Re: [PATCH v6 17/22] arm64: mm: Add page fault trace points

[Will Deacon <will@kernel.org>]

On Wed, Apr 30, 2025 at 01:02:32PM +0200, Nam Cao wrote:
> Add page fault trace points, which are useful to implement RV monitor which
> watches page faults.
> 
> Signed-off-by: Nam Cao <namcao@linutronix.de>
> ---
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: linux-arm-kernel@lists.infradead.org
> ---
>  arch/arm64/mm/fault.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index ef63651099a9..e3f096b0dffd 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -44,6 +44,9 @@
>  #include <asm/tlbflush.h>
>  #include <asm/traps.h>
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/exceptions.h>
> +
>  struct fault_info {
>  	int	(*fn)(unsigned long far, unsigned long esr,
>  		      struct pt_regs *regs);
> @@ -559,6 +562,11 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
>  	if (kprobe_page_fault(regs, esr))
>  		return 0;
>  
> +	if (user_mode(regs))
> +		trace_page_fault_user(addr, regs, esr);
> +	else
> +		trace_page_fault_kernel(addr, regs, esr);

Why is this after kprobe_page_fault()?

It's also a shame that the RV monitor can't hook into perf, as we
already have a sw event for page faults that you could use instead of
adding something new.

Will