1. 26 9月, 2014 1 次提交
  2. 31 7月, 2014 1 次提交
    • P
      MIPS: ftrace: Fix dynamic tracing of kernel modules · dce0e7d5
      Petri Gynther 提交于
      Dynamic tracing of kernel modules is broken on 32-bit MIPS. When modules
      are loaded, the kernel crashes when dynamic tracing is enabled with:
       cd /sys/kernel/debug/tracing
       echo > set_ftrace_filter
       echo function > current_tracer
      
      1) arch/mips/kernel/ftrace.c
      When the kernel boots, or when a module is initialized, ftrace_make_nop()
      modifies every _mcount call site to eliminate the ftrace overhead.
      However, when ftrace is later enabled for a call site, ftrace_make_call()
      does not currently restore the _mcount call correctly for module call sites.
      Added ftrace_modify_code_2r() and modified ftrace_make_call() to fix this.
      
      2) arch/mips/kernel/mcount.S
      _mcount assembly routine is supposed to have the caller's _mcount call site
      address in register a0. However, a0 is currently not calculated correctly for
      module call sites. a0 should be (ra - 20) or (ra - 24), depending on whether
      the kernel was built with KBUILD_MCOUNT_RA_ADDRESS or not.
      
      This fix has been tested on Broadcom BMIPS5000 processor. Dynamic tracing
      now works for both built-in functions and module functions.
      Signed-off-by: NPetri Gynther <pgynther@google.com>
      Cc: linux-mips@linux-mips.org
      Cc: rostedt@goodmis.org
      Cc: alcooperx@gmail.com
      Cc: cminyard@mvista.com
      Patchwork: https://patchwork.linux-mips.org/patch/7476/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      dce0e7d5
  3. 19 7月, 2014 1 次提交
  4. 03 9月, 2013 1 次提交
  5. 11 6月, 2013 1 次提交
  6. 05 4月, 2013 1 次提交
  7. 31 1月, 2013 1 次提交
    • A
      MIPS: Function tracer: Fix broken function tracing · 58b69401
      Al Cooper 提交于
      Function tracing is currently broken for all 32 bit MIPS platforms.
      When tracing is enabled, the kernel immediately hangs on boot.
      This is a result of commit b732d439
      that changes the kernel/trace/Kconfig file so that is no longer
      forces FRAME_POINTER when FUNCTION_TRACING is enabled.
      
      MIPS frame pointers are generally considered to be useless because
      they cannot be used to unwind the stack. Unfortunately the MIPS
      function tracing code has bugs that are masked by the use of frame
      pointers. This commit fixes the bugs so that MIPS frame pointers
      don't need to be enabled.
      
      The bugs are a result of the odd calling sequence used to call the trace
      routine. This calling sequence is inserted into every traceable function
      when the tracing CONFIG option is enabled. This sequence is generated
      for 32bit MIPS platforms by the compiler via the "-pg" flag.
      
      Part of the sequence is "addiu sp,sp,-8" in the delay slot after every
      call to the trace routine "_mcount" (some legacy thing where 2 arguments
      used to be pushed on the stack). The _mcount routine is expected to
      adjust the sp by +8 before returning.  So when not disabled, the original
      jalr and addiu will be there, so _mcount has to adjust sp.
      
      The problem is that when tracing is disabled for a function, the
      "jalr _mcount" instruction is replaced with a nop, but the
      "addiu sp,sp,-8" is still executed and the stack pointer is left
      trashed. When frame pointers are enabled the problem is masked
      because any access to the stack is done through the frame
      pointer and the stack pointer is restored from the frame pointer when
      the function returns.
      
      This patch writes two nops starting at the address of the "jalr _mcount"
      instruction whenever tracing is disabled. This means that the
      "addiu sp,sp.-8" will be converted to a nop along with the "jalr".  When
      disabled, there will be two nops.
      
      This is SMP safe because the first time this happens is during
      ftrace_init() which is before any other processor has been started.
      Subsequent calls to enable/disable tracing when other CPUs ARE running
      will still be safe because the enable will only change the first nop
      to a "jalr" and the disable, while writing 2 nops, will only be changing
      the "jalr". This patch also stops using stop_machine() to call the
      tracer enable/disable routines and calls them directly because the
      routines are SMP safe.
      
      When the kernel first boots we have to be able to handle the gcc
      generated jalr, addui sequence until ftrace_init gets a chance to run
      and change the sequence. At this point mcount just adjusts the stack
      and returns. When ftrace_init runs, we convert the jalr/addui to nops.
      Then whenever tracing is enabled we convert the first nop to a "jalr
      mcount+8". The mcount+8 entry point skips the stack adjust.
      
