[PATCH v3 2/2] riscv: Add jump-label implementation
Emil Renner Berthing
kernel at esmil.dk
Tue Jul 14 03:40:44 EDT 2020
Add jump-label implementation based on the ARM64 version
and add CONFIG_JUMP_LABEL=y to the defconfigs.
Signed-off-by: Emil Renner Berthing <kernel at esmil.dk>
Reviewed-by: Björn Töpel <bjorn.topel at gmail.com>
Tested-by: Björn Töpel <bjorn.topel at gmail.com>
---
Tested on the HiFive Unleashed board.
Changes since v2:
- Add missing asm/asm.h include.
Reported-by: kernel test robot <lkp at intel.com>
Changes since v1:
- WARN and give up gracefully if the jump offset cannot be
represented in a JAL instruction.
- Add missing braces.
- Add CONFIG_JUMP_LABEL=y to defconfigs.
All suggested by Björn Töpel.
Changes since RFC:
- Use RISCV_PTR and RISCV_LGPTR macros to match struct jump_table
also in 32bit kernels.
- Remove unneeded branch ? 1 : 0, thanks Björn
- Fix \n\n instead of \n\t mistake
.../core/jump-labels/arch-support.txt | 2 +-
arch/riscv/Kconfig | 2 +
arch/riscv/configs/defconfig | 1 +
arch/riscv/configs/nommu_k210_defconfig | 1 +
arch/riscv/configs/nommu_virt_defconfig | 1 +
arch/riscv/configs/rv32_defconfig | 1 +
arch/riscv/include/asm/jump_label.h | 60 +++++++++++++++++++
arch/riscv/kernel/Makefile | 2 +
arch/riscv/kernel/jump_label.c | 49 +++++++++++++++
9 files changed, 118 insertions(+), 1 deletion(-)
create mode 100644 arch/riscv/include/asm/jump_label.h
create mode 100644 arch/riscv/kernel/jump_label.c
diff --git a/Documentation/features/core/jump-labels/arch-support.txt b/Documentation/features/core/jump-labels/arch-support.txt
index 632a1c7aefa2..760243d18ed7 100644
--- a/Documentation/features/core/jump-labels/arch-support.txt
+++ b/Documentation/features/core/jump-labels/arch-support.txt
@@ -23,7 +23,7 @@
| openrisc: | TODO |
| parisc: | ok |
| powerpc: | ok |
- | riscv: | TODO |
+ | riscv: | ok |
| s390: | ok |
| sh: | TODO |
| sparc: | ok |
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c6d4f7771bff..3beb844c5951 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -48,6 +48,8 @@ config RISCV
select GENERIC_TIME_VSYSCALL if MMU && 64BIT
select HANDLE_DOMAIN_IRQ
select HAVE_ARCH_AUDITSYSCALL
+ select HAVE_ARCH_JUMP_LABEL
+ select HAVE_ARCH_JUMP_LABEL_RELATIVE
select HAVE_ARCH_KASAN if MMU && 64BIT
select HAVE_ARCH_KGDB
select HAVE_ARCH_KGDB_QXFER_PKT
diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
index 4da4886246a4..d58c93efb603 100644
--- a/arch/riscv/configs/defconfig
+++ b/arch/riscv/configs/defconfig
@@ -17,6 +17,7 @@ CONFIG_BPF_SYSCALL=y
CONFIG_SOC_SIFIVE=y
CONFIG_SOC_VIRT=y
CONFIG_SMP=y
+CONFIG_JUMP_LABEL=y
CONFIG_MODULES=y
CONFIG_MODULE_UNLOAD=y
CONFIG_NET=y
diff --git a/arch/riscv/configs/nommu_k210_defconfig b/arch/riscv/configs/nommu_k210_defconfig
index b48138e329ea..cd1df62b13c7 100644
--- a/arch/riscv/configs/nommu_k210_defconfig
+++ b/arch/riscv/configs/nommu_k210_defconfig
@@ -33,6 +33,7 @@ CONFIG_SMP=y
CONFIG_NR_CPUS=2
CONFIG_CMDLINE="earlycon console=ttySIF0"
CONFIG_CMDLINE_FORCE=y
+CONFIG_JUMP_LABEL=y
# CONFIG_BLOCK is not set
CONFIG_BINFMT_FLAT=y
# CONFIG_COREDUMP is not set
diff --git a/arch/riscv/configs/nommu_virt_defconfig b/arch/riscv/configs/nommu_virt_defconfig
index cf74e179bf90..f27596e9663e 100644
--- a/arch/riscv/configs/nommu_virt_defconfig
+++ b/arch/riscv/configs/nommu_virt_defconfig
@@ -30,6 +30,7 @@ CONFIG_MAXPHYSMEM_2GB=y
CONFIG_SMP=y
CONFIG_CMDLINE="root=/dev/vda rw earlycon=uart8250,mmio,0x10000000,115200n8 console=ttyS0"
CONFIG_CMDLINE_FORCE=y
+CONFIG_JUMP_LABEL=y
# CONFIG_BLK_DEV_BSG is not set
CONFIG_PARTITION_ADVANCED=y
