perf srcline: Make addr2line configuration failure more verbose

To aid debugging why it fails. Also, combine the loops for reading a
line for the llvm/binutils cases.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Changbin Du <changbin.du@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tom Rix <trix@redhat.com>
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20230613034817.1356114-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/srcline.c

@@ -443,7 +443,7 @@ enum a2l_style {
 	LLVM,
 };
 
-static enum a2l_style addr2line_configure(struct child_process *a2l)
+static enum a2l_style addr2line_configure(struct child_process *a2l, const char *dso_name)
 {
 	static bool cached;
 	static enum a2l_style style;
@@ -452,6 +452,7 @@ static enum a2l_style addr2line_configure(struct child_process *a2l)
 		char buf[128];
 		struct io io;
 		int ch;
+		int lines;
 
 		if (write(a2l->in, ",\n", 2) != 2)
 			return BROKEN;
@@ -461,19 +462,29 @@ static enum a2l_style addr2line_configure(struct child_process *a2l)
 		if (ch == ',') {
 			style = LLVM;
 			cached = true;
+			lines = 1;
 		} else if (ch == '?') {
 			style = GNU_BINUTILS;
 			cached = true;
+			lines = 2;
 		} else {
-			style = BROKEN;
+			if (!symbol_conf.disable_add2line_warn) {
+				char *output = NULL;
+				size_t output_len;
+
+				io__getline(&io, &output, &output_len);
+				pr_warning("%s %s: addr2line configuration failed\n",
+					   __func__, dso_name);
+				pr_warning("\t%c%s", ch, output);
+			}
+			return BROKEN;
 		}
-		do {
+		while (lines) {
 			ch = io__get_char(&io);
-		} while (ch > 0 && ch != '\n');
-		if (style == GNU_BINUTILS) {
-			do {
-				ch = io__get_char(&io);
-			} while (ch > 0 && ch != '\n');
+			if (ch <= 0)
+				break;
+			if (ch == '\n')
+				lines--;
 		}
 		/* Ignore SIGPIPE in the event addr2line exits. */
 		signal(SIGPIPE, SIG_IGN);
@@ -593,12 +604,9 @@ static int addr2line(const char *dso_name, u64 addr,
 			pr_warning("%s %s: addr2line_subprocess_init failed\n", __func__, dso_name);
 		goto out;
 	}
-	a2l_style = addr2line_configure(a2l);
-	if (a2l_style == BROKEN) {
-		if (!symbol_conf.disable_add2line_warn)
-			pr_warning("%s: addr2line configuration failed\n", __func__);
+	a2l_style = addr2line_configure(a2l, dso_name);
+	if (a2l_style == BROKEN)
 		goto out;
-	}
 
 	/*
 	 * Send our request and then *deliberately* send something that can't be interpreted as