objtool: Limit unreachable warnings to once per function

Unreachable instruction warnings are limited to once per object file.
That no longer makes sense for vmlinux validation, which might have
more unreachable instructions lurking in other places.  Change it to
once per function.

Note this affects some other (much rarer) non-fatal warnings as well.
In general I think one-warning-per-function makes sense, as related
warnings can accumulate quickly and we want to eventually get back to
failing the build with -Werror anyway.

Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/9d38f881bfc34e031c74e4e90064ccb3e49f599a.1681853186.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0fcf99c914000b43bfde600f32c4cea15453eb68..98e6c3b5fefc1e98094c051805ac0a92d4031602 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4514,6 +4514,7 @@ static int validate_sls(struct objtool_file *file)
 static int validate_reachable_instructions(struct objtool_file *file)
 {
        struct instruction *insn;
+       int warnings = 0;
 
        if (file->ignore_unreachables)
                return 0;
@@ -4523,10 +4524,10 @@ static int validate_reachable_instructions(struct objtool_file *file)
                        continue;
 
                WARN_INSN(insn, "unreachable instruction");
-               return 1;
+               warnings++;
        }
 
-       return 0;
+       return warnings;
 }
 
 int check(struct objtool_file *file)

diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index e1ca588eb69d15d62d2486f5d8dec7549efdc8ab..78e2d0fc21ca4234ce7fa7e071987b335da8e090 100644 (file)
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -61,6 +61,7 @@ struct symbol {
        u8 return_thunk      : 1;
        u8 fentry            : 1;
        u8 profiling_func    : 1;
+       u8 warned            : 1;
        struct list_head pv_target;
        struct list_head reloc_list;
 };

diff --git a/tools/objtool/include/objtool/warn.h b/tools/objtool/include/objtool/warn.h
index b1c920dc9516c97206170da148577e4cd0c46867..f195deab456e44edf95334a3c84d22f9bb863f5a 100644 (file)
--- a/tools/objtool/include/objtool/warn.h
+++ b/tools/objtool/include/objtool/warn.h
@@ -55,7 +55,12 @@ static inline char *offstr(struct section *sec, unsigned long offset)
 
 #define WARN_INSN(insn, format, ...)                                   \
 ({                                                                     \
-       WARN_FUNC(format, insn->sec, insn->offset,  ##__VA_ARGS__);     \
+       struct instruction *_insn = (insn);                             \
+       if (!_insn->sym || !_insn->sym->warned)                         \
+               WARN_FUNC(format, _insn->sec, _insn->offset,            \
+                         ##__VA_ARGS__);                               \
+       if (_insn->sym)                                                 \
+               _insn->sym->warned = 1;                                 \
 })
 
 #define BT_FUNC(format, insn, ...)                     \