# CONFIG_MSDOS_PARTITION is not set
diff --git a/arch/riscv/configs/rv32_defconfig b/arch/riscv/configs/rv32_defconfig
index 05bbf5240569..3a55f0e00d6c 100644
--- a/arch/riscv/configs/rv32_defconfig
+++ b/arch/riscv/configs/rv32_defconfig
@@ -17,6 +17,7 @@ CONFIG_BPF_SYSCALL=y
CONFIG_SOC_VIRT=y
CONFIG_ARCH_RV32I=y
CONFIG_SMP=y
+CONFIG_JUMP_LABEL=y
CONFIG_MODULES=y
CONFIG_MODULE_UNLOAD=y
CONFIG_NET=y
diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
new file mode 100644
index 000000000000..38af2ec7b9bf
--- /dev/null
+++ b/arch/riscv/include/asm/jump_label.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Emil Renner Berthing
+ *
+ * Based on arch/arm64/include/asm/jump_label.h
+ */
+#ifndef __ASM_JUMP_LABEL_H
+#define __ASM_JUMP_LABEL_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+#include <asm/asm.h>
+
+#define JUMP_LABEL_NOP_SIZE 4
+
+static __always_inline bool arch_static_branch(struct static_key *key,
+ bool branch)
+{
+ asm_volatile_goto(
+ " .option push \n\t"
+ " .option norelax \n\t"
+ " .option norvc \n\t"
+ "1: nop \n\t"
+ " .option pop \n\t"
+ " .pushsection __jump_table, \"aw\" \n\t"
+ " .align " RISCV_LGPTR " \n\t"
+ " .long 1b - ., %l[label] - . \n\t"
+ " " RISCV_PTR " %0 - . \n\t"
+ " .popsection \n\t"
+ : : "i"(&((char *)key)[branch]) : : label);
+
+ return false;
+label:
+ return true;
+}
+
+static __always_inline bool arch_static_branch_jump(struct static_key *key,
+ bool branch)
+{
+ asm_volatile_goto(
+ " .option push \n\t"
+ " .option norelax \n\t"
+ " .option norvc \n\t"
+ "1: jal zero, %l[label] \n\t"
+ " .option pop \n\t"
+ " .pushsection __jump_table, \"aw\" \n\t"
+ " .align " RISCV_LGPTR " \n\t"
+ " .long 1b - ., %l[label] - . \n\t"
+ " " RISCV_PTR " %0 - . \n\t"
+ " .popsection \n\t"
+ : : "i"(&((char *)key)[branch]) : : label);
+
+ return false;
+label:
+ return true;
+}
+
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_JUMP_LABEL_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index b355cf485671..a5287ab9f7f2 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -53,4 +53,6 @@ endif
obj-$(CONFIG_HOTPLUG_CPU) += cpu-hotplug.o
obj-$(CONFIG_KGDB) += kgdb.o
+obj-$(CONFIG_JUMP_LABEL) += jump_label.o
+
clean:
diff --git a/arch/riscv/kernel/jump_label.c b/arch/riscv/kernel/jump_label.c
new file mode 100644
index 000000000000..1bab1abc1aa5
--- /dev/null
+++ b/arch/riscv/kernel/jump_label.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Emil Renner Berthing
+ *
+ * Based on arch/arm64/kernel/jump_label.c
+ */
+#include <linux/kernel.h>
+#include <linux/jump_label.h>
+#include <asm/bug.h>
+#include <asm/patch.h>
+
+#define RISCV_INSN_NOP 0x00000013U
+#define RISCV_INSN_JAL 0x0000006fU
+
+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) {
+ long offset = jump_entry_target(entry) - jump_entry_code(entry);
+
+ if (WARN_ON(offset & 1 || offset < -524288 || offset >= 524288))
+ return;
+
+ insn = RISCV_INSN_JAL |
+ (((u32)offset & GENMASK(19, 12)) << (12 - 12)) |
+ (((u32)offset & GENMASK(11, 11)) << (20 - 11)) |
+ (((u32)offset & GENMASK(10, 1)) << (21 - 1)) |
+ (((u32)offset & GENMASK(20, 20)) << (31 - 20));
+ } else {
+ insn = RISCV_INSN_NOP;
+ }
+
+ patch_text_nosync(addr, &insn, sizeof(insn));
+}
+
+void arch_jump_label_transform_static(struct jump_entry *entry,
+ enum jump_label_type type)
+{
+ /*
+ * We use the same instructions in the arch_static_branch and
+ * arch_static_branch_jump inline functions, so there's no
+ * need to patch them up here.
+ * The core will call arch_jump_label_transform when those
+ * instructions need to be replaced.
+ */
+}
--
2.27.0
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