ARM: arm_set_cpsr() handles T and J bits

Have arm_set_cpsr() handle the two core state flags, updating
the CPU state.  This eliminates code in various debug_entry()
paths, and marginally improves handling of the J bit.

Catch and comment a few holes in the handling of the J bit on
ARM926ejs cores ... it's unlikely our users will care about
Jazelle mode, but we can at least warn of Impending Doom.  If
anyone does use it, these breadcrumbs may help them to find
the right path through the code.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

7 files changed, 52 insertions, 79 deletions

diff --git a/src/target/arm720t.c b/src/target/arm720t.c
index ac7e4888..3aa77ea4 100644
--- a/src/target/arm720t.c
+++ b/src/target/arm720t.c
@@ -354,7 +354,6 @@ static int arm720t_soft_reset_halt(struct target *target)
 	cpsr |= 0xd3;
 	arm_set_cpsr(armv4_5, cpsr);
 	armv4_5->cpsr->dirty = 1;
-	armv4_5->core_state = ARMV4_5_STATE_ARM;
 
 	/* start fetching from 0x0 */
 	buf_set_u32(armv4_5->core_cache->reg_list[15].value, 0, 32, 0x0);
diff --git a/src/target/arm7_9_common.c b/src/target/arm7_9_common.c
index 9580f62e..19fe98d8 100644
--- a/src/target/arm7_9_common.c
+++ b/src/target/arm7_9_common.c
@@ -1223,6 +1223,8 @@ int arm7_9_soft_reset_halt(struct target *target)
 		arm7_9->change_to_arm(target, &r0_thumb, &pc_thumb);
 	}
 
+	/* REVISIT likewise for bit 5 -- switch Jazelle-to-ARM */
+
 	/* all register content is now invalid */
 	register_cache_invalidate(armv4_5->core_cache);
 
@@ -1234,7 +1236,6 @@ int arm7_9_soft_reset_halt(struct target *target)
 	cpsr |= 0xd3;
 	arm_set_cpsr(armv4_5, cpsr);
 	armv4_5->cpsr->dirty = 1;
-	armv4_5->core_state = ARMV4_5_STATE_ARM;
 
 	/* start fetching from 0x0 */
 	buf_set_u32(armv4_5->core_cache->reg_list[15].value, 0, 32, 0x0);
@@ -1334,7 +1335,7 @@ static int arm7_9_debug_entry(struct target *target)
 	uint32_t context[16];
 	uint32_t* context_p[16];
 	uint32_t r0_thumb, pc_thumb;
-	uint32_t cpsr;
+	uint32_t cpsr, cpsr_mask = 0;
 	int retval;
 	struct arm7_9_common *arm7_9 = target_to_arm7_9(target);
 	struct armv4_5_common_s *armv4_5 = &arm7_9->armv4_5_common;
@@ -1379,11 +1380,21 @@ static int arm7_9_debug_entry(struct target *target)
 		LOG_DEBUG("target entered debug from Thumb state");
 		/* Entered debug from Thumb mode */
 		armv4_5->core_state = ARMV4_5_STATE_THUMB;
+		cpsr_mask = 1 << 5;
 		arm7_9->change_to_arm(target, &r0_thumb, &pc_thumb);
-		LOG_DEBUG("r0_thumb: 0x%8.8" PRIx32 ", pc_thumb: 0x%8.8" PRIx32 "", r0_thumb, pc_thumb);
-	}
-	else
-	{
+		LOG_DEBUG("r0_thumb: 0x%8.8" PRIx32
+			", pc_thumb: 0x%8.8" PRIx32, r0_thumb, pc_thumb);
+	} else if (buf_get_u32(dbg_stat->value, 5, 1)) {
+		/* \todo Get some vaguely correct handling of Jazelle, if
+		 * anyone ever uses it and full info becomes available.
+		 * See ARM9EJS TRM B.7.1 for how to switch J->ARM; and
+		 * B.7.3 for the reverse.  That'd be the bare minimum...
+		 */
+		LOG_DEBUG("target entered debug from Jazelle state");
+		armv4_5->core_state = ARMV4_5_STATE_JAZELLE;
+		cpsr_mask = 1 << 24;
+		LOG_ERROR("Jazelle debug entry -- BROKEN!");
+	} else {
 		LOG_DEBUG("target entered debug from ARM state");
 		/* Entered debug from ARM mode */
 		armv4_5->core_state = ARMV4_5_STATE_ARM;
@@ -1399,11 +1410,10 @@ static int arm7_9_debug_entry(struct target *target)
 	if ((retval = jtag_execute_queue()) != ERROR_OK)
 		return retval;
 
