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ARM: fix Thumb mode handling when single-stepping register based branch insns 

Currently, OpenOCD is always caching the PC value without the T bit.
This means that assignment to the PC register must clear that bit and set
the processor state to Thumb when it is set.  And when the PC register
value is transferred to another register or stored into memory then
the T bit must be restored.

Discussion: It is arguable if OpenOCd should have preserved the original
PC value which would have greatly simplified this code.  The processor
state could then be obtained simply by getting at bit 0 of the PC.  This
however would require special handling elsewhere instead since the T bit
is not always relevant (like when PC is used with ALU insns or as an index
with some addressing modes).  It is unclear which way would be simpler in
the end.

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
__archive__
Nicolas Pitre 2009-10-27 01:14:34 -04:00 committed by David Brownell
parent 068a6c7895
commit 68937cadfb
1 changed files with 33 additions and 22 deletions
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53
src/target/arm_simulator.c
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@ -380,7 +380,8 @@ int arm_simulate_step_core(target_t *target, uint32_t *dry_run_pc, struct arm_si
else if (instruction.type == ARM_BL)
{
uint32_t old_pc = sim->get_reg(sim, 15);
sim->set_reg_mode(sim, 14, old_pc + 4);
int T = (sim->get_state(sim) == ARMV4_5_STATE_THUMB);
sim->set_reg_mode(sim, 14, old_pc + 4 + T);
sim->set_reg(sim, 15, target);
}
else if (instruction.type == ARM_BX)
@ -398,7 +399,8 @@ int arm_simulate_step_core(target_t *target, uint32_t *dry_run_pc, struct arm_si
else if (instruction.type == ARM_BLX)
{
uint32_t old_pc = sim->get_reg(sim, 15);
sim->set_reg_mode(sim, 14, old_pc + 4);
int T = (sim->get_state(sim) == ARMV4_5_STATE_THUMB);
sim->set_reg_mode(sim, 14, old_pc + 4 + T);
if (target & 0x1)
{
@ -465,24 +467,24 @@ int arm_simulate_step_core(target_t *target, uint32_t *dry_run_pc, struct arm_si
if (dry_run_pc)
{
if (instruction.info.data_proc.Rd == 15)
{
*dry_run_pc = Rd;
return ERROR_OK;
}
*dry_run_pc = Rd & ~1;
else
{
*dry_run_pc = current_pc + instruction_size;
}
return ERROR_OK;
}
else
{
if (instruction.info.data_proc.Rd == 15) {
sim->set_reg_mode(sim, 15, Rd & ~1);
if (Rd & 1)
sim->set_state(sim, ARMV4_5_STATE_THUMB);
else
sim->set_state(sim, ARMV4_5_STATE_ARM);
return ERROR_OK;
}
sim->set_reg_mode(sim, instruction.info.data_proc.Rd, Rd);
LOG_WARNING("no updating of flags yet");
if (instruction.info.data_proc.Rd == 15)
return ERROR_OK;
}
}
/* compare instructions (CMP, CMN, TST, TEQ) */
@ -566,15 +568,9 @@ int arm_simulate_step_core(target_t *target, uint32_t *dry_run_pc, struct arm_si
if (dry_run_pc)
{
if (instruction.info.load_store.Rd == 15)
{
*dry_run_pc = load_value;
return ERROR_OK;
}
*dry_run_pc = load_value & ~1;
else
{
*dry_run_pc = current_pc + instruction_size;
}
return ERROR_OK;
}
else
@ -584,11 +580,17 @@ int arm_simulate_step_core(target_t *target, uint32_t *dry_run_pc, struct arm_si
{
sim->set_reg_mode(sim, instruction.info.load_store.Rn, modified_address);
}
sim->set_reg_mode(sim, instruction.info.load_store.Rd, load_value);
if (instruction.info.load_store.Rd == 15)
if (instruction.info.load_store.Rd == 15) {
sim->set_reg_mode(sim, 15, load_value & ~1);
if (load_value & 1)
sim->set_state(sim, ARMV4_5_STATE_THUMB);
else
sim->set_state(sim, ARMV4_5_STATE_ARM);
return ERROR_OK;
}
sim->set_reg_mode(sim, instruction.info.load_store.Rd, load_value);
}
}
/* load multiple instruction */
else if (instruction.type == ARM_LDM)
@ -636,7 +638,7 @@ int arm_simulate_step_core(target_t *target, uint32_t *dry_run_pc, struct arm_si
{
if (instruction.info.load_store_multiple.register_list & 0x8000)
{
*dry_run_pc = load_values[15];
*dry_run_pc = load_values[15] & ~1;
return ERROR_OK;
}
}
@ -657,9 +659,18 @@ int arm_simulate_step_core(target_t *target, uint32_t *dry_run_pc, struct arm_si
{
if (instruction.info.load_store_multiple.register_list & (1 << i))
{
if (i == 15) {
uint32_t val = load_values[i];
sim->set_reg_mode(sim, i, val & ~1);
if (val & 1)
sim->set_state(sim, ARMV4_5_STATE_THUMB);
else
sim->set_state(sim, ARMV4_5_STATE_ARM);
} else {
sim->set_reg_mode(sim, i, load_values[i]);
}
}
}
if (update_cpsr)
{