diff mbox series

[2/5] riscv: Add KGDB support

Message ID 1583225231-26187-1-git-send-email-vincent.chen@sifive.com (mailing list archive)
State New, archived
Headers show
Series riscv: Add KGDB and KDB support | expand

Commit Message

Vincent Chen March 3, 2020, 8:47 a.m. UTC 
The skeleton of RISC-V KGDB port.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
---
 arch/riscv/Kconfig              |   1 +
 arch/riscv/include/asm/Kbuild   |   1 -
 arch/riscv/include/asm/kdebug.h |  12 +++
 arch/riscv/include/asm/kgdb.h   |  71 ++++++++++++++
 arch/riscv/kernel/Makefile      |   1 +
 arch/riscv/kernel/kgdb.c        | 199 ++++++++++++++++++++++++++++++++++++++++
 arch/riscv/kernel/traps.c       |   5 +
 7 files changed, 289 insertions(+), 1 deletion(-)
 create mode 100644 arch/riscv/include/asm/kdebug.h
 create mode 100644 arch/riscv/include/asm/kgdb.h
 create mode 100644 arch/riscv/kernel/kgdb.c

Comments

Palmer Dabbelt March 18, 2020, 10:09 p.m. UTC | #1 
On Tue, 03 Mar 2020 00:47:11 PST (-0800), vincent.chen@sifive.com wrote:
> The skeleton of RISC-V KGDB port.
>
> Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
> ---
>  arch/riscv/Kconfig              |   1 +
>  arch/riscv/include/asm/Kbuild   |   1 -
>  arch/riscv/include/asm/kdebug.h |  12 +++
>  arch/riscv/include/asm/kgdb.h   |  71 ++++++++++++++
>  arch/riscv/kernel/Makefile      |   1 +
>  arch/riscv/kernel/kgdb.c        | 199 ++++++++++++++++++++++++++++++++++++++++
>  arch/riscv/kernel/traps.c       |   5 +
>  7 files changed, 289 insertions(+), 1 deletion(-)
>  create mode 100644 arch/riscv/include/asm/kdebug.h
>  create mode 100644 arch/riscv/include/asm/kgdb.h
>  create mode 100644 arch/riscv/kernel/kgdb.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 73f029eae0cc..108794f4aa45 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -66,6 +66,7 @@ config RISCV
>  	select ARCH_HAS_GCOV_PROFILE_ALL
>  	select HAVE_COPY_THREAD_TLS
>  	select HAVE_ARCH_KASAN if MMU && 64BIT
> +	select HAVE_ARCH_KGDB
>
>  config ARCH_MMAP_RND_BITS_MIN
>  	default 18 if 64BIT
> diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
> index ec0ca8c6ab64..625e46cbdec8 100644
> --- a/arch/riscv/include/asm/Kbuild
> +++ b/arch/riscv/include/asm/Kbuild
> @@ -15,7 +15,6 @@ generic-y += hardirq.h
>  generic-y += hw_irq.h
>  generic-y += irq_regs.h
>  generic-y += irq_work.h
> -generic-y += kdebug.h
>  generic-y += kmap_types.h
>  generic-y += kvm_para.h
>  generic-y += local.h
> diff --git a/arch/riscv/include/asm/kdebug.h b/arch/riscv/include/asm/kdebug.h
> new file mode 100644
> index 000000000000..85ac00411f6e
