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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 <[email protected]> Co-developed-by: Fei Gao <[email protected]> Co-developed-by: xiatianyi <[email protected]>
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zhusonghe committed Oct 17, 2024
1 parent a4020f1 commit 0097f6b
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Showing 2 changed files with 100 additions and 8 deletions.
105 changes: 97 additions & 8 deletions src/target/riscv/riscv.c
View file
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 @@ -1576,6 +1576,7 @@ 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 @@ -1589,21 +1590,100 @@ static int riscv_trigger_detect_hit_bits(struct target *target, int64_t *unique_
if (riscv_reg_set(target, GDB_REGNO_TSELECT, i) != ERROR_OK)
return ERROR_FAIL;

uint64_t tdata1;
uint64_t tdata1, tdata1_test_rb;
if (riscv_reg_get(target, &tdata1, GDB_REGNO_TDATA1) != ERROR_OK)
return ERROR_FAIL;
int type = get_field(tdata1, CSR_TDATA1_TYPE(riscv_xlen(target)));

uint64_t hit_mask = 0;
bool mcontrol_hit_not_supported = false;
bool mcontrol6_hit_not_supported = false;
switch (type) {
case CSR_TDATA1_TYPE_LEGACY:
/* Doesn't support hit bit. */
break;
case CSR_TDATA1_TYPE_MCONTROL:
hit_mask = CSR_MCONTROL_HIT;
/* Check if mcontrol.hit is implemented */
if ((tdata1 & hit_mask) == 0) {
uint64_t tdata1_test =
set_field(tdata1, CSR_MCONTROL_HIT, 1);
if (riscv_reg_set(target,
GDB_REGNO_TDATA1, tdata1_test) != ERROR_OK)
return ERROR_FAIL;
if (riscv_reg_get(target,
&tdata1_test_rb, GDB_REGNO_TDATA1) != ERROR_OK)
return ERROR_FAIL;
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_hit != tdata1_test_rb_hit)
mcontrol_hit_not_supported = true;
if (riscv_reg_set(target, GDB_REGNO_TDATA1,
tdata1_test & ~hit_mask) != ERROR_OK)
return ERROR_FAIL;
}

if (get_field(tdata1, CSR_MCONTROL_TIMING)
== CSR_MCONTROL_TIMING_BEFORE
&& (mcontrol_hit_not_supported || (tdata1 & hit_mask)))
r->need_single_step = true;
break;
case CSR_TDATA1_TYPE_MCONTROL6:
hit_mask = CSR_MCONTROL6_HIT0 | CSR_MCONTROL6_HIT1;
int hit0 = get_field(tdata1, CSR_MCONTROL6_HIT0);
int hit1 = get_field(tdata1, CSR_MCONTROL6_HIT1);
int trigger_retired_info = (hit1 << 1) | hit0;
/* Check if mcontrol6.hit0[1] is not implemented. */
if (trigger_retired_info == 0) {
for (unsigned int j = 0; j < 2; j++) {
uint64_t tdata1_test =
set_field(tdata1, CSR_MCONTROL6_HIT0, j);
for (unsigned int k = 0; k < 2; k++) {
tdata1_test =
set_field(tdata1_test, CSR_MCONTROL6_HIT1, k);
if (riscv_reg_set(target,
GDB_REGNO_TDATA1, tdata1_test) != ERROR_OK)
return ERROR_FAIL;
if (riscv_reg_get(target,
&tdata1_test_rb, GDB_REGNO_TDATA1) != ERROR_OK)
return ERROR_FAIL;
int tdata1_test_hit0 =
get_field(tdata1_test, CSR_MCONTROL6_HIT0);
int tdata1_test_rb_hit0 =
get_field(tdata1_test_rb, CSR_MCONTROL6_HIT0);
int tdata1_test_hit1 =
get_field(tdata1_test, CSR_MCONTROL6_HIT1);
int tdata1_test_rb_hit1 =
get_field(tdata1_test_rb, CSR_MCONTROL6_HIT1);
int trigger_retired_test_info =
(tdata1_test_hit1 << 1) | tdata1_test_hit0;
int trigger_retired_test_rb_info =
(tdata1_test_rb_hit1 << 1) | tdata1_test_rb_hit0;
if (trigger_retired_test_info == 0)
continue;

if (trigger_retired_test_info
!= trigger_retired_test_rb_info) {
mcontrol6_hit_not_supported = true;
} else {
mcontrol6_hit_not_supported = false;
if (riscv_reg_set(target, GDB_REGNO_TDATA1,
tdata1_test & ~hit_mask) != ERROR_OK)
return ERROR_FAIL;
goto done;
}
}
if (riscv_reg_set(target, GDB_REGNO_TDATA1,
tdata1_test & ~hit_mask) != ERROR_OK)
return ERROR_FAIL;
}
}
done:
if (mcontrol6_hit_not_supported
|| trigger_retired_info == CSR_MCONTROL6_HIT0_BEFORE)
r->need_single_step = true;
break;
case CSR_TDATA1_TYPE_ICOUNT:
hit_mask = CSR_ICOUNT_HIT;
Expand Down Expand Up @@ -2553,10 +2633,19 @@ 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
View file
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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