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Date: Tue, 30 Aug 2016 23:10:34 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Cc: acme@...nel.org, linux-kernel@...r.kernel.org,
peterz@...radead.org, mingo@...hat.com,
alexander.shishkin@...ux.intel.com, wangnan0@...wei.com,
hemant@...ux.vnet.ibm.com, naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [PATCH v2] perf probe: Move dwarf specific functions to
dwarf-aux.c
On Tue, 30 Aug 2016 14:09:37 +0530
Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com> wrote:
> Move generic dwarf related functions from util/probe-finder.c to
> util/dwarf-aux.c. Functions name and their prototype are also
> changed accordingly. No functionality changes.
Great!
Looks good to me :)
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
Thanks!
>
> Suggested-by: Masami Hiramatsu <mhiramat@...nel.org>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
> ---
> Changes in v2:
> - Add comments about functions prototype and their usage
> - Replace function parameter names with more generic names
>
> tools/perf/util/dwarf-aux.c | 179 +++++++++++++++++++++++++++++++++++++++++
> tools/perf/util/dwarf-aux.h | 8 ++
> tools/perf/util/probe-finder.c | 136 +------------------------------
> 3 files changed, 189 insertions(+), 134 deletions(-)
>
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index a347b19..faec899 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -1085,3 +1085,182 @@ int die_get_var_range(Dwarf_Die *sp_die __maybe_unused,
> return -ENOTSUP;
> }
> #endif
> +
> +/*
> + * die_has_loclist - Check if DW_AT_location of @vr_die is a location list
> + * @vr_die: a variable DIE
> + */
> +static bool die_has_loclist(Dwarf_Die *vr_die)
> +{
> + Dwarf_Attribute loc;
> + int tag = dwarf_tag(vr_die);
> +
> + if (tag != DW_TAG_formal_parameter &&
> + tag != DW_TAG_variable)
> + return false;
> +
> + return (dwarf_attr_integrate(vr_die, DW_AT_location, &loc) &&
> + dwarf_whatform(&loc) == DW_FORM_sec_offset);
> +}
> +
> +/*
> + * die_is_optimized_target - Check if target program is compiled with
> + * optimization
> + * @cu_die: a CU DIE
> + *
> + * For any object in given CU whose DW_AT_location is a location list,
> + * target program is compiled with optimization. This is applicable to
> + * clang as well.
> + */
> +bool die_is_optimized_target(Dwarf_Die *cu_die)
> +{
> + Dwarf_Die tmp_die;
> +
> + if (die_has_loclist(cu_die))
> + return true;
> +
> + if (!dwarf_child(cu_die, &tmp_die) &&
> + die_is_optimized_target(&tmp_die))
> + return true;
> +
> + if (!dwarf_siblingof(cu_die, &tmp_die) &&
> + die_is_optimized_target(&tmp_die))
> + return true;
> +
> + return false;
> +}
> +
> +/*
> + * die_search_idx - Search index of given line address
> + * @lines: Line records of single CU
> + * @nr_lines: Number of @lines
> + * @addr: address we are looking for
> + * @idx: index to be set by this function (return value)
> + *
> + * Search for @addr by looping over every lines of CU. If address
> + * matches, set index of that line in @idx. Note that single source
> + * line can have multiple line records. i.e. single source line can
> + * have multiple index.
> + */
> +static bool die_search_idx(Dwarf_Lines *lines, unsigned long nr_lines,
> + Dwarf_Addr addr, unsigned long *idx)
> +{
> + unsigned long i;
> + Dwarf_Addr tmp;
> +
> + for (i = 0; i < nr_lines; i++) {
> + if (dwarf_lineaddr(dwarf_onesrcline(lines, i), &tmp))
> + return false;
> +
> + if (tmp == addr) {
> + *idx = i;
> + return true;
> + }
> + }
> + return false;
> +}
> +
> +/*
> + * die_get_postprologue_addr - Search next address after function prologue
> + * @entrypc_idx: entrypc index
> + * @lines: Line records of single CU
> + * @nr_lines: Number of @lines
> + * @hignpc: high PC address of function
> + * @postprologue_addr: Next address after function prologue (return value)
> + *
> + * Look for prologue-end marker. If there is no explicit marker, return
> + * address of next line record or next source line.
