Subject: [PATCH] n_tty: use kmalloc() instead of vmalloc() to avoid crash on armada-xp

From: [email-masked] (Stas Sergeev)
Date: Tue, 10 Mar 2015 19:54:22 +0300

Hello, the patch below is needed for a successful boot on armada-xp.

-=-=-=-=-=-=-=-=-=# Don't remove this line #=-=-=-=-=-=-=-=-=-
This fixes the following crash at boot:

 Unhandled fault: external abort on non-linefetch (0x808) at 0xf00ca018
 Internal error: : 808 [#1] SMP ARM

 CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.0.0-rc1 #3
 Hardware name: Marvell Armada 370/XP (Device Tree)
 task: ed41e800 ti: ed43e000 task.ti: ed43e000
 PC is at _set_bit+0x28/0x50
 LR is at n_tty_set_termios+0x328/0x358
 pc : [<c01bc858>]    lr : [<c0207314>]    psr: 40000113
 sp : ed43fd00  ip : 00000000  fp : 00000000
 r10: 00000002  r9 : 00000000  r8 : ec930200
 r7 : 00000000  r6 : f00ca018  r5 : f00ca000  r4 : ed69cc00
 r3 : 00002000  r2 : 00002000  r1 : f00ca018  r0 : 00000000
 Flags: nZcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
 Control: 10c5387d  Table: 0000406a  DAC: 00000015
 Process swapper/0 (pid: 1, stack limit = 0xed43e220)

The offending instruction in _set_bit() is "strex r0, r2, [r1]"
For some reason the exclusive access instructions do not like the
vmalloc() space... While there may be another fix to make them
fine about vmalloc() space, it still looks like a good idea to
use kmalloc() for allocating a small (sub-page) struct.

Signed-off-by: Stas Sergeev <[email-masked]>
---
 drivers/tty/n_tty.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index cf6e0f2..e03622e 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -50,7 +50,6 @@
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/ratelimit.h>
-#include <linux/vmalloc.h>

 /* number of characters left in xmit buffer before select has we have
room */
@@ -1892,7 +1891,7 @@ static void n_tty_close(struct tty_struct *tty)
     if (tty->link)
         n_tty_packet_mode_flush(tty);
 
-    vfree(ldata);
+    kfree(ldata);
     tty->disc_data = NULL;
 }
 
@@ -1911,7 +1910,7 @@ static int n_tty_open(struct tty_struct *tty)
     struct n_tty_data *ldata;
 
     /* Currently a malloc failure here can panic */
-    ldata = vmalloc(sizeof(*ldata));
+    ldata = kmalloc(sizeof(*ldata), GFP_KERNEL);
     if (!ldata)
         goto err;
 
-- 
1.7.9.5