riscv: Add setjmp/longjmp code

To support efi_loader we need to have platform support for setjmp/longjmp.
Add it here.

Signed-off-by: Alexander Graf <agraf@suse.de>

arch/riscv/include/asm/setjmp.h

@@ -0,0 +1,26 @@
+/*
+ * (C) Copyright 2018 Alexander Graf <agraf@suse.de>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _SETJMP_H_
+#define _SETJMP_H_	1
+
+/*
+ * This really should be opaque, but the EFI implementation wrongly
+ * assumes that a 'struct jmp_buf_data' is defined.
+ */
+struct jmp_buf_data {
+	/* x2, x8, x9, x18, x19, x20, x21, x22, x23, x24, x25, x26, x27, sp */
+	unsigned long s_regs[12];	/* s0 - s11 */
+	unsigned long ra;
+	unsigned long sp;
+};
+
+typedef struct jmp_buf_data jmp_buf[1];
+
+int setjmp(jmp_buf jmp);
+void longjmp(jmp_buf jmp, int ret);
+
+#endif /* _SETJMP_H_ */

arch/riscv/lib/Makefile

@@ -10,3 +10,4 @@ obj-$(CONFIG_CMD_BOOTM) += bootm.o
 obj-$(CONFIG_CMD_GO) += boot.o
 obj-y	+= cache.o
 obj-y	+= interrupts.o
+obj-y   += setjmp.o

arch/riscv/lib/setjmp.S

@@ -0,0 +1,66 @@
+/*
+ * (C) 2018 Alexander Graf <agraf@suse.de>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <config.h>
+#include <linux/linkage.h>
+
+#ifdef CONFIG_CPU_RISCV_64
+#define STORE_IDX(reg, idx)	sd reg, (idx*8)(a0)
+#define LOAD_IDX(reg, idx)	ld reg, (idx*8)(a0)
+#else
+#define STORE_IDX(reg, idx)	sw reg, (idx*4)(a0)
+#define LOAD_IDX(reg, idx)	lw reg, (idx*4)(a0)
+#endif
+
+.pushsection .text.setjmp, "ax"
+ENTRY(setjmp)
+	/* Preserve all callee-saved registers and the SP */
+	STORE_IDX(s0, 0)
+	STORE_IDX(s1, 1)
+	STORE_IDX(s2, 2)
+	STORE_IDX(s3, 3)
+	STORE_IDX(s4, 4)
+	STORE_IDX(s5, 5)
+	STORE_IDX(s6, 6)
+	STORE_IDX(s7, 7)
+	STORE_IDX(s8, 8)
+	STORE_IDX(s9, 9)
+	STORE_IDX(s10, 10)
+	STORE_IDX(s11, 11)
+	STORE_IDX(ra, 12)
+	STORE_IDX(sp, 13)
+	li  a0, 0
+	ret
+ENDPROC(setjmp)
+.popsection
+
+.pushsection .text.longjmp, "ax"
+ENTRY(longjmp)
+	LOAD_IDX(s0, 0)
+	LOAD_IDX(s1, 1)
+	LOAD_IDX(s2, 2)
+	LOAD_IDX(s3, 3)
+	LOAD_IDX(s4, 4)
+	LOAD_IDX(s5, 5)
+	LOAD_IDX(s6, 6)
+	LOAD_IDX(s7, 7)
+	LOAD_IDX(s8, 8)
+	LOAD_IDX(s9, 9)
+	LOAD_IDX(s10, 10)
+	LOAD_IDX(s11, 11)
+	LOAD_IDX(ra, 12)
+	LOAD_IDX(sp, 13)
+
+	/* Move the return value in place, but return 1 if passed 0. */
+	beq a1, zero, longjmp_1
+	mv a0, a1
+	ret
+
+	longjmp_1:
+	li a0, 1
+	ret
+ENDPROC(longjmp)
+.popsection