user/sven/linux.git/kernel/debug, branch v5.4.69

kgdb: Avoid suspicious RCU usage warning

2020-07-09T07:37:51Z

[ Upstream commit 440ab9e10e2e6e5fd677473ee6f9e3af0f6904d6 ] At times when I'm using kgdb I see a splat on my console about suspicious RCU usage. I managed to come up with a case that could reproduce this that looked like this: WARNING: suspicious RCU usage 5.7.0-rc4+ #609 Not tainted ----------------------------- kernel/pid.c:395 find_task_by_pid_ns() needs rcu_read_lock() protection! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by swapper/0/1: #0: ffffff81b6b8e988 (&dev->mutex){....}-{3:3}, at: __device_attach+0x40/0x13c #1: ffffffd01109e9e8 (dbg_master_lock){....}-{2:2}, at: kgdb_cpu_enter+0x20c/0x7ac #2: ffffffd01109ea90 (dbg_slave_lock){....}-{2:2}, at: kgdb_cpu_enter+0x3ec/0x7ac stack backtrace: CPU: 7 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc4+ #609 Hardware name: Google Cheza (rev3+) (DT) Call trace: dump_backtrace+0x0/0x1b8 show_stack+0x1c/0x24 dump_stack+0xd4/0x134 lockdep_rcu_suspicious+0xf0/0x100 find_task_by_pid_ns+0x5c/0x80 getthread+0x8c/0xb0 gdb_serial_stub+0x9d4/0xd04 kgdb_cpu_enter+0x284/0x7ac kgdb_handle_exception+0x174/0x20c kgdb_brk_fn+0x24/0x30 call_break_hook+0x6c/0x7c brk_handler+0x20/0x5c do_debug_exception+0x1c8/0x22c el1_sync_handler+0x3c/0xe4 el1_sync+0x7c/0x100 rpmh_rsc_probe+0x38/0x420 platform_drv_probe+0x94/0xb4 really_probe+0x134/0x300 driver_probe_device+0x68/0x100 __device_attach_driver+0x90/0xa8 bus_for_each_drv+0x84/0xcc __device_attach+0xb4/0x13c device_initial_probe+0x18/0x20 bus_probe_device+0x38/0x98 device_add+0x38c/0x420 If I understand properly we should just be able to blanket kgdb under one big RCU read lock and the problem should go away. We'll add it to the beast-of-a-function known as kgdb_cpu_enter(). With this I no longer get any splats and things seem to work fine. Signed-off-by: Douglas Anderson Link: https://lore.kernel.org/r/20200602154729.v2.1.I70e0d4fd46d5ed2aaf0c98a355e8e1b7a5bb7e4e@changeid Signed-off-by: Daniel Thompson Signed-off-by: Sasha Levin

kgdb: Prevent infinite recursive entries to the debugger

2020-06-22T07:30:54Z

[ 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

2020-06-22T07:30:54Z

[ 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

2019-09-26T00:51:40Z

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

2019-09-03T10:19:41Z

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

2019-09-03T10:19:31Z

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

2019-05-21T08:50:46Z

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

2019-05-14T12:44:24Z

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()

2019-05-12T08:50:44Z

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

2019-05-12T08:50:43Z

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