From: Kurt Garloff <kurt@garloff.de>
Subject: Need to restore sigprocmask when not returning from signal handler

I stumbled over the fine details of signal handling:
A second SIGILL would not have been delivered to the handler as it was
blocked when invoking the handler for the first time. As we can't return
from the handler, we need to restore the process' signal mask ourselves
and reenable delivery.

Signed-off-by: Kurt Garloff <kurt@garloff.de>

Index: find_nonzero.c
===================================================================
RCS file: /home/cvsroot/dd_rescue/find_nonzero.c,v
retrieving revision 1.44
retrieving revision 1.46
diff -u -p -r1.44 -r1.46
--- find_nonzero.c	21 Feb 2014 12:51:43 -0000	1.44
+++ find_nonzero.c	6 Mar 2014 12:14:18 -0000	1.46
@@ -24,6 +24,14 @@ static jmp_buf sigill_jmp;
 static void ill_handler(int sig)
 {
 	have_feature = 0;
+	/* As we can't return from handler (as it would result in 
+	 * reexecuting the illegal instruction again - we jump back
+	 * using longjmp) -- we have to restore signal delivery, so the
+	 * program context is back to normal. Otherwise a second
+	 * probe_procedure would not handle SIGILL. */
+	sigset_t sigmask;
+	sigemptyset(&sigmask); sigaddset(&sigmask, sig);
+	sigprocmask(SIG_UNBLOCK, &sigmask, NULL);
 	longjmp(sigill_jmp, 1);
 }
 
Index: archdep.h
===================================================================
RCS file: /home/cvsroot/dd_rescue/archdep.h,v
retrieving revision 1.6
retrieving revision 1.7
diff -u -p -r1.6 -r1.7
--- archdep.h	25 Feb 2014 16:06:35 -0000	1.6
+++ archdep.h	6 Mar 2014 12:20:46 -0000	1.7
@@ -28,7 +28,7 @@ void probe_sse2();
 #define have_avx2 0
 #define have_sse42 0
 #define ARCH_DETECT do {} while (0)
-#define ARCH_DECLS
+#define ARCH_DECLS ARCH_DECL_386
 #elif defined(NO_AVX2) /* compiler does not support -mavx2 */
 #define have_avx2 0
 extern char have_sse42;