Add RISC-V support.

This supports both 0.11 and 0.13 versions of the debug spec.

Support for `-rtos riscv` will come in a separate commit since it was
easy to separate out, and is likely to be more controversial.

Flash support for the SiFive boards will also come in a later commit.

Change-Id: I1d38fe669c2041b4e21a5c54a091594aac3e2190
Signed-off-by: Tim Newsome <tim@sifive.com>
Reviewed-on: http://openocd.zylin.com/4578
Tested-by: jenkins
Reviewed-by: Liviu Ionescu <ilg@livius.net>
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>

src/target/riscv/program.h

@@ -0,0 +1,75 @@
+#ifndef TARGET__RISCV__PROGRAM_H
+#define TARGET__RISCV__PROGRAM_H
+
+#include "riscv.h"
+
+#define RISCV_MAX_DEBUG_BUFFER_SIZE 32
+#define RISCV_REGISTER_COUNT 32
+#define RISCV_DSCRATCH_COUNT 2
+
+/* The various RISC-V debug specifications all revolve around setting up
+ * program buffers and executing them on the target.  This structure contains a
+ * single program, which can then be executed on targets.  */
+struct riscv_program {
+	struct target *target;
+
+	uint32_t debug_buffer[RISCV_MAX_DEBUG_BUFFER_SIZE];
+
+	/* Number of 32-bit instructions in the program. */
+	size_t instruction_count;
+
+	/* Side effects of executing this program.  These must be accounted for
+	 * in order to maintain correct executing of the target system.  */
+	bool writes_xreg[RISCV_REGISTER_COUNT];
+
+	/* XLEN on the target. */
+	int target_xlen;
+};
+
+/* Initializes a program with the header. */
+int riscv_program_init(struct riscv_program *p, struct target *t);
+
+/* Write the program to the program buffer. */
+int riscv_program_write(struct riscv_program *program);
+
+/* Executes a program, returning 0 if the program successfully executed.  Note
+ * that this may cause registers to be saved or restored, which could result to
+ * calls to things like riscv_save_register which itself could require a
+ * program to execute.  That's OK, just make sure this eventually terminates.
+ * */
+int riscv_program_exec(struct riscv_program *p, struct target *t);
+int riscv_program_load(struct riscv_program *p, struct target *t);
+
+/* Clears a program, removing all the state associated with it. */
+int riscv_program_clear(struct riscv_program *p, struct target *t);
+
+/* A lower level interface, you shouldn't use this unless you have a reason. */
+int riscv_program_insert(struct riscv_program *p, riscv_insn_t i);
+
+/* There is hardware support for saving at least one register.  This register
+ * doesn't need to be saved/restored the usual way, which is useful during
+ * early initialization when we can't save/restore arbitrary registerrs to host
+ * memory. */
+int riscv_program_save_to_dscratch(struct riscv_program *p, enum gdb_regno to_save);
+
+/* Helpers to assembly various instructions.  Return 0 on success.  These might
+ * assembly into a multi-instruction sequence that overwrites some other
+ * register, but those will be properly saved and restored. */
+int riscv_program_lwr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno a, int o);
+int riscv_program_lhr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno a, int o);
+int riscv_program_lbr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno a, int o);
+
+int riscv_program_swr(struct riscv_program *p, enum gdb_regno s, enum gdb_regno a, int o);
+int riscv_program_shr(struct riscv_program *p, enum gdb_regno s, enum gdb_regno a, int o);
+int riscv_program_sbr(struct riscv_program *p, enum gdb_regno s, enum gdb_regno a, int o);
+
+int riscv_program_csrr(struct riscv_program *p, enum gdb_regno d, enum gdb_regno csr);
+int riscv_program_csrw(struct riscv_program *p, enum gdb_regno s, enum gdb_regno csr);
+
+int riscv_program_fence_i(struct riscv_program *p);
+int riscv_program_fence(struct riscv_program *p);
+int riscv_program_ebreak(struct riscv_program *p);
+
+int riscv_program_addi(struct riscv_program *p, enum gdb_regno d, enum gdb_regno s, int16_t i);
+
+#endif