> + */
> +static bool die_get_postprologue_addr(unsigned long entrypc_idx,
> + Dwarf_Lines *lines,
> + unsigned long nr_lines,
> + Dwarf_Addr highpc,
> + Dwarf_Addr *postprologue_addr)
> +{
> + unsigned long i;
> + int entrypc_lno, lno;
> + Dwarf_Line *line;
> + Dwarf_Addr addr;
> + bool p_end;
> +
> + /* entrypc_lno is actual source line number */
> + line = dwarf_onesrcline(lines, entrypc_idx);
> + if (dwarf_lineno(line, &entrypc_lno))
> + return false;
> +
> + for (i = entrypc_idx; i < nr_lines; i++) {
> + line = dwarf_onesrcline(lines, i);
> +
> + if (dwarf_lineaddr(line, &addr) ||
> + dwarf_lineno(line, &lno) ||
> + dwarf_lineprologueend(line, &p_end))
> + return false;
> +
> + /* highpc is exclusive. [entrypc,highpc) */
> + if (addr >= highpc)
> + break;
> +
> + /* clang supports prologue-end marker */
> + if (p_end)
> + break;
> +
> + /* Actual next line in source */
> + if (lno != entrypc_lno)
> + break;
> +
> + /*
> + * Single source line can have multiple line records.
> + * For Example,
> + * void foo() { printf("hello\n"); }
> + * contains two line records. One points to declaration and
> + * other points to printf() line. Variable 'lno' won't get
> + * incremented in this case but 'i' will.
> + */
> + if (i != entrypc_idx)
> + break;
> + }
> +
> + dwarf_lineaddr(line, postprologue_addr);
> + if (*postprologue_addr >= highpc)
> + dwarf_lineaddr(dwarf_onesrcline(lines, i - 1),
> + postprologue_addr);
> +
> + return true;
> +}
> +
> +/*
> + * die_skip_prologue - Use next address after prologue as probe location
> + * @sp_die: a subprogram DIE
> + * @cu_die: a CU DIE
> + * @entrypc: entrypc of the function
> + *
> + * Function prologue prepares stack and registers before executing function
> + * logic. When target program is compiled without optimization, function
> + * parameter information is only valid after prologue. When we probe entrypc
> + * of the function, and try to record function parameter, it contains
> + * garbage value.
> + */
> +void die_skip_prologue(Dwarf_Die *sp_die, Dwarf_Die *cu_die,
> + Dwarf_Addr *entrypc)
> +{
> + size_t nr_lines = 0;
> + unsigned long entrypc_idx = 0;
> + Dwarf_Lines *lines = NULL;
> + Dwarf_Addr postprologue_addr;
> + Dwarf_Addr highpc;
> +
> + if (dwarf_highpc(sp_die, &highpc))
> + return;
> +
> + if (dwarf_getsrclines(cu_die, &lines, &nr_lines))
> + return;
> +
> + if (!die_search_idx(lines, nr_lines, *entrypc, &entrypc_idx))
> + return;
> +
> + if (!die_get_postprologue_addr(entrypc_idx, lines, nr_lines,
> + highpc, &postprologue_addr))
> + return;
> +
> + *entrypc = postprologue_addr;
> +}
> diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
> index dc0ce1a..8b6d2f8 100644
> --- a/tools/perf/util/dwarf-aux.h
> +++ b/tools/perf/util/dwarf-aux.h
> @@ -125,4 +125,12 @@ int die_get_typename(Dwarf_Die *vr_die, struct strbuf *buf);
> /* Get the name and type of given variable DIE, stored as "type\tname" */
> int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf);
> int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf);
> +
> +/* Check if target program is compiled with optimization */
> +bool die_is_optimized_target(Dwarf_Die *cu_die);
> +
> +/* Use next address after prologue as probe location */
> +void die_skip_prologue(Dwarf_Die *sp_die, Dwarf_Die *cu_die,
> + Dwarf_Addr *entrypc);
> +
> #endif
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 945cf7a..72f1152 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -901,138 +901,6 @@ static int find_probe_point_lazy(Dwarf_Die *sp_die, struct probe_finder *pf)
> return die_walk_lines(sp_die, probe_point_lazy_walker, pf);
> }
>
> -static bool var_has_loclist(Dwarf_Die *cu_die)
> -{
> - Dwarf_Attribute loc;
> - int tag = dwarf_tag(cu_die);
> -
> - if (tag != DW_TAG_formal_parameter &&
> - tag != DW_TAG_variable)
> - return false;
> -
> - return (dwarf_attr_integrate(cu_die, DW_AT_location, &loc) &&
> - dwarf_whatform(&loc) == DW_FORM_sec_offset);
> -}
> -
> -/*
> - * For any object in given CU whose DW_AT_location is a location list,
> - * target program is compiled with optimization.
