Merge tag 'v5.5-rc3' into sched/core, to pick up fixes

[sfrench/cifs-2.6.git] / arch / arc / include / asm / jump_label.h

diff --git a/arch/arc/include/asm/jump_label.h b/arch/arc/include/asm/jump_label.h
new file mode 100644 (file)
index 0000000..9d96180
--- /dev/null
+++ b/arch/arc/include/asm/jump_label.h
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARC_JUMP_LABEL_H
+#define _ASM_ARC_JUMP_LABEL_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/stringify.h>
+#include <linux/types.h>
+
+#define JUMP_LABEL_NOP_SIZE 4
+
+/*
+ * NOTE about '.balign 4':
+ *
+ * To make atomic update of patched instruction available we need to guarantee
+ * that this instruction doesn't cross L1 cache line boundary.
+ *
+ * As of today we simply align instruction which can be patched by 4 byte using
+ * ".balign 4" directive. In that case patched instruction is aligned with one
+ * 16-bit NOP_S if this is required.
+ * However 'align by 4' directive is much stricter than it actually required.
+ * It's enough that our 32-bit instruction don't cross L1 cache line boundary /
+ * L1 I$ fetch block boundary which can be achieved by using
+ * ".bundle_align_mode" assembler directive. That will save us from adding
+ * useless NOP_S padding in most of the cases.
+ *
+ * TODO: switch to ".bundle_align_mode" directive using whin it will be
+ * supported by ARC toolchain.
+ */
+
+static __always_inline bool arch_static_branch(struct static_key *key,
+                                              bool branch)
+{
+       asm_volatile_goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)"   \n"
+                "1:                                                    \n"
+                "nop                                                   \n"
+                ".pushsection __jump_table, \"aw\"                     \n"
+                ".word 1b, %l[l_yes], %c0                              \n"
+                ".popsection                                           \n"
+                : : "i" (&((char *)key)[branch]) : : l_yes);
+
+       return false;
+l_yes:
+       return true;
+}
+
+static __always_inline bool arch_static_branch_jump(struct static_key *key,
+                                                   bool branch)
+{
+       asm_volatile_goto(".balign "__stringify(JUMP_LABEL_NOP_SIZE)"   \n"
+                "1:                                                    \n"
+                "b %l[l_yes]                                           \n"
+                ".pushsection __jump_table, \"aw\"                     \n"
+                ".word 1b, %l[l_yes], %c0                              \n"
+                ".popsection                                           \n"
+                : : "i" (&((char *)key)[branch]) : : l_yes);
+
+       return false;
+l_yes:
+       return true;
+}
+
+typedef u32 jump_label_t;
+
+struct jump_entry {
+       jump_label_t code;
+       jump_label_t target;
+       jump_label_t key;
+};
+
+#endif  /* __ASSEMBLY__ */
+#endif