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Subject: Re: [PATCH 09/15] powerpc/watchpoint: Convert thread_struct->hw_brk
 to an array
To:     Ravi Bangoria <ravi.bangoria@linux.ibm.com>, mpe@ellerman.id.au,
        mikey@neuling.org
Cc:     apopple@linux.ibm.com, paulus@samba.org, npiggin@gmail.com,
        naveen.n.rao@linux.vnet.ibm.com, peterz@infradead.org,
        jolsa@kernel.org, oleg@redhat.com, fweisbec@gmail.com,
        mingo@kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org
References: <20200309085806.155823-1-ravi.bangoria@linux.ibm.com>
 <20200309085806.155823-10-ravi.bangoria@linux.ibm.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <0fc9489d-9955-f649-9007-ce6f5da345be@c-s.fr>
Date:   Tue, 17 Mar 2020 11:37:46 +0100
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Le 09/03/2020 à 09:58, Ravi Bangoria a écrit :
> So far powerpc hw supported only one watchpoint. But Future Power
> architecture is introducing 2nd DAWR. Convert thread_struct->hw_brk
> into an array.

Looks like you are doing a lot more than that in this patch.

Should this patch be splitted in two parts ?

Christophe

> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
> ---
>   arch/powerpc/include/asm/processor.h |  2 +-
>   arch/powerpc/kernel/process.c        | 43 ++++++++++++++++++++--------
>   arch/powerpc/kernel/ptrace.c         | 42 ++++++++++++++++++++-------
>   arch/powerpc/kernel/ptrace32.c       |  4 +--
>   arch/powerpc/kernel/signal.c         |  9 ++++--
>   5 files changed, 72 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
> index 666b2825278c..57a8fac2e72b 100644
> --- a/arch/powerpc/include/asm/processor.h
> +++ b/arch/powerpc/include/asm/processor.h
> @@ -183,7 +183,7 @@ struct thread_struct {
>   	 */
>   	struct perf_event *last_hit_ubp;
>   #endif /* CONFIG_HAVE_HW_BREAKPOINT */
> -	struct arch_hw_breakpoint hw_brk; /* info on the hardware breakpoint */
> +	struct arch_hw_breakpoint hw_brk[HBP_NUM_MAX]; /* hardware breakpoint info */
>   	unsigned long	trap_nr;	/* last trap # on this thread */
>   	u8 load_slb;			/* Ages out SLB preload cache entries */
>   	u8 load_fp;
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index f6bb2586fa5d..42ff62ef749c 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -704,21 +704,25 @@ void switch_booke_debug_regs(struct debug_reg *new_debug)
>   EXPORT_SYMBOL_GPL(switch_booke_debug_regs);
>   #else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
>   #ifndef CONFIG_HAVE_HW_BREAKPOINT
> -static void set_breakpoint(struct arch_hw_breakpoint *brk)
> +static void set_breakpoint(struct arch_hw_breakpoint *brk, int i)
>   {
>   	preempt_disable();
> -	__set_breakpoint(brk, 0);
> +	__set_breakpoint(brk, i);
>   	preempt_enable();
>   }
>   
>   static void set_debug_reg_defaults(struct thread_struct *thread)
>   {
> -	thread->hw_brk.address = 0;
> -	thread->hw_brk.type = 0;
> -	thread->hw_brk.len = 0;
> -	thread->hw_brk.hw_len = 0;
> -	if (ppc_breakpoint_available())
> -		set_breakpoint(&thread->hw_brk);
> +	int i;
> +
> +	for (i = 0; i < nr_wp_slots(); i++) {
> +		thread->hw_brk[i].address = 0;
> +		thread->hw_brk[i].type = 0;
> +		thread->hw_brk[i].len = 0;
> +		thread->hw_brk[i].hw_len = 0;
> +		if (ppc_breakpoint_available())
> +			set_breakpoint(&thread->hw_brk[i], i);
> +	}
>   }
