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VincentZWCpalmer-dabbelt
VincentZWC
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riscv: Add KGDB support
The skeleton of RISC-V KGDB port. Signed-off-by: Vincent Chen <[email protected]> Reviewed-by: Palmer Dabbelt <[email protected]> Signed-off-by: Palmer Dabbelt <[email protected]>
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‎arch/riscv/Kconfig

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@@ -68,6 +68,7 @@ config RISCV
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select ARCH_HAS_GCOV_PROFILE_ALL
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select HAVE_COPY_THREAD_TLS
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select HAVE_ARCH_KASAN if MMU && 64BIT
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select HAVE_ARCH_KGDB
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config ARCH_MMAP_RND_BITS_MIN
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default 18 if 64BIT

‎arch/riscv/include/asm/kdebug.h

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@@ -0,0 +1,12 @@
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/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef _ASM_ARC_KDEBUG_H
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#define _ASM_ARC_KDEBUG_H
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enum die_val {
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DIE_UNUSED,
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DIE_TRAP,
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DIE_OOPS
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};
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#endif

‎arch/riscv/include/asm/kgdb.h

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@@ -0,0 +1,106 @@
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/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef __ASM_KGDB_H_
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#define __ASM_KGDB_H_
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#ifdef __KERNEL__
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#define GDB_SIZEOF_REG sizeof(unsigned long)
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#define DBG_MAX_REG_NUM (33)
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#define NUMREGBYTES ((DBG_MAX_REG_NUM) * GDB_SIZEOF_REG)
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#define CACHE_FLUSH_IS_SAFE 1
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#define BUFMAX 2048
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#ifdef CONFIG_RISCV_ISA_C
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#define BREAK_INSTR_SIZE 2
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#else
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#define BREAK_INSTR_SIZE 4
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#endif
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#ifndef __ASSEMBLY__
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extern int kgdb_has_hit_break(unsigned long addr);
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extern unsigned long kgdb_compiled_break;
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static inline void arch_kgdb_breakpoint(void)
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{
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asm(".global kgdb_compiled_break\n"
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".option norvc\n"
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"kgdb_compiled_break: ebreak\n"
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".option rvc\n");
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}
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#endif /* !__ASSEMBLY__ */
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#define DBG_REG_ZERO "zero"
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#define DBG_REG_RA "ra"
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#define DBG_REG_SP "sp"
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#define DBG_REG_GP "gp"
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#define DBG_REG_TP "tp"
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#define DBG_REG_T0 "t0"
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#define DBG_REG_T1 "t1"
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#define DBG_REG_T2 "t2"
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#define DBG_REG_FP "fp"
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#define DBG_REG_S1 "s1"
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#define DBG_REG_A0 "a0"
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#define DBG_REG_A1 "a1"
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#define DBG_REG_A2 "a2"
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#define DBG_REG_A3 "a3"
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#define DBG_REG_A4 "a4"
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#define DBG_REG_A5 "a5"
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#define DBG_REG_A6 "a6"
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#define DBG_REG_A7 "a7"
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#define DBG_REG_S2 "s2"
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#define DBG_REG_S3 "s3"
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#define DBG_REG_S4 "s4"
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#define DBG_REG_S5 "s5"
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#define DBG_REG_S6 "s6"
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#define DBG_REG_S7 "s7"
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#define DBG_REG_S8 "s8"
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#define DBG_REG_S9 "s9"
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#define DBG_REG_S10 "s10"
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#define DBG_REG_S11 "s11"
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#define DBG_REG_T3 "t3"
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#define DBG_REG_T4 "t4"
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#define DBG_REG_T5 "t5"
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#define DBG_REG_T6 "t6"
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#define DBG_REG_EPC "pc"
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#define DBG_REG_ZERO_OFF 0
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#define DBG_REG_RA_OFF 1
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#define DBG_REG_SP_OFF 2
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#define DBG_REG_GP_OFF 3
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#define DBG_REG_TP_OFF 4
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#define DBG_REG_T0_OFF 5
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#define DBG_REG_T1_OFF 6
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#define DBG_REG_T2_OFF 7
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#define DBG_REG_FP_OFF 8
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#define DBG_REG_S1_OFF 9
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#define DBG_REG_A0_OFF 10
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#define DBG_REG_A1_OFF 11
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#define DBG_REG_A2_OFF 12
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#define DBG_REG_A3_OFF 13
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#define DBG_REG_A4_OFF 14
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#define DBG_REG_A5_OFF 15
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#define DBG_REG_A6_OFF 16
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#define DBG_REG_A7_OFF 17
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#define DBG_REG_S2_OFF 18
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#define DBG_REG_S3_OFF 19
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#define DBG_REG_S4_OFF 20
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#define DBG_REG_S5_OFF 21
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#define DBG_REG_S6_OFF 22
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#define DBG_REG_S7_OFF 23
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#define DBG_REG_S8_OFF 24
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#define DBG_REG_S9_OFF 25
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#define DBG_REG_S10_OFF 26
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#define DBG_REG_S11_OFF 27
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#define DBG_REG_T3_OFF 28
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#define DBG_REG_T4_OFF 29
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#define DBG_REG_T5_OFF 30
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#define DBG_REG_T6_OFF 31
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#define DBG_REG_EPC_OFF 32
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#define DBG_REG_STATUS_OFF 33
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#define DBG_REG_BADADDR_OFF 34
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#define DBG_REG_CAUSE_OFF 35
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#endif
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#endif

