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target/riscv:Perform single step before resume if necessary
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Two cases where single step is needed before resume:
1. ebreak used in software breakpoint;
2. a trigger that is taken just before the instruction
   that triggered it is retired.

Signed-off-by: Songhe Zhu <zhusonghe@eswincomputing.com> Co-developed-by: Fei Gao <gaofei@eswincomputing.com> Co-developed-by: xiatianyi <xiatianyi@eswincomputing.com>
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zhusonghe committed Oct 22, 2024
1 parent a4020f1 commit 1062402
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Showing 2 changed files with 125 additions and 7 deletions.
129 changes: 122 additions & 7 deletions src/target/riscv/riscv.c
Original file line number Diff line number Diff line change
Expand Up @@ -623,12 +623,12 @@ static int find_first_trigger_by_id(struct target *target, int unique_id)

static unsigned int count_trailing_ones(riscv_reg_t reg)
{
assert(sizeof(riscv_reg_t) * 8 == 64);
for (unsigned int i = 0; i < 64; i++) {
const unsigned int riscv_reg_bits = sizeof(riscv_reg_t) * CHAR_BIT;
for (unsigned int i = 0; i < riscv_reg_bits; i++) {
if ((1 & (reg >> i)) == 0)
return i;
}
return 64;
return riscv_reg_bits;
}

static int set_trigger(struct target *target, unsigned int idx, riscv_reg_t tdata1, riscv_reg_t tdata2)
Expand Down Expand Up @@ -1561,6 +1561,100 @@ int riscv_remove_watchpoint(struct target *target,
return ERROR_OK;
}

typedef enum {
M_HIT_ERROR,
M_HIT_NOT_SUPPORTED,
M_NOT_HIT,
M_HIT
} mctrlhitstatus;

static mctrlhitstatus check_mcontrol_hit_status(struct target *target, riscv_reg_t tdata1,
uint64_t hit_mask)
{
if (tdata1 & hit_mask)
return M_HIT;
const riscv_reg_t tdata1_test = set_field(tdata1, CSR_MCONTROL_HIT, 1);
if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_test) != ERROR_OK)
return M_HIT_ERROR;
riscv_reg_t tdata1_test_rb;
if (riscv_reg_get(target, &tdata1_test_rb, GDB_REGNO_TDATA1) != ERROR_OK)
return M_HIT_ERROR;
int tdata1_test_hit = get_field(tdata1_test, CSR_MCONTROL_HIT);
int tdata1_test_rb_hit = get_field(tdata1_test_rb, CSR_MCONTROL_HIT);
if (tdata1_test_rb_hit != tdata1_test_hit)
return M_HIT_NOT_SUPPORTED;

if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_test_rb & ~hit_mask) != ERROR_OK)
return M_HIT_ERROR;
return M_NOT_HIT;
}

typedef enum {
M6_HIT_ERROR,
M6_HIT_NOT_SUPPORTED,
M6_NOT_HIT,
M6_HIT_BEFORE,
M6_HIT_AFTER,
M6_HIT_IMM_AFTER
} mctrl6hitstatus;

static mctrl6hitstatus check_mcontrol6_hit_status(struct target *target,
riscv_reg_t tdata1, uint64_t hit_mask)
{
int hit0 = get_field(tdata1, CSR_MCONTROL6_HIT0);
int hit1 = get_field(tdata1, CSR_MCONTROL6_HIT1);
int hit_info = (hit1 << 1) | hit0;
if (hit_info == CSR_MCONTROL6_HIT0_BEFORE)
return M6_HIT_BEFORE;

if (hit_info == CSR_MCONTROL6_HIT0_AFTER)
return M6_HIT_AFTER;

if (hit_info == CSR_MCONTROL6_HIT0_IMMEDIATELY_AFTER)
return M6_HIT_IMM_AFTER;

if (hit_info == CSR_MCONTROL6_HIT0_FALSE) {
/* Check timing "before" support. */
riscv_reg_t tdata1_hit_before_test = set_field(tdata1, CSR_MCONTROL6_HIT0, 1);
if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_hit_before_test) != ERROR_OK)
return M6_HIT_ERROR;
riscv_reg_t tdata1_test_rb;
if (riscv_reg_get(target, &tdata1_test_rb, GDB_REGNO_TDATA1) != ERROR_OK)
return M6_HIT_ERROR;
if (tdata1_test_rb == tdata1_hit_before_test) {
if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_test_rb & ~hit_mask) != ERROR_OK)
return M6_HIT_ERROR;
return M6_NOT_HIT;
}