>   #endif /* !CONFIG_HAVE_HW_BREAKPOINT */
>   #endif	/* CONFIG_PPC_ADV_DEBUG_REGS */
> @@ -1141,6 +1145,24 @@ static inline void restore_sprs(struct thread_struct *old_thread,
>   	thread_pkey_regs_restore(new_thread, old_thread);
>   }
>   
> +#ifndef CONFIG_HAVE_HW_BREAKPOINT
> +static void switch_hw_breakpoint(struct task_struct *new)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_wp_slots(); i++) {
> +		if (unlikely(!hw_brk_match(this_cpu_ptr(&current_brk[i]),
> +					   &new->thread.hw_brk[i]))) {
> +			__set_breakpoint(&new->thread.hw_brk[i], i);
> +		}
> +	}
> +}
> +#else
> +static void switch_hw_breakpoint(struct task_struct *new)
> +{
> +}
> +#endif
> +
>   struct task_struct *__switch_to(struct task_struct *prev,
>   	struct task_struct *new)
>   {
> @@ -1172,10 +1194,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
>    * For PPC_BOOK3S_64, we use the hw-breakpoint interfaces that would
>    * schedule DABR
>    */
> -#ifndef CONFIG_HAVE_HW_BREAKPOINT
> -	if (unlikely(!hw_brk_match(this_cpu_ptr(&current_brk[0]), &new->thread.hw_brk)))
> -		__set_breakpoint(&new->thread.hw_brk, 0);
> -#endif /* CONFIG_HAVE_HW_BREAKPOINT */
> +	switch_hw_breakpoint(new);
>   #endif
>   
>   	/*
> diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
> index dd46e174dbe7..f6d7955fc61e 100644
> --- a/arch/powerpc/kernel/ptrace.c
> +++ b/arch/powerpc/kernel/ptrace.c
> @@ -2382,6 +2382,11 @@ void ptrace_triggered(struct perf_event *bp,
>   }
>   #endif /* CONFIG_HAVE_HW_BREAKPOINT */
>   
> +/*
> + * ptrace_set_debugreg() fakes DABR and DABR is only one. So even if
> + * internal hw supports more than one watchpoint, we support only one
> + * watchpoint with this interface.
> + */
>   static int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
>   			       unsigned long data)
>   {
> @@ -2451,7 +2456,7 @@ static int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
>   			return ret;
>   		}
>   		thread->ptrace_bps[0] = bp;
> -		thread->hw_brk = hw_brk;
> +		thread->hw_brk[0] = hw_brk;
>   		return 0;
>   	}
>   
> @@ -2473,7 +2478,7 @@ static int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
>   	if (set_bp && (!ppc_breakpoint_available()))
>   		return -ENODEV;
>   #endif /* CONFIG_HAVE_HW_BREAKPOINT */
> -	task->thread.hw_brk = hw_brk;
> +	task->thread.hw_brk[0] = hw_brk;
>   #else /* CONFIG_PPC_ADV_DEBUG_REGS */
>   	/* As described above, it was assumed 3 bits were passed with the data
>   	 *  address, but we will assume only the mode bits will be passed
> @@ -2824,9 +2829,23 @@ static int set_dac_range(struct task_struct *child,
>   }
>   #endif /* CONFIG_PPC_ADV_DEBUG_DAC_RANGE */
>   
> +#ifndef CONFIG_PPC_ADV_DEBUG_REGS
> +static int empty_hw_brk(struct thread_struct *thread)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_wp_slots(); i++) {
> +		if (!thread->hw_brk[i].address)
> +			return i;
> +	}
> +	return -1;
> +}
> +#endif
> +
>   static long ppc_set_hwdebug(struct task_struct *child,
>   		     struct ppc_hw_breakpoint *bp_info)
>   {
> +	int i;
>   #ifdef CONFIG_HAVE_HW_BREAKPOINT
>   	int len = 0;
>   	struct thread_struct *thread = &(child->thread);
> @@ -2919,15 +2938,16 @@ static long ppc_set_hwdebug(struct task_struct *child,
>   	if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT)
>   		return -EINVAL;
>   