> --- /dev/null
> +++ b/arch/riscv/include/asm/kdebug.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef _ASM_ARC_KDEBUG_H
> +#define _ASM_ARC_KDEBUG_H
> +
> +enum die_val {
> +	DIE_UNUSED,
> +	DIE_TRAP,
> +	DIE_OOPS
> +};
> +
> +#endif
> diff --git a/arch/riscv/include/asm/kgdb.h b/arch/riscv/include/asm/kgdb.h
> new file mode 100644
> index 000000000000..e3b455932506
> --- /dev/null
> +++ b/arch/riscv/include/asm/kgdb.h
> @@ -0,0 +1,71 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef __ASM_KGDB_H_
> +#define __ASM_KGDB_H_
> +
> +#ifdef __KERNEL__
> +
> +#define GDB_SIZEOF_REG sizeof(unsigned long)
> +
> +#define DBG_MAX_REG_NUM (33)
> +#define NUMREGBYTES ((DBG_MAX_REG_NUM) * GDB_SIZEOF_REG)
> +#define CACHE_FLUSH_IS_SAFE     1
> +#define BUFMAX                  2048
> +#ifdef CONFIG_RISCV_ISA_C
> +#define BREAK_INSTR_SIZE	2
> +#else
> +#define BREAK_INSTR_SIZE	4
> +#endif
> +#define CACHE_FLUSH_IS_SAFE 1
> +
> +#ifndef	__ASSEMBLY__
> +
> +extern int kgdb_has_hit_break(unsigned long addr);
> +extern unsigned long kgdb_compiled_break;
> +
> +static inline void arch_kgdb_breakpoint(void)
> +{
> +	asm(".global kgdb_compiled_break\n"
> +	    ".option norvc\n"
> +	    "kgdb_compiled_break: ebreak\n"
> +	    ".option rvc\n");
> +}
> +
> +#endif /* !__ASSEMBLY__ */
> +
> +#define PT_REG_ZERO "zero"
> +#define PT_REG_RA "ra"
> +#define PT_REG_SP "sp"
> +#define PT_REG_GP "gp"
> +#define PT_REG_TP "tp"
> +#define PT_REG_T0 "t0"
> +#define PT_REG_T1 "t1"
> +#define PT_REG_T2 "t2"
> +#define PT_REG_FP "fp"
> +#define PT_REG_S1 "s1"
> +#define PT_REG_A0 "a0"
> +#define PT_REG_A1 "a1"
> +#define PT_REG_A2 "a2"
> +#define PT_REG_A3 "a3"
> +#define PT_REG_A4 "a4"
> +#define PT_REG_A5 "a5"
> +#define PT_REG_A6 "a6"
> +#define PT_REG_A7 "a7"
> +#define PT_REG_S2 "s2"
> +#define PT_REG_S3 "s3"
> +#define PT_REG_S4 "s4"
> +#define PT_REG_S5 "s5"
> +#define PT_REG_S6 "s6"
> +#define PT_REG_S7 "s7"
> +#define PT_REG_S8 "s8"
> +#define PT_REG_S9 "s9"
> +#define PT_REG_S10 "s10"
> +#define PT_REG_S11 "s11"
> +#define PT_REG_T3 "t3"
> +#define PT_REG_T4 "t4"
> +#define PT_REG_T5 "t5"
> +#define PT_REG_T6 "t6"
> +#define PT_REG_SEPC "pc"
> +
> +#endif
> +#endif
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index f40205cb9a22..8956543f7d6b 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -42,5 +42,6 @@ obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o
>  obj-$(CONFIG_PERF_EVENTS)	+= perf_callchain.o
>  obj-$(CONFIG_HAVE_PERF_REGS)	+= perf_regs.o
>  obj-$(CONFIG_RISCV_SBI)		+= sbi.o
> +obj-$(CONFIG_KGDB)		+= kgdb.o
>
>  clean:
> diff --git a/arch/riscv/kernel/kgdb.c b/arch/riscv/kernel/kgdb.c
