signal/alpha: Replace TRAP_FIXME with TRAP_UNK

Using an si_code of 0 that aliases with SI_USER is clearly the wrong
thing to do, and causes problems in interesting ways.

For it really is not clear to me if using TRAP_UNK bugcheck or
the default case of gentrap is really the best way to handle
things. There is certainly enough information that that a more
specific si_code could potentially be used. That said TRAP_UNK
is definitely an improvement over 0 as it removes the ambiguiuty
of what si_code of 0 with SIGTRAP means on alpha.

Recent history suggests no actually cares about crazy corner cases of
the kernel behavior like this so I don't expect any regressions from
changing this. However if something does happen this change is easy
to revert.

Cc: Helge Deller <[e-mail]>
Cc: Richard Henderson <[e-mail]>
Cc: Ivan Kokshaysky <[e-mail]>
Cc: Matt Turner <[e-mail]>
Cc: [e-mail]
Fixes: 0a635c7a84cf ("Fill in siginfo_t.")
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Signed-off-by: "Eric W. Biederman" <[e-mail]>

arch/alpha/include/uapi/asm/siginfo.h

···
 
 #include <asm-generic/siginfo.h>
 
-/*
- * SIGTRAP si_codes
- */
-#ifdef __KERNEL__
-#define TRAP_FIXME	0	/* Broken dup of SI_USER */
-#endif /* __KERNEL__ */
-
 #endif

arch/alpha/kernel/traps.c

···
 	      case 1: /* bugcheck */
 		info.si_signo = SIGTRAP;
 		info.si_errno = 0;
-		info.si_code = TRAP_FIXME;
+		info.si_code = TRAP_UNK;
 		info.si_addr = (void __user *) regs->pc;
 		info.si_trapno = 0;
 		send_sig_info(SIGTRAP, &info, current);
···
 		case GEN_SUBRNG7:
 		default:
 			signo = SIGTRAP;
-			code = TRAP_FIXME;
+			code = TRAP_UNK;
 			break;
 		}