      [ralf@linux-mips.org: Folded in  Steven Rostedt's build fix.]
      Signed-off-by: NAl Cooper <alcooperx@gmail.com>
      Cc: rostedt@goodmis.org
      Cc: ddaney.cavm@gmail.com
      Cc: linux-mips@linux-mips.org
      Cc: linux-kernel@vger.kernel.org
      Patchwork: https://patchwork.linux-mips.org/patch/4806/
      Patchwork: https://patchwork.linux-mips.org/patch/4841/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      58b69401
  8. 05 8月, 2010 1 次提交
  9. 06 7月, 2010 4 次提交
  10. 27 2月, 2010 1 次提交
  11. 17 12月, 2009 8 次提交
    • W
      MIPS: Tracing: Make function graph tracer work with -mmcount-ra-address · 7326c4e5
      Wu Zhangjin 提交于
      That thread "MIPS: Add option to pass return address location to
      _mcount" from "David Daney <ddaney@caviumnetworks.com>" have added a new
      option -mmcount-ra-address to gcc(4.5) for MIPS to transfer the location
      of the return address to _mcount.
      
      Benefit from this new feature, function graph tracer on MIPS will be
      easier and safer to hijack the return address of the kernel function,
      which will save some overhead and make the whole thing more reliable.
      
      In this patch, at first, try to enable the option -mmcount-ra-address in
      arch/mips/Makefile with cc-option, if gcc support it, it will be
      enabled, otherwise, no side effect.
      
      and then, we need to support this new option of gcc 4.5 and also support
      the old gcc versions.
      
      with _mcount in the old gcc versions, it's not easy to get the location
      of return address(tracing: add function graph tracer support for MIPS),
         so, we do it in a C function: ftrace_get_parent_addr(ftrace.c), but
         with -mmcount-ra-address, only several instructions need to get what
         we want, so, I put into asm(mcount.S). and also, as the $12(t0) is
         used by -mmcount-ra-address for transferring the localtion of return
         address to _mcount, we need to save it into the stack and restore it
         when enabled dynamic function tracer, 'Cause we have called
         "ftrace_call" before "ftrace_graph_caller", which may destroy
         $12(t0).
      
      (Thanks to David for providing that -mcount-ra-address and giving the
       idea of KBUILD_MCOUNT_RA_ADDRESS, both of them have made the whole
       thing more beautiful!)
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/681/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      7326c4e5
    • W
      MIPS: Tracing: Reserve $12(t0) for mcount-ra-address of gcc 4.5 · fc49a3be
      Wu Zhangjin 提交于
      A new option -mmcount-ra-address for gcc 4.5 have been sent by David
      Daney <ddaney@caviumnetworks.com> in the thread "MIPS: Add option to
      pass return address location to _mcount", which help to record the
      location of the return address(ra) for the function graph tracer of MIPS
      to hijack the return address easier and safer. that option used the
      $12(t0) register by default, so, we reserve it for it, and use t1,t2,t3
      instead of t0,t1,t2.
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/680/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      fc49a3be
    • W
      MIPS: Tracing: Make ftrace for MIPS work without -fno-omit-frame-pointer · 046199ca
      Wu Zhangjin 提交于
      When remove the -fno-omit-frame-pointer, gcc will not save the frame
      pointer for us, we need to save one ourselves.
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/679/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      046199ca
    • W
      MIPS: Tracing: Add dynamic function graph tracer for MIPS · e17ff5fe
      Wu Zhangjin 提交于
      This patch make function graph tracer work with dynamic function tracer.
      
      To share the source code of dynamic function tracer(MCOUNT_SAVE_REGS),
      and avoid restoring the whole saved registers, we need to restore the ra
      register from the stack.
      
      (NOTE: This not work with 32bit! need to ensure why!)
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/678/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      e17ff5fe
    • W
      MIPS: Tracing: Add function graph tracer support for MIPS · 29c5d346
      Wu Zhangjin 提交于
      The implementation of function graph tracer for MIPS is a little
      different from X86.
      
      in MIPS, gcc(with -pg) only transfer the caller's return address(at) and
      the _mcount's return address(ra) to us.
      