> new file mode 100644
> index 000000000000..0a3fe5d672f1
> --- /dev/null
> +++ b/arch/riscv/kernel/kgdb.c
> @@ -0,0 +1,199 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <linux/ptrace.h>
> +#include <linux/kdebug.h>
> +#include <linux/bug.h>
> +#include <linux/kgdb.h>
> +#include <linux/irqflags.h>
> +#include <linux/string.h>
> +#include <asm/cacheflush.h>
> +
> +enum {
> +	NOT_KGDB_BREAK = 0,
> +	KGDB_SW_BREAK,
> +	KGDB_COMPILED_BREAK,
> +};
> +
> +struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
> +	{PT_REG_ZERO, GDB_SIZEOF_REG, -1},
> +	{PT_REG_RA, GDB_SIZEOF_REG, offsetof(struct pt_regs, ra)},
> +	{PT_REG_SP, GDB_SIZEOF_REG, offsetof(struct pt_regs, sp)},
> +	{PT_REG_GP, GDB_SIZEOF_REG, offsetof(struct pt_regs, gp)},
> +	{PT_REG_TP, GDB_SIZEOF_REG, offsetof(struct pt_regs, tp)},
> +	{PT_REG_T0, GDB_SIZEOF_REG, offsetof(struct pt_regs, t0)},
> +	{PT_REG_T1, GDB_SIZEOF_REG, offsetof(struct pt_regs, t1)},
> +	{PT_REG_T2, GDB_SIZEOF_REG, offsetof(struct pt_regs, t2)},
> +	{PT_REG_FP, GDB_SIZEOF_REG, offsetof(struct pt_regs, s0)},
> +	{PT_REG_S1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
> +	{PT_REG_A0, GDB_SIZEOF_REG, offsetof(struct pt_regs, a0)},
> +	{PT_REG_A1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
> +	{PT_REG_A2, GDB_SIZEOF_REG, offsetof(struct pt_regs, a2)},
> +	{PT_REG_A3, GDB_SIZEOF_REG, offsetof(struct pt_regs, a3)},
> +	{PT_REG_A4, GDB_SIZEOF_REG, offsetof(struct pt_regs, a4)},
> +	{PT_REG_A5, GDB_SIZEOF_REG, offsetof(struct pt_regs, a5)},
> +	{PT_REG_A6, GDB_SIZEOF_REG, offsetof(struct pt_regs, a6)},
> +	{PT_REG_A7, GDB_SIZEOF_REG, offsetof(struct pt_regs, a7)},
> +	{PT_REG_S2, GDB_SIZEOF_REG, offsetof(struct pt_regs, s2)},
> +	{PT_REG_S3, GDB_SIZEOF_REG, offsetof(struct pt_regs, s3)},
> +	{PT_REG_S4, GDB_SIZEOF_REG, offsetof(struct pt_regs, s4)},
> +	{PT_REG_S5, GDB_SIZEOF_REG, offsetof(struct pt_regs, s5)},
> +	{PT_REG_S6, GDB_SIZEOF_REG, offsetof(struct pt_regs, s6)},
> +	{PT_REG_S7, GDB_SIZEOF_REG, offsetof(struct pt_regs, s7)},
> +	{PT_REG_S8, GDB_SIZEOF_REG, offsetof(struct pt_regs, s8)},
> +	{PT_REG_S9, GDB_SIZEOF_REG, offsetof(struct pt_regs, s9)},
> +	{PT_REG_S10, GDB_SIZEOF_REG, offsetof(struct pt_regs, s10)},
> +	{PT_REG_S11, GDB_SIZEOF_REG, offsetof(struct pt_regs, s11)},
> +	{PT_REG_T3, GDB_SIZEOF_REG, offsetof(struct pt_regs, t3)},
> +	{PT_REG_T4, GDB_SIZEOF_REG, offsetof(struct pt_regs, t4)},
> +	{PT_REG_T5, GDB_SIZEOF_REG, offsetof(struct pt_regs, t5)},
> +	{PT_REG_T6, GDB_SIZEOF_REG, offsetof(struct pt_regs, t6)},
> +	{PT_REG_SEPC, GDB_SIZEOF_REG, offsetof(struct pt_regs, epc)},

