1. 01 6月, 2012 1 次提交
    • S
      ftrace: Synchronize variable setting with breakpoints · a192cd04
      Steven Rostedt 提交于
      When the function tracer starts modifying the code via breakpoints
      it sets a variable (modifying_ftrace_code) to inform the breakpoint
      handler to call the ftrace int3 code.
      
      But there's no synchronization between setting this code and the
      handler, thus it is possible for the handler to be called on another
      CPU before it sees the variable. This will cause a kernel crash as
      the int3 handler will not know what to do with it.
      
      I originally added smp_mb()'s to force the visibility of the variable
      but H. Peter Anvin suggested that I just make it atomic.
      
      [ Added comments as suggested by Peter Zijlstra ]
      Suggested-by: NH. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      a192cd04
  2. 17 5月, 2012 1 次提交
  3. 04 5月, 2012 1 次提交
  4. 28 4月, 2012 2 次提交
    • S
      ftrace/x86: Remove the complex ftrace NMI handling code · 4a6d70c9
      Steven Rostedt 提交于
      As ftrace function tracing would require modifying code that could
      be executed in NMI context, which is not stopped with stop_machine(),
      ftrace had to do a complex algorithm with various stages of setup
      and memory barriers to make it work.
      
      With the new breakpoint method, this is no longer required. The changes
      to the code can be done without any problem in NMI context, as well as
      without stop machine altogether. Remove the complex code as it is
      no longer needed.
      
      Also, a lot of the notrace annotations could be removed from the
      NMI code as it is now safe to trace them. With the exception of
      do_nmi itself, which does some special work to handle running in
      the debug stack. The breakpoint method can cause NMIs to double
      nest the debug stack if it's not setup properly, and that is done
      in do_nmi(), thus that function must not be traced.
      
      (Note the arch sh may want to do the same)
      
      Cc: Paul Mundt <lethal@linux-sh.org>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      4a6d70c9
    • S
      ftrace/x86: Have arch x86_64 use breakpoints instead of stop machine · 08d636b6
      Steven Rostedt 提交于
      This method changes x86 to add a breakpoint to the mcount locations
      instead of calling stop machine.
      
      Now that iret can be handled by NMIs, we perform the following to
      update code:
      
      1) Add a breakpoint to all locations that will be modified
      
      2) Sync all cores
      
      3) Update all locations to be either a nop or call (except breakpoint
         op)
      
      4) Sync all cores
      
      5) Remove the breakpoint with the new code.
      
      6) Sync all cores
      
      [
        Added updates that Masami suggested:
         Use unlikely(modifying_ftrace_code) in int3 trap to keep kprobes efficient.
         Don't use NOTIFY_* in ftrace handler in int3 as it is not a notifier.
      ]
      
      Cc: H. Peter Anvin <hpa@zytor.com>
      Acked-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      08d636b6
  5. 26 5月, 2011 1 次提交
  6. 19 4月, 2011 1 次提交
  7. 10 3月, 2011 1 次提交
    • S
      ftrace/graph: Trace function entry before updating index · 722b3c74
      Steven Rostedt 提交于
      Currently the index to the ret_stack is updated and the real return address
      is saved in the ret_stack. Then we call the trace function. The trace
      function could decide that it doesn't want to trace this function
      (ex. set_graph_function does not match) and it will return 0 which means
      not to trace this call.
      
      The normal function graph tracer has this code:
      
      	if (!(trace->depth || ftrace_graph_addr(trace->func)) ||
      	      ftrace_graph_ignore_irqs())
      		return 0;
      
      What this states is, if the trace depth (which is curr_ret_stack)
      is zero (top of nested functions) then test if we want to trace this
      function. If this function is not to be traced, then return  0 and
      the rest of the function graph tracer logic will not trace this function.
      
      The problem arises when an interrupt comes in after we updated the
      curr_ret_stack. The next function that gets called will have a trace->depth
      of 1. Which fools this trace code into thinking that we are in a nested
      function, and that we should trace. This causes interrupts to be traced
      when they should not be.
      
