fix fault handling

Hi,

skas has a design bug: PTRACE_FAULTINFO doesn't pass enougth informations. Specifically the trap_no is missing, so you don't know for sure whenever the SIGSEGV was a page fault or a general protection fault. I think that should be fixed in skas4 (where we'll break backward compatibility anyway).

For the time being I've tried to fix that with the patch below, which makes the uml kernel pass through general protection SEGV to the app and seems to have no ill side effects.

Gerd

@@ -54,6 +54,17 @@
 		panic("handle_segv - PTRACE_FAULTINFO failed, errno = %d\n",
 		      errno);
 
+	if (!(fault.is_write & 4)) {
+		/*
+		    kernel fault -- likely that was general
+ 		    protection fault (trap_no = 13), not a
+		    page fault (trap_no = 14).  But we don't
+		    know for sure as PTRACE_FAULTINFO doesn't
+		    tell us :-/
+		*/
+		bad_segv(fault.addr, 0, fault.is_write);
+		return;
+	}
 	segv(fault.addr, 0, FAULT_WRITE(fault.is_write), 1, NULL);
 }
 

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Yeah, this is the biggest technical mistake in skas3. I left it because I didn't really want to touch the skas3 patch again, and instead fix it in skas4.

Jeff

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