[PATCH v6] rethook: add riscv rethook implementation.

[Binglei Wang <l3b2w1@gmail.com>]

From: Binglei Wang <l3b2w1@gmail.com>

Implement the kretprobes on riscv arch by using rethook mechanism
which abstracts general kretprobe info into a struct rethook_node
to be embedded in the struct kretprobe_instance.

1. remove arch dependent kretprobe implementation
2. replace __kretprobe_trampoline with arch_hook_trampoline

Signed-off-by: Binglei Wang <l3b2w1@gmail.com>
---
 arch/riscv/Kconfig                            |  1 +
 arch/riscv/kernel/probes/Makefile             |  2 +-
 arch/riscv/kernel/probes/kprobes.c            | 13 ----------
 arch/riscv/kernel/probes/rethook.c            | 26 +++++++++++++++++++
 arch/riscv/kernel/probes/rethook.h            |  8 ++++++
 ...obes_trampoline.S => rethook_trampoline.S} |  0
 6 files changed, 36 insertions(+), 14 deletions(-)
 create mode 100644 arch/riscv/kernel/probes/rethook.c
 create mode 100644 arch/riscv/kernel/probes/rethook.h
 rename arch/riscv/kernel/probes/{kprobes_trampoline.S => rethook_trampoline.S} (100%)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index ed66c31e4..c5cae0825 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -97,6 +97,7 @@ config RISCV
 	select HAVE_KPROBES if !XIP_KERNEL
 	select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL
 	select HAVE_KRETPROBES if !XIP_KERNEL
+	select HAVE_RETHOOK if !XIP_KERNEL
 	select HAVE_MOVE_PMD
 	select HAVE_MOVE_PUD
 	select HAVE_PCI
diff --git a/arch/riscv/kernel/probes/Makefile b/arch/riscv/kernel/probes/Makefile
index 7f0840dcc..9a96a7038 100644
--- a/arch/riscv/kernel/probes/Makefile
+++ b/arch/riscv/kernel/probes/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_KPROBES)		+= kprobes.o decode-insn.o simulate-insn.o
-obj-$(CONFIG_KPROBES)		+= kprobes_trampoline.o
 obj-$(CONFIG_KPROBES_ON_FTRACE)	+= ftrace.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o decode-insn.o simulate-insn.o
+obj-$(CONFIG_KPROBES)		+= rethook.o rethook_trampoline.o
 CFLAGS_REMOVE_simulate-insn.o = $(CC_FLAGS_FTRACE)
diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index e6e950b7c..f21592d20 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -345,19 +345,6 @@ int __init arch_populate_kprobe_blacklist(void)
 	return ret;
 }
 
-void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
-{
-	return (void *)kretprobe_trampoline_handler(regs, NULL);
-}
-
-void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
-				      struct pt_regs *regs)
-{
-	ri->ret_addr = (kprobe_opcode_t *)regs->ra;
-	ri->fp = NULL;
-	regs->ra = (unsigned long) &__kretprobe_trampoline;
-}
-
 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 {
 	return 0;
diff --git a/arch/riscv/kernel/probes/rethook.c b/arch/riscv/kernel/probes/rethook.c
new file mode 100644
index 000000000..edfeaa256
--- /dev/null
+++ b/arch/riscv/kernel/probes/rethook.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic return hook for riscv.
+ */
+
+#include <linux/kprobes.h>
+#include <linux/rethook.h>
+#include "rethook.h"
+
+/* This is called from arch_rethook_trampoline() */
+unsigned long __used arch_rethook_trampoline_callback(struct pt_regs *regs)
+{
+	return rethook_trampoline_handler(regs, regs->s0);
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
+
+
+void arch_rethook_prepare(struct rethook_node *rhn, struct pt_regs *regs, bool mcount)
+{
+	rhn->ret_addr = regs->ra;
+	rhn->frame = regs->s0;
+
+	/* replace return addr with trampoline */
+	regs->ra = (u64)arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);
diff --git a/arch/riscv/kernel/probes/rethook.h b/arch/riscv/kernel/probes/rethook.h
new file mode 100644
index 000000000..cc573d701
--- /dev/null
+++ b/arch/riscv/kernel/probes/rethook.h
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#ifndef __RISCV_RETHOOK_H
+#define __RISCV_RETHOOK_H
+
+unsigned long arch_rethook_trampoline_callback(struct pt_regs *regs);
+void arch_rethook_prepare(struct rethook_node *rhn, struct pt_regs *regs, bool mcount);
+
+#endif
diff --git a/arch/riscv/kernel/probes/kprobes_trampoline.S b/arch/riscv/kernel/probes/rethook_trampoline.S
similarity index 100%
rename from arch/riscv/kernel/probes/kprobes_trampoline.S
rename to arch/riscv/kernel/probes/rethook_trampoline.S
-- 
2.27.0