      The solution is to trace the function first and then update the ret_stack.
      Reported-by: Nzhiping zhong <xzhong86@163.com>
      Reported-by: Nwu zhangjin <wuzhangjin@gmail.com>
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      722b3c74
  8. 30 12月, 2010 1 次提交
  9. 18 11月, 2010 1 次提交
    • M
      x86: Add RO/NX protection for loadable kernel modules · 84e1c6bb
      matthieu castet 提交于
      This patch is a logical extension of the protection provided by
      CONFIG_DEBUG_RODATA to LKMs. The protection is provided by
      splitting module_core and module_init into three logical parts
      each and setting appropriate page access permissions for each
      individual section:
      
       1. Code: RO+X
       2. RO data: RO+NX
       3. RW data: RW+NX
      
      In order to achieve proper protection, layout_sections() have
      been modified to align each of the three parts mentioned above
      onto page boundary. Next, the corresponding page access
      permissions are set right before successful exit from
      load_module(). Further, free_module() and sys_init_module have
      been modified to set module_core and module_init as RW+NX right
      before calling module_free().
      
      By default, the original section layout and access flags are
      preserved. When compiled with CONFIG_DEBUG_SET_MODULE_RONX=y,
      the patch will page-align each group of sections to ensure that
      each page contains only one type of content and will enforce
      RO/NX for each group of pages.
      
        -v1: Initial proof-of-concept patch.
        -v2: The patch have been re-written to reduce the number of #ifdefs
             and to make it architecture-agnostic. Code formatting has also
             been corrected.
        -v3: Opportunistic RO/NX protection is now unconditional. Section
             page-alignment is enabled when CONFIG_DEBUG_RODATA=y.
        -v4: Removed most macros and improved coding style.
        -v5: Changed page-alignment and RO/NX section size calculation
        -v6: Fixed comments. Restricted RO/NX enforcement to x86 only
        -v7: Introduced CONFIG_DEBUG_SET_MODULE_RONX, added
             calls to set_all_modules_text_rw() and set_all_modules_text_ro()
             in ftrace
        -v8: updated for compatibility with linux 2.6.33-rc5
        -v9: coding style fixes
       -v10: more coding style fixes
       -v11: minor adjustments for -tip
       -v12: minor adjustments for v2.6.35-rc2-tip
       -v13: minor adjustments for v2.6.37-rc1-tip
      Signed-off-by: NSiarhei Liakh <sliakh.lkml@gmail.com>
      Signed-off-by: NXuxian Jiang <jiang@cs.ncsu.edu>
      Acked-by: NArjan van de Ven <arjan@linux.intel.com>
      Reviewed-by: NJames Morris <jmorris@namei.org>
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      Cc: Andi Kleen <ak@muc.de>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Stephen Rothwell <sfr@canb.auug.org.au>
      Cc: Dave Jones <davej@redhat.com>
      Cc: Kees Cook <kees.cook@canonical.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      LKML-Reference: <4CE2F914.9070106@free.fr>
      [ minor cleanliness edits, -v14: build failure fix ]
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      84e1c6bb
  10. 21 9月, 2010 1 次提交
  11. 25 2月, 2010 1 次提交
    • S
      ftrace: Remove memory barriers from NMI code when not needed · 0c54dd34
      Steven Rostedt 提交于
      The code in stop_machine that modifies the kernel text has a bit
      of logic to handle the case of NMIs. stop_machine does not prevent
      NMIs from executing, and if an NMI were to trigger on another CPU
      as the modifying CPU is changing the NMI text, a GPF could result.
      
      To prevent the GPF, the NMI calls ftrace_nmi_enter() which may
      modify the code first, then any other NMIs will just change the
      text to the same content which will do no harm. The code that
      stop_machine called must wait for NMIs to finish while it changes
      each location in the kernel. That code may also change the text
      to what the NMI changed it to. The key is that the text will never
      change content while another CPU is executing it.
      
      To make the above work, the call to ftrace_nmi_enter() must also
      do a smp_mb() as well as atomic_inc().  But for applications like
      perf that require a high number of NMIs for profiling, this can have
      a dramatic effect on the system. Not only is it doing a full memory
      barrier on both nmi_enter() as well as nmi_exit() it is also
      modifying a global variable with an atomic operation. This kills
      performance on large SMP machines.
      
      Since the memory barriers are only needed when ftrace is in the
      process of modifying the text (which is seldom), this patch
      adds a "modifying_code" variable that gets set before stop machine
      is executed and cleared afterwards.
      
