From: Michel Pollet <buserror@gmail.com>
Date: Wed, 10 Jan 2018 09:26:54 +0000 (+0000)
Subject: core: Added support for PC overflow
X-Git-Tag: v1.6~1
X-Git-Url: https://git.htl-mechatronik.at/public/?a=commitdiff_plain;h=7a77ebb65ab202837e4713f8758f096a39c0d95a;p=sx%2Fsimavr.git

core: Added support for PC overflow

Added a special opcode at the end of flash to catch PC overflow, and
'wrap it'. Also log the condition.
This allow that case to be handled without having to add a
modulo/division for each instruction.

Signed-off-by: Michel Pollet <buserror@gmail.com>
---

diff --git a/simavr/sim/sim_avr.c b/simavr/sim/sim_avr.c
index 1878b41..d33400a 100644
--- a/simavr/sim/sim_avr.c
+++ b/simavr/sim/sim_avr.c
@@ -96,8 +96,9 @@ int
 avr_init(
 		avr_t * avr)
 {
-	avr->flash = malloc(avr->flashend + 1);
+	avr->flash = malloc(avr->flashend + 4);
 	memset(avr->flash, 0xff, avr->flashend + 1);
+	*((uint16_t*)&avr->flash[avr->flashend + 1]) = AVR_OVERFLOW_OPCODE;
 	avr->codeend = avr->flashend;
 	avr->data = malloc(avr->ramend + 1);
 	memset(avr->data, 0, avr->ramend + 1);
diff --git a/simavr/sim/sim_core.c b/simavr/sim/sim_core.c
index f3b163d..7be739b 100644
--- a/simavr/sim/sim_core.c
+++ b/simavr/sim/sim_core.c
@@ -1363,6 +1363,13 @@ run_one_again:
 
 		case 0xf000: {
 			switch (opcode & 0xfe00) {
+				case 0xf100: {	/* simavr special opcodes */
+					if (opcode == 0xf1f1) { // AVR_OVERFLOW_OPCODE
+						printf("FLASH overflow, soft reset\n");
+						new_pc = 0;
+						TRACE_JUMP();
+					}
+				}	break;
 				case 0xf000:
 				case 0xf200:
 				case 0xf400:
diff --git a/simavr/sim/sim_core.h b/simavr/sim/sim_core.h
index fa99638..403c119 100644
--- a/simavr/sim/sim_core.h
+++ b/simavr/sim/sim_core.h
@@ -129,6 +129,12 @@ static inline void avr_sreg_set(avr_t * avr, uint8_t flag, uint8_t ival)
 				avr_sreg_set(avr, i, (src & (1 << i)) != 0); \
 		}
 
+/*
+ * Opcode is sitting at the end of the flash to catch PC overflows.
+ * Apparently it's used by some code to simulate soft reset?
+ */
+#define AVR_OVERFLOW_OPCODE 0xf1f1
+
 #ifdef __cplusplus
 };
 #endif