linux-kernel - [PATCH] objtool: Refactor insn search in add_dead

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Date:   Mon, 23 Oct 2017 10:31:08 +0530
From:   Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: [PATCH] objtool: Refactor insn search in add_dead_ends()

Move the search for instruction dead_end into helper function
__add_dead_ends(), instead of duplicating the search for unreachable
and reachable sections in add_dead_ends().

Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
---
 tools/objtool/check.c | 108 +++++++++++++++++++++++---------------------------
 1 file changed, 50 insertions(+), 58 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index c0e26ad1fa7e..c82966b3ad96 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -303,36 +303,23 @@ static int decode_instructions(struct objtool_file *file)
 	return ret;
 }
 
-/*
- * Mark "ud2" instructions and manually annotated dead ends.
- */
-static int add_dead_ends(struct objtool_file *file)
+static int __add_dead_ends(struct objtool_file *file, struct section *sec,
+			   bool unreachable_sec)
 {
-	struct section *sec;
-	struct rela *rela;
+	char warn_str[12] = "unreachable";
 	struct instruction *insn;
+	struct rela *rela;
 	bool found;
 
-	/*
-	 * By default, "ud2" is a dead end unless otherwise annotated, because
-	 * GCC 7 inserts it for certain divide-by-zero cases.
-	 */
-	for_each_insn(file, insn)
-		if (insn->type == INSN_BUG)
-			insn->dead_end = true;
-
-	/*
-	 * Check for manually annotated dead ends.
-	 */
-	sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
-	if (!sec)
-		goto reachable;
+	if (!unreachable_sec)
+		strcpy(warn_str, "reachable");
 
 	list_for_each_entry(rela, &sec->rela_list, list) {
 		if (rela->sym->type != STT_SECTION) {
-			WARN("unexpected relocation symbol type in %s", sec->name);
+			WARN("Unexpected relocation symbol type in %s",	sec->name);
 			return -1;
 		}
+
 		insn = find_insn(file, rela->sym->sec, rela->addend);
 		if (insn)
 			insn = list_prev_entry(insn, list);
@@ -346,19 +333,54 @@ static int add_dead_ends(struct objtool_file *file)
 			}
 
 			if (!found) {
-				WARN("can't find unreachable insn at %s+0x%x",
-				     rela->sym->sec->name, rela->addend);
+				WARN("can't find %s insn at %s+0x%x",
+					warn_str, rela->sym->sec->name,
+						rela->addend);
 				return -1;
 			}
 		} else {
-			WARN("can't find unreachable insn at %s+0x%x",
-			     rela->sym->sec->name, rela->addend);
+			WARN("can't find %s insn at %s+0x%x",
+				warn_str, rela->sym->sec->name, rela->addend);
 			return -1;
 		}
 
-		insn->dead_end = true;
+		/*
+		 * reachable section's insn->dead_end are false.
+		 */
+		insn->dead_end = unreachable_sec;
 	}
 
+	return 0;
+}
+
+/*
+ * Mark "ud2" instructions and manually annotated dead ends.
+ */
+static int add_dead_ends(struct objtool_file *file)
+{
+	struct section *sec;
+	struct instruction *insn;
+	int ret;
+
+	/*
+	 * By default, "ud2" is a dead end unless otherwise annotated, because
+	 * GCC 7 inserts it for certain divide-by-zero cases.
+	 */
+	for_each_insn(file, insn)
+		if (insn->type == INSN_BUG)
+			insn->dead_end = true;
+
+	/*
+	 * Check for manually annotated dead ends.
+	 */
+	sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
+	if (!sec)
+		goto reachable;
+
+	ret = __add_dead_ends(file, sec, true);
+	if (ret == -1)
+		return ret;
+
 reachable:
 	/*
 	 * These manually annotated reachable checks are needed for GCC 4.4,
@@ -370,38 +392,8 @@ static int add_dead_ends(struct objtool_file *file)
 	if (!sec)
 		return 0;
 
-	list_for_each_entry(rela, &sec->rela_list, list) {
-		if (rela->sym->type != STT_SECTION) {
-			WARN("unexpected relocation symbol type in %s", sec->name);
-			return -1;
-		}
-		insn = find_insn(file, rela->sym->sec, rela->addend);
-		if (insn)
-			insn = list_prev_entry(insn, list);
-		else if (rela->addend == rela->sym->sec->len) {
-			found = false;
-			list_for_each_entry_reverse(insn, &file->insn_list, list) {
-				if (insn->sec == rela->sym->sec) {
-					found = true;
-					break;
-				}
-			}
-
-			if (!found) {
-				WARN("can't find reachable insn at %s+0x%x",
-				     rela->sym->sec->name, rela->addend);
-				return -1;
-			}
-		} else {
-			WARN("can't find reachable insn at %s+0x%x",
-			     rela->sym->sec->name, rela->addend);
-			return -1;
-		}
-
-		insn->dead_end = false;
-	}
-
-	return 0;
+	ret = __add_dead_ends(file, sec, false);
+	return ret;
 }
 
 /*
-- 
2.7.4