Unverified Commit c22b0bcb authored by Guo Ren's avatar Guo Ren Committed by Palmer Dabbelt
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riscv: Add kprobes supported 

This patch enables "kprobe & kretprobe" to work with ftrace
interface. It utilized software breakpoint as single-step
mechanism.

Some instructions which can't be single-step executed must be
simulated in kernel execution slot, such as: branch, jal, auipc,
la ...

Some instructions should be rejected for probing and we use a
blacklist to filter, such as: ecall, ebreak, ...

We use ebreak & c.ebreak to replace origin instruction and the
kprobe handler prepares an executable memory slot for out-of-line
execution with a copy of the original instruction being probed.
In execution slot we add ebreak behind original instruction to
simulate a single-setp mechanism.

The patch is based on packi's work [1] and csky's work [2].
 - The kprobes_trampoline.S is all from packi's patch
 - The single-step mechanism is new designed for riscv without hw
   single-step trap
 - The simulation codes are from csky
 - Frankly, all codes refer to other archs' implementation

 [1] https://lore.kernel.org/linux-riscv/20181113195804.22825-1-me@packi.ch/
 [2] https://lore.kernel.org/linux-csky/20200403044150.20562-9-guoren@kernel.org/



Signed-off-by: default avatarGuo Ren <guoren@linux.alibaba.com>
Co-developed-by: default avatarPatrick Stählin <me@packi.ch>
Signed-off-by: default avatarPatrick Stählin <me@packi.ch>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Tested-by: default avatarZong Li <zong.li@sifive.com>
Reviewed-by: default avatarPekka Enberg <penberg@kernel.org>
Cc: Patrick Stählin <me@packi.ch>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: default avatarPalmer Dabbelt <palmerdabbelt@google.com>
parent afc76b8b

arch/riscv/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -71,6 +71,8 @@ config RISCV 
	select HAVE_GCC_PLUGINS

	select HAVE_GENERIC_VDSO if MMU && 64BIT

	select HAVE_IRQ_TIME_ACCOUNTING

	select HAVE_KPROBES

	select HAVE_KRETPROBES

	select HAVE_PCI

	select HAVE_PERF_EVENTS

	select HAVE_PERF_REGS

arch/riscv/include/asm/kprobes.h

+40 −0
Original line number Diff line number Diff line
@@ -11,4 +11,44 @@ 


#include <asm-generic/kprobes.h>



#ifdef CONFIG_KPROBES

#include <linux/types.h>

#include <linux/ptrace.h>

#include <linux/percpu.h>



#define __ARCH_WANT_KPROBES_INSN_SLOT

#define MAX_INSN_SIZE			2



#define flush_insn_slot(p)		do { } while (0)

#define kretprobe_blacklist_size	0



#include <asm/probes.h>



struct prev_kprobe {

	struct kprobe *kp;

	unsigned int status;

};



/* Single step context for kprobe */

struct kprobe_step_ctx {

	unsigned long ss_pending;

	unsigned long match_addr;

};



/* per-cpu kprobe control block */

struct kprobe_ctlblk {

	unsigned int kprobe_status;

	unsigned long saved_status;

	struct prev_kprobe prev_kprobe;

	struct kprobe_step_ctx ss_ctx;

};



void arch_remove_kprobe(struct kprobe *p);

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);

void kretprobe_trampoline(void);

void __kprobes *trampoline_probe_handler(struct pt_regs *regs);



#endif /* CONFIG_KPROBES */

#endif /* _ASM_RISCV_KPROBES_H */

arch/riscv/include/asm/probes.h

0 → 100644
+24 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */



#ifndef _ASM_RISCV_PROBES_H

#define _ASM_RISCV_PROBES_H



typedef u32 probe_opcode_t;

typedef bool (probes_handler_t) (u32 opcode, unsigned long addr, struct pt_regs *);



/* architecture specific copy of original instruction */

struct arch_probe_insn {

	probe_opcode_t *insn;

	probes_handler_t *handler;

	/* restore address after simulation */

	unsigned long restore;

};



#ifdef CONFIG_KPROBES

typedef u32 kprobe_opcode_t;

struct arch_specific_insn {

	struct arch_probe_insn api;

};

#endif



#endif /* _ASM_RISCV_PROBES_H */

arch/riscv/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ obj-y += riscv_ksyms.o 
obj-y	+= stacktrace.o

obj-y	+= cacheinfo.o

obj-y	+= patch.o

obj-y	+= probes/

obj-$(CONFIG_MMU) += vdso.o vdso/



obj-$(CONFIG_RISCV_M_MODE)	+= traps_misaligned.o

arch/riscv/kernel/probes/Makefile

0 → 100644
+4 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

obj-$(CONFIG_KPROBES)		+= kprobes.o decode-insn.o simulate-insn.o

obj-$(CONFIG_KPROBES)		+= kprobes_trampoline.o

CFLAGS_REMOVE_simulate-insn.o = $(CC_FLAGS_FTRACE)