‎arch/riscv/kernel/Makefile

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@@ -51,5 +51,6 @@ ifeq ($(CONFIG_RISCV_SBI), y)
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obj-$(CONFIG_SMP) += cpu_ops_sbi.o
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endif
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obj-$(CONFIG_HOTPLUG_CPU) += cpu-hotplug.o
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obj-$(CONFIG_KGDB) += kgdb.o
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clean:

‎arch/riscv/kernel/kgdb.c

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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2020 SiFive
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*/
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#include <linux/ptrace.h>
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#include <linux/kdebug.h>
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#include <linux/bug.h>
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#include <linux/kgdb.h>
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#include <linux/irqflags.h>
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#include <linux/string.h>
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#include <asm/cacheflush.h>
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enum {
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NOT_KGDB_BREAK = 0,
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KGDB_SW_BREAK,
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KGDB_COMPILED_BREAK,
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};
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struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
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{DBG_REG_ZERO, GDB_SIZEOF_REG, -1},
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{DBG_REG_RA, GDB_SIZEOF_REG, offsetof(struct pt_regs, ra)},
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{DBG_REG_SP, GDB_SIZEOF_REG, offsetof(struct pt_regs, sp)},
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{DBG_REG_GP, GDB_SIZEOF_REG, offsetof(struct pt_regs, gp)},
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{DBG_REG_TP, GDB_SIZEOF_REG, offsetof(struct pt_regs, tp)},
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{DBG_REG_T0, GDB_SIZEOF_REG, offsetof(struct pt_regs, t0)},
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{DBG_REG_T1, GDB_SIZEOF_REG, offsetof(struct pt_regs, t1)},
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{DBG_REG_T2, GDB_SIZEOF_REG, offsetof(struct pt_regs, t2)},
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{DBG_REG_FP, GDB_SIZEOF_REG, offsetof(struct pt_regs, s0)},
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{DBG_REG_S1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
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{DBG_REG_A0, GDB_SIZEOF_REG, offsetof(struct pt_regs, a0)},
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{DBG_REG_A1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
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{DBG_REG_A2, GDB_SIZEOF_REG, offsetof(struct pt_regs, a2)},
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{DBG_REG_A3, GDB_SIZEOF_REG, offsetof(struct pt_regs, a3)},
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{DBG_REG_A4, GDB_SIZEOF_REG, offsetof(struct pt_regs, a4)},
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{DBG_REG_A5, GDB_SIZEOF_REG, offsetof(struct pt_regs, a5)},
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{DBG_REG_A6, GDB_SIZEOF_REG, offsetof(struct pt_regs, a6)},
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{DBG_REG_A7, GDB_SIZEOF_REG, offsetof(struct pt_regs, a7)},