A bit pedantic, but we've removed S from all of these now that we support
M-mode kernels.  I don't care enough to re-spin the patch set :)

> +};
> +
> +char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
> +{
> +	if (regno >= DBG_MAX_REG_NUM || regno < 0)
> +		return NULL;
> +
> +	if (dbg_reg_def[regno].offset != -1)
> +		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
> +		       dbg_reg_def[regno].size);
> +	else
> +		memset(mem, 0, dbg_reg_def[regno].size);
> +	return dbg_reg_def[regno].name;
> +}
> +
> +int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
> +{
> +	if (regno >= DBG_MAX_REG_NUM || regno < 0)
> +		return -EINVAL;
> +
> +	if (dbg_reg_def[regno].offset != -1)
> +		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
> +		       dbg_reg_def[regno].size);
> +	return 0;
> +}
> +
> +void
> +sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
> +{
> +	/* Initialize to zero */
> +	memset((char *)gdb_regs, 0, NUMREGBYTES);
> +
> +	gdb_regs[2] = task->thread.sp;
> +	gdb_regs[8] = task->thread.s[0];
> +	gdb_regs[9] = task->thread.s[1];
> +	gdb_regs[18] = task->thread.s[2];
> +	gdb_regs[19] = task->thread.s[3];
> +	gdb_regs[20] = task->thread.s[4];
> +	gdb_regs[21] = task->thread.s[5];
> +	gdb_regs[22] = task->thread.s[6];
> +	gdb_regs[23] = task->thread.s[7];
> +	gdb_regs[24] = task->thread.s[8];
> +	gdb_regs[25] = task->thread.s[10];
> +	gdb_regs[26] = task->thread.s[11];
> +	gdb_regs[32] = task->thread.ra;

While it's usually a bit ugly to just have numbers here, I think it's OK in
this case as the GDB register ordering was defined quite early on and is a bit
idiosyncratic.  If we need to map this multiple times it might be better to
have some sort of mechanism with names, though.

> +}
> +
> +void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
> +{
> +	regs->epc = pc;
> +}
> +
> +static inline void kgdb_arch_update_addr(struct pt_regs *regs,
> +					 char *remcom_in_buffer)
> +{
> +	unsigned long addr;
> +	char *ptr;
> +
> +	ptr = &remcom_in_buffer[1];
> +	if (kgdb_hex2long(&ptr, &addr))
> +		regs->epc = addr;
> +}
> +
> +int kgdb_arch_handle_exception(int vector, int signo, int err_code,
> +			       char *remcom_in_buffer, char *remcom_out_buffer,
> +			       struct pt_regs *regs)
> +{
> +	int err = 0;
> +
> +	switch (remcom_in_buffer[0]) {
> +	case 'c':
