linux-kernel - Re: [PATCH 3/5] arm64: Handle TRAP

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Message-ID: <20160906161139.GG19605@e104818-lin.cambridge.arm.com>
Date:   Tue, 6 Sep 2016 17:11:39 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Pratyush Anand <panand@...hat.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
        will.deacon@....com, Yang Shi <yang.shi@...aro.org>,
        steve.capper@...aro.org, srikar@...ux.vnet.ibm.com,
        Suzuki K Poulose <suzuki.poulose@....com>,
        vijaya.kumar@...iumnetworks.com, linux-kernel@...r.kernel.org,
        oleg@...hat.com, dave.long@...aro.org,
        Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
        wcohen@...hat.com, Anna-Maria Gleixner <anna-maria@...utronix.de>
Subject: Re: [PATCH 3/5] arm64: Handle TRAP_HWBRKPT for user mode as well

On Tue, Aug 02, 2016 at 11:00:07AM +0530, Pratyush Anand wrote:
> --- a/arch/arm64/kernel/debug-monitors.c
> +++ b/arch/arm64/kernel/debug-monitors.c
> @@ -246,6 +246,8 @@ static void send_user_sigtrap(int si_code)
>  static int single_step_handler(unsigned long addr, unsigned int esr,
>  			       struct pt_regs *regs)
>  {
> +	bool handler_found = false;
> +
>  	/*
>  	 * If we are stepping a pending breakpoint, call the hw_breakpoint
>  	 * handler first.
> @@ -253,7 +255,14 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
>  	if (!reinstall_suspended_bps(regs))
>  		return 0;
>  
> -	if (user_mode(regs)) {
> +#ifdef	CONFIG_KPROBES
> +	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
> +		handler_found = true;
> +#endif
> +	if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
> +		handler_found = true;
> +
> +	if (!handler_found && user_mode(regs)) {
>  		send_user_sigtrap(TRAP_HWBKPT);

Could we register kprobe_single_step_handler() via register_set_hook()
and only invoke call_step_hook() above?

-- 
Catalin