arm64: kernel: refactor code to install/uninstall breakpoints

Most of the code executed to install and uninstall breakpoints is
common and can be factored out in a function that through a runtime
operations type provides the requested implementation.

This patch creates a common function that can be used to install/uninstall
breakpoints and defines the set of operations that can be carried out
through it.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index ff516f6..e894591 100644 (file)
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -169,15 +169,63 @@ static enum debug_el debug_exception_level(int privilege)
        }
 }
 
-/*
- * Install a perf counter breakpoint.
+enum hw_breakpoint_ops {
+       HW_BREAKPOINT_INSTALL,
+       HW_BREAKPOINT_UNINSTALL
+};
+
+/**
+ * hw_breakpoint_slot_setup - Find and setup a perf slot according to
+ *                           operations
+ *
+ * @slots: pointer to array of slots
+ * @max_slots: max number of slots
+ * @bp: perf_event to setup
+ * @ops: operation to be carried out on the slot
+ *
+ * Return:
+ *     slot index on success
+ *     -ENOSPC if no slot is available/matches
+ *     -EINVAL on wrong operations parameter
  */
-int arch_install_hw_breakpoint(struct perf_event *bp)
+static int hw_breakpoint_slot_setup(struct perf_event **slots, int max_slots,
+                                   struct perf_event *bp,
+                                   enum hw_breakpoint_ops ops)
+{
+       int i;
+       struct perf_event **slot;
+
+       for (i = 0; i < max_slots; ++i) {
+               slot = &slots[i];
+               switch (ops) {
+               case HW_BREAKPOINT_INSTALL:
+                       if (!*slot) {
+                               *slot = bp;
+                               return i;
+                       }
+                       break;
+               case HW_BREAKPOINT_UNINSTALL:
+                       if (*slot == bp) {
+                               *slot = NULL;
+                               return i;
+                       }
+                       break;
+               default:
+                       pr_warn_once("Unhandled hw breakpoint ops %d\n", ops);
+                       return -EINVAL;
+               }
+       }
+       return -ENOSPC;
+}
+
+static int hw_breakpoint_control(struct perf_event *bp,
+                                enum hw_breakpoint_ops ops)
 {
        struct arch_hw_breakpoint *info = counter_arch_bp(bp);
-       struct perf_event **slot, **slots;
+       struct perf_event **slots;
        struct debug_info *debug_info = &current->thread.debug;
        int i, max_slots, ctrl_reg, val_reg, reg_enable;
+       enum debug_el dbg_el = debug_exception_level(info->ctrl.privilege);
        u32 ctrl;
 
        if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
@@ -196,67 +244,53 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
                reg_enable = !debug_info->wps_disabled;
        }
 
-       for (i = 0; i < max_slots; ++i) {
-               slot = &slots[i];
+       i = hw_breakpoint_slot_setup(slots, max_slots, bp, ops);
 
-               if (!*slot) {
-                       *slot = bp;
-                       break;
-               }
-       }
+       if (WARN_ONCE(i < 0, "Can't find any breakpoint slot"))
+               return i;
 
-       if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot"))
-               return -ENOSPC;
+       switch (ops) {
+       case HW_BREAKPOINT_INSTALL:
+               /*
+                * Ensure debug monitors are enabled at the correct exception
+                * level.
+                */
+               enable_debug_monitors(dbg_el);
 
-       /* Ensure debug monitors are enabled at the correct exception level.  */
-       enable_debug_monitors(debug_exception_level(info->ctrl.privilege));
+               /* Setup the address register. */
+               write_wb_reg(val_reg, i, info->address);
 
-       /* Setup the address register. */
-       write_wb_reg(val_reg, i, info->address);
+               /* Setup the control register. */
+               ctrl = encode_ctrl_reg(info->ctrl);
+               write_wb_reg(ctrl_reg, i,
+                            reg_enable ? ctrl | 0x1 : ctrl & ~0x1);
+               break;
+       case HW_BREAKPOINT_UNINSTALL:
+               /* Reset the control register. */
+               write_wb_reg(ctrl_reg, i, 0);
 
-       /* Setup the control register. */
-       ctrl = encode_ctrl_reg(info->ctrl);
-       write_wb_reg(ctrl_reg, i, reg_enable ? ctrl | 0x1 : ctrl & ~0x1);
+               /*
+                * Release the debug monitors for the correct exception
+                * level.
+                */
+               disable_debug_monitors(dbg_el);
+               break;
+       }
 
        return 0;
 }
 
-void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+/*
+ * Install a perf counter breakpoint.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
 {
-       struct arch_hw_breakpoint *info = counter_arch_bp(bp);
-       struct perf_event **slot, **slots;
-       int i, max_slots, base;
-
-       if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
-               /* Breakpoint */
-               base = AARCH64_DBG_REG_BCR;
-               slots = this_cpu_ptr(bp_on_reg);
-               max_slots = core_num_brps;
-       } else {
-               /* Watchpoint */
-               base = AARCH64_DBG_REG_WCR;
-               slots = this_cpu_ptr(wp_on_reg);
-               max_slots = core_num_wrps;
-       }
-
-       /* Remove the breakpoint. */
-       for (i = 0; i < max_slots; ++i) {
-               slot = &slots[i];
-
-               if (*slot == bp) {
-                       *slot = NULL;
-                       break;
-               }
-       }
-
-       if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot"))
-               return;
-
-       /* Reset the control register. */
-       write_wb_reg(base, i, 0);
+       return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL);
+}
 
-       /* Release the debug monitors for the correct exception level.  */
-       disable_debug_monitors(debug_exception_level(info->ctrl.privilege));
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+       hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL);
 }
 
 static int get_hbp_len(u8 hbp_len)