target/riscv/riscv.c: support auto-selection of software breakpoint size

Add auto-selection of breakpoint size for RISC-V targets. The new length
depends on C extension. If the C extension is used, the auto-selected
length is 2 bytes. Otherwise, the default length is 4 bytes.

Change-Id: Ie3473514beace15b76714aa6d5441122cd3262aa
Signed-off-by: Kulyatskaya Alexandra <a.kulyatskaya@syntacore.com>

Author: AlexandraKulyatskaya

src/target/riscv/riscv.c

@@ -1609,6 +1609,16 @@ static int riscv_add_breakpoint(struct target *target, struct breakpoint *breakp
 	LOG_TARGET_DEBUG(target, "@0x%" TARGET_PRIxADDR, breakpoint->address);
 	assert(breakpoint);
 	if (breakpoint->type == BKPT_SOFT) {
+		if (breakpoint->length == 0) {
+			breakpoint->length = riscv_supports_extension(target, 'c') ? 2 : 4; 
+			uint8_t *instr_buffer = (uint8_t *)realloc (breakpoint->orig_instr, breakpoint->length);
+			if (!instr_buffer) {
+				LOG_ERROR("Fail to realloc memory with original instruction");
+				return ERROR_FAIL;
+			}
+			breakpoint->orig_instr = instr_buffer;
+		}
+
 		/** @todo check RVC for size/alignment */
 		if (!(breakpoint->length == 4 || breakpoint->length == 2)) {
 			LOG_TARGET_ERROR(target, "Invalid breakpoint length %d", breakpoint->length);

testsuite/ocd.basic/auto_selection_bp_size.exp

@@ -0,0 +1,42 @@
+proc is_c_extension {} {
+    set misa [ocdtlb_rsp_get [ocdtlb_run_expect "reg misa"]]
+    set c_ext_bit 2
+    return [expr {($misa >> $c_ext_bit) & 1}]
+}
+
+proc check_bp {ENTRY_ADDR length} {
+    ocdtlb_run_expect "bp $ENTRY_ADDR 0"
+    set real_bp_memory [ocdtlb_run_expect "read_memory $ENTRY_ADDR 8 4"]
+    ocdtlb_run_expect "rbp $ENTRY_ADDR"
+
+    ocdtlb_run_expect "bp $ENTRY_ADDR $length"
+    set expected_bp_memory [ocdtlb_run_expect "read_memory $ENTRY_ADDR 8 4"]
+    ocdtlb_run_expect "rbp $ENTRY_ADDR"
+
+    ocdtlb_expect_equal $real_bp_memory $expected_bp_memory
+}
+
+proc run_test {} {
+    set default_bin_prefix [tool_state_get default_bin_prefix]
+    ocd_compile_executable "basic.S" "$default_bin_prefix.exe"
+
+    # created by compile executable
+    set ENTRY_ADDR [tool_state_get_program_symbol _entry]
+
+    ocd_connect
+
+    ocdtlb_run_expect "targets 0"
+    ocdtlb_run_expect "halt"
+
+    if {[is_c_extension]} {
+        set length 2
+    } else {
+        set length 4
+    }
+
+    check_bp $ENTRY_ADDR $length
+
+    return [ocd_test_pass]
+}
+
+return [run_test]