[glibc] aarch64: update NEWS about branch protection

[glibc] aarch64: update NEWS about branch protection

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=42c9e9af22dc645c06395879d36a565c6dc19f3a

commit 42c9e9af22dc645c06395879d36a565c6dc19f3a
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Wed Jul 29 08:27:27 2020 +0100

    aarch64: update NEWS about branch protection
    
    After some discussions it seems the original news was not clear
    and that it is valid to manually pass the branch protection flags
    iff GCC target libs are built with them too. The main difference
    between manually passing the flags and using the configure
    option is that the latter also makes branch protection the
    default in GCC which may not be desirable in some cases.
    
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>

Diff:
---
 NEWS | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 7454a4bfa0..e48d7438e2 100644
--- a/NEWS
+++ b/NEWS
@@ -70,7 +70,9 @@ Major new features:
 
 * AArch64 now supports standard branch protection security hardening
   in glibc when it is built with a GCC that is configured with
-  --enable-standard-branch-protection.  This includes branch target
+  --enable-standard-branch-protection (or if -mbranch-protection=standard
+  flag is passed when building both GCC target libraries and glibc,
+  in either case a custom GCC is needed).  This includes branch target
   identification (BTI) and pointer authentication for return addresses
   (PAC-RET).  They require armv8.5-a and armv8.3-a architecture
   extensions respectively for the protection to be effective,