Re: [PATCH -tip V2] [BUGFIX] perf probe: Fix to find lineinformation for probe list

[Arnaldo Carvalho de Melo]

Em Mon, Oct 07, 2013 at 12:53:40PM +0900, Masami Hiramatsu escreveu:
> Ping? :)

I'll send a perf/urgent pull req later today, this patch is there.

- Arnaldo
 
> (2013/09/30 18:21), Masami Hiramatsu wrote:
> > Fix to find the correct (as much as possible) line information
> > for listing probes. Without this fix, perf probe --list action
> > will show incorrect line information as below;
> > 
> > # perf probe getname_flags
> > # perf probe -l
> >   probe:getname_flags  (on getname_flags@ksrc/linux-3/fs/namei.c)
> >   probe:getname_flags_1 (on getname:-89@x86/include/asm/current.h)
> >   probe:getname_flags_2 (on user_path_at_empty:-2054@x86/include/asm/current.h)
> > 
> > The minus line number is obviously wrong, and current.h is not
> > related to the probe point. Deeper investigation discovered
> > that there were 2 issues related to this bug, and minor typos too.
> > 
> > 1st issue is the rack of considering about nested inlined
> > functions, which causes the wrong (relative) line number.
> > 2nd issue is that the dwarf line info is not correct at
> > those points. It points 14th line of current.h.
> > 
> > Since it seems that the line info includes somewhat unreliable
> > information, this fixes perf to try to find correct line information
> > from both of debuginfo and line info as below.
> > 
> > 1) Probe address is the entry of a function instance
> >   In this case, the line is set as the function declared line.
> > 
> > 2) Probe address is the entry of an expanded inline function block
> >   In this case, the line is set as the function call-site line.
> >   This means that the line number is relative from the entry line
> >   of caller function (which can be an inlined function if nested)
> > 
> > 3) Probe address is inside a function instance or an expanded
> >    inline function block
> >   In this case, perf probe queries the line number from lineinfo
> >   and verify the function declared file is same as the file name
> >   queried from lineinfo.
> >   If the file name is different, it is a failure case. The probe
> >   address is shown as symbol+offset.
> > 
> > 4) Probe address is not in the any function instance
> >   This is a failure case, the probe address is shown as
> >   symbol+offset.
> > 
> > With this fix, perf probe -l shows correct probe lines as below;
> > 
> > # perf probe -l
> >   probe:getname_flags  (on getname_flags@ksrc/linux-3/fs/namei.c)
> >   probe:getname_flags_1 (on getname:2@ksrc/linux-3/fs/namei.c)
> >   probe:getname_flags_2 (on user_path_at_empty:4@ksrc/linux-3/fs/namei.c)
> > 
> > Changes at v2:
> >  - Fix typos in the function comments. (Thanks to Namhyung Kim)
> >  - Use die_find_top_inlinefunc instead of die_find_inlinefunc_next.
> > 
> > Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> > Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> > Cc: Paul Mackerras <paulus@xxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
> > Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> > ---
> >  tools/perf/util/dwarf-aux.c    |   25 +++++++++++++++++---
> >  tools/perf/util/dwarf-aux.h    |    6 ++++-
> >  tools/perf/util/probe-finder.c |   49 +++++++++++++++++++++++++++-------------
> >  3 files changed, 59 insertions(+), 21 deletions(-)
> > 
> > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> > index e23bde1..7defd77 100644
> > --- a/tools/perf/util/dwarf-aux.c
> > +++ b/tools/perf/util/dwarf-aux.c
> > @@ -426,7 +426,7 @@ static int __die_search_func_cb(Dwarf_Die *fn_die, void *data)
> >   * @die_mem: a buffer for result DIE
> >   *
> >   * Search a non-inlined function DIE which includes @addr. Stores the
> > - * DIE to @die_mem and returns it if found. Returns NULl if failed.
> > + * DIE to @die_mem and returns it if found. Returns NULL if failed.
> >   */
> >  Dwarf_Die *die_find_realfunc(Dwarf_Die *cu_die, Dwarf_Addr addr,
> >  				    Dwarf_Die *die_mem)
> > @@ -454,15 +454,32 @@ static int __die_find_inline_cb(Dwarf_Die *die_mem, void *data)
> >  }
> >  
> >  /**
> > + * die_find_top_inlinefunc - Search the top inlined function at given address
> > + * @sp_die: a subprogram DIE which including @addr
> > + * @addr: target address
> > + * @die_mem: a buffer for result DIE
> > + *
> > + * Search an inlined function DIE which includes @addr. Stores the
> > + * DIE to @die_mem and returns it if found. Returns NULL if failed.
> > + * Even if several inlined functions are expanded recursively, this
> > + * doesn't trace it down, and returns the topmost one.
> > + */
> > +Dwarf_Die *die_find_top_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
> > +				   Dwarf_Die *die_mem)
> > +{
> > +	return die_find_child(sp_die, __die_find_inline_cb, &addr, die_mem);
> > +}
> > +
> > +/**
> >   * die_find_inlinefunc - Search an inlined function at given address
> > - * @cu_die: a CU DIE which including @addr
