Re: [PATCH v3] LoongArch: Add KGDB support

From: Huacai Chen
Date: Tue Aug 22 2023 - 03:41:39 EST

On Thu, Aug 17, 2023 at 11:28 AM Hui Li <lihui@xxxxxxxxxxx> wrote:
>
> Kgdb is intended to be used as a source level debugger for the Linux
> kernel. It is used along with gdb to debug a Linux kernel. gdb can be
> used to "break in" to the kernel to inspect memory, variables and regs
> similar to the way an application developer would use gdb to debug an
> application.
>
> Implement the following features for LoongArch:
>
> (1) Connect to the kernel on the target machine through GDB on the
> development machine.
>
> (2) The debugged kernel can be inserted the software breakpoint.
>
> (3) The debugged kernel can run and stop at the breakpoint.
>
> (4) The debugged kernel can resume running from the breakpoint.
>
> (5) The debugged kernel can be removed breakpoints.
>
> (6) Query the value of the general register of the kernel on target
> machine through GDB on the development machine.
>
> (7) When GDB on the development machine exits debugging, the kernel
> on target machine can resume execution normally.
>
> (8) Add hardware breakpoints/watchpoints support.
>
> (9) Add Software single-step support for KDB.
>
> Co-developed-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
> Signed-off-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
> Co-developed-by: Binbin Zhou <zhoubinbin@xxxxxxxxxxx>
> Signed-off-by: Binbin Zhou <zhoubinbin@xxxxxxxxxxx>
> Signed-off-by: Hui Li <lihui@xxxxxxxxxxx>
> ---
> arch/loongarch/Kconfig | 1 +
> arch/loongarch/include/asm/kgdb.h | 106 ++++
> arch/loongarch/include/asm/stackframe.h | 4 +
> arch/loongarch/kernel/Makefile | 2 +
> arch/loongarch/kernel/entry.S | 5 +
> arch/loongarch/kernel/kgdb.c | 749 ++++++++++++++++++++++++
> arch/loongarch/kernel/traps.c | 8 +
> 7 files changed, 875 insertions(+)
> create mode 100644 arch/loongarch/include/asm/kgdb.h
> create mode 100644 arch/loongarch/kernel/kgdb.c
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index c379951adb30..46b4c217da14 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -95,6 +95,7 @@ config LOONGARCH
> select HAVE_ARCH_JUMP_LABEL_RELATIVE
> select HAVE_ARCH_KASAN
> select HAVE_ARCH_KFENCE
> + select HAVE_ARCH_KGDB
> select HAVE_ARCH_MMAP_RND_BITS if MMU
> select HAVE_ARCH_SECCOMP_FILTER
> select HAVE_ARCH_TRACEHOOK
> diff --git a/arch/loongarch/include/asm/kgdb.h b/arch/loongarch/include/asm/kgdb.h
> new file mode 100644
> index 000000000000..df46afe9114a
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kgdb.h
> @@ -0,0 +1,106 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2023 Loongson Technology Corporation Limited
> + */
> +
> +#ifndef _ASM_LOONGARCH_KGDB_H
> +#define _ASM_LOONGARCH_KGDB_H
> +
> +#define GDB_SIZEOF_REG sizeof(u64)
> +
> +/* gdb remote procotol expects the following register layout. */
> +
> +/*
> + * General purpose regs:
> + * r0-r31: 64 bit
> + * orig_a0: 64 bit
> + * pc : 64 bit
> + * csr_badvaddr: 64 bit
> + */
> +#define DBG_PT_REGS_BASE 0
> +#define DBG_PT_REGS_NUM 35
> +#define DBG_PT_REGS_END (DBG_PT_REGS_BASE + DBG_PT_REGS_NUM - 1)
> +
> +/*
> + * Floating point regs:
> + * f0-f31: 64 bit
> + */
> +#define DBG_FPR_BASE (DBG_PT_REGS_END + 1)
> +#define DBG_FPR_NUM 32
> +#define DBG_FPR_END (DBG_FPR_BASE + DBG_FPR_NUM - 1)
> +
> +/*
> + * Condition Flag regs:
> + * fcc0-fcc8: 1 bit
> + */
> +#define DBG_FCC_BASE (DBG_FPR_END + 1)
> +#define DBG_FCC_NUM 8
> +#define DBG_FCC_END (DBG_FCC_BASE + DBG_FCC_NUM - 1)
> +
> +/*
> + * Floating-point Control and Status reg:
> + * fcsr: 32 bit
> + */
> +#define DBG_FCSR_NUM 1
> +#define DBG_FCSR (DBG_FCC_END + 1)
> +
> +#define DBG_SCR_BASE (DBG_FCSR + 1)
> +#define DBG_SCR_NUM 4
> +#define DBG_SCR_END (DBG_SCR_BASE + DBG_SCR_NUM - 1)
> +
> +#define DBG_MAX_REG_NUM (DBG_SCR_END + 1)
> +
> +/*
> + * Size of I/O buffer for gdb packet.
