Message-Id: <1472546377-25612-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com>
Date:   Tue, 30 Aug 2016 14:09:37 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:     acme@...nel.org, mhiramat@...nel.org
Cc:     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,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: [PATCH v2] perf probe: Move dwarf specific functions to dwarf-aux.c

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.

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

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