[PATCH v5 13/14] perf: Re-Add make_absolute_path

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

revert_make_absolute_path.patch

From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

perf probe for uprobes would use make_absolute_path.
make_absolute_path can be used to convert a file name to a dso name.

so if user specifies the function to be traced as malloc@/lib/libc.so.6
it needs to be converted to malloc@libc-2.5.so

This patch reverts a part of a41794cdd7ee94a5199e14f642c26d649d383fa5
---

 tools/perf/util/abspath.c |   81 +++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/cache.h   |    1 +
 2 files changed, 82 insertions(+), 0 deletions(-)


diff --git a/tools/perf/util/abspath.c b/tools/perf/util/abspath.c
index 0e76aff..a791dd4 100644
--- a/tools/perf/util/abspath.c
+++ b/tools/perf/util/abspath.c
@@ -1,5 +1,86 @@
 #include "cache.h"
 
+/*
+ * Do not use this for inspecting *tracked* content.  When path is a
+ * symlink to a directory, we do not want to say it is a directory when
+ * dealing with tracked content in the working tree.
+ */
+static int is_directory(const char *path)
+{
+	struct stat st;
+	return (!stat(path, &st) && S_ISDIR(st.st_mode));
+}
+
+/* We allow "recursive" symbolic links. Only within reason, though. */
+#define MAXDEPTH 5
+
+const char *make_absolute_path(const char *path)
+{
+	static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1];
+	char cwd[1024] = "";
+	int buf_index = 1, len;
+
+	int depth = MAXDEPTH;
+	char *last_elem = NULL;
+	struct stat st;
+
+	if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
+		die ("Too long path: %.*s", 60, path);
+
+	while (depth--) {
+		if (!is_directory(buf)) {
+			char *last_slash = strrchr(buf, '/');
+			if (last_slash) {
+				*last_slash = '\0';
+				last_elem = xstrdup(last_slash + 1);
+			} else {
+				last_elem = xstrdup(buf);
+				*buf = '\0';
+			}
+		}
+
+		if (*buf) {
+			if (!*cwd && !getcwd(cwd, sizeof(cwd)))
+				die ("Could not get current working directory");
+
+			if (chdir(buf))
+				die ("Could not switch to '%s'", buf);
+		}
+		if (!getcwd(buf, PATH_MAX))
+			die ("Could not get current working directory");
+
+		if (last_elem) {
+			len = strlen(buf);
+
+			if (len + strlen(last_elem) + 2 > PATH_MAX)
+				die ("Too long path name: '%s/%s'",
+						buf, last_elem);
+			buf[len] = '/';
+			strcpy(buf + len + 1, last_elem);
+			free(last_elem);
+			last_elem = NULL;
+		}
+
+		if (!lstat(buf, &st) && S_ISLNK(st.st_mode)) {
+			len = readlink(buf, next_buf, PATH_MAX);
+			if (len < 0)
+				die ("Invalid symlink: %s", buf);
+			if (PATH_MAX <= len)
+				die("symbolic link too long: %s", buf);
+			next_buf[len] = '\0';
+			buf = next_buf;
+			buf_index = 1 - buf_index;
+			next_buf = bufs[buf_index];
+		} else
+			break;
+	}
+
+	if (*cwd && chdir(cwd))
+		die ("Could not change back to '%s'", cwd);
+
+	return buf;
+}
+
 static const char *get_pwd_cwd(void)
 {
 	static char cwd[PATH_MAX + 1];
diff --git a/tools/perf/util/cache.h b/tools/perf/util/cache.h
index 27e9ebe..0dfed40 100644
--- a/tools/perf/util/cache.h
+++ b/tools/perf/util/cache.h
@@ -73,6 +73,7 @@ static inline int is_absolute_path(const char *path)
 	return path[0] == '/';
 }
 
+const char *make_absolute_path(const char *path);
 const char *make_nonrelative_path(const char *path);
 char *strip_path_suffix(const char *path, const char *suffix);