[PATCH v3 2/3] malloc: Remove LD_TRACE_PRELINKING usage from mtrace

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

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>
---
 NEWS             |  4 ++++
 elf/dl-main.h    |  3 +++
 elf/rtld.c       | 22 +++++++++++--------
 malloc/mtrace.pl | 55 +++++++++++++++++++++++++++---------------------
 4 files changed, 51 insertions(+), 33 deletions(-)

diff --git a/NEWS b/NEWS
index 9bef1058b5..88815bcad1 100644
--- a/NEWS
+++ b/NEWS
@@ -193,6 +193,10 @@ Deprecated and removed features, and other changes affecting compatibility:
   removal of the LD_TRACE_PRELINKING, and LD_USE_LOAD_BIAS, environment
   variables and their functionality in the dynamic loader.
 
+* The LD_TRACE_PRELINKING environment variable has been removed.  Similar
+  functionality to obtain the program mapping address can be achieved by
+  using LD_TRACE_LOADED_OBJECTS to value of 2.
+
 Changes to build and runtime requirements:
 
 * The audit module interface version LAV_CURRENT is increased to enable
diff --git a/elf/dl-main.h b/elf/dl-main.h
index 3e32f254c5..e4fa19ee4e 100644
--- a/elf/dl-main.h
+++ b/elf/dl-main.h
@@ -94,6 +94,9 @@ struct dl_main_state
 
   enum rtld_mode mode;
 
+  /* True if program should be also printed for rtld_mode_trace.  */
+  bool mode_trace_program;
+
   /* True if any of the debugging options is enabled.  */
   bool any_debug;
 
diff --git a/elf/rtld.c b/elf/rtld.c
index 5f089038e1..aa18256d86 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -2104,18 +2104,18 @@ dl_main (const ElfW(Phdr) *phdr,
 	_dl_printf ("\tstatically linked\n");
       else
 	{
-	  for (l = main_map->l_next; l; l = l->l_next)
+	  for (l = state.mode_trace_program ? main_map : main_map->l_next;
+	       l; l = l->l_next) {
 	    if (l->l_faked)
 	      /* The library was not found.  */
-	      _dl_printf ("\t%s => not found\n", l->l_libname->name);
-	    else if (strcmp (l->l_libname->name, l->l_name) == 0)
-	      _dl_printf ("\t%s (0x%0*Zx)\n", l->l_libname->name,
-			  (int) sizeof l->l_map_start * 2,
-			  (size_t) l->l_map_start);
+	      _dl_printf ("\t%s => not found\n",  l->l_libname->name);
 	    else
-	      _dl_printf ("\t%s => %s (0x%0*Zx)\n", l->l_libname->name,
-			  l->l_name, (int) sizeof l->l_map_start * 2,
+	      _dl_printf ("\t%s => %s (0x%0*Zx)\n",
+			  DSO_FILENAME (l->l_libname->name),
+			  DSO_FILENAME (l->l_name),
+			  (int) sizeof l->l_map_start * 2,
 			  (size_t) l->l_map_start);
+	  }
 	}
 
       if (__glibc_unlikely (state.mode != rtld_mode_trace))
@@ -2676,7 +2676,11 @@ process_envvars (struct dl_main_state *state)
 	case 20:
 	  /* The mode of the dynamic linker can be set.  */
 	  if (memcmp (envline, "TRACE_LOADED_OBJECTS", 20) == 0)
-	    state->mode = rtld_mode_trace;
+	    {
+	      state->mode = rtld_mode_trace;
+	      state->mode_trace_program
+		= _dl_strtoul (&envline[21], NULL) > 1;
+	    }
 	  break;
 
 	  /* We might have some extra environment variable to handle.  This
diff --git a/malloc/mtrace.pl b/malloc/mtrace.pl
index 042df725eb..3e7bd6852d 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};
 	    }
-- 
2.32.0