diff --git a/tracefile/test.sh b/tracefile/test.sh
index a93ffa1..1a470db 100644
--- a/tracefile/test.sh
+++ b/tracefile/test.sh
@@ -19,3 +19,6 @@ mkdir -p t/1/2/3
 parallel -vj1 doit \
 	 ::: '' -l -u \
 	 ::: tt/tt/../tt/test.img `pwd`/tt/tt/../tt/test.img t/1/../1/2/3/test.img `pwd`/t/1/../1/2/3/test.img | grep test.img
+
+# opening file relative to file descriptor of openat
+tracefile lscpu | grep /sys/devices/system/cpu/cpu0/cache/index0/level
diff --git a/tracefile/tracefile b/tracefile/tracefile
index 1cf0fb6..e064109 100755
--- a/tracefile/tracefile
+++ b/tracefile/tracefile
@@ -266,17 +266,36 @@ while(<IN>) {
     # [pid 30817] stat("t/tar.gz", {st_mode=S_IFREG|0644, st_size=140853248, ...}) = 0
     # openat(AT_FDCWD, "/tmp/a", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666) = 3
     if(/^(\[[^]]+\])? # Match pid
-       \s*([^\" ]+)   # function
+       \s*([^\" ]+)   # function e.g. openat
        [(]            # (
-       [^"]*          # E.g. AT_FDCWD
+       ([^",]*)       # E.g. AT_FDCWD or 4
+       [^"]*          # E.g. ,
        "              # "
        (([^\\"]|\\[\\"nt])*) # content of string with \n \" \t \\
-       "(.*)/x)     # Rest
+       "(.*)/x)       # Rest
     {
 	# Matches the strace structure for a file
 	my $function = $2;
-	my $file = shell_unquote($3);
-	my $addinfo = $5;
+	my $first_arg = $3;
+	my $file = shell_unquote($4);
+	my $addinfo = $6;
+	if($function eq "openat"
+	   or
+	   $function eq "faccessat") {
+	    # openat(AT_FDCWD, "/sys/devices/system/cpu", O_RDONLY|O_CLOEXEC) = 4
+	    # openat(4, "kernel_max", O_RDONLY|O_CLOEXEC) = 5
+	    # faccessat(4, "cpu0/cache/index4", F_OK) = -1 ENOENT
+	    # openat can open a file descriptor
+	    # openat/faccessat can open relative to a file descriptor
+	    $addinfo =~ /= (-?\d+)(\s[^=]*)?$/ || die $addinfo,$_;
+	    my $fd = $1;
+	    if($first_arg eq "AT_FDCWD") {
+		$fd{$fd} = $file;
+	    } elsif($first_arg =~ /^\d+$/) {
+		$file = $fd{$first_arg}."/".$file;
+	    } else { die $first_arg,$_; }
+	    $fd{$fd} = $file;
+	}
 	# Relative to $dir
 	$file =~ s:^([^/]):$dir/$1:;
 	$file =~ s:/\./:/:g; # /./ => /