objtool: Add option to print section addresses

To help prevent objtool users from having to do math to convert function
addresses to section addresses, and to help out with finding data
addresses reported by IBT validation, add an option to print the section
address in addition to the function address.

Normal:

  vmlinux.o: warning: objtool: fixup_exception()+0x2d1: unreachable instruction

With '--sec-address':

  vmlinux.o: warning: objtool: fixup_exception()+0x2d1 (.text+0x76c51): unreachable instruction

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/2cea4d5299d53d1a4c09212a6ad7820aa46fda7a.1650300597.git.jpoimboe@redhat.com

3 files changed, 19 insertions, 14 deletions

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 8c3eed5b67e4..6acfebd2c6ca 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -50,6 +50,7 @@ const struct option check_options[] = {
 	OPT_BOOLEAN(0, "module", &opts.module, "object is part of a kernel module"),
 	OPT_BOOLEAN(0, "no-fp", &opts.no_fp, "skip frame pointer validation"),
 	OPT_BOOLEAN(0, "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
+	OPT_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
 	OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
 	OPT_BOOLEAN(0, "vmlinux", &opts.vmlinux, "vmlinux.o validation"),
 
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 44548e24473c..e0972fbfa09e 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -28,6 +28,7 @@ struct opts {
 	bool module;
 	bool no_fp;
 	bool no_unreachable;
+	bool sec_address;
 	bool stats;
 	bool vmlinux;
 };
diff --git a/tools/objtool/include/objtool/warn.h b/tools/objtool/include/objtool/warn.h
index c4bde3e2a79c..a3e79ae75f2e 100644
--- a/tools/objtool/include/objtool/warn.h
+++ b/tools/objtool/include/objtool/warn.h
@@ -11,30 +11,33 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <objtool/builtin.h>
 #include <objtool/elf.h>
 
 extern const char *objname;
 
 static inline char *offstr(struct section *sec, unsigned long offset)
 {
-	struct symbol *func;
-	char *name, *str;
-	unsigned long name_off;
+	bool is_text = (sec->sh.sh_flags & SHF_EXECINSTR);
+	struct symbol *sym = NULL;
+	char *str;
+	int len;
 
-	func = find_func_containing(sec, offset);
-	if (!func)
-		func = find_symbol_containing(sec, offset);
-	if (func) {
-		name = func->name;
-		name_off = offset - func->offset;
+	if (is_text)
+		sym = find_func_containing(sec, offset);
+	if (!sym)
+		sym = find_symbol_containing(sec, offset);
+
+	if (sym) {
+		str = malloc(strlen(sym->name) + strlen(sec->name) + 40);
+		len = sprintf(str, "%s+0x%lx", sym->name, offset - sym->offset);
+		if (opts.sec_address)
+			sprintf(str+len, " (%s+0x%lx)", sec->name, offset);
 	} else {
-		name = sec->name;
-		name_off = offset;
+		str = malloc(strlen(sec->name) + 20);
+		sprintf(str, "%s+0x%lx", sec->name, offset);
 	}
 
-	str = malloc(strlen(name) + 20);
-	sprintf(str, "%s+0x%lx", name, name_off);
-
 	return str;
 }