@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.371 2021/05/05 15:36:17 thorpej Exp $ */
+/* $NetBSD: machdep.c,v 1.372 2021/05/24 21:00:12 thorpej Exp $ */
 
 /*-
  * Copyright (c) 1998, 1999, 2000, 2019, 2020 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
 
 #include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
 
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.371 2021/05/05 15:36:17 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.372 2021/05/24 21:00:12 thorpej Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1525,6 +1525,8 @@
 	frame.sf_uc.uc_flags = _UC_SIGMASK;
 	frame.sf_uc.uc_sigmask = *mask;
 	frame.sf_uc.uc_link = l->l_ctxlink;
+	frame.sf_uc.uc_flags |= (l->l_sigstk.ss_flags & SS_ONSTACK)
+	    ? _UC_SETSTACK : _UC_CLRSTACK;
 	sendsig_reset(l, sig);
 	mutex_exit(p->p_lock);
 	cpu_getmcontext(l, &frame.sf_uc.uc_mcontext, &frame.sf_uc.uc_flags);
@@ -1885,8 +1887,10 @@
 		frame->tf_regs[FRAME_PC] = gr[_REG_PC];
 		frame->tf_regs[FRAME_PS] = gr[_REG_PS];
 	}
+
 	if (flags & _UC_TLSBASE)
 		lwp_setprivate(l, (void *)(uintptr_t)gr[_REG_UNIQUE]);
+
 	/* Restore floating point register context, if any. */
 	if (flags & _UC_FPU) {
 		/* If we have an FP register context, get rid of it. */
@@ -1895,6 +1899,13 @@
 		    sizeof (pcb->pcb_fp));
 		l->l_md.md_flags = mcp->__fpregs.__fp_fpcr & MDLWP_FP_C;
 	}
+
+	mutex_enter(l->l_proc->p_lock);
+	if (flags & _UC_SETSTACK)
+		l->l_sigstk.ss_flags |= SS_ONSTACK;
+	if (flags & _UC_CLRSTACK)
+		l->l_sigstk.ss_flags &= ~SS_ONSTACK;
+	mutex_exit(l->l_proc->p_lock);
 
 	return (0);
 }

@@ -1,4 +1,4 @@
-/*	$NetBSD: mcontext.h,v 1.10 2019/12/27 00:32:16 kamil Exp $	*/
+/*	$NetBSD: mcontext.h,v 1.11 2021/05/24 21:00:12 thorpej Exp $	*/
 
 /*-
  * Copyright (c) 2001 The NetBSD Foundation, Inc.
@@ -94,6 +94,8 @@
 
 /* Machine-dependent uc_flags */
 #define _UC_TLSBASE	0x20	/* valid process-unique value in _REG_UNIQUE */
+#define _UC_SETSTACK	0x00010000
+#define _UC_CLRSTACK	0x00020000
 
 #define _UC_MACHINE_SP(uc)	((uc)->uc_mcontext.__gregs[_REG_SP])
 #define _UC_MACHINE_FP(uc)	((uc)->uc_mcontext.__gregs[_REG_S6])