[PATCHv2 00/50] Add log level to show_stack()

Changes to v2:
- Removed excessive pr_cont("\n") (nits by Senozhatsky)
- Leave backtrace debugging messages with pr_debug()
  (noted by Russell King and Will Deacon)
- Correct microblaze_unwind_inner() declaration
  (Thanks to Michal Simek and kbuild test robot)
- Fix copy'n'paste typo in show_stack_loglvl() for sparc
  (kbuild robot)
- Fix backtrace output on xtensa
  (Thanks Max Filippov)
- Add loglevel to show_stack() on s390 (kbuild robot)
- Collected all Reviewed-by and Acked-by (thanks!)

Add log level argument to show_stack().
Done in three stages:
1. Introducing show_stack_loglvl() for every architecture
2. Migrating old users with an explicit log level
3. Renaming show_stack_loglvl() into show_stack()

Justification:
o It's a design mistake to move a business-logic decision
  into platform realization detail.
o I have currently two patches sets that would benefit from this work:
  Removing console_loglevel jumps in sysrq driver [1]
  Hung task warning before panic [2] - suggested by Tetsuo (but he
  probably didn't realise what it would involve).
o While doing (1), (2) the backtraces were adjusted to headers
  and other messages for each situation - so there won't be a situation
  when the backtrace is printed, but the headers are missing because
  they have lesser log level (or the reverse).

The least important for upstream, but maybe still worth to note that
every company I've worked in so far had an off-list patch to print
backtrace with the needed log level (but only for the architecture they
cared about).
If you have other ideas how you will benefit from show_stack() with
a log level - please, reply to this cover letter.

See also discussion on v1:
https://lore.kernel.org/linux-riscv/20191106083538.z5nlpuf64cigxigh@pathway.suse.cz/

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Slaby <redacted>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <redacted>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

Thanks,
Dmitry

[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
[2]: https://lkml.kernel.org/r/41fd7652-df1f-26f6-aba0-b87ebae07db6@i-love.sakura.ne.jp

Dmitry Safonov (50):
  kallsyms/printk: Add loglvl to print_ip_sym()
  alpha: Add show_stack_loglvl()
  arc: Add show_stack_loglvl()
  arm/asm: Add loglvl to c_backtrace()
  arm: Add loglvl to unwind_backtrace()
  arm: Add loglvl to dump_backtrace()
  arm: Wire up dump_backtrace_{entry,stm}
  arm: Add show_stack_loglvl()
  arm64: Add loglvl to dump_backtrace()
  arm64: Add show_stack_loglvl()
  c6x: Add show_stack_loglvl()
  csky: Add show_stack_loglvl()
  h8300: Add show_stack_loglvl()
  hexagon: Add show_stack_loglvl()
  ia64: Pass log level as arg into ia64_do_show_stack()
  ia64: Add show_stack_loglvl()
  m68k: Add show_stack_loglvl()
  microblaze: Add loglvl to microblaze_unwind_inner()
  microblaze: Add loglvl to microblaze_unwind()
  microblaze: Add show_stack_loglvl()
  mips: Add show_stack_loglvl()
  nds32: Add show_stack_loglvl()
  nios2: Add show_stack_loglvl()
  openrisc: Add show_stack_loglvl()
  parisc: Add show_stack_loglvl()
  powerpc: Add show_stack_loglvl()
  riscv: Add show_stack_loglvl()
  s390: Add show_stack_loglvl()
  sh: Add loglvl to dump_mem()
  sh: Remove needless printk()
  sh: Add loglvl to printk_address()
  sh: Add loglvl to show_trace()
  sh: Add show_stack_loglvl()
  sparc: Add show_stack_loglvl()
  um/sysrq: Remove needless variable sp
  um: Add show_stack_loglvl()
  unicore32: Remove unused pmode argument in c_backtrace()
  unicore32: Add loglvl to c_backtrace()
  unicore32: Add show_stack_loglvl()
  x86: Add missing const qualifiers for log_lvl
  x86: Add show_stack_loglvl()
  xtensa: Add loglvl to show_trace()
  xtensa: Add show_stack_loglvl()
  sysrq: Use show_stack_loglvl()
  x86/amd_gart: Print stacktrace for a leak with KERN_ERR
  power: Use show_stack_loglvl()
  kdb: Don't play with console_loglevel
  sched: Print stack trace with KERN_INFO
  kernel: Use show_stack_loglvl()
  kernel: Rename show_stack_loglvl() => show_stack()

