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Re: [PATCH] target/riscv: set tval for triggered watchpoints
From: |
Sergey Matyukevich |
Subject: |
Re: [PATCH] target/riscv: set tval for triggered watchpoints |
Date: |
Tue, 31 Jan 2023 10:58:09 +0300 |
Hi Bin,
> > > According to priviledged spec, if [sm]tval is written with a nonzero
> > > value when a breakpoint exception occurs, then [sm]tval will contain
> > > the faulting virtual address. Set tval to hit address when breakpoint
> > > exception is triggered by hardware watchpoint.
> > >
> > > Signed-off-by: Sergey Matyukevich <sergey.matyukevich@syntacore.com>
> >
> > Thanks!
> >
> > Applied to riscv-to-apply.next
>
> Oops, too quick, but I have one comment :)
>
> >
> > Alistair
> >
> > > ---
> > > target/riscv/cpu_helper.c | 3 +++
> > > target/riscv/debug.c | 1 +
> > > 2 files changed, 4 insertions(+)
> > >
> > > diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> > > index 9a28816521..d3be8c0511 100644
> > > --- a/target/riscv/cpu_helper.c
> > > +++ b/target/riscv/cpu_helper.c
> > > @@ -1641,6 +1641,9 @@ void riscv_cpu_do_interrupt(CPUState *cs)
> > > case RISCV_EXCP_VIRT_INSTRUCTION_FAULT:
> > > tval = env->bins;
> > > break;
> > > + case RISCV_EXCP_BREAKPOINT:
> > > + tval = env->badaddr;
>
> RISCV_EXCP_BREAKPOINT may come from 'ebreak' so we should test if this
> exception comes from the debug module.
>
> The spec also says about icount trigger that:
>
> "If the trigger fires with action =0 then zero is written to the tval
> CSR on the breakpoint trap."
>
> So we can't blindly set tval for every breakpoint exception.
>
Thanks for catching ! Initial idea was to set badaddr value only when
it is needed in target/riscv/debug.c. For instance, icount code does
not set badaddr, so tval will remain zero. On the other hand, breakpoint
exception may come from ebreak and badaddr may keep non-zero value from
some previous unrelated exception.
Explicit check should be more safe, e.g. something like that:
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index d3be8c0511..f1a0c65ad3 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -1642,7 +1642,10 @@ void riscv_cpu_do_interrupt(CPUState *cs)
tval = env->bins;
break;
case RISCV_EXCP_BREAKPOINT:
- tval = env->badaddr;
+ if (cs->watchpoint_hit) {
+ tval = cs->watchpoint_hit->hitaddr;
+ cs->watchpoint_hit = NULL;
+ }
break;
default:
break;
diff --git a/target/riscv/debug.c b/target/riscv/debug.c
index 48ef3c59ea..b091293069 100644
--- a/target/riscv/debug.c
+++ b/target/riscv/debug.c
@@ -761,8 +761,6 @@ void riscv_cpu_debug_excp_handler(CPUState *cs)
if (cs->watchpoint_hit) {
if (cs->watchpoint_hit->flags & BP_CPU) {
- env->badaddr = cs->watchpoint_hit->hitaddr;
- cs->watchpoint_hit = NULL;
do_trigger_action(env, DBG_ACTION_BP);
}
} else {
I will a fixup after testing.
Regards,
Sergey