linux-kernel - [PATCH 026/173] parisc : Remove broken line wrapping handling pdc_iodc

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Date:	Mon, 25 Apr 2011 22:02:58 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.org
Cc:	Guy Martin <gmsoft@...icoman.be>,
	James Bottomley <James.Bottomley@...e.de>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [PATCH 026/173] parisc : Remove broken line wrapping handling pdc_iodc_print()

2.6.27.59-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Guy Martin <gmsoft@...icoman.be>

commit fbea668498e93bb38ac9226c7af9120a25957375 upstream.

Remove the broken line wrapping handling in pdc_iodc_print().
It is broken in 3 ways :
  - It doesn't keep track of the current screen position, it just
    assumes that the new buffer will be printed at the begining of the
    screen.
  - It doesn't take in account that non printable characters won't
    increase the current position on the screen.
  - And last but not least, it triggers a kernel panic if a backspace
    is the first char in the provided buffer :

 Backtrace:
  [<0000000040128ec4>] pdc_console_write+0x44/0x78
  [<0000000040128f18>] pdc_console_tty_write+0x20/0x38
  [<000000004032f1ac>] n_tty_write+0x2a4/0x550
  [<000000004032b158>] tty_write+0x1e0/0x2d8
  [<00000000401bb420>] vfs_write+0xb8/0x188
  [<00000000401bb630>] sys_write+0x68/0xb8
  [<0000000040104eb8>] syscall_exit+0x0/0x14

Most terminals handle the line wrapping just fine. I've confirmed that
it works correctly on a C8000 with both vga and serial output.

Signed-off-by: Guy Martin <gmsoft@...icoman.be>
Signed-off-by: James Bottomley <James.Bottomley@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/parisc/kernel/firmware.c |   13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

--- a/arch/parisc/kernel/firmware.c
+++ b/arch/parisc/kernel/firmware.c
@@ -1126,15 +1126,13 @@ int pdc_iodc_print(const unsigned char *
 	unsigned int i;
 	unsigned long flags;
 
-	for (i = 0; i < count && i < 79;) {
+	for (i = 0; i < count;) {
 		switch(str[i]) {
 		case '\n':
 			iodc_dbuf[i+0] = '\r';
 			iodc_dbuf[i+1] = '\n';
 			i += 2;
 			goto print;
-		case '\b':	/* BS */
-			i--; /* overwrite last */
 		default:
 			iodc_dbuf[i] = str[i];
 			i++;
@@ -1142,15 +1140,6 @@ int pdc_iodc_print(const unsigned char *
 		}
 	}
 
-	/* if we're at the end of line, and not already inserting a newline,
-	 * insert one anyway. iodc console doesn't claim to support >79 char
-	 * lines. don't account for this in the return value.
-	 */
-	if (i == 79 && iodc_dbuf[i-1] != '\n') {
-		iodc_dbuf[i+0] = '\r';
-		iodc_dbuf[i+1] = '\n';
-	}
-
 print:
         spin_lock_irqsave(&pdc_lock, flags);
         real32_call(PAGE0->mem_cons.iodc_io,


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