> +	case 'D':
> +	case 'k':
> +		if (remcom_in_buffer[0] == 'c')
> +			kgdb_arch_update_addr(regs, remcom_in_buffer);
> +		atomic_set(&kgdb_cpu_doing_single_step, -1);
> +		kgdb_single_step = 0;
> +		break;
> +	default:
> +		err = -1;
> +	}
> +
> +	return err;
> +}
> +
> +int kgdb_riscv_kgdbbreak(unsigned long addr)
> +{
> +	if (atomic_read(&kgdb_setting_breakpoint))
> +		if (addr == (unsigned long)&kgdb_compiled_break)
> +			return KGDB_COMPILED_BREAK;
> +
> +	return kgdb_has_hit_break(addr);
> +}
> +
> +static int kgdb_riscv_notify(struct notifier_block *self, unsigned long cmd,
> +			     void *ptr)
> +{
> +	struct die_args *args = (struct die_args *)ptr;
> +	struct pt_regs *regs = args->regs;
> +	unsigned long flags;
> +	int type;
> +
> +	if (user_mode(regs))
> +		return NOTIFY_DONE;
> +
> +	type = kgdb_riscv_kgdbbreak(regs->epc);
> +	if (type == NOT_KGDB_BREAK && cmd == DIE_TRAP)
> +		return NOTIFY_DONE;
> +
> +	local_irq_save(flags);
> +	if (kgdb_handle_exception(1, args->signr, cmd, regs))
> +		return NOTIFY_DONE;
> +
> +	if (type == KGDB_COMPILED_BREAK)
> +		regs->epc += 4;
> +
> +	local_irq_restore(flags);
> +
> +	return NOTIFY_STOP;
> +}
> +
> +static struct notifier_block kgdb_notifier = {
> +	.notifier_call = kgdb_riscv_notify,
> +};
> +
> +int kgdb_arch_init(void)
> +{
> +	register_die_notifier(&kgdb_notifier);
> +
> +	return 0;
> +}
> +
> +void kgdb_arch_exit(void)
> +{
> +	unregister_die_notifier(&kgdb_notifier);
> +}
> +
> +/*
> + * Global data
> + */
> +#ifdef CONFIG_RISCV_ISA_C
> +const struct kgdb_arch arch_kgdb_ops = {
> +	.gdb_bpt_instr = {0x02, 0x90},	/* c.ebreak */
> +};
> +#else
> +const struct kgdb_arch arch_kgdb_ops = {
> +	.gdb_bpt_instr = {0x73, 0x00, 0x10, 0x00},	/* ebreak */
> +};
> +#endif
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index f4cad5163bf2..7e017c2131cf 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -125,6 +125,11 @@ asmlinkage __visible void do_trap_break(struct pt_regs *regs)
>  {
>  	if (user_mode(regs))
>  		force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->epc);
> +#ifdef CONFIG_KGDB
> +	else if (notify_die(DIE_TRAP, "EBREAK", regs, 0, regs->cause, SIGTRAP)
> +								== NOTIFY_STOP)
> +		return;
> +#endif
>  	else if (report_bug(regs->epc, regs) == BUG_TRAP_TYPE_WARN)
>  		regs->epc += get_break_insn_length(regs->epc);
>  	else

Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
diff mbox series

Patch

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 73f029eae0cc..108794f4aa45 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -66,6 +66,7 @@  config RISCV
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select HAVE_COPY_THREAD_TLS
 	select HAVE_ARCH_KASAN if MMU && 64BIT
+	select HAVE_ARCH_KGDB
 
 config ARCH_MMAP_RND_BITS_MIN
 	default 18 if 64BIT
diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
index ec0ca8c6ab64..625e46cbdec8 100644
--- a/arch/riscv/include/asm/Kbuild
+++ b/arch/riscv/include/asm/Kbuild
@@ -15,7 +15,6 @@  generic-y += hardirq.h
 generic-y += hw_irq.h
 generic-y += irq_regs.h
 generic-y += irq_work.h
-generic-y += kdebug.h
 generic-y += kmap_types.h
 generic-y += kvm_para.h
 generic-y += local.h
diff --git a/arch/riscv/include/asm/kdebug.h b/arch/riscv/include/asm/kdebug.h
new file mode 100644
index 000000000000..85ac00411f6e
--- /dev/null
+++ b/arch/riscv/include/asm/kdebug.h
@@ -0,0 +1,12 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _ASM_ARC_KDEBUG_H
+#define _ASM_ARC_KDEBUG_H
+
+enum die_val {
+	DIE_UNUSED,
+	DIE_TRAP,
+	DIE_OOPS
+};
+
+#endif
diff --git a/arch/riscv/include/asm/kgdb.h b/arch/riscv/include/asm/kgdb.h
new file mode 100644
index 000000000000..e3b455932506
--- /dev/null
+++ b/arch/riscv/include/asm/kgdb.h
@@ -0,0 +1,71 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_KGDB_H_
+#define __ASM_KGDB_H_
+
+#ifdef __KERNEL__
+
+#define GDB_SIZEOF_REG sizeof(unsigned long)
+
+#define DBG_MAX_REG_NUM (33)
+#define NUMREGBYTES ((DBG_MAX_REG_NUM) * GDB_SIZEOF_REG)
+#define CACHE_FLUSH_IS_SAFE     1
+#define BUFMAX                  2048
+#ifdef CONFIG_RISCV_ISA_C
+#define BREAK_INSTR_SIZE	2
+#else
+#define BREAK_INSTR_SIZE	4
+#endif
+#define CACHE_FLUSH_IS_SAFE 1
+
+#ifndef	__ASSEMBLY__
+
+extern int kgdb_has_hit_break(unsigned long addr);
+extern unsigned long kgdb_compiled_break;
+
+static inline void arch_kgdb_breakpoint(void)
+{
+	asm(".global kgdb_compiled_break\n"
+	    ".option norvc\n"
+	    "kgdb_compiled_break: ebreak\n"
+	    ".option rvc\n");
+}
+
+#endif /* !__ASSEMBLY__ */
+
+#define PT_REG_ZERO "zero"
+#define PT_REG_RA "ra"
+#define PT_REG_SP "sp"
+#define PT_REG_GP "gp"
+#define PT_REG_TP "tp"
+#define PT_REG_T0 "t0"
+#define PT_REG_T1 "t1"
+#define PT_REG_T2 "t2"
+#define PT_REG_FP "fp"
+#define PT_REG_S1 "s1"
+#define PT_REG_A0 "a0"
+#define PT_REG_A1 "a1"
+#define PT_REG_A2 "a2"
+#define PT_REG_A3 "a3"
+#define PT_REG_A4 "a4"
+#define PT_REG_A5 "a5"
+#define PT_REG_A6 "a6"
+#define PT_REG_A7 "a7"
+#define PT_REG_S2 "s2"
+#define PT_REG_S3 "s3"
+#define PT_REG_S4 "s4"
+#define PT_REG_S5 "s5"
+#define PT_REG_S6 "s6"
+#define PT_REG_S7 "s7"
+#define PT_REG_S8 "s8"
+#define PT_REG_S9 "s9"
+#define PT_REG_S10 "s10"
+#define PT_REG_S11 "s11"
+#define PT_REG_T3 "t3"
+#define PT_REG_T4 "t4"
+#define PT_REG_T5 "t5"
+#define PT_REG_T6 "t6"
+#define PT_REG_SEPC "pc"
+
+#endif
+#endif
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index f40205cb9a22..8956543f7d6b 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -42,5 +42,6 @@  obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_callchain.o
 obj-$(CONFIG_HAVE_PERF_REGS)	+= perf_regs.o
 obj-$(CONFIG_RISCV_SBI)		+= sbi.o
+obj-$(CONFIG_KGDB)		+= kgdb.o
 