-	/* if the core has been executing in Thumb state, set the T bit */
-	if (armv4_5->core_state == ARMV4_5_STATE_THUMB)
-		cpsr |= 0x20;
-
-	arm_set_cpsr(armv4_5, cpsr);
+	/* Sync our CPSR copy with J or T bits EICE reported, but
+	 * which we then erased by putting the core into ARM mode.
+	 */
+	arm_set_cpsr(armv4_5, cpsr | cpsr_mask);
 
 	if (!is_arm_mode(armv4_5->core_mode))
 	{
diff --git a/src/target/arm920t.c b/src/target/arm920t.c
index 739df3ea..8a03554f 100644
--- a/src/target/arm920t.c
+++ b/src/target/arm920t.c
@@ -603,7 +603,6 @@ int arm920t_soft_reset_halt(struct target *target)
 	cpsr |= 0xd3;
 	arm_set_cpsr(armv4_5, cpsr);
 	armv4_5->cpsr->dirty = 1;
-	armv4_5->core_state = ARMV4_5_STATE_ARM;
 
 	/* start fetching from 0x0 */
 	buf_set_u32(armv4_5->core_cache->reg_list[15].value, 0, 32, 0x0);
diff --git a/src/target/arm926ejs.c b/src/target/arm926ejs.c
index 7ecc7824..aa299890 100644
--- a/src/target/arm926ejs.c
+++ b/src/target/arm926ejs.c
@@ -572,7 +572,6 @@ int arm926ejs_soft_reset_halt(struct target *target)
 	cpsr |= 0xd3;
 	arm_set_cpsr(armv4_5, cpsr);
 	armv4_5->cpsr->dirty = 1;
-	armv4_5->core_state = ARMV4_5_STATE_ARM;
 
 	/* start fetching from 0x0 */
 	buf_set_u32(armv4_5->core_cache->reg_list[15].value, 0, 32, 0x0);
diff --git a/src/target/armv4_5.c b/src/target/armv4_5.c
index 3156c666..22e11869 100644
--- a/src/target/armv4_5.c
+++ b/src/target/armv4_5.c
@@ -372,6 +372,24 @@ void arm_set_cpsr(struct arm *arm, uint32_t cpsr)
 	arm->spsr = (mode == ARMV4_5_MODE_USR || mode == ARMV4_5_MODE_SYS)
 			? NULL
 			: arm->core_cache->reg_list + arm->map[16];
+
+	/* Older ARMs won't have the J bit */
+	enum armv4_5_state state;
+
+	if (cpsr & (1 << 5)) {	/* T */
+		if (cpsr & (1 << 24)) {	/* J */
+			LOG_WARNING("ThumbEE -- incomplete support");
+			state = ARM_STATE_THUMB_EE;
+		} else
+			state = ARMV4_5_STATE_THUMB;
+	} else {
+		if (cpsr & (1 << 24)) {	/* J */
+			LOG_ERROR("Jazelle state handling is BROKEN!");
+			state = ARMV4_5_STATE_JAZELLE;
+		} else
+			state = ARMV4_5_STATE_ARM;
+	}
+	arm->core_state = state;
 }
 
 /**
@@ -481,49 +499,27 @@ static int armv4_5_set_core_reg(struct reg *reg, uint8_t *buf)
 	/* Except for CPSR, the "reg" command exposes a writeback model
 	 * for the register cache.
 	 */
-	buf_set_u32(reg->value, 0, 32, value);
-	reg->dirty = 1;
-	reg->valid = 1;
+	if (reg == armv4_5_target->cpsr) {
+		arm_set_cpsr(armv4_5_target, value);
 