/* Check timing "after" support. */
riscv_reg_t tdata1_hit_after_test = set_field(tdata1, CSR_MCONTROL6_HIT1, 1);
if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_hit_after_test) != ERROR_OK)
return M6_HIT_ERROR;
if (riscv_reg_get(target, &tdata1_test_rb, GDB_REGNO_TDATA1) != ERROR_OK)
return M6_HIT_ERROR;
if (tdata1_test_rb == tdata1_hit_after_test) {
if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_test_rb & ~hit_mask) != ERROR_OK)
return M6_HIT_ERROR;
return M6_NOT_HIT;
}

/* Check timing "imm after" support. */
riscv_reg_t tdata1_hit_imm_after_test = tdata1_hit_before_test | tdata1_hit_after_test;
if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_hit_imm_after_test) != ERROR_OK)
return M6_HIT_ERROR;
if (riscv_reg_get(target, &tdata1_test_rb, GDB_REGNO_TDATA1) != ERROR_OK)
return M6_HIT_ERROR;
if (tdata1_test_rb == tdata1_hit_imm_after_test) {
if (riscv_reg_set(target, GDB_REGNO_TDATA1, tdata1_test_rb & ~hit_mask) != ERROR_OK)
return M6_HIT_ERROR;
return M6_NOT_HIT;
}
}
return M6_HIT_NOT_SUPPORTED;
}


/**
* Look at the trigger hit bits to find out which trigger is the reason we're
* halted. Sets *unique_id to the unique ID of that trigger. If *unique_id is
Expand All @@ -1576,6 +1670,7 @@ static int riscv_trigger_detect_hit_bits(struct target *target, int64_t *unique_

// FIXME: Add hit bits support detection and caching
RISCV_INFO(r);
r->need_single_step = false;

riscv_reg_t tselect;
if (riscv_reg_get(target, &tselect, GDB_REGNO_TSELECT) != ERROR_OK)
Expand All @@ -1601,9 +1696,20 @@ static int riscv_trigger_detect_hit_bits(struct target *target, int64_t *unique_
break;
case CSR_TDATA1_TYPE_MCONTROL:
hit_mask = CSR_MCONTROL_HIT;
mctrlhitstatus hit_status = check_mcontrol_hit_status(target, tdata1, hit_mask);
if (hit_status == M_HIT_ERROR)
return ERROR_FAIL;
if (get_field(tdata1, CSR_MCONTROL_TIMING) == CSR_MCONTROL_TIMING_BEFORE
&& (hit_status == M_HIT_NOT_SUPPORTED || hit_status == M_HIT))
r->need_single_step = true;
break;
case CSR_TDATA1_TYPE_MCONTROL6:
hit_mask = CSR_MCONTROL6_HIT0 | CSR_MCONTROL6_HIT1;
mctrl6hitstatus hit12_status = check_mcontrol6_hit_status(target, tdata1, hit_mask);
if (hit12_status == M6_HIT_ERROR)
return ERROR_FAIL;
if (hit12_status == M6_HIT_BEFORE || hit12_status == M6_HIT_NOT_SUPPORTED)
r->need_single_step = true;
break;
case CSR_TDATA1_TYPE_ICOUNT:
hit_mask = CSR_ICOUNT_HIT;
Expand Down Expand Up @@ -2553,10 +2659,19 @@ static int resume_prep(struct target *target, int current,
if (handle_breakpoints) {
/* To be able to run off a trigger, we perform a step operation and then
* resume. If handle_breakpoints is true then step temporarily disables
* pending breakpoints so we can safely perform the step. */
if (old_or_new_riscv_step_impl(target, current, address, handle_breakpoints,
false /* callbacks are not called */) != ERROR_OK)
return ERROR_FAIL;
* pending breakpoints so we can safely perform the step.
*
* Two cases where single step is needed before resuming:
* 1. ebreak used in software breakpoint;
* 2. a trigger that is taken just before the instruction that triggered it is retired.
*/
if (target->debug_reason == DBG_REASON_BREAKPOINT
|| (target->debug_reason == DBG_REASON_WATCHPOINT
&& r->need_single_step)) {
if (old_or_new_riscv_step_impl(target, current, address, handle_breakpoints,
false /* callbacks are not called */) != ERROR_OK)
return ERROR_FAIL;
}
}

if (r->get_hart_state) {
Expand Down
3 changes: 3 additions & 0 deletions src/target/riscv/riscv.h
Original file line number Diff line number Diff line change
Expand Up @@ -152,6 +152,9 @@ struct riscv_info {
/* record the tinfo of each trigger */
unsigned int trigger_tinfo[RISCV_MAX_TRIGGERS];

/* record the dpc that triggered it is retired. */
bool need_single_step;

/* For each physical trigger contains:
* -1: the hwbp is available
* -4: The trigger is used by the itrigger command
Expand Down

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