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Date: Mon, 07 Oct 2013 12:53:40 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc: Namhyung Kim <namhyung@...nel.org>, Ingo Molnar <mingo@...hat.com>,
Paul Mackerras <paulus@...ba.org>,
lkml <linux-kernel@...r.kernel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH -tip V2] [BUGFIX] perf probe: Fix to find line information
for probe list
Ping? :)
(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@...c/linux-3/fs/namei.c)
> probe:getname_flags_1 (on getname:-89@.../include/asm/current.h)
> probe:getname_flags_2 (on user_path_at_empty:-2054@.../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@...c/linux-3/fs/namei.c)
> probe:getname_flags_1 (on getname:2@...c/linux-3/fs/namei.c)
> probe:getname_flags_2 (on user_path_at_empty:4@...c/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@...achi.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
> Cc: Namhyung Kim <namhyung@...nel.org>
> ---
> 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@...achi.com
--
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