AArch64: Read pauth registers

Initialise the pauth registers when creating a target description, and store
the regnum of the first pauth register.

Use ptrace to read the registers in the pauth feature.

Do not allow the registers to be written.

gdb/ChangeLog:

	* aarch64-linux-nat.c (fetch_pauth_masks_from_thread): New
	function.
	(aarch64_linux_nat_target::fetch_registers): Read pauth registers.
	* aarch64-tdep.c (aarch64_cannot_store_register): New function.
	(aarch64_gdbarch_init): Add puth registers.
	* aarch64-tdep.h (struct gdbarch_tdep): Add pauth features.
	* arch/aarch64.h (AARCH64_PAUTH_DMASK_REGNUM): New define.
	(AARCH64_PAUTH_CMASK_REGNUM): Likewise.

1 files changed, 8 insertions, 0 deletions

diff --git a/gdb/aarch64-tdep.h b/gdb/aarch64-tdep.h
index 3db6bee9f3f..f9fc8965f02 100644
--- a/gdb/aarch64-tdep.h
+++ b/gdb/aarch64-tdep.h
@@ -87,6 +87,14 @@ struct gdbarch_tdep
   {
     return vq != 0;
   }
+
+  int pauth_reg_base;
+
+  /* Returns true if the target supports pauth.  */
+  bool has_pauth () const
+  {
+    return pauth_reg_base != -1;
+  }
 };
 
 const target_desc *aarch64_read_description (uint64_t vq, bool pauth_p);