19421939  *	@tty: terminal device
1943
- *	@b: user data
1940
+ *	@kbp: data
19441941  *	@nr: size of data
19451942  *
19461943  *	Helper function to speed up n_tty_read.  It is only called when
1947
- *	ICANON is off; it copies characters straight from the tty queue to
1948
- *	user space directly.  It can be profitably called twice; once to
1949
- *	drain the space from the tail pointer to the (physical) end of the
1950
- *	buffer, and once to drain the space from the (physical) beginning of
1951
- *	the buffer to head pointer.
1944
+ *	ICANON is off; it copies characters straight from the tty queue.
19521945  *
19531946  *	Called under the ldata->atomic_read_lock sem
1947
+ *
1948
+ *	Returns true if it successfully copied data, but there is still
1949
+ *	more data to be had.
19541950  *
19551951  *	n_tty_read()/consumer path:
19561952  *		caller holds non-exclusive termios_rwsem
19571953  *		read_tail published
19581954  */
19591955 
1960
-static int copy_from_read_buf(struct tty_struct *tty,
1961
-				      unsigned char __user **b,
1956
+static bool copy_from_read_buf(struct tty_struct *tty,
1957
+				      unsigned char **kbp,
19621958 				      size_t *nr)
19631959 
19641960 {
19651961 	struct n_tty_data *ldata = tty->disc_data;
1966
-	int retval;
19671962 	size_t n;
19681963 	bool is_eof;
19691964 	size_t head = smp_load_acquire(&ldata->commit_head);
19701965 	size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
19711966 
1972
-	retval = 0;
19731967 	n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
19741968 	n = min(*nr, n);
19751969 	if (n) {
19761970 		unsigned char *from = read_buf_addr(ldata, tail);
1977
-		retval = copy_to_user(*b, from, n);
1978
-		n -= retval;
1971
+		memcpy(*kbp, from, n);
19791972 		is_eof = n == 1 && *from == EOF_CHAR(tty);
19801973 		tty_audit_add_data(tty, from, n);
19811974 		zero_buffer(tty, from, n);
....@@ -1983,22 +1976,25 @@
19831976 		/* Turn single EOF into zero-length read */
19841977 		if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
19851978 		    (head == ldata->read_tail))
1986
-			n = 0;
1987
-		*b += n;
1979
+			return false;
1980
+		*kbp += n;
19881981 		*nr -= n;
1982
+
1983
+		/* If we have more to copy, let the caller know */
1984
+		return head != ldata->read_tail;
19891985 	}
1990
-	return retval;
1986
+	return false;
19911987 }
19921988 
19931989 /**
19941990  *	canon_copy_from_read_buf	-	copy read data in canonical mode
19951991  *	@tty: terminal device
1996
- *	@b: user data
1992
+ *	@kbp: data
19971993  *	@nr: size of data
19981994  *
19991995  *	Helper function for n_tty_read.  It is only called when ICANON is on;
20001996  *	it copies one line of input up to and including the line-delimiting
2001
- *	character into the user-space buffer.
1997
+ *	character into the result buffer.
