Currently, single-stepping is tied to GDB debugging. This means that when
EXCP_DEBUG is returned, a debug exception is triggered in many cases. We
define a new EXCP_SINGLESTEP to differentiate the case where we want a
single step to not be tied to a debug exception. We also define a new flag
for cpu->singlestep_enabled called SSTEP_NODEBUG which is set when we want
to use single-step for purposes other than debugging.
Signed-off-by: Joelle van Dyne <j...@getutm.app>
---
include/exec/cpu-common.h | 1 +
include/hw/core/cpu.h | 1 +
target/arm/internals.h | 3 ++-
accel/tcg/cpu-exec.c | 35 +++++++++++++++++++++++++----------
cpu-target.c | 7 +++++--
5 files changed, 34 insertions(+), 13 deletions(-)
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index b1d76d6985..e1c798b07d 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -22,6 +22,7 @@
#define EXCP_HALTED 0x10003 /* cpu is halted (waiting for external event)
*/
#define EXCP_YIELD 0x10004 /* cpu wants to yield timeslice to another */
#define EXCP_ATOMIC 0x10005 /* stop-the-world and emulate atomic */
+#define EXCP_SINGLESTEP 0x10006 /* singlestep without debugging */
void cpu_exec_init_all(void);
void cpu_exec_step_atomic(CPUState *cpu);
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index fb397cdfc5..e3c8450f8f 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -1072,6 +1072,7 @@ void qemu_init_vcpu(CPUState *cpu);
#define SSTEP_ENABLE 0x1 /* Enable simulated HW single stepping */
#define SSTEP_NOIRQ 0x2 /* Do not use IRQ while single stepping */
#define SSTEP_NOTIMER 0x4 /* Do not Timers while single stepping */
+#define SSTEP_NODEBUG 0x8 /* Single-stepping is not for debugging */
/**
* cpu_single_step:
diff --git a/target/arm/internals.h b/target/arm/internals.h
index 863a84edf8..961cd9927a 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -57,7 +57,8 @@ static inline bool excp_is_internal(int excp)
|| excp == EXCP_HALTED
|| excp == EXCP_EXCEPTION_EXIT
|| excp == EXCP_KERNEL_TRAP
- || excp == EXCP_SEMIHOST;
+ || excp == EXCP_SEMIHOST
+ || excp == EXCP_SINGLESTEP;
}
/*
diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 8b773d8847..6b4e63e69e 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -349,7 +349,7 @@ static bool check_for_breakpoints_slow(CPUState *cpu, vaddr
pc,
* so that one could (gdb) singlestep into the guest kernel's
* architectural breakpoint handler.
*/
- if (cpu->singlestep_enabled) {
+ if (cpu->singlestep_enabled && !(cpu->singlestep_enabled & SSTEP_NODEBUG))
{
return false;
}
@@ -529,7 +529,11 @@ cpu_tb_exec(CPUState *cpu, TranslationBlock *itb, int
*tb_exit)
* is handled in cpu_handle_exception.
*/
if (unlikely(cpu->singlestep_enabled) && cpu->exception_index == -1) {
- cpu->exception_index = EXCP_DEBUG;
+ if (!(cpu->singlestep_enabled & SSTEP_NODEBUG)) {
+ cpu->exception_index = EXCP_DEBUG;
+ } else {
+ cpu->exception_index = EXCP_SINGLESTEP;
+ }
cpu_loop_exit(cpu);
}
@@ -781,13 +785,20 @@ static inline bool cpu_handle_exception(CPUState *cpu,
int *ret)
cpu->exception_index = -1;
if (unlikely(cpu->singlestep_enabled)) {
- /*
- * After processing the exception, ensure an EXCP_DEBUG is
- * raised when single-stepping so that GDB doesn't miss the
- * next instruction.
- */
- *ret = EXCP_DEBUG;
- cpu_handle_debug_exception(cpu);
+ if (!(cpu->singlestep_enabled & SSTEP_NODEBUG)) {
+ /*
+ * After processing the exception, ensure an EXCP_DEBUG is
+ * raised when single-stepping so that GDB doesn't miss the
+ * next instruction.
+ */
+ *ret = EXCP_DEBUG;
+ cpu_handle_debug_exception(cpu);
+ } else {
+ /*
+ * In case of non-debug single step, just return
+ */
+ *ret = EXCP_SINGLESTEP;
+ }
return true;
}
} else if (!replay_has_interrupt()) {
@@ -892,7 +903,11 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
* next instruction.
*/
if (unlikely(cpu->singlestep_enabled)) {
- cpu->exception_index = EXCP_DEBUG;
+ if (!(cpu->singlestep_enabled & SSTEP_NODEBUG)) {
+ cpu->exception_index = EXCP_DEBUG;
+ } else {
+ cpu->exception_index = EXCP_SINGLESTEP;
+ }
bql_unlock();
return true;
}
diff --git a/cpu-target.c b/cpu-target.c
index 667688332c..6293477ed9 100644
--- a/cpu-target.c
+++ b/cpu-target.c
@@ -322,9 +322,12 @@ void list_cpus(void)
CPU loop after each instruction */
void cpu_single_step(CPUState *cpu, int enabled)
{
- if (cpu->singlestep_enabled != enabled) {
- cpu->singlestep_enabled = enabled;
+ int previous = cpu->singlestep_enabled;
+ bool prev_debug_en = previous && !(previous & SSTEP_NODEBUG);
+ bool cur_debug_en = enabled && !(enabled & SSTEP_NODEBUG);
+ cpu->singlestep_enabled = enabled;
+ if (prev_debug_en != cur_debug_en) {
#if !defined(CONFIG_USER_ONLY)
const AccelOpsClass *ops = cpus_get_accel();
if (ops->update_guest_debug) {
--
2.41.0