> + * considering to hold all register contents, size is set
> + */
> +#define BUFMAX 2048
> +
> +/*
> + * Number of bytes required for gdb_regs buffer.
> + * PT_REGS and FPR: 8 bytes; FCSR: 4 bytes; FCC: 1 bytes.
> + * GDB fails to connect for size beyond this with error
> + * "'g' packet reply is too long"
> + */
> +#define NUMREGBYTES ((DBG_PT_REGS_NUM + DBG_FPR_NUM) * sizeof(GDB_SIZEOF_REG) + \
> + 1 + DBG_FCSR_NUM * 4)
> +
> +#define BREAK_INSTR_SIZE 4
> +#define CACHE_FLUSH_IS_SAFE 0
> +
> +/* Register numbers of various important registers. */
> +enum dbg_loongarch_regnum {
> + DBG_LOONGARCH_ZERO = 0,
> + DBG_LOONGARCH_RA,
> + DBG_LOONGARCH_TP,
> + DBG_LOONGARCH_SP,
> + DBG_LOONGARCH_A0,
> + DBG_LOONGARCH_FP = 22,
> + DBG_LOONGARCH_S0,
> + DBG_LOONGARCH_S1,
> + DBG_LOONGARCH_S2,
> + DBG_LOONGARCH_S3,
> + DBG_LOONGARCH_S4,
> + DBG_LOONGARCH_S5,
> + DBG_LOONGARCH_S6,
> + DBG_LOONGARCH_S7,
> + DBG_LOONGARCH_S8,
> + DBG_LOONGARCH_ORIG_A0 = 32,
> + DBG_LOONGARCH_PC,
> + DBG_LOONGARCH_BADV = 34,
> + DBG_LOONGARCH_SCR0 = 76,
> + DBG_LOONGARCH_SCR1,
> + DBG_LOONGARCH_SCR2,
> + DBG_LOONGARCH_SCR3 = 79
I found that SCR0~SCR3 doesn't exist on the gdb side, so please update
the gdb to get things working. Otherwise this patch will miss the 6.6
cycle.

Huacai

> +};
> +
> +#ifdef CONFIG_KGDB
> +void arch_kgdb_breakpoint(void);
> +void kgdb_compiled_break(void);
> +bool kgdb_breakpoint_handler(struct pt_regs *regs);
> +extern int dbg_kdb_mode;
> +#else /* !CONFIG_KGDB */
> +static inline bool kgdb_breakpoint_handler(struct pt_regs *regs) { return false; }
> +#endif /* CONFIG_KGDB */
> +
> +#endif /* __ASM_KGDB_H_ */
> diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
> index 7df80e6ae9d2..4fb1e6408b98 100644
> --- a/arch/loongarch/include/asm/stackframe.h
> +++ b/arch/loongarch/include/asm/stackframe.h
> @@ -158,6 +158,10 @@
> cfi_st u0, PT_R21, \docfi
> csrrd u0, PERCPU_BASE_KS
> 9:
> +#ifdef CONFIG_KGDB
> + li.w t0, CSR_CRMD_WE
> + csrxchg t0, t0, LOONGARCH_CSR_CRMD
> +#endif
> .endm
>
> .macro SAVE_ALL docfi=0
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 6601b6d00738..c44ecd27b52c 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -68,4 +68,6 @@ obj-$(CONFIG_UPROBES) += uprobes.o
>
> obj-$(CONFIG_JUMP_LABEL) += jump_label.o
>
> +obj-$(CONFIG_KGDB) += kgdb.o
> +
> CPPFLAGS_vmlinux.lds := $(KBUILD_CFLAGS)
> diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
> index d737e3cf42d3..00654322348e 100644
> --- a/arch/loongarch/kernel/entry.S
> +++ b/arch/loongarch/kernel/entry.S
> @@ -58,6 +58,11 @@ SYM_FUNC_START(handle_syscall)
>
> SAVE_STATIC
>
> +#ifdef CONFIG_KGDB
> + li.w t1, CSR_CRMD_WE
> + csrxchg t1, t1, LOONGARCH_CSR_CRMD
> +#endif
> +
> move u0, t0
> li.d tp, ~_THREAD_MASK
> and tp, tp, sp
> diff --git a/arch/loongarch/kernel/kgdb.c b/arch/loongarch/kernel/kgdb.c
> new file mode 100644
> index 000000000000..b1c5924c703e
> --- /dev/null
> +++ b/arch/loongarch/kernel/kgdb.c
> @@ -0,0 +1,749 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * LoongArch KGDB support
> + *
> + * Copyright (C) 2023 Loongson Technology Corporation Limited
> + */
> +
> +#include <linux/hw_breakpoint.h>
> +#include <linux/kdebug.h>
> +#include <linux/kgdb.h>
> +#include <linux/processor.h>
> +#include <linux/ptrace.h>
> +#include <linux/sched.h>
> +#include <linux/smp.h>
> +
> +#include <asm/fpu.h>
> +#include <asm/hw_breakpoint.h>
> +#include <asm/inst.h>
> +#include <asm/irq_regs.h>
> +#include <asm/ptrace.h>
> +#include <asm/sigcontext.h>
> +
> +int kgdb_watch_activated;
> +static unsigned long stepped_address;
> +static unsigned int stepped_opcode;
> +
> +struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
> + { "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) },
> + { "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) },
