parisc: Add static branch and JUMP_LABEL feature

Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 55 insertions, 0 deletions

diff --git a/arch/parisc/kernel/jump_label.c b/arch/parisc/kernel/jump_label.c
new file mode 100644
index 000000000000..d2f3cb12e282
--- /dev/null
+++ b/arch/parisc/kernel/jump_label.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Helge Deller <deller@gmx.de>
+ *
+ * Based on arch/arm64/kernel/jump_label.c
+ */
+#include <linux/kernel.h>
+#include <linux/jump_label.h>
+#include <linux/bug.h>
+#include <asm/alternative.h>
+#include <asm/patch.h>
+
+static inline int reassemble_17(int as17)
+{
+	return (((as17 & 0x10000) >> 16) |
+		((as17 & 0x0f800) << 5) |
+		((as17 & 0x00400) >> 8) |
+		((as17 & 0x003ff) << 3));
+}
+
+void arch_jump_label_transform(struct jump_entry *entry,
+			       enum jump_label_type type)
+{
+	void *addr = (void *)jump_entry_code(entry);
+	u32 insn;
+
+	if (type == JUMP_LABEL_JMP) {
+		void *target = (void *)jump_entry_target(entry);
+		int distance = target - addr;
+		/*
+		 * Encode the PA1.1 "b,n" instruction with a 17-bit
+		 * displacement.  In case we hit the BUG(), we could use
+		 * another branch instruction with a 22-bit displacement on
+		 * 64-bit CPUs instead. But this seems sufficient for now.
+		 */
+		distance -= 8;
+		BUG_ON(distance > 262143 || distance < -262144);
+		insn = 0xe8000002 | reassemble_17(distance >> 2);
+	} else {
+		insn = INSN_NOP;
+	}
+
+	patch_text(addr, insn);
+}
+
+void arch_jump_label_transform_static(struct jump_entry *entry,
+				      enum jump_label_type type)
+{
+	/*
+	 * We use the architected NOP in arch_static_branch, so there's no
+	 * need to patch an identical NOP over the top of it here. The core
+	 * will call arch_jump_label_transform from a module notifier if the
+	 * NOP needs to be replaced by a branch.
+	 */
+}