      For the kernel part without -mlong-calls:
      
      move at, ra
      jal _mcount
      
      For the module part with -mlong-calls:
      
      lui v1, hi16bit_of_mcount
      addiu v1, v1, low16bit_of_mcount
      move at, ra
      jal _mcount
      
      Without -mlong-calls,
      
      if the function is a leaf, it will not save the return address(ra):
      
      ffffffff80101298 <au1k_wait>:
      ffffffff80101298:       67bdfff0        daddiu  sp,sp,-16
      ffffffff8010129c:       ffbe0008        sd      s8,8(sp)
      ffffffff801012a0:       03a0f02d        move    s8,sp
      ffffffff801012a4:       03e0082d        move    at,ra
      ffffffff801012a8:       0c042930        jal     ffffffff8010a4c0 <_mcount>
      ffffffff801012ac:       00020021        nop
      
      so, we can hijack it directly in _mcount, but if the function is non-leaf, the
      return address is saved in the stack.
      
      ffffffff80133030 <copy_process>:
      ffffffff80133030:       67bdff50        daddiu  sp,sp,-176
      ffffffff80133034:       ffbe00a0        sd      s8,160(sp)
      ffffffff80133038:       03a0f02d        move    s8,sp
      ffffffff8013303c:       ffbf00a8        sd      ra,168(sp)
      ffffffff80133040:       ffb70098        sd      s7,152(sp)
      ffffffff80133044:       ffb60090        sd      s6,144(sp)
      ffffffff80133048:       ffb50088        sd      s5,136(sp)
      ffffffff8013304c:       ffb40080        sd      s4,128(sp)
      ffffffff80133050:       ffb30078        sd      s3,120(sp)
      ffffffff80133054:       ffb20070        sd      s2,112(sp)
      ffffffff80133058:       ffb10068        sd      s1,104(sp)
      ffffffff8013305c:       ffb00060        sd      s0,96(sp)
      ffffffff80133060:       03e0082d        move    at,ra
      ffffffff80133064:       0c042930        jal     ffffffff8010a4c0 <_mcount>
      ffffffff80133068:       00020021        nop
      
      but we can not get the exact stack address(which saved ra) directly in
      _mcount, we need to search the content of at register in the stack space
      or search the "s{d,w} ra, offset(sp)" instruction in the text. 'Cause we
      can not prove there is only a match in the stack space, so, we search
      the text instead.
      
      as we can see, if the first instruction above "move at, ra" is not a
      store instruction, there should be a leaf function, so we hijack the at
      register directly via putting &return_to_handler into it, otherwise, we
      search the "s{d,w} ra, offset(sp)" instruction to get the stack offset,
      and then the stack address. we use the above copy_process() as an
      example, we at last find "ffbf00a8", 0xa8 is the stack offset, we plus
      it with s8(fp), that is the stack address, we hijack the content via
      writing the &return_to_handler in.
      
      If with -mlong-calls, since there are two more instructions above "move
      at, ra", so, we can move the pointer to the position above "lui v1,
      hi16bit_of_mcount".
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/677/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      29c5d346
    • W
      MIPS: Tracing: Add dynamic function tracer support · 538f1952
      Wu Zhangjin 提交于
      With dynamic function tracer, by default, _mcount is defined as an
      "empty" function, it returns directly without any more action . When
      enabling it in user-space, it will jump to a real tracing
      function(ftrace_caller), and do the real job for us.
      
      Differ from the static function tracer, dynamic function tracer provides
      two functions ftrace_make_call()/ftrace_make_nop() to enable/disable the
      tracing of some indicated kernel functions(set_ftrace_filter).
      
      In the -v4 version, the implementation of this support is basically the same as
      X86 version does: _mcount is implemented as an empty function and ftrace_caller
      is implemented as a real tracing function respectively.
      
      But in this version, to support module tracing with the help of
      -mlong-calls in arch/mips/Makefile:
      
      MODFLAGS += -mlong-calls.
      
      The stuff becomes a little more complex. We need to cope with two
      different type of calling to _mcount.
      
      For the kernel part, the calling to _mcount(result of "objdump -hdr
      vmlinux"). is like this:
      
      	108:   03e0082d        move    at,ra
      	10c:   0c000000        jal     0 <fpcsr_pending>
                              10c: R_MIPS_26  _mcount
                              10c: R_MIPS_NONE        *ABS*
                              10c: R_MIPS_NONE        *ABS*
      	110:   00020021        nop
      
      For the module with -mlong-calls, it looks like this:
      
      	c:	3c030000 	lui	v1,0x0
      			c: R_MIPS_HI16	_mcount
      			c: R_MIPS_NONE	*ABS*
      			c: R_MIPS_NONE	*ABS*
      	10:	64630000 	daddiu	v1,v1,0
      			10: R_MIPS_LO16	_mcount
      			10: R_MIPS_NONE	*ABS*
      			10: R_MIPS_NONE	*ABS*
      	14:	03e0082d 	move	at,ra
      	18:	0060f809 	jalr	v1
      