 clean:
diff --git a/arch/riscv/kernel/kgdb.c b/arch/riscv/kernel/kgdb.c
new file mode 100644
index 000000000000..0a3fe5d672f1
--- /dev/null
+++ b/arch/riscv/kernel/kgdb.c
@@ -0,0 +1,199 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/ptrace.h>
+#include <linux/kdebug.h>
+#include <linux/bug.h>
+#include <linux/kgdb.h>
+#include <linux/irqflags.h>
+#include <linux/string.h>
+#include <asm/cacheflush.h>
+
+enum {
+	NOT_KGDB_BREAK = 0,
+	KGDB_SW_BREAK,
+	KGDB_COMPILED_BREAK,
+};
+
+struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
+	{PT_REG_ZERO, GDB_SIZEOF_REG, -1},
+	{PT_REG_RA, GDB_SIZEOF_REG, offsetof(struct pt_regs, ra)},
+	{PT_REG_SP, GDB_SIZEOF_REG, offsetof(struct pt_regs, sp)},
+	{PT_REG_GP, GDB_SIZEOF_REG, offsetof(struct pt_regs, gp)},
+	{PT_REG_TP, GDB_SIZEOF_REG, offsetof(struct pt_regs, tp)},
+	{PT_REG_T0, GDB_SIZEOF_REG, offsetof(struct pt_regs, t0)},
+	{PT_REG_T1, GDB_SIZEOF_REG, offsetof(struct pt_regs, t1)},
+	{PT_REG_T2, GDB_SIZEOF_REG, offsetof(struct pt_regs, t2)},
+	{PT_REG_FP, GDB_SIZEOF_REG, offsetof(struct pt_regs, s0)},
+	{PT_REG_S1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
+	{PT_REG_A0, GDB_SIZEOF_REG, offsetof(struct pt_regs, a0)},
+	{PT_REG_A1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
+	{PT_REG_A2, GDB_SIZEOF_REG, offsetof(struct pt_regs, a2)},
+	{PT_REG_A3, GDB_SIZEOF_REG, offsetof(struct pt_regs, a3)},
+	{PT_REG_A4, GDB_SIZEOF_REG, offsetof(struct pt_regs, a4)},
+	{PT_REG_A5, GDB_SIZEOF_REG, offsetof(struct pt_regs, a5)},
+	{PT_REG_A6, GDB_SIZEOF_REG, offsetof(struct pt_regs, a6)},
+	{PT_REG_A7, GDB_SIZEOF_REG, offsetof(struct pt_regs, a7)},
+	{PT_REG_S2, GDB_SIZEOF_REG, offsetof(struct pt_regs, s2)},
+	{PT_REG_S3, GDB_SIZEOF_REG, offsetof(struct pt_regs, s3)},
+	{PT_REG_S4, GDB_SIZEOF_REG, offsetof(struct pt_regs, s4)},
+	{PT_REG_S5, GDB_SIZEOF_REG, offsetof(struct pt_regs, s5)},
+	{PT_REG_S6, GDB_SIZEOF_REG, offsetof(struct pt_regs, s6)},
+	{PT_REG_S7, GDB_SIZEOF_REG, offsetof(struct pt_regs, s7)},
+	{PT_REG_S8, GDB_SIZEOF_REG, offsetof(struct pt_regs, s8)},
+	{PT_REG_S9, GDB_SIZEOF_REG, offsetof(struct pt_regs, s9)},
+	{PT_REG_S10, GDB_SIZEOF_REG, offsetof(struct pt_regs, s10)},
+	{PT_REG_S11, GDB_SIZEOF_REG, offsetof(struct pt_regs, s11)},
+	{PT_REG_T3, GDB_SIZEOF_REG, offsetof(struct pt_regs, t3)},
+	{PT_REG_T4, GDB_SIZEOF_REG, offsetof(struct pt_regs, t4)},
+	{PT_REG_T5, GDB_SIZEOF_REG, offsetof(struct pt_regs, t5)},
+	{PT_REG_T6, GDB_SIZEOF_REG, offsetof(struct pt_regs, t6)},
+	{PT_REG_SEPC, GDB_SIZEOF_REG, offsetof(struct pt_regs, epc)},
+};
+
+char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
+{
+	if (regno >= DBG_MAX_REG_NUM || regno < 0)
+		return NULL;
+
+	if (dbg_reg_def[regno].offset != -1)
+		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
+		       dbg_reg_def[regno].size);
+	else
+		memset(mem, 0, dbg_reg_def[regno].size);
+	return dbg_reg_def[regno].name;
+}
+
+int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
+{
+	if (regno >= DBG_MAX_REG_NUM || regno < 0)
+		return -EINVAL;
+
+	if (dbg_reg_def[regno].offset != -1)
+		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
+		       dbg_reg_def[regno].size);
+	return 0;
+}
+
+void
+sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
