[glibc/nsz/pacbti-v7] aarch64: add NEWS entry about branch protection support

[glibc/nsz/pacbti-v7] aarch64: add NEWS entry about branch protection support

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=90d6dfb05675c96e1f4cd35187d2fb783fc00204

commit 90d6dfb05675c96e1f4cd35187d2fb783fc00204
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Thu Jun 11 18:19:40 2020 +0100

    aarch64: add NEWS entry about branch protection support
    
    This is a new security feature that relies on architecture
    extensions and needs glibc to be built with a gcc configured
    with branch protection.

Diff:
---
 NEWS | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/NEWS b/NEWS
index d7282b4ad5..5083f5eacf 100644
--- a/NEWS
+++ b/NEWS
@@ -67,6 +67,17 @@ Major new features:
   They should be used instead of sys_errlist and sys_nerr, both are
   thread and async-signal safe.  These functions are GNU extensions.
 
+* 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
+  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,
+  otherwise the used instructions are nops.  User code can use PAC-RET
+  without libc support, but BTI requires a libc that is built with BTI
+  support, otherwise runtime objects linked into user code will not be
+  BTI compatible.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * The deprecated <sys/sysctl.h> header and the sysctl function have been