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{DBG_REG_S2, GDB_SIZEOF_REG, offsetof(struct pt_regs, s2)},
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{DBG_REG_S3, GDB_SIZEOF_REG, offsetof(struct pt_regs, s3)},
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{DBG_REG_S4, GDB_SIZEOF_REG, offsetof(struct pt_regs, s4)},
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{DBG_REG_S5, GDB_SIZEOF_REG, offsetof(struct pt_regs, s5)},
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{DBG_REG_S6, GDB_SIZEOF_REG, offsetof(struct pt_regs, s6)},
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{DBG_REG_S7, GDB_SIZEOF_REG, offsetof(struct pt_regs, s7)},
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{DBG_REG_S8, GDB_SIZEOF_REG, offsetof(struct pt_regs, s8)},
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{DBG_REG_S9, GDB_SIZEOF_REG, offsetof(struct pt_regs, s9)},
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{DBG_REG_S10, GDB_SIZEOF_REG, offsetof(struct pt_regs, s10)},
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{DBG_REG_S11, GDB_SIZEOF_REG, offsetof(struct pt_regs, s11)},
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{DBG_REG_T3, GDB_SIZEOF_REG, offsetof(struct pt_regs, t3)},
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{DBG_REG_T4, GDB_SIZEOF_REG, offsetof(struct pt_regs, t4)},
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{DBG_REG_T5, GDB_SIZEOF_REG, offsetof(struct pt_regs, t5)},
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{DBG_REG_T6, GDB_SIZEOF_REG, offsetof(struct pt_regs, t6)},
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{DBG_REG_EPC, GDB_SIZEOF_REG, offsetof(struct pt_regs, epc)},
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};
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char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
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{
58+
if (regno >= DBG_MAX_REG_NUM || regno < 0)
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return NULL;
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if (dbg_reg_def[regno].offset != -1)
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memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
63+
dbg_reg_def[regno].size);
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else
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memset(mem, 0, dbg_reg_def[regno].size);
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return dbg_reg_def[regno].name;
67+
}
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int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
70+
{
71+
if (regno >= DBG_MAX_REG_NUM || regno < 0)
72+
return -EINVAL;
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74+
if (dbg_reg_def[regno].offset != -1)
75+
memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
76+
dbg_reg_def[regno].size);
77+
return 0;
78+
}
79+
80+
void
81+
sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
82+
{
83+
/* Initialize to zero */
84+
memset((char *)gdb_regs, 0, NUMREGBYTES);
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86+
gdb_regs[DBG_REG_SP_OFF] = task->thread.sp;
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gdb_regs[DBG_REG_FP_OFF] = task->thread.s[0];
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gdb_regs[DBG_REG_S1_OFF] = task->thread.s[1];
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gdb_regs[DBG_REG_S2_OFF] = task->thread.s[2];
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gdb_regs[DBG_REG_S3_OFF] = task->thread.s[3];
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gdb_regs[DBG_REG_S4_OFF] = task->thread.s[4];
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gdb_regs[DBG_REG_S5_OFF] = task->thread.s[5];
