powerpc/watchpoint: Convert thread_struct->hw_brk to an array

So far powerpc hw supported only one watchpoint. But Power10 is
introducing 2nd DAWR. Convert thread_struct->hw_brk into an array.
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-10-ravi.bangoria@linux.ibm.com

arch/powerpc/include/asm/processor.h

@@ -187,7 +187,7 @@ 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;

arch/powerpc/kernel/process.c

@@ -711,21 +711,49 @@ 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(int i, struct arch_hw_breakpoint *brk)
 {
 	preempt_disable();
-	__set_breakpoint(0, brk);
+	__set_breakpoint(i, brk);
 	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;
+	int i;
+	struct arch_hw_breakpoint null_brk = {0};
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		thread->hw_brk[i] = null_brk;
 		if (ppc_breakpoint_available())
-		set_breakpoint(&thread->hw_brk);
+			set_breakpoint(i, &thread->hw_brk[i]);
+	}
+}
+
+static inline bool hw_brk_match(struct arch_hw_breakpoint *a,
+				struct arch_hw_breakpoint *b)
+{
+	if (a->address != b->address)
+		return false;
+	if (a->type != b->type)
+		return false;
+	if (a->len != b->len)
+		return false;
+	/* no need to check hw_len. it's calculated from address and len */
+	return true;
+}
+
+static void switch_hw_breakpoint(struct task_struct *new)
+{
+	int i;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (likely(hw_brk_match(this_cpu_ptr(&current_brk[i]),
+					&new->thread.hw_brk[i])))
+			continue;
+
+		__set_breakpoint(i, &new->thread.hw_brk[i]);
+	}
 }
 #endif /* !CONFIG_HAVE_HW_BREAKPOINT */
 #endif	/* CONFIG_PPC_ADV_DEBUG_REGS */
@@ -829,19 +857,6 @@ bool ppc_breakpoint_available(void)
 }
 EXPORT_SYMBOL_GPL(ppc_breakpoint_available);
 
-static inline bool hw_brk_match(struct arch_hw_breakpoint *a,
-			      struct arch_hw_breakpoint *b)
-{
-	if (a->address != b->address)
-		return false;
-	if (a->type != b->type)
-		return false;
-	if (a->len != b->len)
-		return false;
-	/* no need to check hw_len. it's calculated from address and len */
-	return true;
-}
-
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 
 static inline bool tm_enabled(struct task_struct *tsk)
@@ -1174,8 +1189,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
  * schedule DABR
  */
 #ifndef CONFIG_HAVE_HW_BREAKPOINT
-	if (unlikely(!hw_brk_match(this_cpu_ptr(&current_brk[0]), &new->thread.hw_brk)))
-		__set_breakpoint(0, &new->thread.hw_brk);
+	switch_hw_breakpoint(new);
 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
 #endif
 

arch/powerpc/kernel/ptrace/ptrace-noadv.c

@@ -67,11 +67,16 @@ int ptrace_get_debugreg(struct task_struct *child, unsigned long addr,
 	/* We only support one DABR and no IABRS at the moment */
 	if (addr > 0)
 		return -EINVAL;
-	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));
 	return put_user(dabr_fake, datalp);
 }
 
+/*
+ * 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.
+ */
 int ptrace_set_debugreg(struct task_struct *task, unsigned long addr, unsigned long data)
 {
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
@@ -137,7 +142,7 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr, unsigned l
 			return ret;
 
 		thread->ptrace_bps[0] = bp;
-		thread->hw_brk = hw_brk;
+		thread->hw_brk[0] = hw_brk;
 		return 0;
 	}
 
@@ -159,12 +164,24 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr, unsigned l
 	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;
 	return 0;
 }
 
+static int find_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;
+}
+
 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;
@@ -223,15 +240,16 @@ long ppc_set_hwdebug(struct task_struct *child, struct ppc_hw_breakpoint *bp_inf
 	if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT)
 		return -EINVAL;
 
-	if (child->thread.hw_brk.address)
+	i = find_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;
 }
 
 long ppc_del_hwdebug(struct task_struct *child, long data)
@@ -241,7 +259,7 @@ long ppc_del_hwdebug(struct task_struct *child, long data)
 	struct thread_struct *thread = &child->thread;
 	struct perf_event *bp;
 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
-	if (data != 1)
+	if (data < 1 || data > nr_wp_slots())
 		return -EINVAL;
 
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
@@ -254,11 +272,11 @@ long ppc_del_hwdebug(struct task_struct *child, long data)
 	}
 	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;

arch/powerpc/kernel/ptrace/ptrace32.c

@@ -259,8 +259,8 @@ 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;

arch/powerpc/kernel/signal.c

@@ -265,15 +265,20 @@ static void do_signal(struct task_struct *tsk)
 		return;               /* no signals delivered */
 	}
 
-#ifndef CONFIG_PPC_ADV_DEBUG_REGS
         /*
 	 * Reenable the DABR before delivering the signal to
 	 * 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(0, &tsk->thread.hw_brk);
-#endif
+	if (!IS_ENABLED(CONFIG_PPC_ADV_DEBUG_REGS)) {
+		int i;
+
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (tsk->thread.hw_brk[i].address && tsk->thread.hw_brk[i].type)
+				__set_breakpoint(i, &tsk->thread.hw_brk[i]);
+		}
+	}
+
 	/* Re-enable the breakpoints for the signal stack */
 	thread_change_pc(tsk, tsk->thread.regs);