Re: droid 4 in v4.18-rc: grep -r adasfasd /sys/ oopses

Pavel Machek
2018-07-09T10:28:59Z

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Hi!

> > grep in /sys produces a nasty oops:
> >
> > I guess next step is trying to find out which file that is..
>
> Let me see...
>
> openat(6, "suspend",
> O_RDONLY|O_NOCTTY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW) = 4
> fstat64(4, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> read(4, 0x4d2000, 32768) = -1 EINVAL (Invalid argument)
> write(2, "grep: ", 6grep: ) = 6
> write(2, "/sys/kernel/debug/pm_debug/cefus"...,
> 47/sys/kernel/debug/pm_debug/cefuse_pwrdm/suspend) = 47
> write(2, ": Invalid argument", 18: Invalid argument) = 18
> write(2, "\n", 1
> ) = 1
> close(4) = 0
> close(6) = 0
> openat(5, "time", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW)
> = 4
> fstat64(4, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
> read(4, "cefuse_pwrdm (OFF),OFF:641441757"..., 32768) = 849
> read(4, "", 28672) = 0
> close(4) = 0
> openat(5, "count",
> O_RDONLY|O_NOCTTY|O_NONBLOCK|O_LARGEFILE|O_NOFOLLOW) = 4
> Connection to usb closed by remote host.
> Connection to usb closed.
> pavel@half:~$
>
> Ok, so it seems to be:
>
> user@devuan:~$ cat /sys/kernel/debug/pm_debug/count
> (oops).
>
> The file seems to be world-readable.
>
> user@devuan:~$ ls -al /sys/kernel/debug/pm_debug/count
> -r--r--r-- 1 root root 0 Jan 1 1970 /sys/kernel/debug/pm_debug/count
>
> But on PC, that file does not exist.

Ok, it is easier to reproduce like this:

sudo mount /dev/zero -t debugfs /sys/kernel/debug/
sudo cat /sys/kernel/debug/pm_debug/count

I tried adding debugging like this:

diff --git a/arch/arm/mach-omap2/pm-debug.c b/arch/arm/mach-omap2/pm-debug.c
index cba72de..ed98da8 100644
--- a/arch/arm/mach-omap2/pm-debug.c
+++ b/arch/arm/mach-omap2/pm-debug.c
@@ -78,14 +78,17 @@ static int clkdm_dbg_show_counter(struct clockdomain *clkdm, void *user)
{
struct seq_file *s = (struct seq_file *)user;

+ printk("cmp...\n");
if (strcmp(clkdm->name, "emu_clkdm") == 0 ||
strcmp(clkdm->name, "wkup_clkdm") == 0 ||
strncmp(clkdm->name, "dpll", 4) == 0)
return 0;

+ printk("printf...\n");
seq_printf(s, "%s->%s (%d)\n", clkdm->name, clkdm->pwrdm.ptr->name,
clkdm->usecount);

+ printk("done...\n");
return 0;
}

But it seems to crash outside show_counter function:

[ 100.345062] cpcap-usb-phy cpcap-usb-phy.0: connected to USB host
[ 102.049743] cmp...
[ 102.051910] printf...
[ 102.054351] done...
[ 102.056579] cmp...
[ 102.058685] printf...
...
[ 102.319427] printf...
[ 102.323211] done...
[ 102.326843] ------------[ cut here ]------------
[ 102.333190] WARNING: CPU: 0 PID: 2360 at
drivers/bus/omap_l3_noc.c:147 l3_int
errupt_handler+0x23c/0x380
[ 102.344696] 44000000.ocp:L3 Custom Error: MASTER MPU TARGET L4PER2
(Read): Da
ta Access in User mode during Functional access