> -	if (child->thread.hw_brk.address)
> +	i = empty_hw_brk(&child->thread);
> +	if (i < 0)
>   		return -ENOSPC;
>   
>   	if (!ppc_breakpoint_available())
>   		return -ENODEV;
>   
> -	child->thread.hw_brk = brk;
> +	child->thread.hw_brk[i] = brk;
>   
> -	return 1;
> +	return i + 1;
>   #endif /* !CONFIG_PPC_ADV_DEBUG_DVCS */
>   }
>   
> @@ -2955,7 +2975,7 @@ static long ppc_del_hwdebug(struct task_struct *child, long data)
>   	}
>   	return rc;
>   #else
> -	if (data != 1)
> +	if (data < 1 || data > nr_wp_slots())
>   		return -EINVAL;
>   
>   #ifdef CONFIG_HAVE_HW_BREAKPOINT
> @@ -2967,11 +2987,11 @@ static long ppc_del_hwdebug(struct task_struct *child, long data)
>   		ret = -ENOENT;
>   	return ret;
>   #else /* CONFIG_HAVE_HW_BREAKPOINT */
> -	if (child->thread.hw_brk.address == 0)
> +	if (child->thread.hw_brk[data - 1].address == 0)
>   		return -ENOENT;
>   
> -	child->thread.hw_brk.address = 0;
> -	child->thread.hw_brk.type = 0;
> +	child->thread.hw_brk[data - 1].address = 0;
> +	child->thread.hw_brk[data - 1].type = 0;
>   #endif /* CONFIG_HAVE_HW_BREAKPOINT */
>   
>   	return 0;
> @@ -3124,8 +3144,8 @@ long arch_ptrace(struct task_struct *child, long request,
>   #ifdef CONFIG_PPC_ADV_DEBUG_REGS
>   		ret = put_user(child->thread.debug.dac1, datalp);
>   #else
> -		dabr_fake = ((child->thread.hw_brk.address & (~HW_BRK_TYPE_DABR)) |
> -			     (child->thread.hw_brk.type & HW_BRK_TYPE_DABR));
> +		dabr_fake = ((child->thread.hw_brk[0].address & (~HW_BRK_TYPE_DABR)) |
> +			     (child->thread.hw_brk[0].type & HW_BRK_TYPE_DABR));
>   		ret = put_user(dabr_fake, datalp);
>   #endif
>   		break;
> diff --git a/arch/powerpc/kernel/ptrace32.c b/arch/powerpc/kernel/ptrace32.c
> index f37eb53de1a1..e227cd320b46 100644
> --- a/arch/powerpc/kernel/ptrace32.c
> +++ b/arch/powerpc/kernel/ptrace32.c
> @@ -270,8 +270,8 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
>   		ret = put_user(child->thread.debug.dac1, (u32 __user *)data);
>   #else
>   		dabr_fake = (
> -			(child->thread.hw_brk.address & (~HW_BRK_TYPE_DABR)) |
> -			(child->thread.hw_brk.type & HW_BRK_TYPE_DABR));
> +			(child->thread.hw_brk[0].address & (~HW_BRK_TYPE_DABR)) |
> +			(child->thread.hw_brk[0].type & HW_BRK_TYPE_DABR));
>   		ret = put_user(dabr_fake, (u32 __user *)data);
>   #endif
>   		break;
> diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
> index 8bc6cc55420a..3116896e89a6 100644
> --- a/arch/powerpc/kernel/signal.c
> +++ b/arch/powerpc/kernel/signal.c
> @@ -107,6 +107,9 @@ static void do_signal(struct task_struct *tsk)
>   	struct ksignal ksig = { .sig = 0 };
>   	int ret;
>   	int is32 = is_32bit_task();
> +#ifndef CONFIG_PPC_ADV_DEBUG_REGS
> +	int i;
> +#endif
>   
>   	BUG_ON(tsk != current);
>   
> @@ -128,8 +131,10 @@ static void do_signal(struct task_struct *tsk)
>   	 * user space. The DABR will have been cleared if it
>   	 * triggered inside the kernel.
>   	 */
> -	if (tsk->thread.hw_brk.address && tsk->thread.hw_brk.type)
> -		__set_breakpoint(&tsk->thread.hw_brk, 0);
> +	for (i = 0; i < nr_wp_slots(); i++) {
> +		if (tsk->thread.hw_brk[i].address && tsk->thread.hw_brk[i].type)
> +			__set_breakpoint(&tsk->thread.hw_brk[i], i);
> +	}
>   #endif
>   	/* Re-enable the breakpoints for the signal stack */
>   	thread_change_pc(tsk, tsk->thread.regs);
>