Revert "powerpc/hw-breakpoint: Use generic hw-breakpoint interfaces for new PPC ptrace flags"

This reverts commit 1b788400.

It causes oopses when passed incorrect arguments and has a
design fault using IPIs with interrupts disabled.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

Documentation/powerpc/ptrace.txt

@@ -127,22 +127,6 @@ Some examples of using the structure to:
   p.addr2           = (uint64_t) end_range;
   p.condition_value = 0;
 
-- set a watchpoint in server processors (BookS)
-
-  p.version         = 1;
-  p.trigger_type    = PPC_BREAKPOINT_TRIGGER_RW;
-  p.addr_mode       = PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE;
-  or
-  p.addr_mode       = PPC_BREAKPOINT_MODE_EXACT;
-
-  p.condition_mode  = PPC_BREAKPOINT_CONDITION_NONE;
-  p.addr            = (uint64_t) begin_range;
-  /* For PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE addr2 needs to be specified, where
-   * addr2 - addr <= 8 Bytes.
-   */
-  p.addr2           = (uint64_t) end_range;
-  p.condition_value = 0;
-
 3. PTRACE_DELHWDEBUG
 
 Takes an integer which identifies an existing breakpoint or watchpoint

arch/powerpc/kernel/ptrace.c

@@ -1336,12 +1336,6 @@ static int set_dac_range(struct task_struct *child,
 static long ppc_set_hwdebug(struct task_struct *child,
 		     struct ppc_hw_breakpoint *bp_info)
 {
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-	int len = 0;
-	struct thread_struct *thread = &(child->thread);
-	struct perf_event *bp;
-	struct perf_event_attr attr;
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
 #ifndef CONFIG_PPC_ADV_DEBUG_REGS
 	unsigned long dabr;
 #endif
@@ -1385,9 +1379,13 @@ static long ppc_set_hwdebug(struct task_struct *child,
 	 */
 	if ((bp_info->trigger_type & PPC_BREAKPOINT_TRIGGER_RW) == 0 ||
 	    (bp_info->trigger_type & ~PPC_BREAKPOINT_TRIGGER_RW) != 0 ||
+	    bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT ||
 	    bp_info->condition_mode != PPC_BREAKPOINT_CONDITION_NONE)
 		return -EINVAL;
 
+	if (child->thread.dabr)
+		return -ENOSPC;
+
 	if ((unsigned long)bp_info->addr >= TASK_SIZE)
 		return -EIO;
 
@@ -1397,63 +1395,15 @@ static long ppc_set_hwdebug(struct task_struct *child,
 		dabr |= DABR_DATA_READ;
 	if (bp_info->trigger_type & PPC_BREAKPOINT_TRIGGER_WRITE)
 		dabr |= DABR_DATA_WRITE;
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-	if (ptrace_get_breakpoints(child) < 0)
-		return -ESRCH;
-
-	/*
-	 * Check if the request is for 'range' breakpoints. We can
-	 * support it if range < 8 bytes.
-	 */
-	if (bp_info->addr_mode == PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE) {
-		len = bp_info->addr2 - bp_info->addr;
-	} else if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT) {
-		ptrace_put_breakpoints(child);
-		return -EINVAL;
-	}
-	bp = thread->ptrace_bps[0];
-	if (bp) {
-		ptrace_put_breakpoints(child);
-		return -ENOSPC;
-	}
-
-	/* Create a new breakpoint request if one doesn't exist already */
-	hw_breakpoint_init(&attr);
-	attr.bp_addr = (unsigned long)bp_info->addr & ~HW_BREAKPOINT_ALIGN;
-	attr.bp_len = len;
-	arch_bp_generic_fields(dabr & (DABR_DATA_WRITE | DABR_DATA_READ),
-								&attr.bp_type);
-
-	thread->ptrace_bps[0] = bp = register_user_hw_breakpoint(&attr,
-					       ptrace_triggered, NULL, child);
-	if (IS_ERR(bp)) {
-		thread->ptrace_bps[0] = NULL;
-		ptrace_put_breakpoints(child);
-		return PTR_ERR(bp);
-	}
-
-	ptrace_put_breakpoints(child);
-	return 1;
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
-
-	if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT)
-		return -EINVAL;
-
-	if (child->thread.dabr)
-		return -ENOSPC;
 
 	child->thread.dabr = dabr;
+
 	return 1;
 #endif /* !CONFIG_PPC_ADV_DEBUG_DVCS */
 }
 
 static long ppc_del_hwdebug(struct task_struct *child, long addr, long data)
 {
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-	int ret = 0;
-	struct thread_struct *thread = &(child->thread);
-	struct perf_event *bp;
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 	int rc;
 
@@ -1473,25 +1423,10 @@ static long ppc_del_hwdebug(struct task_struct *child, long addr, long data)
 #else
 	if (data != 1)
 		return -EINVAL;
-
-#ifdef CONFIG_HAVE_HW_BREAKPOINT
-	if (ptrace_get_breakpoints(child) < 0)
-		return -ESRCH;
-
-	bp = thread->ptrace_bps[0];
-	if (bp) {
-		unregister_hw_breakpoint(bp);
-		thread->ptrace_bps[0] = NULL;
-	} else
-		ret = -ENOENT;
-	ptrace_put_breakpoints(child);
-	return ret;
-#else /* CONFIG_HAVE_HW_BREAKPOINT */
 	if (child->thread.dabr == 0)
 		return -ENOENT;
 
 	child->thread.dabr = 0;
-#endif /* CONFIG_HAVE_HW_BREAKPOINT */
 
 	return 0;
 #endif
@@ -1598,7 +1533,7 @@ long arch_ptrace(struct task_struct *child, long request,
 		dbginfo.data_bp_alignment = 4;
 #endif
 		dbginfo.sizeof_condition = 0;
-		dbginfo.features = PPC_DEBUG_FEATURE_DATA_BP_RANGE;
+		dbginfo.features = 0;
 #endif /* CONFIG_PPC_ADV_DEBUG_REGS */
 
 		if (!access_ok(VERIFY_WRITE, datavp,