20021998  *
20031999  *	NB: When termios is changed from non-canonical to canonical mode and
20042000  *	the read buffer contains data, n_tty_set_termios() simulates an EOF
....@@ -2013,21 +2009,22 @@
20132009  *		read_tail published
20142010  */
20152011 
2016
-static int canon_copy_from_read_buf(struct tty_struct *tty,
2017
-				    unsigned char __user **b,
2018
-				    size_t *nr)
2012
+static bool canon_copy_from_read_buf(struct tty_struct *tty,
2013
+				     unsigned char **kbp,
2014
+				     size_t *nr)
20192015 {
20202016 	struct n_tty_data *ldata = tty->disc_data;
20212017 	size_t n, size, more, c;
20222018 	size_t eol;
2023
-	size_t tail;
2024
-	int ret, found = 0;
2019
+	size_t tail, canon_head;
2020
+	int found = 0;
20252021 
20262022 	/* N.B. avoid overrun if nr == 0 */
20272023 	if (!*nr)
2028
-		return 0;
2024
+		return false;
20292025 
2030
-	n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2026
+	canon_head = smp_load_acquire(&ldata->canon_head);
2027
+	n = min(*nr, canon_head - ldata->read_tail);
20312028 
20322029 	tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
20332030 	size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
....@@ -2049,18 +2046,14 @@
20492046 		n += N_TTY_BUF_SIZE;
20502047 	c = n + found;
20512048 
2052
-	if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
2053
-		c = min(*nr, c);
2049
+	if (!found || read_buf(ldata, eol) != __DISABLED_CHAR)
20542050 		n = c;
2055
-	}
20562051 
20572052 	n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
20582053 		    __func__, eol, found, n, c, tail, more);
20592054 
2060
-	ret = tty_copy_to_user(tty, *b, tail, n);
2061
-	if (ret)
2062
-		return -EFAULT;
2063
-	*b += n;
2055
+	tty_copy(tty, *kbp, tail, n);
2056
+	*kbp += n;
20642057 	*nr -= n;
20652058 
20662059 	if (found)
....@@ -2073,12 +2066,41 @@
20732066 		else
20742067 			ldata->push = 0;
20752068 		tty_audit_push();
2069
+		return false;
20762070 	}
2077
-	return 0;
2071
+
2072
+	/* No EOL found - do a continuation retry if there is more data */
2073
+	return ldata->read_tail != canon_head;
20782074 }
20792075 
2080
-extern ssize_t redirected_tty_write(struct file *, const char __user *,
2081
-							size_t, loff_t *);
2076
+/*
2077
+ * If we finished a read at the exact location of an
2078
+ * EOF (special EOL character that's a __DISABLED_CHAR)
2079
+ * in the stream, silently eat the EOF.
2080
+ */
2081
+static void canon_skip_eof(struct tty_struct *tty)
2082
+{
2083
+	struct n_tty_data *ldata = tty->disc_data;
2084
+	size_t tail, canon_head;
2085
+
2086
+	canon_head = smp_load_acquire(&ldata->canon_head);
2087
+	tail = ldata->read_tail;
2088
+
2089
+	// No data?
2090
+	if (tail == canon_head)
2091
+		return;
2092
+
2093
+	// See if the tail position is EOF in the circular buffer
2094
+	tail &= (N_TTY_BUF_SIZE - 1);
2095
+	if (!test_bit(tail, ldata->read_flags))
2096
+		return;
2097
+	if (read_buf(ldata, tail) != __DISABLED_CHAR)
2098
+		return;
2099
+
2100
+	// Clear the EOL bit, skip the EOF char.
2101
+	clear_bit(tail, ldata->read_flags);
2102
+	smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
2103
+}
20822104 
20832105 /**
20842106  *	job_control		-	check job control
....@@ -2101,7 +2123,7 @@
21012123 	/* NOTE: not yet done after every sleep pending a thorough
21022124 	   check of the logic of this change. -- jlc */
21032125 	/* don't stop on /dev/console */
2104
-	if (file->f_op->write == redirected_tty_write)
2126
+	if (file->f_op->write_iter == redirected_tty_write)
21052127 		return 0;
21062128 
21072129 	return __tty_check_change(tty, SIGTTIN);
....@@ -2128,10 +2150,11 @@
21282150  */
21292151 
21302152 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2131
-			 unsigned char __user *buf, size_t nr)
2153
+			  unsigned char *kbuf, size_t nr,
2154
+			  void **cookie, unsigned long offset)
21322155 {
21332156 	struct n_tty_data *ldata = tty->disc_data;
2134
-	unsigned char __user *b = buf;
2157
+	unsigned char *kb = kbuf;
21352158 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
21362159 	int c;
21372160 	int minimum, time;
....@@ -2139,6 +2162,37 @@
21392162 	long timeout;
21402163 	int packet;
21412164 	size_t tail;
2165
+
2166
+	/*
2167
+	 * Is this a continuation of a read started earler?
2168
+	 *
2169
+	 * If so, we still hold the atomic_read_lock and the
2170
+	 * termios_rwsem, and can just continue to copy data.
2171
+	 */
2172
+	if (*cookie) {
2173
+		if (ldata->icanon && !L_EXTPROC(tty)) {
2174
+			/*
2175
+			 * If we have filled the user buffer, see
2176
+			 * if we should skip an EOF character before
2177
+			 * releasing the lock and returning done.