      The NMIs will check this variable and store it in a per CPU
      "save_modifying_code" variable that it will use to check if it
      needs to do the memory barriers and atomic dec on NMI exit.
      Acked-by: NPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      0c54dd34
  12. 17 2月, 2010 1 次提交
  13. 03 11月, 2009 1 次提交
  14. 14 10月, 2009 1 次提交
    • F
      tracing: Move syscalls metadata handling from arch to core · c44fc770
      Frederic Weisbecker 提交于
      Most of the syscalls metadata processing is done from arch.
      But these operations are mostly generic accross archs. Especially now
      that we have a common variable name that expresses the number of
      syscalls supported by an arch: NR_syscalls, the only remaining bits
      that need to reside in arch is the syscall nr to addr translation.
      
      v2: Compare syscalls symbols only after the "sys" prefix so that we
          avoid spurious mismatches with archs that have syscalls wrappers,
          in which case syscalls symbols have "SyS" prefixed aliases.
          (Reported by: Heiko Carstens)
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      Acked-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Masami Hiramatsu <mhiramat@redhat.com>
      Cc: Jason Baron <jbaron@redhat.com>
      Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Paul Mundt <lethal@linux-sh.org>
      c44fc770
  15. 12 10月, 2009 1 次提交
  16. 27 8月, 2009 1 次提交
    • J
      tracing: Convert event tracing code to use NR_syscalls · 57421dbb
      Jason Baron 提交于
      Convert the syscalls event tracing code to use NR_syscalls, instead of
      FTRACE_SYSCALL_MAX. NR_syscalls is standard accross most arches, and
      reduces code confusion/complexity.
      Signed-off-by: NJason Baron <jbaron@redhat.com>
      Cc: Paul Mundt <lethal@linux-sh.org>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
      Cc: Jiaying Zhang <jiayingz@google.com>
      Cc: Martin Bligh <mbligh@google.com>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Josh Stone <jistone@redhat.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: H. Peter Anwin <hpa@zytor.com>
      Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      LKML-Reference: <9b4f1a84ecae57cc6599412772efa36f0d2b815b.1251146513.git.jbaron@redhat.com>
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      57421dbb
  17. 12 8月, 2009 3 次提交
    • J
      tracing: Add individual syscalls tracepoint id support · 64c12e04
      Jason Baron 提交于
      The current state of syscalls tracepoints generates only one event id
      for every syscall events.
      
      This patch associates an id with each syscall trace event, so that we
      can identify each syscall trace event using the 'perf' tool.
      Signed-off-by: NJason Baron <jbaron@redhat.com>
      Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
      Cc: Jiaying Zhang <jiayingz@google.com>
      Cc: Martin Bligh <mbligh@google.com>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Masami Hiramatsu <mhiramat@redhat.com>
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      64c12e04
    • J
      tracing: Call arch_init_ftrace_syscalls at boot · 066e0378
      Jason Baron 提交于
      Call arch_init_ftrace_syscalls at boot, so we can determine early the
      set of syscalls for the syscall trace events.
      Signed-off-by: NJason Baron <jbaron@redhat.com>
      Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
      Cc: Jiaying Zhang <jiayingz@google.com>
      Cc: Martin Bligh <mbligh@google.com>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Masami Hiramatsu <mhiramat@redhat.com>
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      066e0378
    • J
      tracing: Map syscall name to number · eeac19a7
      Jason Baron 提交于
      Add a new function to support translating a syscall name to number at
      runtime.
      This allows the syscall event tracer to map syscall names to number.
      Signed-off-by: NJason Baron <jbaron@redhat.com>
      Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
      Cc: Jiaying Zhang <jiayingz@google.com>
      Cc: Martin Bligh <mbligh@google.com>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Masami Hiramatsu <mhiramat@redhat.com>
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      eeac19a7
  18. 06 8月, 2009 1 次提交
  19. 19 6月, 2009 1 次提交
    • S
      function-graph: add stack frame test · 71e308a2
      Steven Rostedt 提交于
      In case gcc does something funny with the stack frames, or the return
      from function code, we would like to detect that.
      
      An arch may implement passing of a variable that is unique to the
      function and can be saved on entering a function and can be tested
      when exiting the function. Usually the frame pointer can be used for
      this purpose.
      
      This patch also implements this for x86. Where it passes in the stack
      frame of the parent function, and will test that frame on exit.
      