+{
+	/* Initialize to zero */
+	memset((char *)gdb_regs, 0, NUMREGBYTES);
+
+	gdb_regs[2] = task->thread.sp;
+	gdb_regs[8] = task->thread.s[0];
+	gdb_regs[9] = task->thread.s[1];
+	gdb_regs[18] = task->thread.s[2];
+	gdb_regs[19] = task->thread.s[3];
+	gdb_regs[20] = task->thread.s[4];
+	gdb_regs[21] = task->thread.s[5];
+	gdb_regs[22] = task->thread.s[6];
+	gdb_regs[23] = task->thread.s[7];
+	gdb_regs[24] = task->thread.s[8];
+	gdb_regs[25] = task->thread.s[10];
+	gdb_regs[26] = task->thread.s[11];
+	gdb_regs[32] = task->thread.ra;
+}
+
+void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
+{
+	regs->epc = pc;
+}
+
+static inline void kgdb_arch_update_addr(struct pt_regs *regs,
+					 char *remcom_in_buffer)
+{
+	unsigned long addr;
+	char *ptr;
+
+	ptr = &remcom_in_buffer[1];
+	if (kgdb_hex2long(&ptr, &addr))
+		regs->epc = addr;
+}
+
+int kgdb_arch_handle_exception(int vector, int signo, int err_code,
+			       char *remcom_in_buffer, char *remcom_out_buffer,
+			       struct pt_regs *regs)
+{
+	int err = 0;
+
+	switch (remcom_in_buffer[0]) {
+	case 'c':
+	case 'D':
+	case 'k':
+		if (remcom_in_buffer[0] == 'c')
+			kgdb_arch_update_addr(regs, remcom_in_buffer);
+		atomic_set(&kgdb_cpu_doing_single_step, -1);
+		kgdb_single_step = 0;
+		break;
+	default:
+		err = -1;
+	}
+
+	return err;
+}
+
+int kgdb_riscv_kgdbbreak(unsigned long addr)
+{
+	if (atomic_read(&kgdb_setting_breakpoint))
+		if (addr == (unsigned long)&kgdb_compiled_break)
+			return KGDB_COMPILED_BREAK;
+
+	return kgdb_has_hit_break(addr);
+}
+
+static int kgdb_riscv_notify(struct notifier_block *self, unsigned long cmd,
+			     void *ptr)
+{
+	struct die_args *args = (struct die_args *)ptr;
+	struct pt_regs *regs = args->regs;
+	unsigned long flags;
+	int type;
+
+	if (user_mode(regs))
+		return NOTIFY_DONE;
+
+	type = kgdb_riscv_kgdbbreak(regs->epc);
+	if (type == NOT_KGDB_BREAK && cmd == DIE_TRAP)
+		return NOTIFY_DONE;
+
+	local_irq_save(flags);
+	if (kgdb_handle_exception(1, args->signr, cmd, regs))
+		return NOTIFY_DONE;
+
+	if (type == KGDB_COMPILED_BREAK)
+		regs->epc += 4;
+
+	local_irq_restore(flags);
+
+	return NOTIFY_STOP;
+}
+
+static struct notifier_block kgdb_notifier = {
+	.notifier_call = kgdb_riscv_notify,
+};
+
+int kgdb_arch_init(void)
+{
+	register_die_notifier(&kgdb_notifier);
+
+	return 0;
+}
+
+void kgdb_arch_exit(void)
+{
+	unregister_die_notifier(&kgdb_notifier);
+}
+
+/*
+ * Global data
+ */
+#ifdef CONFIG_RISCV_ISA_C
+const struct kgdb_arch arch_kgdb_ops = {
+	.gdb_bpt_instr = {0x02, 0x90},	/* c.ebreak */
+};
+#else
+const struct kgdb_arch arch_kgdb_ops = {
+	.gdb_bpt_instr = {0x73, 0x00, 0x10, 0x00},	/* ebreak */
+};
+#endif
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index f4cad5163bf2..7e017c2131cf 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -125,6 +125,11 @@  asmlinkage __visible void do_trap_break(struct pt_regs *regs)
 {
 	if (user_mode(regs))
 		force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->epc);
+#ifdef CONFIG_KGDB
+	else if (notify_die(DIE_TRAP, "EBREAK", regs, 0, regs->cause, SIGTRAP)
+								== NOTIFY_STOP)
+		return;
+#endif
 	else if (report_bug(regs->epc, regs) == BUG_TRAP_TYPE_WARN)
 		regs->epc += get_break_insn_length(regs->epc);
 	else