objtool: Skip all "unreachable instruction" warnings for gcov kernels

[cascardo/linux.git] / tools / objtool / builtin-check.c

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index bd09d0e..4490601 100644 (file)
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -97,6 +97,19 @@ static struct instruction *next_insn_same_sec(struct objtool_file *file,
        return next;
 }
 
+static bool gcov_enabled(struct objtool_file *file)
+{
+       struct section *sec;
+       struct symbol *sym;
+
+       list_for_each_entry(sec, &file->elf->sections, list)
+               list_for_each_entry(sym, &sec->symbol_list, list)
+                       if (!strncmp(sym->name, "__gcov_.", 8))
+                               return true;
+
+       return false;
+}
+
 #define for_each_insn(file, insn)                                      \
        list_for_each_entry(insn, &file->insn_list, list)
 
@@ -175,6 +188,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
                "__stack_chk_fail",
                "panic",
                "do_exit",
+               "do_task_dead",
                "__module_put_and_exit",
                "complete_and_exit",
                "kvm_spurious_fault",
@@ -712,6 +726,7 @@ static struct rela *find_switch_table(struct objtool_file *file,
                                      struct instruction *insn)
 {
        struct rela *text_rela, *rodata_rela;
+       struct instruction *orig_insn = insn;
 
        text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
        if (text_rela && text_rela->sym == file->rodata->sym) {
@@ -732,10 +747,16 @@ static struct rela *find_switch_table(struct objtool_file *file,
 
        /* case 3 */
        func_for_each_insn_continue_reverse(file, func, insn) {
-               if (insn->type == INSN_JUMP_UNCONDITIONAL ||
-                   insn->type == INSN_JUMP_DYNAMIC)
+               if (insn->type == INSN_JUMP_DYNAMIC)
                        break;
 
+               /* allow small jumps within the range */
+               if (insn->type == INSN_JUMP_UNCONDITIONAL &&
+                   insn->jump_dest &&
+                   (insn->jump_dest->offset <= insn->offset ||
+                    insn->jump_dest->offset >= orig_insn->offset))
+                   break;
+
                text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
                                                    insn->len);
                if (text_rela && text_rela->sym == file->rodata->sym)
@@ -1033,34 +1054,6 @@ static int validate_branch(struct objtool_file *file,
        return 0;
 }
 
-static bool is_gcov_insn(struct instruction *insn)
-{
-       struct rela *rela;
-       struct section *sec;
-       struct symbol *sym;
-       unsigned long offset;
-
-       rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
-       if (!rela)
-               return false;
-
-       if (rela->sym->type != STT_SECTION)
-               return false;
-
-       sec = rela->sym->sec;
-       offset = rela->addend + insn->offset + insn->len - rela->offset;
-
-       list_for_each_entry(sym, &sec->symbol_list, list) {
-               if (sym->type != STT_OBJECT)
-                       continue;
-
-               if (offset >= sym->offset && offset < sym->offset + sym->len)
-                       return (!memcmp(sym->name, "__gcov0.", 8));
-       }
-
-       return false;
-}
-
 static bool is_kasan_insn(struct instruction *insn)
 {
        return (insn->type == INSN_CALL &&
@@ -1082,9 +1075,6 @@ static bool ignore_unreachable_insn(struct symbol *func,
        if (insn->type == INSN_NOP)
                return true;
 
-       if (is_gcov_insn(insn))
-               return true;
-
        /*
         * Check if this (or a subsequent) instruction is related to
         * CONFIG_UBSAN or CONFIG_KASAN.
@@ -1145,6 +1135,19 @@ static int validate_functions(struct objtool_file *file)
                                    ignore_unreachable_insn(func, insn))
                                        continue;
 
+                               /*
+                                * gcov produces a lot of unreachable
+                                * instructions.  If we get an unreachable
+                                * warning and the file has gcov enabled, just
+                                * ignore it, and all other such warnings for
+                                * the file.
+                                */
+                               if (!file->ignore_unreachables &&
+                                   gcov_enabled(file)) {
+                                       file->ignore_unreachables = true;
+                                       continue;
+                               }
+
                                WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
                                warnings++;
                        }