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

From: Peter Hurley
Date: Tue Mar 10 2015 - 13:35:15 EST


On 03/10/2015 12:54 PM, Stas Sergeev wrote:
> 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.

NAK.

struct n_tty_data is order 2, not sub-page.

The abort means something else is wrong; that's what needs
tracking down and fixing.

AFAIK this is not happening on any other ARM platform.

Regards,
Peter Hurley

> Signed-off-by: Stas Sergeev <stsp@xxxxxxxxxxxxxxxxxxxxx>
> ---
> 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;
>
>

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