      There was a case in x86_32 with optimize for size (-Os) where, for a
      few functions, gcc would align the stack frame and place a copy of the
      return address into it. The function graph tracer modified the copy and
      not the actual return address. On return from the funtion, it did not go
      to the tracer hook, but returned to the parent. This broke the function
      graph tracer, because the return of the parent (where gcc did not do
      this funky manipulation) returned to the location that the child function
      was suppose to. This caused strange kernel crashes.
      
      This test detected the problem and pointed out where the issue was.
      
      This modifies the parameters of one of the functions that the arch
      specific code calls, so it includes changes to arch code to accommodate
      the new prototype.
      
      Note, I notice that the parsic arch implements its own push_return_trace.
      This is now a generic function and the ftrace_push_return_trace should be
      used instead. This patch does not touch that code.
      
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Helge Deller <deller@gmx.de>
      Cc: Kyle McMartin <kyle@mcmartin.ca>
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      71e308a2
  20. 14 5月, 2009 1 次提交
    • S
      x86/function-graph: fix constraint for recording old return value · aa512a27
      Steven Rostedt 提交于
      After upgrading from gcc 4.2.2 to 4.4.0, the function graph tracer broke.
      Investigating, I found that in the asm that replaces the return value,
      gcc was using the same register for the old value as it was for the
      new value.
      
      	mov	(addr), old
      	mov	new, (addr)
      
      But if old and new are the same register, we clobber new with old!
      I first thought this was a bug in gcc 4.4.0 and reported it:
      
        http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40132
      
      Andrew Pinski responded (quickly), saying that it was correct gcc behavior
      and the code needed to denote old as an "early clobber".
      
      Instead of "=r"(old), we need "=&r"(old).
      
      [Impact: keep function graph tracer from breaking with gcc 4.4.0 ]
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      aa512a27
  21. 09 4月, 2009 1 次提交
    • F
      tracing/syscalls: use a dedicated file header · 47788c58
      Frederic Weisbecker 提交于
      Impact: fix build warnings and possibe compat misbehavior on IA64
      
      Building a kernel on ia64 might trigger these ugly build warnings:
      
      CC      arch/ia64/ia32/sys_ia32.o
      In file included from arch/ia64/ia32/sys_ia32.c:55:
      arch/ia64/ia32/ia32priv.h:290:1: warning: "elf_check_arch" redefined
      In file included from include/linux/elf.h:7,
                       from include/linux/module.h:14,
                       from include/linux/ftrace.h:8,
                       from include/linux/syscalls.h:68,
                       from arch/ia64/ia32/sys_ia32.c:18:
      arch/ia64/include/asm/elf.h:19:1: warning: this is the location of the previous definition
      [...]
      
      sys_ia32.c includes linux/syscalls.h which in turn includes linux/ftrace.h
      to import the syscalls tracing prototypes.
      
      But including ftrace.h can pull too much things for a low level file,
      especially on ia64 where the ia32 private headers conflict with higher
      level headers.
      
      Now we isolate the syscall tracing headers in their own lightweight file.
      Reported-by: NTony Luck <tony.luck@intel.com>
      Tested-by: NTony Luck <tony.luck@intel.com>
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      Acked-by: NTony Luck <tony.luck@intel.com>
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Jason Baron <jbaron@redhat.com>
      Cc: "Frank Ch. Eigler" <fche@redhat.com>
      Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
      Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
      Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
      Cc: Jiaying Zhang <jiayingz@google.com>
      Cc: Michael Rubin <mrubin@google.com>
      Cc: Martin Bligh <mbligh@google.com>
      Cc: Michael Davidson <md@google.com>
      LKML-Reference: <20090408184058.GB6017@nowhere>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      47788c58
  22. 07 4月, 2009 1 次提交
  23. 24 3月, 2009 1 次提交
  24. 19 3月, 2009 1 次提交
    • L
      ftrace: protect running nmi (V3) · e9d9df44
      Lai Jiangshan 提交于
      When I review the sensitive code ftrace_nmi_enter(), I found
      the atomic variable nmi_running does protect NMI VS do_ftrace_mod_code(),
      but it can not protects NMI(entered nmi) VS NMI(ftrace_nmi_enter()).
      
