The Guarded Control Stack extension implements a shadow stack and the
Linux kernel provides access to 3 registers for it via ptrace.
struct user_gcs {
__u64 features_enabled;
__u64 features_locked;
__u64 gcspr_el0;
};
This commit adds support for reading those from a live process.
The first 2 are pseudo registers based on the real control register and
the 3rd is a real register. This is the stack pointer for the guarded
stack.
I have added a "gcs_" prefix to the "features" registers so that they
have a clear name when shown individually. Also this means they will tab
complete from "gcs", and be next to gcspr_el0 in any sorted lists of
registers.
Guarded Control Stack Registers:
gcs_features_enabled = 0x0000000000000000
gcs_features_locked = 0x0000000000000000
gcspr_el0 = 0x0000000000000000
Testing is more of the usual, where possible I'm writing a register then
doing something in the program to confirm the value was actually sent to
ptrace.
02c6002d1c