malloc: Remove LD_TRACE_PRELINKING usage from mtrace

The fix for BZ#22716 replacde LD_TRACE_LOADED_OBJECTS with
LD_TRACE_PRELINKING so mtrace could record executable address
position.

To provide the same information, LD_TRACE_LOADED_OBJECTS is
extended where a value or '2' also prints the executable address
as well.  It avoid adding another loader environment variable
to be used solely for mtrace.  The vDSO will be printed as
a default library (with '=>' pointing the same name), which is
ok since both mtrace and ldd already handles it.

The mtrace script is changed to also parse the new format.  To
correctly support PIE and non-PIE executables, both the default
mtrace address and the one calculated as used (it fixes mtrace
for non-PIE exectuable as for BZ#22716 for PIE).

Checked on x86_64-linux-gnu.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

1 files changed, 31 insertions, 24 deletions

diff --git a/malloc/mtrace.pl b/malloc/mtrace.pl
index 042df72..3e7bd68 100644
--- a/malloc/mtrace.pl
+++ b/malloc/mtrace.pl
@@ -74,15 +74,14 @@ if ($#ARGV == 0) {
     } else {
 	$prog = "./$binary";
     }
-    # Set the environment variable LD_TRACE_PRELINKING to an empty string so
-    # that we trigger tracing but do not match with the executable or any of
-    # its dependencies.
-    if (open (LOCS, "env LD_TRACE_PRELINKING= $prog |")) {
-	while (<LOCS>) {
+    # Set the environment variable LD_TRACE_LOADED_OBJECTS to 2 so the
+    # executable is also printed.
+    if (open (locs, "env LD_TRACE_LOADED_OBJECTS=2 $prog |")) {
+	while (<locs>) {
 	    chop;
-	    if (/^.*=> (.*) \((0x[0123456789abcdef]*), (0x[0123456789abcdef]*).*/) {
+	    if (/^.*=> (.*) .(0x[0123456789abcdef]*).$/) {
 		$locs{$1} = $2;
-		$rel{$1} = hex($2) - hex($3);
+		$rel{$1} = hex($2);
 	    }
 	}
 	close (LOCS);
@@ -91,6 +90,18 @@ if ($#ARGV == 0) {
     die "Wrong number of arguments, run $progname --help for help.";
 }
 
+sub addr2line {
+    my $addr = pop(@_);
+    my $prog = pop(@_);
+    if (open (ADDR, "addr2line -e $prog $addr|")) {
+	my $line = <ADDR>;
+	chomp $line;
+	close (ADDR);
+	if ($line ne '??:0') {
+	    return $line
+	}
+    }
+}
 sub location {
     my $str = pop(@_);
     return $str if ($str eq "");
@@ -98,11 +109,9 @@ sub location {
 	my $addr = $1;
 	my $fct = $2;
 	return $cache{$addr} if (exists $cache{$addr});
-	if ($binary ne "" && open (ADDR, "addr2line -e $binary $addr|")) {
-	    my $line = <ADDR>;
-	    chomp $line;
-	    close (ADDR);
-	    if ($line ne '??:0') {
+	if ($binary ne "") {
+	    my $line = &addr2line($binary, $addr);
+	    if ($line) {
 		$cache{$addr} = $line;
 		return $cache{$addr};
 	    }
@@ -114,24 +123,22 @@ sub location {
 	my $searchaddr;
 	return $cache{$addr} if (exists $cache{$addr});
 	$searchaddr = sprintf "%#x", hex($addr) + $rel{$prog};
-	if ($binary ne "" && open (ADDR, "addr2line -e $prog $searchaddr|")) {
-	    my $line = <ADDR>;
-	    chomp $line;
-	    close (ADDR);
-	    if ($line ne '??:0') {
-		$cache{$addr} = $line;
-		return $cache{$addr};
+	if ($binary ne "") {
+	    for my $address ($searchaddr, $addr) {
+		my $line = &addr2line($prog, $address);
+		if ($line) {
+		    $cache{$addr} = $line;
+		    return $cache{$addr};
+		}
 	    }
 	}
 	$cache{$addr} = $str = $addr;
     } elsif ($str =~ /^.*[[](0x[^]]*)]$/) {
 	my $addr = $1;
 	return $cache{$addr} if (exists $cache{$addr});
-	if ($binary ne "" && open (ADDR, "addr2line -e $binary $addr|")) {
-	    my $line = <ADDR>;
-	    chomp $line;
-	    close (ADDR);
-	    if ($line ne '??:0') {
+	if ($binary ne "") {
+	    my $line = &addr2line($binary, $addr);
+	    if ($line) {
 		$cache{$addr} = $line;
 		return $cache{$addr};
 	    }