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  1. 31 7月, 2012 3 次提交
  3. 22 7月, 2012 3 次提交
  5. 30 3月, 2012 2 次提交
    • J
      kgdb,debug_core: pass the breakpoint struct instead of address and memory · 98b54aa1
      由 Jason Wessel 提交于 
      There is extra state information that needs to be exposed in the
kgdb_bpt structure for tracking how a breakpoint was installed.  The
debug_core only uses the the probe_kernel_write() to install
breakpoints, but this is not enough for all the archs.  Some arch such
as x86 need to use text_poke() in order to install a breakpoint into a
read only page.

Passing the kgdb_bpt structure to kgdb_arch_set_breakpoint() and
kgdb_arch_remove_breakpoint() allows other archs to set the type
variable which indicates how the breakpoint was installed.

Cc: stable@vger.kernel.org # >= 2.6.36
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
      98b54aa1
    • J
      kdb: Fix smatch warning on dbg_io_ops->is_console · 78724b8e
      由 Jason Wessel 提交于 
      The Smatch tool warned that the change from commit b8adde8d
(kdb: Avoid using dbg_io_ops until it is initialized) should
add another null check later in the kdb_printf().

It is worth noting that the second use of dbg_io_ops->is_console
is protected by the KDB_PAGER state variable which would only
get set when kdb is fully active and initialized.  If we
ever encounter changes or defects in the KDB_PAGER state
we do not want to crash the kernel in a kdb_printf/printk.

CC: Tim Bird <tim.bird@am.sony.com>
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
      78724b8e
  7. 29 3月, 2012 1 次提交
  9. 23 3月, 2012 6 次提交
  11. 20 3月, 2012 1 次提交
  13. 13 1月, 2012 1 次提交
  15. 12 12月, 2011 1 次提交
  17. 01 11月, 2011 2 次提交
  19. 02 8月, 2011 4 次提交
  21. 27 7月, 2011 1 次提交
  23. 31 3月, 2011 1 次提交
  25. 26 3月, 2011 2 次提交
  27. 19 3月, 2011 1 次提交
  29. 18 11月, 2010 2 次提交
  31. 02 11月, 2010 1 次提交
  33. 30 10月, 2010 3 次提交
  35. 23 10月, 2010 5 次提交
    • J
      kdb,debug_core: adjust master cpu switch logic against new debug_core locking · 495363d3
      由 Jason Wessel 提交于 
      The kdb shell needs to enforce switching back to the original CPU that
took the exception before restoring normal kernel execution.  Resuming
from a different CPU than what took the original exception will cause
problems with spin locks that are freed from the a different processor
than had taken the lock.

The special logic in dbg_cpu_switch() can go away entirely with
because the state of what cpus want to be masters or slaves will
remain unchanged between entry and exit of the debug_core exception
context.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
      495363d3
    • J
      debug_core: refactor locking for master/slave cpus · dfee3a7b
      由 Jason Wessel 提交于 
      For quite some time there have been problems with memory barriers and
various races with NMI on multi processor systems using the kernel
debugger.  The algorithm for entering the kernel debug core and
resuming kernel execution was racy and had several known edge case
problems with attempting to debug something on a heavily loaded system
using breakpoints that are hit repeatedly and quickly.

The prior "locking" design entry worked as follows:

  * The atomic counter kgdb_active was used with atomic exchange in
    order to elect a master cpu out of all the cpus that may have
    taken a debug exception.
  * The master cpu increments all elements of passive_cpu_wait[].
  * The master cpu issues the round up cpus message.
  * Each "slave cpu" that enters the debug core increments its own
    element in cpu_in_kgdb[].
  * Each "slave cpu" spins on passive_cpu_wait[] until it becomes 0.
  * The master cpu debugs the system.

The new scheme removes the two arrays of atomic counters and replaces
them with 2 single counters.  One counter is used to count the number
of cpus waiting to become a master cpu (because one or more hit an
exception). The second counter is use to indicate how many cpus have
entered as slave cpus.

The new entry logic works as follows:

  * One or more cpus enters via kgdb_handle_exception() and increments
    the masters_in_kgdb. Each cpu attempts to get the spin lock called
    dbg_master_lock.
  * The master cpu sets kgdb_active to the current cpu.
  * The master cpu takes the spinlock dbg_slave_lock.
  * The master cpu asks to round up all the other cpus.
  * Each slave cpu that is not already in kgdb_handle_exception()
    will enter and increment slaves_in_kgdb.  Each slave will now spin
    try_locking on dbg_slave_lock.
  * The master cpu waits for the sum of masters_in_kgdb and slaves_in_kgdb
    to be equal to the sum of the online cpus.
  * The master cpu debugs the system.

In the new design the kgdb_active can only be changed while holding
dbg_master_lock.  Stress testing has not turned up any further
entry/exit races that existed in the prior locking design.  The prior
locking design suffered from atomic variables not being truly atomic
(in the capacity as used by kgdb) along with memory barrier races.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Acked-by: NDongdong Deng <dongdong.deng@windriver.com>
      dfee3a7b
    • D
      debug_core: disable hw_breakpoints on all cores in kgdb_cpu_enter() · c1bb9a9c
      由 Dongdong Deng 提交于 
      The slave cpus do not have the hw breakpoints disabled upon entry to
the debug_core and as a result could cause unrecoverable recursive
faults on badly placed breakpoints, or get out of sync with the arch
specific hw breakpoint operations.

This patch addresses the problem by invoking kgdb_disable_hw_debug()
earlier in kgdb_enter_cpu for each cpu that enters the debug core.

The hw breakpoint dis/enable flow should be:

master_debug_cpu   slave_debug_cpu
         \              /
          kgdb_cpu_enter
                |
        kgdb_disable_hw_debug --> uninstall pre-enabled hw_breakpoint
                |
 do add/rm dis/enable operates to hw_breakpoints on master_debug_cpu..
                |
        correct_hw_break --> correct/install the enabled hw_breakpoint
                |
           leave_kgdb
Signed-off-by: NDongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
      c1bb9a9c
    • J
      kdb,kgdb: fix sparse fixups · 91b152aa
      由 Jason Wessel 提交于 
      Fix the following sparse warnings:

kdb_main.c:328:5: warning: symbol 'kdbgetu64arg' was not declared. Should it be static?
kgdboc.c:246:12: warning: symbol 'kgdboc_early_init' was not declared. Should it be static?
kgdb.c:652:26: warning: incorrect type in argument 1 (different address spaces)
kgdb.c:652:26:    expected void const *ptr
kgdb.c:652:26:    got struct perf_event *[noderef] <asn:3>*pev

The one in kgdb.c required the (void * __force) because of the return
code from register_wide_hw_breakpoint looking like:

        return (void __percpu __force *)ERR_PTR(err);
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
      91b152aa
    • J
      kdb: Fix oops in kdb_unregister · 75d14ede
      由 Jason Wessel 提交于 
      Nothing should try to use kdb_commands directly as sometimes it is
null.  Instead, use the for_each_kdbcmd() iterator.

This particular problem dates back to the initial kdb merge (2.6.35),
but at that point nothing was dynamically unregistering commands from
the kdb shell.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
      75d14ede