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Subject[PATCH v2 1/2] serial: imx: fix detach/attach of serial console
Date
From: Stefan Agner <stefan@agner.ch>

If the device used as a serial console gets detached/attached at runtime,
register_console() will try to call imx_uart_setup_console(), but this
is not possible since it is marked as __init.

For instance

# cat /sys/devices/virtual/tty/console/active
tty1 ttymxc0
# echo -n N > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
# echo -n Y > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console

[ 73.166649] 8<--- cut here ---
[ 73.167005] Unable to handle kernel paging request at virtual address c154d928
[ 73.167601] pgd = 55433e84
[ 73.167875] [c154d928] *pgd=8141941e(bad)
[ 73.168304] Internal error: Oops: 8000000d [#1] SMP ARM
[ 73.168429] Modules linked in:
[ 73.168522] CPU: 0 PID: 536 Comm: sh Not tainted 5.15.0-rc6-00056-g3968ddcf05fb #3
[ 73.168675] Hardware name: Freescale i.MX6 Ultralite (Device Tree)
[ 73.168791] PC is at imx_uart_console_setup+0x0/0x238
[ 73.168927] LR is at try_enable_new_console+0x98/0x124
[ 73.169056] pc : [<c154d928>] lr : [<c0196f44>] psr: a0000013
[ 73.169178] sp : c2ef5e70 ip : 00000000 fp : 00000000
[ 73.169281] r10: 00000000 r9 : c02cf970 r8 : 00000000
[ 73.169389] r7 : 00000001 r6 : 00000001 r5 : c1760164 r4 : c1e0fb08
[ 73.169512] r3 : c154d928 r2 : 00000000 r1 : efffcbd1 r0 : c1760164
[ 73.169641] Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
[ 73.169782] Control: 10c5387d Table: 8345406a DAC: 00000051
[ 73.169895] Register r0 information: non-slab/vmalloc memory
[ 73.170032] Register r1 information: non-slab/vmalloc memory
[ 73.170158] Register r2 information: NULL pointer
[ 73.170273] Register r3 information: non-slab/vmalloc memory
[ 73.170397] Register r4 information: non-slab/vmalloc memory
[ 73.170521] Register r5 information: non-slab/vmalloc memory
[ 73.170647] Register r6 information: non-paged memory
[ 73.170771] Register r7 information: non-paged memory
[ 73.170892] Register r8 information: NULL pointer
[ 73.171009] Register r9 information: non-slab/vmalloc memory
[ 73.171142] Register r10 information: NULL pointer
[ 73.171259] Register r11 information: NULL pointer
[ 73.171375] Register r12 information: NULL pointer
[ 73.171494] Process sh (pid: 536, stack limit = 0xcd1ba82f)
[ 73.171621] Stack: (0xc2ef5e70 to 0xc2ef6000)
[ 73.171731] 5e60: ???????? ???????? ???????? ????????
[ 73.171899] 5e80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.172059] 5ea0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.172217] 5ec0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.172377] 5ee0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.172537] 5f00: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.172698] 5f20: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.172856] 5f40: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.173016] 5f60: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.173177] 5f80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.173336] 5fa0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.173496] 5fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.173654] 5fe0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.173826] [<c0196f44>] (try_enable_new_console) from [<c01984a8>] (register_console+0x10c/0x2ec)
[ 73.174053] [<c01984a8>] (register_console) from [<c06e2c90>] (console_store+0x14c/0x168)
[ 73.174262] [<c06e2c90>] (console_store) from [<c0383718>] (kernfs_fop_write_iter+0x110/0x1cc)
[ 73.174470] [<c0383718>] (kernfs_fop_write_iter) from [<c02cf5f4>] (vfs_write+0x31c/0x548)
[ 73.174679] [<c02cf5f4>] (vfs_write) from [<c02cf970>] (ksys_write+0x60/0xec)
[ 73.174863] [<c02cf970>] (ksys_write) from [<c0100080>] (ret_fast_syscall+0x0/0x1c)
[ 73.175052] Exception stack(0xc2ef5fa8 to 0xc2ef5ff0)
[ 73.175167] 5fa0: ???????? ???????? ???????? ???????? ???????? ????????
[ 73.175327] 5fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[ 73.175486] 5fe0: ???????? ???????? ???????? ????????
[ 73.175608] Code: 00000000 00000000 00000000 00000000 (00000000)
[ 73.175744] ---[ end trace 9b75121265109bf1 ]---

A similar issue could be triggered unbinding/binding the serial console
device [*].

Drop __init so that imx_uart_setup_console() can be safely called at
runtime.

[*] https://lore.kernel.org/all/20181114174940.7865-3-stefan@agner.ch/

Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
---
drivers/tty/serial/imx.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 8b121cd869e9..51a9f9423b1a 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2017,7 +2017,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
* If the port was already initialised (eg, by a boot loader),
* try to determine the current setup.
*/
-static void __init
+static void
imx_uart_console_get_options(struct imx_port *sport, int *baud,
int *parity, int *bits)
{
@@ -2076,7 +2076,7 @@ imx_uart_console_get_options(struct imx_port *sport, int *baud,
}
}

-static int __init
+static int
imx_uart_console_setup(struct console *co, char *options)
{
struct imx_port *sport;
--
2.25.1
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