Add GNU properties note for Intel CET in x86_64-xlate.pl

This appears to be emitted with gcc and clang with -fcf-protection
selected, so we should do the same.

We're trying to be smart, and only emit this when the 'endbranch'
pseudo-mnemonic has been used at least once.

This is inspired by and owes to work done by @hjl-tools (github)

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/10875)

diff --git a/crypto/perlasm/x86_64-xlate.pl b/crypto/perlasm/x86_64-xlate.pl
index 4a7ec7a6e9e832e6433a37f0182bf403833f2291..e5644014abfb0338cfff18211c6bd19e5487a324 100755 (executable)
--- a/crypto/perlasm/x86_64-xlate.pl
+++ b/crypto/perlasm/x86_64-xlate.pl
@@ -101,6 +101,24 @@ elsif (!$gas)
     $decor="\$L\$";
 }
 
+my $cet_property = <<'_____';
+       .section ".note.gnu.property", "a"
+       .align 8
+       .long 1f - 0f
+       .long 4f - 1f
+       .long 5
+0:
+       .asciz "GNU"
+1:
+       .align 8
+       .long 0xc0000002
+       .long 3f - 2f
+2:
+       .long 3
+3:
+       .p2align 3
+4:
+_____
 my $current_segment;
 my $current_function;
 my %globals;
@@ -1127,7 +1145,9 @@ my $vprotq = sub {
 # Intel Control-flow Enforcement Technology extension. All functions and
 # indirect branch targets will have to start with this instruction...
 
+my $used_cet = 0;
 my $endbranch = sub {
+    $used_cet = 1;
     (0xf3,0x0f,0x1e,0xfa);
 };
 
@@ -1213,6 +1233,7 @@ while(defined(my $line=<>)) {
     print $line,"\n";
 }
 
+print "$cet_property"                  if ($gas && $used_cet);
 print "\n$current_segment\tENDS\n"     if ($current_segment && $masm);
 print "END\n"                          if ($masm);