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 --git a/NEWS b/NEWS
index d7282b4ad59c22bde1ab5a243c72da1f79fe3cd0..5083f5eacf913bf3d745081f24f727b031e40dd1 100644 (file)
--- 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