      cpu#1                   | cpu#2                 | cpu#3
      ftrace_nmi_enter()      | do_ftrace_mod_code()  |
        not modify            |                       |
      ------------------------|-----------------------|--
      executing               | set mod_code_write = 1|
      executing             --|-----------------------|--------------------
      executing               |                       | ftrace_nmi_enter()
      executing               |                       |    do modify
      ------------------------|-----------------------|-----------------
      ftrace_nmi_exit()       |                       |
      
      cpu#3 may be being modified the code which is still being executed on cpu#1,
      it will have undefined results and possibly take a GPF, this patch
      prevents it occurred.
      Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
      LKML-Reference: <49C0B411.30003@cn.fujitsu.com>
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      e9d9df44
  25. 13 3月, 2009 1 次提交
  26. 05 3月, 2009 1 次提交
  27. 21 2月, 2009 2 次提交
    • S
      ftrace: immediately stop code modification if failure is detected · 90c7ac49
      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
      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
  28. 19 2月, 2009 1 次提交
  29. 11 2月, 2009 3 次提交
  30. 09 2月, 2009 1 次提交
  31. 08 2月, 2009 4 次提交
    • S
      ring-buffer: use generic version of in_nmi · a81bd80a
      Steven Rostedt 提交于
      Impact: clean up
      
      Now that a generic in_nmi is available, this patch removes the
      special code in the ring_buffer and implements the in_nmi generic
      version instead.
      
      With this change, I was also able to rename the "arch_ftrace_nmi_enter"
      back to "ftrace_nmi_enter" and remove the code from the ring buffer.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      a81bd80a
    • S
      ftrace: change function graph tracer to use new in_nmi · 9a5fd902
      Steven Rostedt 提交于
      The function graph tracer piggy backed onto the dynamic ftracer
      to use the in_nmi custom code for dynamic tracing. The problem
      was (as Andrew Morton pointed out) it really only wanted to bail
      out if the context of the current CPU was in NMI context. But the
      dynamic ftrace in_nmi custom code was true if _any_ CPU happened
      to be in NMI context.
      
      Now that we have a generic in_nmi interface, this patch changes
      the function graph code to use it instead of the dynamic ftarce
      custom code.
      Reported-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      9a5fd902
    • S
      ftrace, x86: rename in_nmi variable · 4e6ea144
      Steven Rostedt 提交于
      Impact: clean up
      
      The in_nmi variable in x86 arch ftrace.c is a misnomer.
      Andrew Morton pointed out that the in_nmi variable is incremented
      by all CPUS. It can be set when another CPU is running an NMI.
      
      Since this is actually intentional, the fix is to rename it to
      what it really is: "nmi_running"
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      4e6ea144
    • S
      ring-buffer: add NMI protection for spinlocks · 78d904b4
      Steven Rostedt 提交于
      Impact: prevent deadlock in NMI
      
      The ring buffers are not yet totally lockless with writing to
      the buffer. When a writer crosses a page, it grabs a per cpu spinlock
      to protect against a reader. The spinlocks taken by a writer are not
      to protect against other writers, since a writer can only write to
      its own per cpu buffer. The spinlocks protect against readers that
      can touch any cpu buffer. The writers are made to be reentrant
      with the spinlocks disabling interrupts.
      
      The problem arises when an NMI writes to the buffer, and that write
      crosses a page boundary. If it grabs a spinlock, it can be racing
      with another writer (since disabling interrupts does not protect
      against NMIs) or with a reader on the same CPU. Luckily, most of the
      users are not reentrant and protects against this issue. But if a
      user of the ring buffer becomes reentrant (which is what the ring
      buffers do allow), if the NMI also writes to the ring buffer then
      we risk the chance of a deadlock.
      
      This patch moves the ftrace_nmi_enter called by nmi_enter() to the
      ring buffer code. It replaces the current ftrace_nmi_enter that is
      used by arch specific code to arch_ftrace_nmi_enter and updates
      the Kconfig to handle it.
      
      When an NMI is called, it will set a per cpu variable in the ring buffer
      code and will clear it when the NMI exits. If a write to the ring buffer
      crosses page boundaries inside an NMI, a trylock is used on the spin
      lock instead. If the spinlock fails to be acquired, then the entry
      is discarded.
      
      This bug appeared in the ftrace work in the RT tree, where event tracing
      is reentrant. This workaround solved the deadlocks that appeared there.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      78d904b4