 arch/alpha/kernel/traps.c            | 22 +++++++--------
 arch/arc/include/asm/bug.h           |  3 ++-
 arch/arc/kernel/stacktrace.c         | 17 +++++++-----
 arch/arc/kernel/troubleshoot.c       |  2 +-
 arch/arm/include/asm/bug.h           |  3 ++-
 arch/arm/include/asm/traps.h         |  3 ++-
 arch/arm/include/asm/unwind.h        |  3 ++-
 arch/arm/kernel/traps.c              | 40 ++++++++++++++++------------
 arch/arm/kernel/unwind.c             |  7 ++---
 arch/arm/lib/backtrace-clang.S       |  9 +++++--
 arch/arm/lib/backtrace.S             | 14 +++++++---
 arch/arm64/include/asm/stacktrace.h  |  3 ++-
 arch/arm64/kernel/process.c          |  2 +-
 arch/arm64/kernel/traps.c            | 19 ++++++-------
 arch/c6x/kernel/traps.c              | 18 +++++++------
 arch/csky/kernel/dumpstack.c         |  9 ++++---
 arch/csky/kernel/ptrace.c            |  4 +--
 arch/h8300/kernel/traps.c            | 12 ++++-----
 arch/hexagon/kernel/traps.c          | 25 ++++++++---------
 arch/ia64/include/asm/ptrace.h       |  1 -
 arch/ia64/kernel/mca.c               |  2 +-
 arch/ia64/kernel/process.c           | 17 ++++++------
 arch/m68k/kernel/traps.c             | 13 ++++-----
 arch/microblaze/include/asm/unwind.h |  3 ++-
 arch/microblaze/kernel/stacktrace.c  |  4 +--
 arch/microblaze/kernel/traps.c       | 12 ++++-----
 arch/microblaze/kernel/unwind.c      | 37 ++++++++++++++-----------
 arch/mips/kernel/traps.c             | 35 ++++++++++++------------
 arch/nds32/kernel/traps.c            | 15 ++++++-----
 arch/nios2/kernel/traps.c            | 17 ++++++------
 arch/openrisc/kernel/traps.c         | 12 +++++----
 arch/parisc/kernel/traps.c           | 24 ++++++++---------
 arch/powerpc/kernel/process.c        | 15 ++++++-----
 arch/powerpc/kernel/stacktrace.c     |  2 +-
 arch/riscv/kernel/stacktrace.c       |  9 ++++---
 arch/s390/kernel/dumpstack.c         | 11 ++++----
 arch/sh/include/asm/kdebug.h         |  6 +++--
 arch/sh/include/asm/processor_32.h   |  2 +-
 arch/sh/kernel/dumpstack.c           | 36 ++++++++++++-------------
 arch/sh/kernel/process_32.c          |  2 +-
 arch/sh/kernel/process_64.c          |  3 +--
 arch/sh/kernel/traps.c               |  4 +--
 arch/sh/mm/fault.c                   |  2 +-
 arch/sparc/kernel/process_32.c       | 10 +++----
 arch/sparc/kernel/process_64.c       |  2 +-
 arch/um/drivers/mconsole_kern.c      |  2 +-
 arch/um/kernel/sysrq.c               | 23 ++++++++--------
 arch/unicore32/kernel/setup.h        |  2 +-
 arch/unicore32/kernel/traps.c        | 34 +++++++++++------------
 arch/unicore32/lib/backtrace.S       | 24 +++++++++++------
 arch/x86/include/asm/stacktrace.h    |  2 +-
 arch/x86/kernel/amd_gart_64.c        |  2 +-
 arch/x86/kernel/dumpstack.c          |  9 ++++---
 arch/xtensa/kernel/traps.c           | 26 ++++++++++--------
 drivers/base/power/main.c            |  2 +-
 drivers/tty/sysrq.c                  |  2 +-
 include/linux/kallsyms.h             |  4 +--
 include/linux/sched/debug.h          |  3 ++-
 kernel/debug/kdb/kdb_bt.c            | 11 +++-----
 kernel/locking/lockdep.c             |  4 +--
 kernel/locking/rtmutex-debug.c       |  2 +-
 kernel/sched/core.c                  |  6 ++---
 kernel/trace/ftrace.c                |  8 +++---
 lib/dump_stack.c                     |  2 +-
 64 files changed, 368 insertions(+), 311 deletions(-)

-- 
2.23.0

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Introduce show_stack_loglvl(), that eventually will substitute
show_stack().

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Dmitry Safonov <redacted>
---
 arch/powerpc/kernel/process.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index fad50db9dcf2..c1ab7f613da4 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c

@@ -2034,7 +2034,8 @@ unsigned long get_wchan(struct task_struct *p)
 
 static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;
 
-void show_stack(struct task_struct *tsk, unsigned long *stack)
+void show_stack_loglvl(struct task_struct *tsk, unsigned long *stack,
+		       const char *loglvl)
 {
 	unsigned long sp, ip, lr, newsp;
 	int count = 0;

@@ -2059,7 +2060,7 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
 	}
 
 	lr = 0;
-	printk("Call Trace:\n");
+	printk("%sCall Trace:\n", loglvl);
 	do {
 		if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD))
 			break;

@@ -2068,7 +2069,8 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
 		newsp = stack[0];
 		ip = stack[STACK_FRAME_LR_SAVE];
 		if (!firstframe || ip != lr) {
-			printk("["REG"] ["REG"] %pS", sp, ip, (void *)ip);
+			printk("%s["REG"] ["REG"] %pS",
+				loglvl, sp, ip, (void *)ip);
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 			ret_addr = ftrace_graph_ret_addr(current,
 						&ftrace_idx, ip, stack);

@@ -2090,8 +2092,9 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
 			struct pt_regs *regs = (struct pt_regs *)
 				(sp + STACK_FRAME_OVERHEAD);
 			lr = regs->link;
-			printk("--- interrupt: %lx at %pS\n    LR = %pS\n",
-			       regs->trap, (void *)regs->nip, (void *)lr);
+			printk("%s--- interrupt: %lx at %pS\n    LR = %pS\n",
+			       loglvl, regs->trap,
+			       (void *)regs->nip, (void *)lr);
 			firstframe = 1;
 		}
 

@@ -2101,6 +2104,11 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
 	put_task_stack(tsk);
 }
 
+void show_stack(struct task_struct *tsk, unsigned long *stack)
+{
+	show_stack_loglvl(tsk, stack, KERN_DEFAULT);
+}
+
 #ifdef CONFIG_PPC64
 /* Called with hard IRQs off */
 void notrace __ppc64_runlatch_on(void)

-- 
2.25.1

Dmitry Safonov [off-list ref] writes:

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Introduce show_stack_loglvl(), that eventually will substitute
show_stack().

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <redacted>
Cc: linuxppc-dev@lists.ozlabs.org
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Dmitry Safonov <redacted>
---
 arch/powerpc/kernel/process.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

Thanks for doing this, it has caused me problems in the past.

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers