[PATCH v6 01/13] riscv/kprobe: Prepare the skeleton to implement RISCV OPTPROBES

[Chen Guokai]

From: Liao Chang <liaochang1 at huawei.com>

Prepare skeleton to implement optimized kprobe on RISCV, although some
architecture specific functions are left blank, they do not change the
correctness of existing kprobe code, on account of these functions just
return zero. To avoid each patch being too complicated to review and
test, these functions will be implemented incrementally.

Signed-off-by: Liao Chang <liaochang1 at huawei.com>
Co-developed-by: Chen Guokai <chenguokai17 at mails.ucas.ac.cn>
Signed-off-by: Chen Guokai <chenguokai17 at mails.ucas.ac.cn>
---
 arch/riscv/Kconfig                        |  1 +
 arch/riscv/include/asm/kprobes.h          | 32 ++++++++++++++
 arch/riscv/kernel/probes/Makefile         |  1 +
 arch/riscv/kernel/probes/opt.c            | 51 +++++++++++++++++++++++
 arch/riscv/kernel/probes/opt_trampoline.S | 12 ++++++
 5 files changed, 97 insertions(+)
 create mode 100644 arch/riscv/kernel/probes/opt.c
 create mode 100644 arch/riscv/kernel/probes/opt_trampoline.S

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 9c687da7756d..48a639c7c055 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -101,6 +101,7 @@ config RISCV
 	select HAVE_KPROBES if !XIP_KERNEL
 	select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL
 	select HAVE_KRETPROBES if !XIP_KERNEL
+	select HAVE_OPTPROBES if !XIP_KERNEL
 	select HAVE_RETHOOK if !XIP_KERNEL
 	select HAVE_MOVE_PMD
 	select HAVE_MOVE_PUD
diff --git a/arch/riscv/include/asm/kprobes.h b/arch/riscv/include/asm/kprobes.h
index e7882ccb0fd4..96cd36e67e2e 100644
--- a/arch/riscv/include/asm/kprobes.h
+++ b/arch/riscv/include/asm/kprobes.h
@@ -41,5 +41,37 @@ int kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr);
 bool kprobe_breakpoint_handler(struct pt_regs *regs);
 bool kprobe_single_step_handler(struct pt_regs *regs);
 
+#ifdef CONFIG_OPTPROBES
+
+/* optinsn template addresses */
+extern __visible kprobe_opcode_t optprobe_template_entry[];
+extern __visible kprobe_opcode_t optprobe_template_end[];
+
+#define MAX_OPTINSN_SIZE				\
+	((unsigned long)optprobe_template_end -		\
+	 (unsigned long)optprobe_template_entry)
+
+/*
+ * For RVI and RVC hybrid encoding kernel, although long jump just needs
+ * 2 RVI instructions(AUIPC/JALR), optimized instructions are 10 bytes long
+ * at most to ensure no RVI would be truncated actually, so it means four
+ * combinations:
+ * - 2 RVI
+ * - 4 RVC
+ * - 2 RVC + 1 RVI
+ * - 3 RVC + 1 RVI (truncated, need padding)
+ */
+#define MAX_COPIED_INSN		4
+#define MAX_OPTIMIZED_LENGTH	10
+
+struct arch_optimized_insn {
+	kprobe_opcode_t copied_insn[MAX_COPIED_INSN];
+	/* detour code buffer */
+	kprobe_opcode_t *insn;
+	unsigned long length;
+	int rd;
+};
+
+#endif /* CONFIG_OPTPROBES */
 #endif /* CONFIG_KPROBES */
 #endif /* _ASM_RISCV_KPROBES_H */
diff --git a/arch/riscv/kernel/probes/Makefile b/arch/riscv/kernel/probes/Makefile
index c40139e9ca47..3d837eb5f9be 100644
--- a/arch/riscv/kernel/probes/Makefile
+++ b/arch/riscv/kernel/probes/Makefile
@@ -3,4 +3,5 @@ obj-$(CONFIG_KPROBES)		+= kprobes.o decode-insn.o simulate-insn.o
 obj-$(CONFIG_RETHOOK)		+= rethook.o rethook_trampoline.o
 obj-$(CONFIG_KPROBES_ON_FTRACE)	+= ftrace.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o decode-insn.o simulate-insn.o
+obj-$(CONFIG_OPTPROBES)		+= opt.o opt_trampoline.o
 CFLAGS_REMOVE_simulate-insn.o = $(CC_FLAGS_FTRACE)
diff --git a/arch/riscv/kernel/probes/opt.c b/arch/riscv/kernel/probes/opt.c
new file mode 100644
index 000000000000..56c8a227c857
--- /dev/null
+++ b/arch/riscv/kernel/probes/opt.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Kernel Probes Jump Optimization (Optprobes)
+ *
+ * Copyright (C) Guokai Chen, 2022
+ * Author: Guokai Chen chenguokai17 at mails.ucas.ac.cn
+ */
+
+#define pr_fmt(fmt)	"optprobe: " fmt
+
+#include <linux/kprobes.h>
+#include <asm/kprobes.h>
+
+int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
+{
+	return 0;
+}
+
+int arch_check_optimized_kprobe(struct optimized_kprobe *op)
+{
+	return 0;
+}
+
+int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
+				  struct kprobe *orig)
+{
+	return 0;
+}
+
+void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
+{
+}
+
+void arch_optimize_kprobes(struct list_head *oplist)
+{
+}
+
+void arch_unoptimize_kprobes(struct list_head *oplist,
+			     struct list_head *done_list)
+{
+}
+
+void arch_unoptimize_kprobe(struct optimized_kprobe *op)
+{
+}
+
+int arch_within_optimized_kprobe(struct optimized_kprobe *op,
+				 kprobe_opcode_t *addr)
+{
+	return 0;
+}
diff --git a/arch/riscv/kernel/probes/opt_trampoline.S b/arch/riscv/kernel/probes/opt_trampoline.S
new file mode 100644
index 000000000000..16160c4367ff
--- /dev/null
+++ b/arch/riscv/kernel/probes/opt_trampoline.S
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2022 Guokai Chen
+ */
+
+#include <linux/linkage.h>
+
+#incldue <asm/csr.h>
+#include <asm/asm-offsets.h>
+
+SYM_ENTRY(optprobe_template_entry, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_ENTRY(optprobe_template_end, SYM_L_GLOBAL, SYM_A_NONE)
-- 
2.34.1