Give control over dcsr.ebreak[msu] bits. (#451)

This allows a user to debug code that uses software breakpoints itself.

Change-Id: If40cb626354e11703017cdf8c5919a31e83ebc3f

doc/openocd.texi

@@ -9511,6 +9511,21 @@ Enable or disable use of a BSCAN tunnel to reach DM.  Supply the width of
 the DM transport TAP's instruction register to enable.  Supply a value of 0 to disable.
 @end deffn
 
+@deffn Command {riscv set_ebreakm} on|off
+Control dcsr.ebreakm. When on (default), M-mode ebreak instructions trap to
+OpenOCD. When off, they generate a breakpoint exception handled internally.
+@end deffn
+
+@deffn Command {riscv set_ebreaks} on|off
+Control dcsr.ebreaks. When on (default), S-mode ebreak instructions trap to
+OpenOCD. When off, they generate a breakpoint exception handled internally.
+@end deffn
+
+@deffn Command {riscv set_ebreaku} on|off
+Control dcsr.ebreaku. When on (default), U-mode ebreak instructions trap to
+OpenOCD. When off, they generate a breakpoint exception handled internally.
+@end deffn
+
 @subsection RISC-V Authentication Commands
 
 The following commands can be used to authenticate to a RISC-V system. Eg.  a

src/target/riscv/riscv-011.c

@@ -1114,7 +1114,10 @@ static int execute_resume(struct target *target, bool step)
 		}
 	}
 
-	info->dcsr |= DCSR_EBREAKM | DCSR_EBREAKH | DCSR_EBREAKS | DCSR_EBREAKU;
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKM, riscv_ebreakm);
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKS, riscv_ebreaks);
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKU, riscv_ebreaku);
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKH, 1);
 	info->dcsr &= ~DCSR_HALT;
 
 	if (step)
@@ -1946,8 +1949,11 @@ static int assert_reset(struct target *target)
 
 	/* Not sure what we should do when there are multiple cores.
 	 * Here just reset the single hart we're talking to. */
-	info->dcsr |= DCSR_EBREAKM | DCSR_EBREAKH | DCSR_EBREAKS |
-		DCSR_EBREAKU | DCSR_HALT;
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKM, riscv_ebreakm);
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKS, riscv_ebreaks);
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKU, riscv_ebreaku);
+	info->dcsr = set_field(info->dcsr, DCSR_EBREAKH, 1);
+	info->dcsr |= DCSR_HALT;
 	if (target->reset_halt)
 		info->dcsr |= DCSR_NDRESET;
 	else

src/target/riscv/riscv-013.c

@@ -4310,9 +4310,9 @@ static int riscv013_on_step_or_resume(struct target *target, bool step)
 	if (result != ERROR_OK)
 		return result;
 	dcsr = set_field(dcsr, CSR_DCSR_STEP, step);
-	dcsr = set_field(dcsr, CSR_DCSR_EBREAKM, 1);
-	dcsr = set_field(dcsr, CSR_DCSR_EBREAKS, 1);
-	dcsr = set_field(dcsr, CSR_DCSR_EBREAKU, 1);
+	dcsr = set_field(dcsr, CSR_DCSR_EBREAKM, riscv_ebreakm);
+	dcsr = set_field(dcsr, CSR_DCSR_EBREAKS, riscv_ebreaks);
+	dcsr = set_field(dcsr, CSR_DCSR_EBREAKU, riscv_ebreaku);
 	return riscv_set_register(target, GDB_REGNO_DCSR, dcsr);
 }
 

src/target/riscv/riscv.c

@@ -252,6 +252,9 @@ int riscv_reset_timeout_sec = DEFAULT_RESET_TIMEOUT_SEC;
 
 bool riscv_prefer_sba;
 bool riscv_enable_virt2phys = true;
+bool riscv_ebreakm = true;
+bool riscv_ebreaks = true;
+bool riscv_ebreaku = true;
 
 bool riscv_enable_virtual;
 
@@ -2465,6 +2468,36 @@ COMMAND_HANDLER(riscv_set_enable_virt2phys)
 	return ERROR_OK;
 }
 
+COMMAND_HANDLER(riscv_set_ebreakm)
+{
+	if (CMD_ARGC != 1) {
+		LOG_ERROR("Command takes exactly 1 parameter");
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+	COMMAND_PARSE_ON_OFF(CMD_ARGV[0], riscv_ebreakm);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(riscv_set_ebreaks)
+{
+	if (CMD_ARGC != 1) {
+		LOG_ERROR("Command takes exactly 1 parameter");
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+	COMMAND_PARSE_ON_OFF(CMD_ARGV[0], riscv_ebreaks);
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(riscv_set_ebreaku)
+{
+	if (CMD_ARGC != 1) {
+		LOG_ERROR("Command takes exactly 1 parameter");
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+	COMMAND_PARSE_ON_OFF(CMD_ARGV[0], riscv_ebreaku);
+	return ERROR_OK;
+}
+
 static const struct command_registration riscv_exec_command_handlers[] = {
 	{
 		.name = "test_compliance",
@@ -2607,6 +2640,30 @@ static const struct command_registration riscv_exec_command_handlers[] = {
 		.usage = "riscv set_enable_virt2phys on|off",
 		.help = "Enable translation from virtual address to physical address."
 	},
+	{
+		.name = "set_ebreakm",
+		.handler = riscv_set_ebreakm,
+		.mode = COMMAND_ANY,
+		.usage = "riscv set_ebreakm on|off",
+		.help = "Control dcsr.ebreakm. When off, M-mode ebreak instructions "
+			"don't trap to OpenOCD. Defaults to on."
+	},
+	{
+		.name = "set_ebreaks",
+		.handler = riscv_set_ebreaks,
+		.mode = COMMAND_ANY,
+		.usage = "riscv set_ebreaks on|off",
+		.help = "Control dcsr.ebreaks. When off, S-mode ebreak instructions "
+			"don't trap to OpenOCD. Defaults to on."
+	},
+	{
+		.name = "set_ebreaku",
+		.handler = riscv_set_ebreaku,
+		.mode = COMMAND_ANY,
+		.usage = "riscv set_ebreaku on|off",
+		.help = "Control dcsr.ebreaku. When off, U-mode ebreak instructions "
+			"don't trap to OpenOCD. Defaults to on."
+	},
 	COMMAND_REGISTRATION_DONE
 };
 

src/target/riscv/riscv.h

@@ -195,6 +195,9 @@ extern int riscv_reset_timeout_sec;
 extern bool riscv_prefer_sba;
 
 extern bool riscv_enable_virtual;
+extern bool riscv_ebreakm;
+extern bool riscv_ebreaks;
+extern bool riscv_ebreaku;
 
 /* Everything needs the RISC-V specific info structure, so here's a nice macro
  * that provides that. */