> - */
> -static bool optimized_target(Dwarf_Die *cu_die)
> -{
> - Dwarf_Die tmp_die;
> -
> - if (var_has_loclist(cu_die))
> - return true;
> -
> - if (!dwarf_child(cu_die, &tmp_die) && optimized_target(&tmp_die))
> - return true;
> -
> - if (!dwarf_siblingof(cu_die, &tmp_die) && optimized_target(&tmp_die))
> - return true;
> -
> - return false;
> -}
> -
> -static bool get_entrypc_idx(Dwarf_Lines *lines, unsigned long nr_lines,
> - Dwarf_Addr pf_addr, unsigned long *entrypc_idx)
> -{
> - unsigned long i;
> - Dwarf_Addr addr;
> -
> - for (i = 0; i < nr_lines; i++) {
> - if (dwarf_lineaddr(dwarf_onesrcline(lines, i), &addr))
> - return false;
> -
> - if (addr == pf_addr) {
> - *entrypc_idx = i;
> - return true;
> - }
> - }
> - return false;
> -}
> -
> -static bool get_postprologue_addr(unsigned long entrypc_idx,
> - Dwarf_Lines *lines,
> - unsigned long nr_lines,
> - Dwarf_Addr highpc,
> - Dwarf_Addr *postprologue_addr)
> -{
> - unsigned long i;
> - int entrypc_lno, lno;
> - Dwarf_Line *line;
> - Dwarf_Addr addr;
> - bool p_end;
> -
> - /* entrypc_lno is actual source line number */
> - line = dwarf_onesrcline(lines, entrypc_idx);
> - if (dwarf_lineno(line, &entrypc_lno))
> - return false;
> -
> - for (i = entrypc_idx; i < nr_lines; i++) {
> - line = dwarf_onesrcline(lines, i);
> -
> - if (dwarf_lineaddr(line, &addr) ||
> - dwarf_lineno(line, &lno) ||
> - dwarf_lineprologueend(line, &p_end))
> - return false;
> -
> - /* highpc is exclusive. [entrypc,highpc) */
> - if (addr >= highpc)
> - break;
> -
> - /* clang supports prologue-end marker */
> - if (p_end)
> - break;
> -
> - /* Actual next line in source */
> - if (lno != entrypc_lno)
> - break;
> -
> - /*
> - * Single source line can have multiple line records.
> - * For Example,
> - * void foo() { printf("hello\n"); }
> - * contains two line records. One points to declaration and
> - * other points to printf() line. Variable 'lno' won't get
> - * incremented in this case but 'i' will.
> - */
> - if (i != entrypc_idx)
> - break;
> - }
> -
> - dwarf_lineaddr(line, postprologue_addr);
> - if (*postprologue_addr >= highpc)
> - dwarf_lineaddr(dwarf_onesrcline(lines, i - 1),
> - postprologue_addr);
> -
> - return true;
> -}
> -
> -static void __skip_prologue(Dwarf_Die *sp_die, struct probe_finder *pf)
> -{
> - size_t nr_lines = 0;
> - unsigned long entrypc_idx = 0;
> - Dwarf_Lines *lines = NULL;
> - Dwarf_Addr postprologue_addr;
> - Dwarf_Addr highpc;
> -
> - if (dwarf_highpc(sp_die, &highpc))
> - return;
> -
> - if (dwarf_getsrclines(&pf->cu_die, &lines, &nr_lines))
> - return;
> -
> - if (!get_entrypc_idx(lines, nr_lines, pf->addr, &entrypc_idx))
> - return;
> -
> - if (!get_postprologue_addr(entrypc_idx, lines, nr_lines,
> - highpc, &postprologue_addr))
> - return;
> -
> - pf->addr = postprologue_addr;
> -}
> -
> static void skip_prologue(Dwarf_Die *sp_die, struct probe_finder *pf)
> {
> struct perf_probe_point *pp = &pf->pev->point;
> @@ -1042,7 +910,7 @@ static void skip_prologue(Dwarf_Die *sp_die, struct probe_finder *pf)
> return;
>
> /* Compiled with optimization? */
> - if (optimized_target(&pf->cu_die))
> + if (die_is_optimized_target(&pf->cu_die))
> return;
>
> /* Don't know entrypc? */
> @@ -1062,7 +930,7 @@ static void skip_prologue(Dwarf_Die *sp_die, struct probe_finder *pf)
> "Probe on address 0x%" PRIx64 " to force probing at the function entry.\n\n",
> pf->addr);
>
> - __skip_prologue(sp_die, pf);
> + die_skip_prologue(sp_die, &pf->cu_die, &pf->addr);
> }
>
> static int probe_point_inline_cb(Dwarf_Die *in_die, void *data)
> --
> 2.5.5
>
--
Masami Hiramatsu <mhiramat@...nel.org>
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