objtool: Print addresses with alternative instructions

All alternatives are disassemble side-by-side when using the --disas
option. However the address of each instruction is not printed because
instructions from different alternatives are not necessarily aligned.

Change this behavior to print the address of each instruction. Spaces
will appear between instructions from the same alternative when
instructions from different alternatives do not have the same alignment.

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/20251121095340.464045-22-alexandre.chartre@oracle.com

Author: achartre

tools/objtool/disas.c

@@ -47,7 +47,11 @@ struct disas_alt {
 	struct alternative *alt;		/* alternative or NULL if default code */
 	char *name;				/* name for this alternative */
 	int width;				/* formatting width */
-	char *insn[DISAS_ALT_INSN_MAX];		/* alternative instructions */
+	struct {
+		char *str;			/* instruction string */
+		int offset;			/* instruction offset */
+	} insn[DISAS_ALT_INSN_MAX];		/* alternative instructions */
+	int insn_idx;				/* index of the next instruction to print */
 };
 
 #define DALT_DEFAULT(dalt)	(!(dalt)->alt)
@@ -361,10 +365,9 @@ char *disas_result(struct disas_context *dctx)
 	disas_print_insn(stdout, dctx, insn, depth, "\n")
 
 /*
- * Print a message in the instruction flow. If insn is not NULL then
- * the instruction address is printed in addition of the message,
- * otherwise only the message is printed. In all cases, the instruction
- * itself is not printed.
+ * Print a message in the instruction flow. If sec is not NULL then the
+ * address at the section offset is printed in addition of the message,
+ * otherwise only the message is printed.
  */
 static int disas_vprint(FILE *stream, struct section *sec, unsigned long offset,
 			int depth, const char *format, va_list ap)
@@ -607,6 +610,7 @@ static int disas_alt_init(struct disas_alt *dalt,
 {
 	dalt->orig_insn = orig_insn;
 	dalt->alt = alt;
+	dalt->insn_idx = 0;
 	dalt->name = alt ? disas_alt_name(alt) : strdup("DEFAULT");
 	if (!dalt->name)
 		return -1;
@@ -615,7 +619,8 @@ static int disas_alt_init(struct disas_alt *dalt,
 	return 0;
 }
 
-static int disas_alt_add_insn(struct disas_alt *dalt, int index, char *insn_str)
+static int disas_alt_add_insn(struct disas_alt *dalt, int index, char *insn_str,
+			      int offset)
 {
 	int len;
 
@@ -626,7 +631,8 @@ static int disas_alt_add_insn(struct disas_alt *dalt, int index, char *insn_str)
 	}
 
 	len = strlen(insn_str);
-	dalt->insn[index] = insn_str;
+	dalt->insn[index].str = insn_str;
+	dalt->insn[index].offset = offset;
 	if (len > dalt->width)
 		dalt->width = len;
 
@@ -641,12 +647,14 @@ static int disas_alt_group(struct disas_context *dctx, struct disas_alt *dalt)
 {
 	struct objtool_file *file;
 	struct instruction *insn;
+	int offset;
 	char *str;
 	int count;
 	int err;
 
 	file = dctx->file;
 	count = 0;
+	offset = 0;
 
 	alt_for_each_insn(file, DALT_GROUP(dalt), insn) {
 
@@ -655,9 +663,10 @@ static int disas_alt_group(struct disas_context *dctx, struct disas_alt *dalt)
 		if (!str)
 			return -1;
 
-		err = disas_alt_add_insn(dalt, count, str);
+		err = disas_alt_add_insn(dalt, count, str, offset);
 		if (err)
 			break;
+		offset += insn->len;
 		count++;
 	}
 
@@ -685,7 +694,7 @@ static int disas_alt_default(struct disas_context *dctx, struct disas_alt *dalt)
 	str = strdup(disas_result(dctx));
 	if (!str)
 		return -1;
-	err = disas_alt_add_insn(dalt, 0, str);
+	err = disas_alt_add_insn(dalt, 0, str, 0);
 	if (err)
 		return -1;
 
@@ -710,9 +719,11 @@ static void disas_alt_print_compact(char *alt_name, struct disas_alt *dalts,
 	for (i = 0; i < alt_count; i++) {
 		printf("%*s= %s\n", len, "", dalts[i].name);
 		for (j = 0; j < insn_count; j++) {
-			if (!dalts[i].insn[j])
+			if (!dalts[i].insn[j].str)
 				break;
-			printf("%*s| %s\n", len, "", dalts[i].insn[j]);
+			disas_print(stdout, orig_insn->sec,
+				    orig_insn->offset + dalts[i].insn[j].offset, 0,
+				    "| %s\n", dalts[i].insn[j].str);
 		}
 		printf("%*s|\n", len, "");
 	}
@@ -811,7 +822,7 @@ static void *disas_alt(struct disas_context *dctx,
 	for (i = 0; i < alt_count; i++) {
 		free(dalts[i].name);
 		for (j = 0; j < insn_count; j++)
-			free(dalts[i].insn[j]);
+			free(dalts[i].insn[j].str);
 	}
 
 	free(alt_name);