linux-stable.git/kernel/debug, branch v5.4.49

kgdb: Prevent infinite recursive entries to the debugger

2020-06-22T07:30:54+00:00

[ Upstream commit 3ca676e4ca60d1834bb77535dafe24169cadacef ]

If we detect that we recursively entered the debugger we should hack
our I/O ops to NULL so that the panic() in the next line won't
actually cause another recursion into the debugger.  The first line of
kgdb_panic() will check this and return.

Signed-off-by: Douglas Anderson 
Reviewed-by: Daniel Thompson 
Link: https://lore.kernel.org/r/20200507130644.v4.6.I89de39f68736c9de610e6f241e68d8dbc44bc266@changeid
Signed-off-by: Daniel Thompson 
Signed-off-by: Sasha Levin

kgdb: Disable WARN_CONSOLE_UNLOCKED for all kgdb

2020-06-22T07:30:54+00:00

[ Upstream commit 202164fbfa2b2ffa3e66b504e0f126ba9a745006 ]

In commit 81eaadcae81b ("kgdboc: disable the console lock when in
kgdb") we avoided the WARN_CONSOLE_UNLOCKED() yell when we were in
kgdboc.  That still works fine, but it turns out that we get a similar
yell when using other I/O drivers.  One example is the "I/O driver"
for the kgdb test suite (kgdbts).  When I enabled that I again got the
same yells.

Even though "kgdbts" doesn't actually interact with the user over the
console, using it still causes kgdb to print to the consoles.  That
trips the same warning:
  con_is_visible+0x60/0x68
  con_scroll+0x110/0x1b8
  lf+0x4c/0xc8
  vt_console_print+0x1b8/0x348
  vkdb_printf+0x320/0x89c
  kdb_printf+0x68/0x90
  kdb_main_loop+0x190/0x860
  kdb_stub+0x2cc/0x3ec
  kgdb_cpu_enter+0x268/0x744
  kgdb_handle_exception+0x1a4/0x200
  kgdb_compiled_brk_fn+0x34/0x44
  brk_handler+0x7c/0xb8
  do_debug_exception+0x1b4/0x228

Let's increment/decrement the "ignore_console_lock_warning" variable
all the time when we enter the debugger.

This will allow us to later revert commit 81eaadcae81b ("kgdboc:
disable the console lock when in kgdb").

Signed-off-by: Douglas Anderson 
Reviewed-by: Greg Kroah-Hartman 
Reviewed-by: Daniel Thompson 
Link: https://lore.kernel.org/r/20200507130644.v4.1.Ied2b058357152ebcc8bf68edd6f20a11d98d7d4e@changeid
Signed-off-by: Daniel Thompson 
Signed-off-by: Sasha Levin

kgdb: don't use a notifier to enter kgdb at panic; call directly

2019-09-26T00:51:40+00:00

Right now kgdb/kdb hooks up to debug panics by registering for the panic
notifier.  This works OK except that it means that kgdb/kdb gets called
_after_ the CPUs in the system are taken offline.  That means that if
anything important was happening on those CPUs (like something that might
have contributed to the panic) you can't debug them.

Specifically I ran into a case where I got a panic because a task was
"blocked for more than 120 seconds" which was detected on CPU 2.  I nicely
got shown stack traces in the kernel log for all CPUs including CPU 0,
which was running 'PID: 111 Comm: kworker/0:1H' and was in the middle of
__mmc_switch().

I then ended up at the kdb prompt where switched over to kgdb to try to
look at local variables of the process on CPU 0.  I found that I couldn't.
Digging more, I found that I had no info on any tasks running on CPUs
other than CPU 2 and that asking kdb for help showed me "Error: no saved
data for this cpu".  This was because all the CPUs were offline.

Let's move the entry of kdb/kgdb to a direct call from panic() and stop
using the generic notifier.  Putting a direct call in allows us to order
things more properly and it also doesn't seem like we're breaking any
abstractions by calling into the debugger from the panic function.

Daniel said:

: This patch changes the way kdump and kgdb interact with each other.
: However it would seem rather odd to have both tools simultaneously armed
: and, even if they were, the user still has the option to use panic_timeout
: to force a kdump to happen.  Thus I think the change of order is
: acceptable.

Link: http://lkml.kernel.org/r/20190703170354.217312-1-dianders@chromium.org
Signed-off-by: Douglas Anderson 
Reviewed-by: Daniel Thompson 
Cc: Jason Wessel 
Cc: Kees Cook 
Cc: Borislav Petkov 
Cc: Thomas Gleixner 
Cc: Feng Tang 
Cc: YueHaibing 
Cc: Sergey Senozhatsky 
Cc: "Steven Rostedt (VMware)" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kgdb: fix comment regarding static function

2019-09-03T10:19:41+00:00

The comment that says that module_event() is not static is clearly
wrong.

Signed-off-by: Nadav Amit 
Signed-off-by: Daniel Thompson

kdb: Replace strncmp with str_has_prefix

2019-09-03T10:19:31+00:00

strncmp(str, const, len) is error-prone.
We had better use newly introduced
str_has_prefix() instead of it.

Signed-off-by: Chuhong Yuan 
Signed-off-by: Daniel Thompson

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