-	if (reg == armv4_5_target->cpsr)
-	{
-		/* FIXME handle J bit too; mostly for ThumbEE, also Jazelle */
-		if (value & 0x20)
-		{
-			/* T bit should be set */
-			if (armv4_5_target->core_state == ARMV4_5_STATE_ARM)
-			{
-				/* change state to Thumb */
-				LOG_DEBUG("changing to Thumb state");
-				armv4_5_target->core_state = ARMV4_5_STATE_THUMB;
-			}
-		}
-		else
-		{
-			/* T bit should be cleared */
-			if (armv4_5_target->core_state == ARMV4_5_STATE_THUMB)
-			{
-				/* change state to ARM */
-				LOG_DEBUG("changing to ARM state");
-				armv4_5_target->core_state = ARMV4_5_STATE_ARM;
-			}
-		}
-
-		/* REVISIT Why only update core for mode change, not also
-		 * for state changes?  Possibly older cores need to stay
-		 * in ARM mode during halt mode debug, not execute Thumb;
-		 * v6/v7a/v7r seem to do that automatically...
+		/* Older cores need help to be in ARM mode during halt
+		 * mode debug, so we clear the J and T bits if we flush.
+		 * For newer cores (v6/v7a/v7r) we don't need that, but
+		 * it won't hurt since CPSR is always flushed anyway.
 		 */
-
-		if (armv4_5_target->core_mode != (enum armv4_5_mode)(value & 0x1f))
-		{
+		if (armv4_5_target->core_mode !=
+				(enum armv4_5_mode)(value & 0x1f)) {
 			LOG_DEBUG("changing ARM core mode to '%s'",
 					arm_mode_name(value & 0x1f));
+			value &= ~((1 << 24) | (1 << 5));
 			armv4_5_target->write_core_reg(target, reg,
 					16, ARMV4_5_MODE_ANY, value);
-			arm_set_cpsr(armv4_5_target, value);
 		}
+	} else {
+		buf_set_u32(reg->value, 0, 32, value);
+		reg->valid = 1;
 	}
+	reg->dirty = 1;
 
 	return ERROR_OK;
 }
@@ -1240,7 +1236,6 @@ int armv4_5_init_arch_info(struct target *target, struct arm *armv4_5)
 
 	armv4_5->common_magic = ARMV4_5_COMMON_MAGIC;
 	arm_set_cpsr(armv4_5, ARMV4_5_MODE_USR);
-	armv4_5->core_state = ARMV4_5_STATE_ARM;
 
 	/* core_type may be overridden by subtype logic */
 	armv4_5->core_type = ARMV4_5_MODE_ANY;
diff --git a/src/target/cortex_a8.c b/src/target/cortex_a8.c
index 71de3b79..fa26b6ab 100644
--- a/src/target/cortex_a8.c
+++ b/src/target/cortex_a8.c
@@ -650,29 +650,6 @@ static int cortex_a8_debug_entry(struct target *target)
 
 	arm_set_cpsr(armv4_5, cpsr);
 
-	i = (cpsr >> 5) & 1;	/* T */
-	i |= (cpsr >> 23) & 1;	/* J << 1 */
-	switch (i) {
-	case 0:	/* J = 0, T = 0 */
-		armv4_5->core_state = ARMV4_5_STATE_ARM;
-		break;
-	case 1:	/* J = 0, T = 1 */
-		armv4_5->core_state = ARMV4_5_STATE_THUMB;
-		break;
-	case 2:	/* J = 1, T = 0 */
-		LOG_WARNING("Jazelle state -- not handled");
-		armv4_5->core_state = ARMV4_5_STATE_JAZELLE;
-		break;
-	case 3:	/* J = 1, T = 1 */
-		/* ThumbEE is very much like Thumb, but some of the
-		 * instructions are different.  Single stepping and
-		 * breakpoints need updating...
-		 */
-		LOG_WARNING("ThumbEE -- incomplete support");
-		armv4_5->core_state = ARM_STATE_THUMB_EE;
-		break;
-	}
-
 	/* update cache */
 	for (i = 0; i <= ARM_PC; i++)
 	{
diff --git a/src/target/xscale.c b/src/target/xscale.c
index 659caec1..e8a3e49f 100644
--- a/src/target/xscale.c
+++ b/src/target/xscale.c
@@ -960,12 +960,6 @@ static int xscale_debug_entry(struct target *target)
 	LOG_DEBUG("target entered debug state in %s mode",
 			 arm_mode_name(armv4_5->core_mode));
 
-	if (buffer[9] & 0x20)
-		armv4_5->core_state = ARMV4_5_STATE_THUMB;
-	else
-		armv4_5->core_state = ARMV4_5_STATE_ARM;
-
-
 	/* get banked registers, r8 to r14, and spsr if not in USR/SYS mode */
 	if ((armv4_5->core_mode != ARMV4_5_MODE_USR) && (armv4_5->core_mode != ARMV4_5_MODE_SYS))
 	{