diff --git a/arch/sh/src/__set_thread_area.c b/arch/sh/src/__set_thread_area.c
new file mode 100644
index 00000000..1d3e0225
--- /dev/null
+++ b/arch/sh/src/__set_thread_area.c
@@ -0,0 +1,34 @@
+#include "pthread_impl.h"
+#include "libc.h"
+#include "sh_atomic.h"
+#include <elf.h>
+
+/* Also perform sh-specific init */
+
+#define CPU_HAS_LLSC 0x0040
+
+__attribute__((__visibility__("hidden"))) unsigned __sh_atomic_model, __sh_nommu;
+
+int __set_thread_area(void *p)
+{
+	size_t *aux;
+	__asm__ __volatile__ ( "ldc %0, gbr" : : "r"(p) : "memory" );
+#ifndef __SH4A__
+	if (__hwcap & CPU_HAS_LLSC) {
+		__sh_atomic_model = SH_A_LLSC;
+		return 0;
+	}
+#if !defined(__SH3__) && !defined(__SH4__)
+	for (aux=libc.auxv; *aux; aux+=2) {
+		if (*aux != AT_PLATFORM) continue;
+		const char *s = (void *)aux[1];
+		if (s[0]!='s' || s[1]!='h' || s[2]!='2' || s[3]-'0'<10u) break;
+		__sh_atomic_model = SH_A_IMASK;
+		__sh_nommu = 1;
+		return 0;
+	}
+#endif
+	/* __sh_atomic_model = SH_A_GUSA; */ /* 0, default */
+#endif
+	return 0;
+}
diff --git a/arch/sh/src/atomic.c b/arch/sh/src/atomic.c
index f8c615f8..7fd73074 100644
--- a/arch/sh/src/atomic.c
+++ b/arch/sh/src/atomic.c
@@ -1,8 +1,26 @@
 #ifndef __SH4A__
 
+#include "sh_atomic.h"
 #include "atomic.h"
 #include "libc.h"
 
+static inline unsigned mask()
+{
+	unsigned sr;
+	__asm__ __volatile__ ( "\n"
+	"	stc sr,r0 \n"
+	"	mov r0,%0 \n"
+	"	or #0xf0,r0 \n"
+	"	ldc r0,sr \n"
+	: "=&r"(sr) : : "memory", "r0" );
+	return sr;
+}
+
+static inline void unmask(unsigned sr)
+{
+	__asm__ __volatile__ ( "ldc %0,sr" : : "r"(sr) : "memory" );
+}
+
 /* gusa is a hack in the kernel which lets you create a sequence of instructions
  * which will be restarted if the process is preempted in the middle of the
  * sequence. It will do for implementing atomics on non-smp systems. ABI is:
@@ -25,11 +43,17 @@
 	"	mov.l " new ", @" mem "\n" \
 	"1:	mov r1, r15\n"
 
-#define CPU_HAS_LLSC 0x0040
-
 int __sh_cas(volatile int *p, int t, int s)
 {
-	if (__hwcap & CPU_HAS_LLSC) return __sh_cas_llsc(p, t, s);
+	if (__sh_atomic_model == SH_A_LLSC) return __sh_cas_llsc(p, t, s);
+
+	if (__sh_atomic_model == SH_A_IMASK) {
+		unsigned sr = mask();
+		int old = *p;
+		if (old==t) *p = s;
+		unmask(sr);
+		return old;
+	}
 
 	int old;
 	__asm__ __volatile__(
@@ -43,7 +67,15 @@ int __sh_cas(volatile int *p, int t, int s)
 
 int __sh_swap(volatile int *x, int v)
 {
-	if (__hwcap & CPU_HAS_LLSC) return __sh_swap_llsc(x, v);
+	if (__sh_atomic_model == SH_A_LLSC) return __sh_swap_llsc(x, v);
+
+	if (__sh_atomic_model == SH_A_IMASK) {
+		unsigned sr = mask();
+		int old = *x;
+		*x = v;
+		unmask(sr);
+		return old;
+	}
 
 	int old;
 	__asm__ __volatile__(
@@ -55,7 +87,15 @@ int __sh_swap(volatile int *x, int v)
 
 int __sh_fetch_add(volatile int *x, int v)
 {
-	if (__hwcap & CPU_HAS_LLSC) return __sh_fetch_add_llsc(x, v);
+	if (__sh_atomic_model == SH_A_LLSC) return __sh_fetch_add_llsc(x, v);
+
+	if (__sh_atomic_model == SH_A_IMASK) {
+		unsigned sr = mask();
+		int old = *x;
+		*x = old + v;
+		unmask(sr);
+		return old;
+	}
 
 	int old, dummy;
 	__asm__ __volatile__(
@@ -69,7 +109,7 @@ int __sh_fetch_add(volatile int *x, int v)
 
 void __sh_store(volatile int *p, int x)
 {
-	if (__hwcap & CPU_HAS_LLSC) return __sh_store_llsc(p, x);
+	if (__sh_atomic_model == SH_A_LLSC) return __sh_store_llsc(p, x);
 	__asm__ __volatile__(
 		"	mov.l %1, @%0\n"
 		: : "r"(p), "r"(x) : "memory");
@@ -77,7 +117,15 @@ void __sh_store(volatile int *p, int x)
 
 void __sh_and(volatile int *x, int v)
 {
-	if (__hwcap & CPU_HAS_LLSC) return __sh_and_llsc(x, v);
+	if (__sh_atomic_model == SH_A_LLSC) return __sh_and_llsc(x, v);
+
+	if (__sh_atomic_model == SH_A_IMASK) {
+		unsigned sr = mask();
+		int old = *x;
+		*x = old & v;
+		unmask(sr);
+		return;
+	}
 
 	int dummy;
 	__asm__ __volatile__(
@@ -89,7 +137,15 @@ void __sh_and(volatile int *x, int v)
 
 void __sh_or(volatile int *x, int v)
 {
-	if (__hwcap & CPU_HAS_LLSC) return __sh_or_llsc(x, v);
+	if (__sh_atomic_model == SH_A_LLSC) return __sh_or_llsc(x, v);
+
+	if (__sh_atomic_model == SH_A_IMASK) {
+		unsigned sr = mask();
+		int old = *x;
+		*x = old | v;
+		unmask(sr);
+		return;
+	}
 
 	int dummy;
 	__asm__ __volatile__(
diff --git a/arch/sh/src/sh_atomic.h b/arch/sh/src/sh_atomic.h
new file mode 100644
index 00000000..054c2a32
--- /dev/null
+++ b/arch/sh/src/sh_atomic.h
@@ -0,0 +1,15 @@
+#ifndef _SH_ATOMIC_H
+#define _SH_ATOMIC_H
+
+#define SH_A_GUSA 0
+#define SH_A_LLSC 1
+#define SH_A_CAS 2
+#if !defined(__SH3__) && !defined(__SH4__)
+#define SH_A_IMASK 3
+#else
+#define SH_A_IMASK -1LL /* unmatchable by unsigned int */
+#endif
+
+extern __attribute__((__visibility__("hidden"))) unsigned __sh_atomic_model;
+
+#endif
diff --git a/src/thread/sh/__set_thread_area.s b/src/thread/sh/__set_thread_area.s
index d9f11810..e69de29b 100644
--- a/src/thread/sh/__set_thread_area.s
+++ b/src/thread/sh/__set_thread_area.s
@@ -1,6 +0,0 @@
-.global __set_thread_area
-.type   __set_thread_area, @function
-__set_thread_area:
-	ldc r4, gbr
-	rts
-	 mov #0, r0