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 a660fc59a89eb266686cb31a9a3e85b3f8742e1f..7d0ca3f5202f846b402b3a69f0e1759b4259298d 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -31,6 +31,18 @@ Major new features:
   pthread_attr_getsigmask_np have been added.  They allow applications
   to specify the signal mask of a thread created with pthread_create.
 
+* 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. It is recommended to use GCC 10 or newer when
+  building glibc with branch protection.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * The deprecated <sys/sysctl.h> header and the sysctl function have been