linux-toradex.git/arch/arm/kernel/kgdb.c, branch v4.10

ARM: 8428/1: kgdb: Fix registers on sleeping tasks

2015-10-03T15:36:45+00:00

Dumping registers from other sleeping tasks in KGDB was totally
failing for me.  All registers were reported as 0 in many cases.

The code was using task_pt_regs(task) to try to get other thread
registers.  This doesn't appear to be the right place to look.  From
my tests, I saw non-zero values in this structure when we were looking
at a kernel thread that had a userspace task associated with it, but
it contained the register values from the userspace task.  So even in
the cases where registers weren't reported as 0 we were still not
showing the right thing.

Instead of using task_pt_regs(task) let's use task_thread_info(task).
This is the same place that is referred to when doing a dump of all
sleeping task stacks (kdb_show_stack() -> show_stack() ->
dump_backtrace() -> unwind_backtrace() -> thread_saved_sp()).

As further evidence that this is the right thing to do, you can find
the following comment in "gdbstub.c" right before it calls
sleeping_thread_to_gdb_regs():
  Pull stuff saved during switch_to; nothing else is accessible (or
  even particularly relevant).  This should be enough for a stack
  trace.
...and if you look at switch_to() it only saves r4-r11, sp and lr.
Those are the same registers that I'm getting out of the
task_thread_info().

With this change you can use "info thread" to see all tasks in the
kernel and you can switch to other tasks and examine them in gdb.

Signed-off-by: Doug Anderson 
Tested-by: Stephen Boyd 
Signed-off-by: Russell King

ARM: 8425/1: kgdb: Don't try to stop the machine when setting breakpoints

2015-09-16T22:58:46+00:00

In (23a4e40 arm: kgdb: Handle read-only text / modules) we moved to
using patch_text() to set breakpoints so that we could handle the case
when we had CONFIG_DEBUG_RODATA.  That patch used patch_text().
Unfortunately, patch_text() assumes that we're not in atomic context
when it runs since it needs to grab a mutex and also wait for other
CPUs to stop (which it does with a completion).

This would result in a stack crawl if you had
CONFIG_DEBUG_ATOMIC_SLEEP and tried to set a breakpoint in kgdb.  The
crawl looked something like:

 BUG: scheduling while atomic: swapper/0/0/0x00010007
 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.2.0-rc7-00133-geb63b34 #1073
 Hardware name: Rockchip (Device Tree)
  (unwind_backtrace) from [] (show_stack+0x20/0x24)
  (show_stack) from [] (dump_stack+0x84/0xb8)
  (dump_stack) from [] (__schedule_bug+0x54/0x6c)
  (__schedule_bug) from [] (__schedule+0x80/0x668)
  (__schedule) from [] (schedule+0xb8/0xd4)
  (schedule) from [] (schedule_timeout+0x2c/0x234)
  (schedule_timeout) from [] (wait_for_common+0xf4/0x188)
  (wait_for_common) from [] (wait_for_completion+0x20/0x24)
  (wait_for_completion) from [] (__stop_cpus+0x58/0x70)
  (__stop_cpus) from [] (stop_cpus+0x3c/0x54)
  (stop_cpus) from [] (__stop_machine+0xcc/0xe8)
  (__stop_machine) from [] (stop_machine+0x34/0x44)
  (stop_machine) from [] (patch_text+0x28/0x34)
  (patch_text) from [] (kgdb_arch_set_breakpoint+0x40/0x4c)
  (kgdb_arch_set_breakpoint) from [] (kgdb_validate_break_address+0x2c/0x60)
  (kgdb_validate_break_address) from [] (dbg_set_sw_break+0x1c/0xdc)
  (dbg_set_sw_break) from [] (gdb_serial_stub+0x9c4/0xba4)
  (gdb_serial_stub) from [] (kgdb_cpu_enter+0x1f8/0x60c)
  (kgdb_cpu_enter) from [] (kgdb_handle_exception+0x19c/0x1d0)
  (kgdb_handle_exception) from [] (kgdb_compiled_brk_fn+0x30/0x3c)
  (kgdb_compiled_brk_fn) from [] (do_undefinstr+0x1a4/0x20c)
  (do_undefinstr) from [] (__und_svc_finish+0x0/0x34)

It turns out that when we're in kgdb all the CPUs are stopped anyway
so there's no reason we should be calling patch_text().  We can
instead directly call __patch_text() which assumes that CPUs have
already been stopped.

Fixes: 23a4e4050ba9 ("arm: kgdb: Handle read-only text / modules")
Reported-by: Aapo Vienamo 
Signed-off-by: Douglas Anderson 
Reviewed-by: Stephen Boyd 
Acked-by: Kees Cook 
Signed-off-by: Russell King

ARM: probes: move all probe code to dedicate directory

2015-01-09T09:36:50+00:00

In discussion on LKML (https://lkml.org/lkml/2014/11/28/158), Russell
King suggests to move all probe related code to arch/arm/probes. This
patch does the work. Due to dependency on 'arch/arm/kernel/patch.h', this
patch also moves patch.h to 'arch/arm/include/asm/patch.h', and related
'#include' directives are also midified to '#include '.

