linux-toradex.git/kernel/debug, branch toradex_5.3.y

treewide: Add SPDX license identifier - Makefile/Kconfig

2019-05-21T08:50:46+00:00

Add SPDX license identifiers to all Make/Kconfig files which:

 - Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

kdb: Fix bound check compiler warning

2019-05-14T12:44:24+00:00

The strncpy() function may leave the destination string buffer
unterminated, better use strscpy() instead.

This fixes the following warning with gcc 8.2:

kernel/debug/kdb/kdb_io.c: In function 'kdb_getstr':
kernel/debug/kdb/kdb_io.c:449:3: warning: 'strncpy' specified bound 256 equals destination size [-Wstringop-truncation]
   strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Wenlin Kang 
Signed-off-by: Daniel Thompson

kdb: do a sanity check on the cpu in kdb_per_cpu()

2019-05-12T08:50:44+00:00

The "whichcpu" comes from argv[3].  The cpu_online() macro looks up the
cpu in a bitmap of online cpus, but if the value is too high then it
could read beyond the end of the bitmap and possibly Oops.

Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
Signed-off-by: Dan Carpenter 
Reviewed-by: Douglas Anderson 
Signed-off-by: Daniel Thompson

kdb: Get rid of broken attempt to print CCVERSION in kdb summary

2019-05-12T08:50:43+00:00

If you drop into kdb and type "summary", it prints out a line that
says this:

  ccversion  CCVERSION

...and I don't mean that it actually prints out the version of the C
compiler.  It literally prints out the string "CCVERSION".

The version of the C Compiler is already printed at boot up and it
doesn't seem useful to replicate this in kdb.  Let's just delete it.
We can also delete the bit of the Makefile that called the C compiler
in an attempt to pass this into kdb.  This will remove one extra call
to the C compiler at Makefile parse time and (very slightly) speed up
builds.

Signed-off-by: Douglas Anderson 
Reviewed-by: Masahiro Yamada 
Signed-off-by: Daniel Thompson

kdb: kdb_support: replace strcpy() by strscpy()

2019-05-02T12:42:01+00:00

The strcpy() function is being deprecated. Replace it by the safer
strscpy() and fix the following Coverity warning:

"You might overrun the 129-character fixed-size string ks_namebuf
by copying name without checking the length."

Addresses-Coverity-ID: 138995 ("Copy into fixed size buffer")
Signed-off-by: Gustavo A. R. Silva 
Signed-off-by: Daniel Thompson

gdbstub: Replace strcpy() by strscpy()

2019-05-02T12:40:27+00:00

The strcpy() function is being deprecated. Replace it by the safer
strscpy() and fix the following Coverity warning:

"You might overrun the 1024-character fixed-size string remcom_in_buffer
by copying cmd without checking the length."

Addresses-Coverity-ID: 138999 ("Copy into fixed size buffer")
Signed-off-by: Gustavo A. R. Silva 
Signed-off-by: Daniel Thompson

gdbstub: mark expected switch fall-throughs

2019-05-02T12:38:04+00:00

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

This patch fixes the following warnings:

kernel/debug/gdbstub.c: In function ‘gdb_serial_stub’:
kernel/debug/gdbstub.c:1031:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
    if (remcom_in_buffer[1] == '\0') {
       ^
kernel/debug/gdbstub.c:1036:3: note: here
   case 'C': /* Exception passing */
   ^~~~
kernel/debug/gdbstub.c:1040:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
    if (tmp == 0)
       ^
kernel/debug/gdbstub.c:1043:3: note: here
   case 'c': /* Continue packet */
   ^~~~
kernel/debug/gdbstub.c:1050:4: warning: this statement may fall through [-Wimplicit-fallthrough=]
    dbg_activate_sw_breakpoints();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/debug/gdbstub.c:1052:3: note: here
   default:
   ^~~~~~~

Warning level 3 was used: -Wimplicit-fallthrough=3

Notice that, in this particular case, the code comment is modified
in accordance with what GCC is expecting to find.

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.

Signed-off-by: Gustavo A. R. Silva 
Acked-by: Jason Wessel 
Signed-off-by: Daniel Thompson

kdb: use bool for binary state indicators

2018-12-30T08:31:52+00:00

defcmd_in_progress  is the state trace for command group processing
- within a command group or not -  usable  is an indicator if a command
set is valid (allocated/non-empty) - so use a bool for those binary
indication here.

Signed-off-by: Nicholas Mc Guire 
Reviewed-by: Daniel Thompson 
Signed-off-by: Daniel Thompson

kdb: Don't back trace on a cpu that didn't round up

2018-12-30T08:31:23+00:00

If you have a CPU that fails to round up and then run 'btc' you'll end
up crashing in kdb becaue we dereferenced NULL.  Let's add a check.
It's wise to also set the task to NULL when leaving the debugger so
that if we fail to round up on a later entry into the debugger we
won't backtrace a stale task.

Signed-off-by: Douglas Anderson 
Acked-by: Daniel Thompson 
Signed-off-by: Daniel Thompson

kgdb: Don't round up a CPU that failed rounding up before

2018-12-30T08:29:13+00:00

If we're using the default implementation of kgdb_roundup_cpus() that
uses smp_call_function_single_async() we can end up hanging
kgdb_roundup_cpus() if we try to round up a CPU that failed to round
up before.

Specifically smp_call_function_single_async() will try to wait on the
csd lock for the CPU that we're trying to round up.  If the previous
round up never finished then that lock could still be held and we'll
just sit there hanging.

There's not a lot of use trying to round up a CPU that failed to round
up before.  Let's keep a flag that indicates whether the CPU started
but didn't finish to round up before.  If we see that flag set then
we'll skip the next round up.

In general we have a few goals here:
- We never want to end up calling smp_call_function_single_async()
  when the csd is still locked.  This is accomplished because
  flush_smp_call_function_queue() unlocks the csd _before_ invoking
  the callback.  That means that when kgdb_nmicallback() runs we know
  for sure the the csd is no longer locked.  Thus when we set
  "rounding_up = false" we know for sure that the csd is unlocked.
- If there are no timeouts rounding up we should never skip a round
  up.

NOTE #1: In general trying to continue running after failing to round
up CPUs doesn't appear to be supported in the debugger.  When I
simulate this I find that kdb reports "Catastrophic error detected"
when I try to continue.  I can overrule and continue anyway, but it
should be noted that we may be entering the land of dragons here.
Possibly the "Catastrophic error detected" was added _because_ of the
future failure to round up, but even so this is an area of the code
that hasn't been strongly tested.

NOTE #2: I did a bit of testing before and after this change.  I
introduced a 10 second hang in the kernel while holding a spinlock
that I could invoke on a certain CPU with 'taskset -c 3 cat /sys/...".

Before this change if I did:
- Invoke hang
- Enter debugger
- g (which warns about Catastrophic error, g again to go anyway)
- g
- Enter debugger

...I'd hang the rest of the 10 seconds without getting a debugger
prompt.  After this change I end up in the debugger the 2nd time after
only 1 second with the standard warning about 'Timed out waiting for
secondary CPUs.'

I'll also note that once the CPU finished waiting I could actually
debug it (aka "btc" worked)

I won't promise that everything works perfectly if the errant CPU
comes back at just the wrong time (like as we're entering or exiting
the debugger) but it certainly seems like an improvement.

NOTE #3: setting 'kgdb_info[cpu].rounding_up = false' is in
kgdb_nmicallback() instead of kgdb_call_nmi_hook() because some
implementations override kgdb_call_nmi_hook().  It shouldn't hurt to
have it in kgdb_nmicallback() in any case.

NOTE #4: this logic is really only needed because there is no API call
like "smp_try_call_function_single_async()" or "smp_csd_is_locked()".
If such an API existed then we'd use it instead, but it seemed a bit
much to add an API like this just for kgdb.

Signed-off-by: Douglas Anderson 
Acked-by: Daniel Thompson 
Signed-off-by: Daniel Thompson