objtool: Only print one warning per function

When objtool discovers an issue, it's very common for it to flood the
terminal with a lot of duplicate warnings.  For example:

  warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
  warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
  warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
  warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
  ...

The first warning is usually all you need.  Change it to only warn once
per function.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/c47f3ca38aa01e2a9b6601f9e38efd414c3f3c18.1457502970.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 25 insertions, 23 deletions

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index bfeee227aaab..7515cb2e879a 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -800,7 +800,7 @@ static int validate_branch(struct objtool_file *file,
         struct instruction *insn;
         struct section *sec;
         unsigned char state;
-        int ret, warnings = 0;
+        int ret;
 
         insn = first;
         sec = insn->sec;
@@ -809,7 +809,7 @@ static int validate_branch(struct objtool_file *file,
         if (insn->alt_group && list_empty(&insn->alts)) {
                 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
                           sec, insn->offset);
-                warnings++;
+                return 1;
         }
 
         while (1) {
@@ -817,10 +817,10 @@ static int validate_branch(struct objtool_file *file,
                         if (frame_state(insn->state) != frame_state(state)) {
                                 WARN_FUNC("frame pointer state mismatch",
                                           sec, insn->offset);
-                                warnings++;
+                                return 1;
                         }
 
-                        return warnings;
+                        return 0;
                 }
 
                 /*
@@ -828,14 +828,15 @@ static int validate_branch(struct objtool_file *file,
                  * the next function.
                  */
                 if (is_fentry_call(insn) && (state & STATE_FENTRY))
-                        return warnings;
+                        return 0;
 
                 insn->visited = true;
                 insn->state = state;
 
                 list_for_each_entry(alt, &insn->alts, list) {
                         ret = validate_branch(file, alt->insn, state);
-                        warnings += ret;
+                        if (ret)
+                                return 1;
                 }
 
                 switch (insn->type) {
@@ -845,7 +846,7 @@ static int validate_branch(struct objtool_file *file,
                                 if (state & STATE_FP_SAVED) {
                                         WARN_FUNC("duplicate frame pointer save",
                                                   sec, insn->offset);
-                                        warnings++;
+                                        return 1;
                                 }
                                 state |= STATE_FP_SAVED;
                         }
@@ -856,7 +857,7 @@ static int validate_branch(struct objtool_file *file,
                                 if (state & STATE_FP_SETUP) {
                                         WARN_FUNC("duplicate frame pointer setup",
                                                   sec, insn->offset);
-                                        warnings++;
+                                        return 1;
                                 }
                                 state |= STATE_FP_SETUP;
                         }
@@ -875,9 +876,9 @@ static int validate_branch(struct objtool_file *file,
                         if (!nofp && has_modified_stack_frame(insn)) {
                                 WARN_FUNC("return without frame pointer restore",
                                           sec, insn->offset);
-                                warnings++;
+                                return 1;
                         }
-                        return warnings;
+                        return 0;
 
                 case INSN_CALL:
                         if (is_fentry_call(insn)) {
@@ -887,16 +888,16 @@ static int validate_branch(struct objtool_file *file,
 
                         ret = dead_end_function(file, insn->call_dest);
                         if (ret == 1)
-                                return warnings;
+                                return 0;
                         if (ret == -1)
-                                warnings++;
+                                return 1;
 
                         /* fallthrough */
                 case INSN_CALL_DYNAMIC:
                         if (!nofp && !has_valid_stack_frame(insn)) {
                                 WARN_FUNC("call without frame pointer save/setup",
                                           sec, insn->offset);
-                                warnings++;
+                                return 1;
                         }
                         break;
 
@@ -905,15 +906,16 @@ static int validate_branch(struct objtool_file *file,
                         if (insn->jump_dest) {
                                 ret = validate_branch(file, insn->jump_dest,
                                                       state);
-                                warnings += ret;
+                                if (ret)
+                                        return 1;
                         } else if (has_modified_stack_frame(insn)) {
                                 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
                                           sec, insn->offset);
-                                warnings++;
+                                return 1;
                         } /* else it's a sibling call */
 
                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
-                                return warnings;
+                                return 0;
 
                         break;
 
@@ -922,13 +924,13 @@ static int validate_branch(struct objtool_file *file,
                             has_modified_stack_frame(insn)) {
                                 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
                                           sec, insn->offset);
-                                warnings++;
+                                return 1;
                         }
 
-                        return warnings;
+                        return 0;
 
                 case INSN_BUG:
-                        return warnings;
+                        return 0;
 
                 default:
                         break;
@@ -937,12 +939,11 @@ static int validate_branch(struct objtool_file *file,
                 insn = next_insn_same_sec(file, insn);
                 if (!insn) {
                         WARN("%s: unexpected end of section", sec->name);
-                        warnings++;
-                        return warnings;
+                        return 1;
                 }
         }
 
-        return warnings;
+        return 0;
 }
 
 static bool is_gcov_insn(struct instruction *insn)
@@ -1055,7 +1056,8 @@ static int validate_functions(struct objtool_file *file)
                                 if (insn->visited)
                                         continue;
 
-                                if (!ignore_unreachable_insn(func, insn)) {
+                                if (!ignore_unreachable_insn(func, insn) &&
+                                    !warnings) {
                                         WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
                                         warnings++;
                                 }