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  1. 23 2月, 2009 2 次提交
  3. 21 2月, 2009 5 次提交
    • S
      ftrace: break out modify loop immediately on detection of error · 4377245a
      由 Steven Rostedt 提交于 
      Impact: added precaution on failure detection

Break out of the modifying loop as soon as a failure is detected.
This is just an added precaution found by code review and was not
found by any bug chasing.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      4377245a
    • S
      ftrace: immediately stop code modification if failure is detected · 90c7ac49
      由 Steven Rostedt 提交于 
      Impact: fix to prevent NMI lockup

If the page fault handler produces a WARN_ON in the modifying of
text, and the system is setup to have a high frequency of NMIs,
we can lock up the system on a failure to modify code.

The modifying of code with NMIs allows all NMIs to modify the code
if it is about to run. This prevents a modifier on one CPU from
modifying code running in NMI context on another CPU. The modifying
is done through stop_machine, so only NMIs must be considered.

But if the write causes the page fault handler to produce a warning,
the print can slow it down enough that as soon as it is done
it will take another NMI before going back to the process context.
The new NMI will perform the write again causing another print and
this will hang the box.

This patch turns off the writing as soon as a failure is detected
and does not wait for it to be turned off by the process context.
This will keep NMIs from getting stuck in this back and forth
of print outs.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      90c7ac49
    • S
      ftrace, x86: make kernel text writable only for conversions · 16239630
      由 Steven Rostedt 提交于 
      Impact: keep kernel text read only

Because dynamic ftrace converts the calls to mcount into and out of
nops at run time, we needed to always keep the kernel text writable.

But this defeats the point of CONFIG_DEBUG_RODATA. This patch converts
the kernel code to writable before ftrace modifies the text, and converts
it back to read only afterward.

The kernel text is converted to read/write, stop_machine is called to
modify the code, then the kernel text is converted back to read only.

The original version used SYSTEM_STATE to determine when it was OK
or not to change the code to rw or ro. Andrew Morton pointed out that
using SYSTEM_STATE is a bad idea since there is no guarantee to what
its state will actually be.

Instead, I moved the check into the set_kernel_text_* functions
themselves, and use a local variable to determine when it is
OK to change the kernel text RW permissions.

[ Update: Ingo Molnar suggested moving the prototypes to cacheflush.h ]
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      16239630
    • F
      tracing/markers: make markers select tracepoints · 91f73f90
      由 Frederic Weisbecker 提交于 
      Sometimes it happens that KConfig dependencies are not handled
like in the following scenario:

- config A
   bool

- config B
   bool
   depends on A

- config C
   bool
   select B

If one selects C, then it will select B without checking its
dependency to A, if A hasn't been selected elsewhere, it will
result in a build failure.

This is what happens on the following build error:

 kernel/built-in.o: In function `marker_update_probe_range':
 (.text+0x52f64): undefined reference to `tracepoint_probe_register_noupdate'
 kernel/built-in.o: In function `marker_update_probe_range':
 (.text+0x52f74): undefined reference to `tracepoint_probe_unregister_noupdate'
 kernel/built-in.o: In function `marker_update_probe_range':
 (.text+0x52fb9): undefined reference to `tracepoint_probe_unregister_noupdate'
 kernel/built-in.o: In function `marker_update_probes':
 marker.c:(.text+0x530ba): undefined reference to `tracepoint_probe_update_all'

CONFIG_KVM_TRACE will select CONFIG_MARKER, but the latter
depends on CONFIG_TRACEPOINTS which will not be selected.
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      91f73f90
    • S
      ftrace: allow archs to preform pre and post process for code modification · 000ab691
      由 Steven Rostedt 提交于 
      This patch creates the weak functions: ftrace_arch_code_modify_prepare
and ftrace_arch_code_modify_post_process that are called before and
after the stop machine is called to modify the kernel text.

If the arch needs to do pre or post processing, it only needs to define
these functions.

[ Update: Ingo Molnar suggested using the name ftrace_arch_code_modify_*
          over using ftrace_arch_modify_* ]
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      000ab691
  5. 20 2月, 2009 12 次提交
  7. 19 2月, 2009 21 次提交