2178
+			 */
2179
+			if (!nr)
2180
+				canon_skip_eof(tty);
2181
+			else if (canon_copy_from_read_buf(tty, &kb, &nr))
2182
+				return kb - kbuf;
2183
+		} else {
2184
+			if (copy_from_read_buf(tty, &kb, &nr))
2185
+				return kb - kbuf;
2186
+		}
2187
+
2188
+		/* No more data - release locks and stop retries */
2189
+		n_tty_kick_worker(tty);
2190
+		n_tty_check_unthrottle(tty);
2191
+		up_read(&tty->termios_rwsem);
2192
+		mutex_unlock(&ldata->atomic_read_lock);
2193
+		*cookie = NULL;
2194
+		return kb - kbuf;
2195
+	}
21422196 
21432197 	c = job_control(tty, file);
21442198 	if (c < 0)
....@@ -2177,17 +2231,13 @@
21772231 		/* First test for status change. */
21782232 		if (packet && tty->link->ctrl_status) {
21792233 			unsigned char cs;
2180
-			if (b != buf)
2234
+			if (kb != kbuf)
21812235 				break;
21822236 			spin_lock_irq(&tty->link->ctrl_lock);
21832237 			cs = tty->link->ctrl_status;
21842238 			tty->link->ctrl_status = 0;
21852239 			spin_unlock_irq(&tty->link->ctrl_lock);
2186
-			if (put_user(cs, b)) {
2187
-				retval = -EFAULT;
2188
-				break;
2189
-			}
2190
-			b++;
2240
+			*kb++ = cs;
21912241 			nr--;
21922242 			break;
21932243 		}
....@@ -2230,33 +2280,35 @@
22302280 		}
22312281 
22322282 		if (ldata->icanon && !L_EXTPROC(tty)) {
2233
-			retval = canon_copy_from_read_buf(tty, &b, &nr);
2234
-			if (retval)
2235
-				break;
2283
+			if (canon_copy_from_read_buf(tty, &kb, &nr))
2284
+				goto more_to_be_read;
22362285 		} else {
2237
-			int uncopied;
2238
-
22392286 			/* Deal with packet mode. */
2240
-			if (packet && b == buf) {
2241
-				if (put_user(TIOCPKT_DATA, b)) {
2242
-					retval = -EFAULT;
2243
-					break;
2244
-				}
2245
-				b++;
2287
+			if (packet && kb == kbuf) {
2288
+				*kb++ = TIOCPKT_DATA;
22462289 				nr--;
22472290 			}
22482291 
2249
-			uncopied = copy_from_read_buf(tty, &b, &nr);
2250
-			uncopied += copy_from_read_buf(tty, &b, &nr);
2251
-			if (uncopied) {
2252
-				retval = -EFAULT;
2253
-				break;
2292
+			/*
2293
+			 * Copy data, and if there is more to be had
2294
+			 * and we have nothing more to wait for, then
2295
+			 * let's mark us for retries.
2296
+			 *
2297
+			 * NOTE! We return here with both the termios_sem
2298
+			 * and atomic_read_lock still held, the retries
2299
+			 * will release them when done.
2300
+			 */
2301
+			if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2302
+more_to_be_read:
2303
+				remove_wait_queue(&tty->read_wait, &wait);
2304
+				*cookie = cookie;
2305
+				return kb - kbuf;
22542306 			}
22552307 		}
22562308 
22572309 		n_tty_check_unthrottle(tty);
22582310 
2259
-		if (b - buf >= minimum)
2311
+		if (kb - kbuf >= minimum)
22602312 			break;
22612313 		if (time)
22622314 			timeout = time;
....@@ -2268,8 +2320,8 @@
22682320 	remove_wait_queue(&tty->read_wait, &wait);
22692321 	mutex_unlock(&ldata->atomic_read_lock);
22702322 
2271
-	if (b - buf)
2272
-		retval = b - buf;
2323
+	if (kb - kbuf)
2324
+		retval = kb - kbuf;
22732325 
22742326 	return retval;
22752327 }
....@@ -2305,7 +2357,7 @@
23052357 	ssize_t retval = 0;
23062358 
23072359 	/* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2308
-	if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2360
+	if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
23092361 		retval = tty_check_change(tty);
23102362 		if (retval)
23112363 			return retval;