Thiago Jung Bauermann [off-list ref] writes:

Ram Pai [off-list ref] writes:

quoted

The value of the AMR register at the time of exception
is made available in gp_regs[PT_AMR] of the siginfo.

The value of the pkey, whose protection got violated,
is made available in si_pkey field of the siginfo structure.

Should the IAMR also be made available?

Also, should the AMR and IAMR be accesible to userspace (e.g., to GDB)
via ptrace and the core file?

Yes if they're part of the thread's context they should be accessible
via ptrace and in core files.

quoted

--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c

@@ -500,6 +500,11 @@ static int save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
 				   (unsigned long) &frame->tramp[2]);
 	}

+#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
+	if (__put_user(get_paca()->paca_amr, &frame->mc_gregs[PT_AMR]))
+		return 1;
+#endif /*  CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
+
 	return 0;
 }

frame->mc_gregs[PT_AMR] has 32 bits, but paca_amr has 64 bits. Does this
work as intended?

I don't understand why we are putting it in there at all?

Is there some special handling of the actual register on signals? I
haven't seen it. In which case the process can get the value of AMR by
reading the register. ??

cheers