MIPS: jump label: Add MIPS support.

In order not to be left behind, we add jump label support for MIPS.

Tested on 64-bit big endian (Octeon), and 32-bit little endian
(malta/qemu).

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jason Baron <jbaron@redhat.com>
Patchwork: https://patchwork.linux-mips.org/patch/1923/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

5 files changed, 110 insertions, 0 deletions

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 2106781d7473..954304068228 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -21,6 +21,7 @@ config MIPS
         select HAVE_DMA_API_DEBUG
         select HAVE_GENERIC_HARDIRQS
         select GENERIC_IRQ_PROBE
+        select HAVE_ARCH_JUMP_LABEL
 
 menu "Machine selection"
 
diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h
new file mode 100644
index 000000000000..7622ccf75076
--- /dev/null
+++ b/arch/mips/include/asm/jump_label.h
@@ -0,0 +1,48 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2010 Cavium Networks, Inc.
+ */
+#ifndef _ASM_MIPS_JUMP_LABEL_H
+#define _ASM_MIPS_JUMP_LABEL_H
+
+#include <linux/types.h>
+
+#ifdef __KERNEL__
+
+#define JUMP_LABEL_NOP_SIZE 4
+
+#ifdef CONFIG_64BIT
+#define WORD_INSN ".dword"
+#else
+#define WORD_INSN ".word"
+#endif
+
+#define JUMP_LABEL(key, label)                                          \
+        do {                                                            \
+                asm goto("1:\tnop\n\t"                                  \
+                        "nop\n\t"                                       \
+                        ".pushsection __jump_table,  \"a\"\n\t"         \
+                        WORD_INSN " 1b, %l[" #label "], %0\n\t"         \
+                        ".popsection\n\t"                               \
+                        : :  "i" (key) :  : label);                     \
+        } while (0)
+
+
+#endif /* __KERNEL__ */
+
+#ifdef CONFIG_64BIT
+typedef u64 jump_label_t;
+#else
+typedef u32 jump_label_t;
+#endif
+
+struct jump_entry {
+        jump_label_t code;
+        jump_label_t target;
+        jump_label_t key;
+};
+
+#endif /* _ASM_MIPS_JUMP_LABEL_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 39773979ca6d..cedee2bcbd18 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -107,4 +107,6 @@ obj-$(CONFIG_MIPS_CPUFREQ)	+= cpufreq/
 
 obj-$(CONFIG_HW_PERF_EVENTS)    += perf_event.o
 
+obj-$(CONFIG_JUMP_LABEL)        += jump_label.o
+
 CPPFLAGS_vmlinux.lds            := $(KBUILD_CFLAGS)
diff --git a/arch/mips/kernel/jump_label.c b/arch/mips/kernel/jump_label.c
new file mode 100644
index 000000000000..6001610cfe55
--- /dev/null
+++ b/arch/mips/kernel/jump_label.c
@@ -0,0 +1,54 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (c) 2010 Cavium Networks, Inc.
+ */
+
+#include <linux/jump_label.h>
+#include <linux/kernel.h>
+#include <linux/memory.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include <linux/cpu.h>
+
+#include <asm/cacheflush.h>
+#include <asm/inst.h>
+
+#ifdef HAVE_JUMP_LABEL
+
+#define J_RANGE_MASK ((1ul << 28) - 1)
+
+void arch_jump_label_transform(struct jump_entry *e,
+                               enum jump_label_type type)
+{
+        union mips_instruction insn;
+        union mips_instruction *insn_p =
+                (union mips_instruction *)(unsigned long)e->code;
+
+        /* Jump only works within a 256MB aligned region. */
+        BUG_ON((e->target & ~J_RANGE_MASK) != (e->code & ~J_RANGE_MASK));
+
+        /* Target must have 4 byte alignment. */
+        BUG_ON((e->target & 3) != 0);
+
+        if (type == JUMP_LABEL_ENABLE) {
+                insn.j_format.opcode = j_op;
+                insn.j_format.target = (e->target & J_RANGE_MASK) >> 2;
+        } else {
+                insn.word = 0; /* nop */
+        }
+
+        get_online_cpus();
+        mutex_lock(&text_mutex);
+        *insn_p = insn;
+
+        flush_icache_range((unsigned long)insn_p,
+                           (unsigned long)insn_p + sizeof(*insn_p));
+
+        mutex_unlock(&text_mutex);
+        put_online_cpus();
+}
+
+#endif /* HAVE_JUMP_LABEL */
diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index d87a72e9fac7..dd940b701963 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -30,6 +30,8 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
+#include <linux/jump_label.h>
+
 #include <asm/pgtable.h>        /* MODULE_START */
 
 struct mips_hi16 {
@@ -382,6 +384,9 @@ int module_finalize(const Elf_Ehdr *hdr,
         const Elf_Shdr *s;
         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 
+        /* Make jump label nops. */
+        jump_label_apply_nops(me);
+
         INIT_LIST_HEAD(&me->arch.dbe_list);
         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
                 if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)