objtool: Add option to trace function validation

Add an option to trace and have information during the validation
of specified functions. Functions are specified with the --trace
option which can be a single function name (e.g. --trace foo to
trace the function with the name "foo"), or a shell wildcard
pattern (e.g. --trace foo* to trace all functions with a name
starting with "foo").

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-11-alexandre.chartre@oracle.com

5 files changed, 86 insertions, 1 deletions

diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index bb0b25eb08ba..991365c10f0e 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -41,6 +41,7 @@ struct opts {
 	const char *output;
 	bool sec_address;
 	bool stats;
+	const char *trace;
 	bool verbose;
 	bool werror;
 };
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index f96aabd7d54d..fde958683485 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -66,7 +66,8 @@ struct instruction {
 	    visited		: 4,
 	    no_reloc		: 1,
 	    hole		: 1,
-	    fake		: 1;
+	    fake		: 1,
+	    trace		: 1;
 		/* 9 bit hole */
 
 	struct alt_group *alt_group;
@@ -143,4 +144,7 @@ struct instruction *next_insn_same_sec(struct objtool_file *file, struct instruc
 
 const char *objtool_disas_insn(struct instruction *insn);
 
+extern size_t sym_name_max_len;
+extern struct disas_context *objtool_disas_ctx;
+
 #endif /* _CHECK_H */
diff --git a/tools/objtool/include/objtool/disas.h b/tools/objtool/include/objtool/disas.h
index 1aee1fbe0bb9..5db75d06f219 100644
--- a/tools/objtool/include/objtool/disas.h
+++ b/tools/objtool/include/objtool/disas.h
@@ -19,6 +19,11 @@ int disas_info_init(struct disassemble_info *dinfo,
 		    const char *options);
 size_t disas_insn(struct disas_context *dctx, struct instruction *insn);
 char *disas_result(struct disas_context *dctx);
+void disas_print_info(FILE *stream, struct instruction *insn, int depth,
+		      const char *format, ...);
+void disas_print_insn(FILE *stream, struct disas_context *dctx,
+		      struct instruction *insn, int depth,
+		      const char *format, ...);
 
 #else /* DISAS */
 
@@ -51,6 +56,12 @@ static inline char *disas_result(struct disas_context *dctx)
 	return NULL;
 }
 
+static inline void disas_print_info(FILE *stream, struct instruction *insn,
+				    int depth, const char *format, ...) {}
+static inline void disas_print_insn(FILE *stream, struct disas_context *dctx,
+				    struct instruction *insn, int depth,
+				    const char *format, ...) {}
+
 #endif /* DISAS */
 
 #endif /* _DISAS_H */
diff --git a/tools/objtool/include/objtool/trace.h b/tools/objtool/include/objtool/trace.h
new file mode 100644
index 000000000000..3f3c830ed114
--- /dev/null
+++ b/tools/objtool/include/objtool/trace.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates.
+ */
+
+#ifndef _TRACE_H
+#define _TRACE_H
+
+#include <objtool/check.h>
+#include <objtool/disas.h>
+
+#ifdef DISAS
+
+extern bool trace;
+extern int trace_depth;
+
+#define TRACE(fmt, ...)						\
+({	if (trace)						\
+		fprintf(stderr, fmt, ##__VA_ARGS__);		\
+})
+
+#define TRACE_INSN(insn, fmt, ...)				\
+({								\
+	if (trace) {						\
+		disas_print_insn(stderr, objtool_disas_ctx,	\
+				 insn, trace_depth - 1,	\
+				 fmt, ##__VA_ARGS__);		\
+		fprintf(stderr, "\n");				\
+		insn->trace = 1;				\
+	}							\
+})
+
+static inline void trace_enable(void)
+{
+	trace = true;
+	trace_depth = 0;
+}
+
+static inline void trace_disable(void)
+{
+	trace = false;
+}
+
+static inline void trace_depth_inc(void)
+{
+	if (trace)
+		trace_depth++;
+}
+
+static inline void trace_depth_dec(void)
+{
+	if (trace)
+		trace_depth--;
+}
+
+#else /* DISAS */
+
+#define TRACE(fmt, ...) ({})
+#define TRACE_INSN(insn, fmt, ...) ({})
+
+static inline void trace_enable(void) {}
+static inline void trace_disable(void) {}
+static inline void trace_depth_inc(void) {}
+static inline void trace_depth_dec(void) {}
+
+#endif
+
+#endif /* _TRACE_H */
diff --git a/tools/objtool/include/objtool/warn.h b/tools/objtool/include/objtool/warn.h
index f32abc7b1be1..25ff7942b4d5 100644
--- a/tools/objtool/include/objtool/warn.h
+++ b/tools/objtool/include/objtool/warn.h
@@ -97,6 +97,7 @@ static inline char *offstr(struct section *sec, unsigned long offset)
 		_len = (_len < 50) ? 50 - _len : 0;		\
 		WARN("  %s: " format "  %*s%s", _str, ##__VA_ARGS__, _len, "", _istr); \
 		free(_str);						\
+		__insn->trace = 1;				\
 	}							\
 })