Following is an overview of this patch:

 ./arch/arm/kernel/               ./arch/arm/probes/
 |-- Makefile                     |-- Makefile
 |-- probes-arm.c          ==>    |-- decode-arm.c
 |-- probes-arm.h          ==>    |-- decode-arm.h
 |-- probes-thumb.c        ==>    |-- decode-thumb.c
 |-- probes-thumb.h        ==>    |-- decode-thumb.h
 |-- probes.c              ==>    |-- decode.c
 |-- probes.h              ==>    |-- decode.h
 |                                |-- kprobes
 |                                |   |-- Makefile
 |-- kprobes-arm.c         ==>    |   |-- actions-arm.c
 |-- kprobes-common.c      ==>    |   |-- actions-common.c
 |-- kprobes-thumb.c       ==>    |   |-- actions-thumb.c
 |-- kprobes.c             ==>    |   |-- core.c
 |-- kprobes.h             ==>    |   |-- core.h
 |-- kprobes-test-arm.c    ==>    |   |-- test-arm.c
 |-- kprobes-test.c        ==>    |   |-- test-core.c
 |-- kprobes-test.h        ==>    |   |-- test-core.h
 |-- kprobes-test-thumb.c  ==>    |   `-- test-thumb.c
 |                                `-- uprobes
 |                                    |-- Makefile
 |-- uprobes-arm.c         ==>        |-- actions-arm.c
 |-- uprobes.c             ==>        |-- core.c
 |-- uprobes.h             ==>        `-- core.h
 |
 `-- patch.h               ==>    arch/arm/include/asm/patch.h

Signed-off-by: Wang Nan 
Acked-by: Masami Hiramatsu 
Signed-off-by: Jon Medhurst

arm: kgdb: Handle read-only text / modules

2014-10-16T21:38:53+00:00

Handle the case where someone has set the text segment of the kernel
as read-only by using the newly introduced "patch" mechanism.

Signed-off-by: Doug Anderson 
[kees: switched structure size check to BUILD_BUG_ON (sboyd)]
Signed-off-by: Kees Cook 
Acked-by: Nicolas Pitre

ARM: 8124/1: don't enter kgdb when userspace executes a kgdb break instruction

2014-08-02T14:20:30+00:00

The kgdb breakpoint hooks (kgdb_brk_fn and kgdb_compiled_brk_fn)
should only be entered when a kgdb break instruction is executed
from the kernel. Otherwise, if kgdb is enabled, a userspace program
can cause the kernel to drop into the debugger by executing either
KGDB_BREAKINST or KGDB_COMPILED_BREAK.

Acked-by: Will Deacon 
Signed-off-by: Omar Sandoval 
Signed-off-by: Russell King

kgdb,arm: fix register dump

2010-10-29T18:14:40+00:00

DBG_MAX_REG_NUM incorrectly had the number of indices in the GDB regs
array rather than the number of registers, leading to an oops when the
"rd" command is used in KDB.

Cc: stable@kernel.org
Signed-off-by: Rabin Vincent 
Signed-off-by: Jason Wessel

ARM: 6326/1: kgdb: fix GDB_MAX_REGS no longer used

2010-08-14T08:28:35+00:00

According to commit 22eeef4bb2a7fd225089c0044060ed1fbf091958

    kgdb,arm: Individual register get/set for arm

It's now replaced by DBG_MAX_REG_NUM.

Cc: Jason Wessel 
Signed-off-by: Eric Miao 
Signed-off-by: Russell King

arm,kgdb: Add ability to trap into debugger on notify_die

2010-08-05T14:22:22+00:00

Now that ARM implements the notify die handlers, add the ability for
the kernel debugger to receive the notifications.

Signed-off-by: Jason Wessel 
CC: Russell King 
CC: linux-arm-kernel@lists.infradead.org

kgdb,arm: Individual register get/set for arm

2010-08-05T14:22:21+00:00

Implement the ability to individually get and set registers for kdb
and kgdb for arm.

Signed-off-by: Jason Wessel 
CC: Russell King 
CC: linux-arm-kernel@lists.infradead.org

kgdb: core changes to support kdb

2010-05-21T02:04:21+00:00

These are the minimum changes to the kgdb core in order to enable an
API to connect a new front end (kdb) to the debug core.

This patch introduces the dbg_kdb_mode variable controls where the
user level I/O is routed.  It will be routed to the gdbstub (kgdb) or
to the kdb front end which is a simple shell available over the kgdboc
connection.

You can switch back and forth between kdb or the gdb stub mode of
operation dynamically.  From gdb stub mode you can blindly type
"$3#33", or from the kdb mode you can enter "kgdb" to switch to the
gdb stub.

The logic in the debug core depends on kdb to look for the typical gdb
connection sequences and return immediately with KGDB_PASS_EVENT if a
gdb serial command sequence is detected.  That should allow a
reasonably seamless transition between kdb -> gdb without leaving the
kernel exception state.  The two gdb serial queries that kdb is
responsible for detecting are the "?" and "qSupported" packets.

CC: Ingo Molnar 
Signed-off-by: Jason Wessel 
Acked-by: Martin Hicks