Support for zisslpcfi in opensbi

Zisslpcfi [1] extension extends risc-v architecture to mitigate against control-flow integrity attacks (ROP/JOP/COP).

Zisslpcfi uses bits (b23-b29) in (m/s/vs) status CSR for enabling cfi in lesser privileged mode and record cfi state. One such state is expected landing pad (ELP). If forward cfi is enabled, indirect call/jmp updates hart's ELP state (1bit) to true. ELP state is cleared only by a landing pad instruction else trap is delivered with ELP state recorded in sstatus CSR.

This two patch series adds following changes to opensbi
- Adds support in opensbi to detect zisslpcfi
- trap redirection updates ELP state accordingly

[1] - https://github.com/riscv/riscv-cfi

Deepak Gupta (2):
include: adding support for zsslpcfi encodings
lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

 include/sbi/riscv_encoding.h |  6 ++++++
 include/sbi/sbi_hart.h       |  2 ++
 lib/sbi/sbi_hart.c           | 21 +++++++++++++++++++++
 lib/sbi/sbi_trap.c           | 18 ++++++++++++++++++
 4 files changed, 47 insertions(+)

2.25.1