As the introduction at
https://community.arm.com/groups/processors/blog/2016/10/27/armv8-a-architecture-2016-additions
ARMv8.3-A includes a new hardware feature called "Pointer Authentication".
This new extension support some new instructions which can sign and
authenticate pointer value.
One utilization of this feature is we can implement Return-Oriented-Programming
protections. For example, we can sign the return address register at function
start then authenticate it before return. If the content is modified
unexpectedly, then exception will happen thus prevent redirecting program's
execution flow.
This type of prevention however requires the original content of return address
be signed that unwinders (C++ EH unwinder, GDB unwinder etc...) can no longer
do backtrace correctly without understanding how to restore the original value
of return address.
Therefore we need to describe any return address or frame related register
mangling through DWARF information.
This patchset includes implementation of such return address siging protection
and AArch64 DWARF operation extension.
Below are comparision of codesize overhead between standard gcc
-fstack-protector-strong and -msign-return-address on AArch64.
linux kernel openssl Protection Scope
(libcrypto + libssl)
-----------------------------------------------------------------------
ssp-strong (gcc) + 2.93% + 2.98% Overflow protect on risky functions
-----------------------------------------------------------------------
sign LR + 1.82% + 2.18% LR protect on All
Please review this patchset.
Thanks.
Jiong Wang (9):
[RFC] Reserve three DW_OP number in vendor extension space
Encoding support for AArch64 DWARF operations
Add commandline support for -march=armv8.3-a
Return address protection support on AArch64
Generate dwarf information for -msign-return-address
Add builtins support for pac/aut/xpac
libgcc, let AArch64 use customized unwinder file
libgcc, runtime support for AArch64 DWARF operations
[RFC] Accelerate -fstack-protector through pointer authentication
gcc/config/aarch64/aarch64-arches.def | 1 +
gcc/config/aarch64/aarch64-builtins.c | 110 ++
gcc/config/aarch64/aarch64-opts.h | 32 +
gcc/config/aarch64/aarch64-protos.h | 1 +
gcc/config/aarch64/aarch64.c | 296 +++-
gcc/config/aarch64/aarch64.h | 54 +
gcc/config/aarch64/aarch64.md | 128 +-
gcc/config/aarch64/aarch64.opt | 45 +
gcc/config/aarch64/predicates.md | 4 +
gcc/defaults.h | 8 +
gcc/doc/extend.texi | 12 +
gcc/doc/invoke.texi | 24 +-
gcc/doc/tm.texi | 8 +
gcc/doc/tm.texi.in | 8 +
gcc.target/aarch64/return_address_sign_1.c | 57 +
gcc.target/aarch64/return_address_sign_scope_1.c | 57 +
include/dwarf2.def | 10 +
libgcc/config.host | 2 +
libgcc/config/aarch64/t-eh-aarch64 | 3 +
libgcc/config/aarch64/unwind-aarch64.c | 1820 ++++++++++++++++++++
