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>

1 files changed, 88 insertions, 54 deletions

diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index ff516f6691e4..e89459123fa3 100644
--- 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)