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gdb_regs[DBG_REG_S6_OFF] = task->thread.s[6];
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gdb_regs[DBG_REG_S7_OFF] = task->thread.s[7];
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gdb_regs[DBG_REG_S8_OFF] = task->thread.s[8];
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gdb_regs[DBG_REG_S9_OFF] = task->thread.s[10];
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gdb_regs[DBG_REG_S10_OFF] = task->thread.s[11];
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gdb_regs[DBG_REG_EPC_OFF] = task->thread.ra;
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}
100+
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void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
102+
{
103+
regs->epc = pc;
104+
}
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static inline void kgdb_arch_update_addr(struct pt_regs *regs,
107+
char *remcom_in_buffer)
108+
{
109+
unsigned long addr;
110+
char *ptr;
111+
112+
ptr = &remcom_in_buffer[1];
113+
if (kgdb_hex2long(&ptr, &addr))
114+
regs->epc = addr;
115+
}
116+
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int kgdb_arch_handle_exception(int vector, int signo, int err_code,
118+
char *remcom_in_buffer, char *remcom_out_buffer,
119+
struct pt_regs *regs)
120+
{
121+
int err = 0;
122+
123+
switch (remcom_in_buffer[0]) {
124+
case 'c':
125+
case 'D':
126+
case 'k':
127+
if (remcom_in_buffer[0] == 'c')
128+
kgdb_arch_update_addr(regs, remcom_in_buffer);
129+
break;
130+
default:
131+
err = -1;
132+
}
133+
134+
return err;
135+
}
136+
137+
int kgdb_riscv_kgdbbreak(unsigned long addr)
138+
{
139+
if (atomic_read(&kgdb_setting_breakpoint))
140+
if (addr == (unsigned long)&kgdb_compiled_break)
141+
return KGDB_COMPILED_BREAK;
142+
143+
return kgdb_has_hit_break(addr);
144+
}
145+
146+
static int kgdb_riscv_notify(struct notifier_block *self, unsigned long cmd,
147+
void *ptr)
148+
{
149+
struct die_args *args = (struct die_args *)ptr;
150+
struct pt_regs *regs = args->regs;
151+
unsigned long flags;
152+
int type;
153+
154+
if (user_mode(regs))
155+
return NOTIFY_DONE;
156+
157+
type = kgdb_riscv_kgdbbreak(regs->epc);
158+
if (type == NOT_KGDB_BREAK && cmd == DIE_TRAP)
159+
return NOTIFY_DONE;
160+
161+
local_irq_save(flags);
162+
if (kgdb_handle_exception(1, args->signr, cmd, regs))
163+
return NOTIFY_DONE;
164+
165+
if (type == KGDB_COMPILED_BREAK)
166+
regs->epc += 4;
167+
168+
local_irq_restore(flags);
169+
170+
return NOTIFY_STOP;
171+
}
172+
173+
static struct notifier_block kgdb_notifier = {
174+
.notifier_call = kgdb_riscv_notify,
175+
};
176+
177+
int kgdb_arch_init(void)
178+
{
179+
register_die_notifier(&kgdb_notifier);
180+
181+
return 0;
182+
}
183+
184+
void kgdb_arch_exit(void)
185+
{
186+
unregister_die_notifier(&kgdb_notifier);
187+
}
188+
189+
/*
190+
* Global data
191+
*/
192+
#ifdef CONFIG_RISCV_ISA_C
193+
const struct kgdb_arch arch_kgdb_ops = {
194+
.gdb_bpt_instr = {0x02, 0x90}, /* c.ebreak */
195+
};
196+
#else
197+
const struct kgdb_arch arch_kgdb_ops = {
198+
.gdb_bpt_instr = {0x73, 0x00, 0x10, 0x00}, /* ebreak */
199+
};
200+
#endif

‎arch/riscv/kernel/traps.c

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Original file line numberDiff line numberDiff line change
@@ -147,6 +147,11 @@ asmlinkage __visible void do_trap_break(struct pt_regs *regs)
147147
{
148148
if (user_mode(regs))
149149
force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->epc);
150+
#ifdef CONFIG_KGDB
151+
else if (notify_die(DIE_TRAP, "EBREAK", regs, 0, regs->cause, SIGTRAP)
152+
== NOTIFY_STOP)
153+
return;
154+
#endif
150155
else if (report_bug(regs->epc, regs) == BUG_TRAP_TYPE_WARN)
151156
regs->epc += get_break_insn_length(regs->epc);
152157
else

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