> > + * @sp_die: a subprogram DIE which including @addr
> >   * @addr: target address
> >   * @die_mem: a buffer for result DIE
> >   *
> >   * Search an inlined function DIE which includes @addr. Stores the
> > - * DIE to @die_mem and returns it if found. Returns NULl if failed.
> > + * DIE to @die_mem and returns it if found. Returns NULL if failed.
> >   * If several inlined functions are expanded recursively, this trace
> > - * it and returns deepest one.
> > + * it down and returns deepest one.
> >   */
> >  Dwarf_Die *die_find_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
> >  			       Dwarf_Die *die_mem)
> > diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
> > index 8658d41..b4fe90c 100644
> > --- a/tools/perf/util/dwarf-aux.h
> > +++ b/tools/perf/util/dwarf-aux.h
> > @@ -79,7 +79,11 @@ extern Dwarf_Die *die_find_child(Dwarf_Die *rt_die,
> >  extern Dwarf_Die *die_find_realfunc(Dwarf_Die *cu_die, Dwarf_Addr addr,
> >  				    Dwarf_Die *die_mem);
> >  
> > -/* Search an inlined function including given address */
> > +/* Search the top inlined function including given address */
> > +extern Dwarf_Die *die_find_top_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
> > +					  Dwarf_Die *die_mem);
> > +
> > +/* Search the deepest inlined function including given address */
> >  extern Dwarf_Die *die_find_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
> >  				      Dwarf_Die *die_mem);
> >  
> > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > index 371476c..c09e0a9 100644
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -1327,8 +1327,8 @@ int debuginfo__find_probe_point(struct debuginfo *self, unsigned long addr,
> >  				struct perf_probe_point *ppt)
> >  {
> >  	Dwarf_Die cudie, spdie, indie;
> > -	Dwarf_Addr _addr, baseaddr;
> > -	const char *fname = NULL, *func = NULL, *tmp;
> > +	Dwarf_Addr _addr = 0, baseaddr = 0;
> > +	const char *fname = NULL, *func = NULL, *basefunc = NULL, *tmp;
> >  	int baseline = 0, lineno = 0, ret = 0;
> >  
> >  	/* Adjust address with bias */
> > @@ -1349,27 +1349,36 @@ int debuginfo__find_probe_point(struct debuginfo *self, unsigned long addr,
> >  	/* Find a corresponding function (name, baseline and baseaddr) */
> >  	if (die_find_realfunc(&cudie, (Dwarf_Addr)addr, &spdie)) {
> >  		/* Get function entry information */
> > -		tmp = dwarf_diename(&spdie);
> > -		if (!tmp ||
> > +		func = basefunc = dwarf_diename(&spdie);
> > +		if (!func ||
> >  		    dwarf_entrypc(&spdie, &baseaddr) != 0 ||
> > -		    dwarf_decl_line(&spdie, &baseline) != 0)
> > +		    dwarf_decl_line(&spdie, &baseline) != 0) {
> > +			lineno = 0;
> >  			goto post;
> > -		func = tmp;
> > +		}
> >  
> > -		if (addr == (unsigned long)baseaddr)
> > +		if (addr == (unsigned long)baseaddr) {
> >  			/* Function entry - Relative line number is 0 */
> >  			lineno = baseline;
> > -		else if (die_find_inlinefunc(&spdie, (Dwarf_Addr)addr,
> > -					     &indie)) {
> > +			fname = dwarf_decl_file(&spdie);
> > +			goto post;
> > +		}
> > +
> > +		/* Track down the inline functions step by step */
> > +		while (die_find_top_inlinefunc(&spdie, (Dwarf_Addr)addr,
> > +						&indie)) {
> > +			/* There is an inline function */
> >  			if (dwarf_entrypc(&indie, &_addr) == 0 &&
> > -			    _addr == addr)
> > +			    _addr == addr) {
> >  				/*
> >  				 * addr is at an inline function entry.
> >  				 * In this case, lineno should be the call-site
> > -				 * line number.
> > +				 * line number. (overwrite lineinfo)
> >  				 */
> >  				lineno = die_get_call_lineno(&indie);
> > -			else {
> > +				fname = die_get_call_file(&indie);
> > +				break;
> > +			} else {
> >  				/*
> >  				 * addr is in an inline function body.
> >  				 * Since lineno points one of the lines
> > @@ -1377,19 +1386,27 @@ int debuginfo__find_probe_point(struct debuginfo *self, unsigned long addr,
> >  				 * be the entry line of the inline function.
> >  				 */
> >  				tmp = dwarf_diename(&indie);
> > -				if (tmp &&
> > -				    dwarf_decl_line(&spdie, &baseline) == 0)
> > -					func = tmp;
> > +				if (!tmp ||
> > +				    dwarf_decl_line(&indie, &baseline) != 0)
> > +					break;
> > +				func = tmp;
> > +				spdie = indie;
> >  			}
> >  		}
> > +		/* Verify the lineno and baseline are in a same file */
> > +		tmp = dwarf_decl_file(&spdie);
> > +		if (!tmp || strcmp(tmp, fname) != 0)
> > +			lineno = 0;
> >  	}
> >  
> >  post:
> >  	/* Make a relative line number or an offset */
> >  	if (lineno)
> >  		ppt->line = lineno - baseline;
> > -	else if (func)
> > +	else if (basefunc) {
> >  		ppt->offset = addr - (unsigned long)baseaddr;
> > +		func = basefunc;
> > +	}
> >  
> >  	/* Duplicate strings */
> >  	if (func) {
> > 
> > 
> > --
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> > 
> 
> 
> -- 
> Masami HIRAMATSU
> IT Management Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
> 
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