sandbox: Add a setjmp() implementation

Add an implementation of setjmp() and longjmp() which rely on the
underlying host C library. Since we cannot know how large the jump buffer
needs to be, pick something that should be suitable and check it at
runtime. At present we need access to the underlying struct as well.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/sandbox/cpu/cpu.c

@@ -9,6 +9,7 @@
 #include <linux/libfdt.h>
 #include <os.h>
 #include <asm/io.h>
+#include <asm/setjmp.h>
 #include <asm/state.h>
 #include <dm/root.h>
 
@@ -164,3 +165,15 @@ ulong timer_get_boot_us(void)
 
 	return (count - base_count) / 1000;
 }
+
+int setjmp(jmp_buf jmp)
+{
+	return os_setjmp((ulong *)jmp, sizeof(*jmp));
+}
+
+void longjmp(jmp_buf jmp, int ret)
+{
+	os_longjmp((ulong *)jmp, ret);
+	while (1)
+		;
+}

arch/sandbox/cpu/os.c

@@ -7,6 +7,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
+#include <setjmp.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -628,3 +629,25 @@ void os_localtime(struct rtc_time *rt)
 	rt->tm_yday = tm->tm_yday;
 	rt->tm_isdst = tm->tm_isdst;
 }
+
+int os_setjmp(ulong *jmp, int size)
+{
+	jmp_buf dummy;
+
+	/*
+	 * We cannot rely on the struct name that jmp_buf uses, so use a
+	 * local variable here
+	 */
+	if (size < sizeof(dummy)) {
+		printf("setjmp: jmpbuf is too small (%d bytes, need %d)\n",
+		       size, sizeof(jmp_buf));
+		return -ENOSPC;
+	}
+
+	return setjmp((struct __jmp_buf_tag *)jmp);
+}
+
+void os_longjmp(ulong *jmp, int ret)
+{
+	longjmp((struct __jmp_buf_tag *)jmp, ret);
+}

arch/sandbox/include/asm/setjmp.h

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) 2018 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#ifndef _SETJMP_H_
+#define _SETJMP_H_
+
+struct jmp_buf_data {
+	/*
+	 * We're not sure how long this should be:
+	 *
+	 *   amd64: 200 bytes
+	 *   arm64: 392 bytes
+	 *   armhf: 392 bytes
+	 *
+	 * So allow space for all of those, plus some extra.
+	 * We don't need to worry about 16-byte alignment, since this does not
+	 * run on Windows.
+	 */
+	ulong data[128];
+};
+
+typedef struct jmp_buf_data jmp_buf[1];
+
+int setjmp(jmp_buf jmp);
+__noreturn void longjmp(jmp_buf jmp, int ret);
+
+#endif /* _SETJMP_H_ */

include/os.h

@@ -330,4 +330,25 @@ int os_spl_to_uboot(const char *fname);
  */
 void os_localtime(struct rtc_time *rt);
 
+/**
+ * os_setjmp() - Call setjmp()
+ *
+ * Call the host system's setjmp() function.
+ *
+ * @jmp: Buffer to store current execution state
+ * @size: Size of buffer
+ * @return normal setjmp() value if OK, -ENOSPC if @size is too small
+ */
+int os_setjmp(ulong *jmp, int size);
+
+/**
+ * os_longjmp() - Call longjmp()
+ *
+ * Call the host system's longjmp() function.
+ *
+ * @jmp: Buffer where previous execution state was stored
+ * @ret: Value to pass to longjmp()
+ */
+void os_longjmp(ulong *jmp, int ret);
+
 #endif