On Wed, 11 Mar 2020 at 06:44, Richard Henderson
<richard.hender...@linaro.org> wrote:
>
> Allow probing of a watchpoint *without* raising an exception.
> This is of most use for no-fault loads, which should indicate
> via some architectural means that the load did not occur.
>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> include/hw/core/cpu.h | 7 +++++++
> exec.c | 19 +++++++++++++++++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index 73e9a869a4..8ec44267a4 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -1090,6 +1090,12 @@ static inline void cpu_check_watchpoint(CPUState *cpu,
> vaddr addr, vaddr len,
> {
> }
>
> +static inline bool cpu_probe_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
> + int flags)
> +{
> + return false;
> +}
> +
> static inline int cpu_watchpoint_address_matches(CPUState *cpu,
> vaddr addr, vaddr len)
> {
> @@ -1104,6 +1110,7 @@ void cpu_watchpoint_remove_by_ref(CPUState *cpu,
> CPUWatchpoint *watchpoint);
> void cpu_watchpoint_remove_all(CPUState *cpu, int mask);
> void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
> MemTxAttrs attrs, int flags, uintptr_t ra);
> +bool cpu_probe_watchpoint(CPUState *cpu, vaddr addr, vaddr len, int flags);
Could we have a doc comment for the new function?
> int cpu_watchpoint_address_matches(CPUState *cpu, vaddr addr, vaddr len);
> #endif
>
> diff --git a/exec.c b/exec.c
> index 0cc500d53a..2b8f601b9e 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2735,6 +2735,25 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr,
> vaddr len,
> }
> }
>
> +bool cpu_probe_watchpoint(CPUState *cpu, vaddr addr, vaddr len, int flags)
> +{
> + CPUClass *cc = CPU_GET_CLASS(cpu);
> + CPUWatchpoint *wp;
> +
> + assert(tcg_enabled());
> +
> + addr = cc->adjust_watchpoint_address(cpu, addr, len);
> + QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
> + if (watchpoint_address_matches(wp, addr, len) &&
> + (wp->flags & flags) &&
> + (!(wp->flags & BP_CPU) ||
> + !cc->debug_check_watchpoint(cpu, wp))) {
> + return true;
> + }
> + }
> + return false;
> +}
Clearly the insn emulation needs to do the right thing for
guest architectural watchpoints, but should a gdb watchpoint
also affect no-fault-load behaviour? I suppose making them
both behave the same way is probably the least-surprising choice.
thanks
-- PMM