      In the kernel version, there is only one "_mcount" string for every
      kernel function, so, we just need to match this one in mcount_regex of
      scripts/recordmcount.pl, but in the module version, we need to choose
      one of the two to match. Herein, I choose the first one with
      "R_MIPS_HI16 _mcount".
      
      and In the kernel verion, without module tracing support, we just need
      to replace "jal _mcount" by "jal ftrace_caller" to do real tracing, and
      filter the tracing of some kernel functions via replacing it by a nop
      instruction.
      
      but as we have described before, the instruction "jal ftrace_caller" only left
      32bit length for the address of ftrace_caller, it will fail when calling from
      the module space. so, herein, we must replace something else.
      
      the basic idea is loading the address of ftrace_caller to v1 via changing these
      two instructions:
      
      	lui	v1,0x0
      	addiu	v1,v1,0
      
      If we want to enable the tracing, we need to replace the above instructions to:
      
      	lui	v1, HI_16BIT_ftrace_caller
      	addiu	v1, v1, LOW_16BIT_ftrace_caller
      
      If we want to stop the tracing of the indicated kernel functions, we
      just need to replace the "jalr v1" to a nop instruction. but we need to
      replace two instructions and encode the above two instructions
      oursevles.
      
      Is there a simpler solution? Yes! Here it is, in this version, we put _mcount
      and ftrace_caller together, which means the address of _mcount and
      ftrace_caller is the same:
      
      _mcount:
      ftrace_caller:
      	j	ftrace_stub
      	 nop
      
      	...(do real tracing here)...
      
      ftrace_stub:
      	jr	ra
      	 move	ra, at
      
      By default, the kernel functions call _mcount, and then jump to ftrace_stub and
      return. and when we want to do real tracing, we just need to remove that "j
      ftrace_stub", and it will run through the two "nop" instructions and then do
      the real tracing job.
      
      what about filtering job? we just need to do this:
      
      	 lui v1, hi_16bit_of_mcount        <--> b 1f (0x10000004)
      	 addiu v1, v1, low_16bit_of_mcount
      	 move at, ra
      	 jalr v1
      	 nop
      	 				     1f: (rec->ip + 12)
      
      In linux-mips64, there will be some local symbols, whose name are
      prefixed by $L, which need to be filtered. thanks goes to Steven for
      writing the mips64-specific function_regex.
      
      In a conclusion, with RISC, things becomes easier with such a "stupid"
      trick, RISC is something like K.I.S.S, and also, there are lots of
      "simple" tricks in the whole ftrace support, thanks goes to Steven and
      the other folks for providing such a wonderful tracing framework!
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/675/Acked-by: NSteven Rostedt <rostedt@goodmis.org>
      Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      538f1952
    • W
      MIPS: Tracing: Enable HAVE_FUNCTION_TRACE_MCOUNT_TEST for MIPS · 69a7d1b3
      Wu Zhangjin 提交于
      There is an exisiting common ftrace_test_stop_func() in
      kernel/trace/ftrace.c, which is used to check the global variable
      ftrace_trace_stop to determine whether stop the function tracing.
      
      This patch implepment the MIPS specific one to speedup the procedure.
      
      Thanks goes to Zhang Le for Cleaning it up.
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/673/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      69a7d1b3
    • W
      MIPS: Tracing: Add static function tracer support for MIPS · d2bb0762
      Wu Zhangjin 提交于
      If -pg of gcc is enabled with CONFIG_FUNCTION_TRACER=y. a calling to
      _mcount will be inserted into each kernel function. so, there is a
      possibility to trace the kernel functions in _mcount.
      
      This patch add the MIPS specific _mcount support for static function
      tracing. by default, ftrace_trace_function is initialized as
      ftrace_stub(an empty function), so, the default _mcount will introduce
      very little overhead. after enabling ftrace in user-space, it will jump
      to a real tracing function and do static function tracing for us.
      
      and -ffunction-sections is incompatible with -pg, so, disable it when
      ftracer is enabled.
      Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
      Reviewed-by: NSteven Rostedt <rostedt@goodmis.org>
      Cc: Nicholas Mc Guire <der.herr@hofr.at>
      Cc: zhangfx@lemote.com
      Cc: Wu Zhangjin <wuzhangjin@gmail.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: linux-kernel@vger.kernel.org
      Cc: linux-mips@linux-mips.org
      Patchwork: http://patchwork.linux-mips.org/patch/672/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>
      d2bb0762