From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Wed, 6 Mar 2013 17:24:34 +0000 (+0100)
Subject: Stop using a large static buffer in getfdpath
X-Git-Tag: v4.8~99
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=61ad0a401c6d1b7b4c1a209f9d61c3790e1e7d15;p=strace

Stop using a large static buffer in getfdpath

   text	   data	    bss	    dec	    hex	filename
 245075	    680	   9836	 255591	  3e667	strace_old
 245143	    680	   5708	 251531	  3d68b	strace

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---

diff --git a/defs.h b/defs.h
index ca5d0883..c20fcc61 100644
--- a/defs.h
+++ b/defs.h
@@ -605,7 +605,7 @@ extern const char *signame(int);
 extern int is_restart_error(struct tcb *);
 extern void pathtrace_select(const char *);
 extern int pathtrace_match(struct tcb *);
-extern const char *getfdpath(struct tcb *, int);
+extern int getfdpath(struct tcb *, int, char *, unsigned);
 
 extern const char *xlookup(const struct xlat *, int);
 
diff --git a/pathtrace.c b/pathtrace.c
index 95643c67..d4c2dc43 100644
--- a/pathtrace.c
+++ b/pathtrace.c
@@ -73,9 +73,10 @@ upathmatch(struct tcb *tcp, unsigned long upath)
 static int
 fdmatch(struct tcb *tcp, int fd)
 {
-	const char *path = getfdpath(tcp, fd);
+	char path[PATH_MAX + 1];
+	int n = getfdpath(tcp, fd, path, sizeof(path));
 
-	return path && pathmatch(path);
+	return n >= 0 && pathmatch(path);
 }
 
 /*
@@ -100,22 +101,24 @@ storepath(const char *path)
 /*
  * Get path associated with fd.
  */
-const char *
-getfdpath(struct tcb *tcp, int fd)
+int
+getfdpath(struct tcb *tcp, int fd, char *buf, unsigned bufsize)
 {
-	static char path[PATH_MAX+1];
 	char linkpath[sizeof("/proc/%u/fd/%u") + 2 * sizeof(int)*3];
 	ssize_t n;
 
 	if (fd < 0)
-		return NULL;
+		return -1;
 
 	sprintf(linkpath, "/proc/%u/fd/%u", tcp->pid, fd);
-	n = readlink(linkpath, path, (sizeof path) - 1);
-	if (n <= 0)
-		return NULL;
-	path[n] = '\0';
-	return path;
+	n = readlink(linkpath, buf, bufsize - 1);
+	/*
+	 * NB: if buf is too small, readlink doesn't fail,
+	 * it returns truncated result (IOW: n == bufsize - 1).
+	 */
+	if (n >= 0)
+		buf[n] = '\0';
+	return n;
 }
 
 /*
diff --git a/util.c b/util.c
index f6e62e9d..0cc43feb 100644
--- a/util.c
+++ b/util.c
@@ -353,10 +353,10 @@ printnum_int(struct tcb *tcp, long addr, const char *fmt)
 void
 printfd(struct tcb *tcp, int fd)
 {
-	const char *p;
+	char path[PATH_MAX + 1];
 
-	if (show_fd_path && (p = getfdpath(tcp, fd)))
-		tprintf("%d<%s>", fd, p);
+	if (show_fd_path && getfdpath(tcp, fd, path, sizeof(path)) >= 0)
+		tprintf("%d<%s>", fd, path);
 	else
 		tprintf("%d", fd);
 }