uml: don't try to handle signals on initial process stack

Code running on the initial UML stack can't receive or process signals since current must be valid when IRQs are handled, and there is no current for this stack. So, instead of using UML_LONGJMP and UML_SETJMP, which are careful to save and restore signal state, and, as a side-effect, handle any deferred signals, start_idle_thread must use the bare equivalents, which don't do anything with signals. Signed-off-by: Jeff Dike <jdike@linux.intel.com> Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

uml: don't try to handle signals on initial process stack
Code running on the initial UML stack can't receive or process signals since current must be valid when IRQs are handled, and there is no current for this stack. So, instead of using UML_LONGJMP and UML_SETJMP, which are careful to save and restore signal state, and, as a side-effect, handle any deferred signals, start_idle_thread must use the bare equivalents, which don't do anything with signals. Signed-off-by: Jeff Dike <jdike@linux.intel.com> Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Jeff Dike · Linus Torvalds
1 parent 63843c265f
Showing 1 changed file with 11 additions and 3 deletions Side-by-side Diff
arch/um/os-Linux/skas/process.c
@@ -494,7 +494,15 @@
 		    SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGALRM,
 		    SIGVTALRM, -1);
  
-	n = UML_SETJMP(&initial_jmpbuf);
+	/*
+	 * Can't use UML_SETJMP or UML_LONGJMP here because they save
+	 * and restore signals, with the possible side-effect of
+	 * trying to handle any signals which came when they were
+	 * blocked, which can't be done on this stack.
+	 * Signals must be blocked when jumping back here and restored
+	 * after returning to the jumper.
+	 */
+	n = setjmp(initial_jmpbuf);
 	switch(n){
 	case INIT_JMP_NEW_THREAD:
 		(*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
@@ -504,7 +512,7 @@
 		break;
 	case INIT_JMP_CALLBACK:
 		(*cb_proc)(cb_arg);
-		UML_LONGJMP(cb_back, 1);
+		longjmp(*cb_back, 1);
 		break;
 	case INIT_JMP_HALT:
 		kmalloc_ok = 0;
@@ -515,7 +523,7 @@
 	default:
 		panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
 	}
-	UML_LONGJMP(switch_buf, 1);
+	longjmp(*switch_buf, 1);
 }
  
 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
...	...	@@ -494,7 +494,15 @@
494	494	SA_ONSTACK \| SA_RESTART, SIGUSR1, SIGIO, SIGALRM,
495	495	SIGVTALRM, -1);
496	496
497		- n = UML_SETJMP(&initial_jmpbuf);
	497	+ /*
	498	+ * Can't use UML_SETJMP or UML_LONGJMP here because they save
	499	+ * and restore signals, with the possible side-effect of
	500	+ * trying to handle any signals which came when they were
	501	+ * blocked, which can't be done on this stack.
	502	+ * Signals must be blocked when jumping back here and restored
	503	+ * after returning to the jumper.
	504	+ */
	505	+ n = setjmp(initial_jmpbuf);
498	506	switch(n){
499	507	case INIT_JMP_NEW_THREAD:
500	508	(*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
...	...	@@ -504,7 +512,7 @@
504	512	break;
505	513	case INIT_JMP_CALLBACK:
506	514	(*cb_proc)(cb_arg);
507		- UML_LONGJMP(cb_back, 1);
	515	+ longjmp(*cb_back, 1);
508	516	break;
509	517	case INIT_JMP_HALT:
510	518	kmalloc_ok = 0;
...	...	@@ -515,7 +523,7 @@
515	523	default:
516	524	panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
517	525	}
518		- UML_LONGJMP(switch_buf, 1);
	526	+ longjmp(*switch_buf, 1);
519	527	}
520	528
521	529	void initial_thread_cb_skas(void (proc)(void ), void *arg)