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From: Fangrui Song <maskray@sourceware.org>
To: glibc-cvs@sourceware.org
Subject: [glibc/maskray/unnest] mtrace: Fix output with PIE and ASLR [BZ
 #22716]
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X-Git-Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f2e33c3268db9adf8e57e991676ed0d5ac74e8a8

commit f2e33c3268db9adf8e57e991676ed0d5ac74e8a8
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Mon Aug 23 08:11:54 2021 +0530

    mtrace: Fix output with PIE and ASLR [BZ #22716]
    
    Record only the relative address of the caller in mtrace file.  Use
    LD_TRACE_PRELINKING to get the executable as well as binary vs
    executable load offsets so that we may compute a base to add to the
    relative address in the mtrace file.  This allows us to get a valid
    address to pass to addr2line in all cases.
    
    Fixes BZ #22716.
    
    Co-authored-by: John Ogness <john.ogness@linutronix.de>
    Reviewed-by: Andreas Schwab <schwab@linux-m68k.org>
    Reviewed-by: DJ Delorie <dj@redhat.com>

Diff:
---
 malloc/mtrace-impl.c |  6 +++---
 malloc/mtrace.pl     | 15 +++++++--------
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/malloc/mtrace-impl.c b/malloc/mtrace-impl.c
index 83008ca18f..f5f19c265c 100644
--- a/malloc/mtrace-impl.c
+++ b/malloc/mtrace-impl.c
@@ -65,9 +65,9 @@ tr_where (const void *caller, Dl_info *info)
 		       offset);
             }
 
-	  fprintf (mallstream, "@ %s%s%s[%p] ", info->dli_fname ? : "",
-		   info->dli_fname ? ":" : "",
-                   buf, caller);
+	  fprintf (mallstream, "@ %s%s%s[0x%" PRIxPTR "] ",
+		   info->dli_fname ? : "", info->dli_fname ? ":" : "", buf,
+		   caller - info->dli_fbase);
         }
       else
         fprintf (mallstream, "@ [%p] ", caller);
diff --git a/malloc/mtrace.pl b/malloc/mtrace.pl
index 6f49c8338d..b1073a1931 100644
--- a/malloc/mtrace.pl
+++ b/malloc/mtrace.pl
@@ -75,11 +75,15 @@ if ($#ARGV == 0) {
     } else {
 	$prog = "./$binary";
     }
-    if (open (LOCS, "env LD_TRACE_LOADED_OBJECTS=1 $prog |")) {
+    # 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= $prog |")) {
 	while (<LOCS>) {
 	    chop;
-	    if (/^.*=> (.*) .(0x[0123456789abcdef]*).$/) {
+	    if (/^.*=> (.*) \((0x[0123456789abcdef]*), (0x[0123456789abcdef]*).*/) {
 		$locs{$1} = $2;
+		$rel{$1} = hex($2) - hex($3);
 	    }
 	}
 	close (LOCS);
@@ -110,12 +114,7 @@ sub location {
 	my $addr = $2;
 	my $searchaddr;
 	return $cache{$addr} if (exists $cache{$addr});
-	if ($locs{$prog} ne "") {
-	    $searchaddr = sprintf "%#x", $addr - $locs{$prog};
-	} else {
-	    $searchaddr = $addr;
-	    $prog = $binary;
-	}
+	$searchaddr = sprintf "%#x", hex($addr) + $rel{$prog};
 	if ($binary ne "" && open (ADDR, "addr2line -e $prog $searchaddr|")) {
 	    my $line = <ADDR>;
 	    chomp $line;