> + { "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) },
> + { "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) },
> + { "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) },
> + { "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) },
> + { "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) },
> + { "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) },
> + { "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) },
> + { "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) },
> + { "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) },
> + { "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) },
> + { "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) },
> + { "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) },
> + { "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) },
> + { "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) },
> + { "r16", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[16]) },
> + { "r17", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[17]) },
> + { "r18", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[18]) },
> + { "r19", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[19]) },
> + { "r20", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[20]) },
> + { "r21", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[21]) },
> + { "r22", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[22]) },
> + { "r23", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[23]) },
> + { "r24", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[24]) },
> + { "r25", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[25]) },
> + { "r26", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[26]) },
> + { "r27", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[27]) },
> + { "r28", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[28]) },
> + { "r29", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[29]) },
> + { "r30", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[30]) },
> + { "r31", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[31]) },
> + { "orig_a0", GDB_SIZEOF_REG, offsetof(struct pt_regs, orig_a0) },
> + { "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, csr_era) },
> + { "badv", GDB_SIZEOF_REG, offsetof(struct pt_regs, csr_badvaddr) },
> + { "f0", GDB_SIZEOF_REG, 0 },
> + { "f1", GDB_SIZEOF_REG, 1 },
> + { "f2", GDB_SIZEOF_REG, 2 },
> + { "f3", GDB_SIZEOF_REG, 3 },
> + { "f4", GDB_SIZEOF_REG, 4 },
> + { "f5", GDB_SIZEOF_REG, 5 },
> + { "f6", GDB_SIZEOF_REG, 6 },
> + { "f7", GDB_SIZEOF_REG, 7 },
> + { "f8", GDB_SIZEOF_REG, 8 },
> + { "f9", GDB_SIZEOF_REG, 9 },
> + { "f10", GDB_SIZEOF_REG, 10 },
> + { "f11", GDB_SIZEOF_REG, 11 },
> + { "f12", GDB_SIZEOF_REG, 12 },
> + { "f13", GDB_SIZEOF_REG, 13 },
> + { "f14", GDB_SIZEOF_REG, 14 },
> + { "f15", GDB_SIZEOF_REG, 15 },
> + { "f16", GDB_SIZEOF_REG, 16 },
> + { "f17", GDB_SIZEOF_REG, 17 },
> + { "f18", GDB_SIZEOF_REG, 18 },
> + { "f19", GDB_SIZEOF_REG, 19 },
> + { "f20", GDB_SIZEOF_REG, 20 },
> + { "f21", GDB_SIZEOF_REG, 21 },
> + { "f22", GDB_SIZEOF_REG, 22 },
> + { "f23", GDB_SIZEOF_REG, 23 },
> + { "f24", GDB_SIZEOF_REG, 24 },
> + { "f25", GDB_SIZEOF_REG, 25 },
> + { "f26", GDB_SIZEOF_REG, 26 },
> + { "f27", GDB_SIZEOF_REG, 27 },
> + { "f28", GDB_SIZEOF_REG, 28 },
> + { "f29", GDB_SIZEOF_REG, 29 },
> + { "f30", GDB_SIZEOF_REG, 30 },
> + { "f31", GDB_SIZEOF_REG, 31 },
> + { "fcc0", 1, 0 },
> + { "fcc1", 1, 1 },
> + { "fcc2", 1, 2 },
> + { "fcc3", 1, 3 },
> + { "fcc4", 1, 4 },
> + { "fcc5", 1, 5 },
> + { "fcc6", 1, 6 },
> + { "fcc7", 1, 7 },
> + { "fcsr", 4, 0 },
> + { "scr0", GDB_SIZEOF_REG, offsetof(struct loongarch_lbt, scr0) },
> + { "scr1", GDB_SIZEOF_REG, offsetof(struct loongarch_lbt, scr1) },
> + { "scr2", GDB_SIZEOF_REG, offsetof(struct loongarch_lbt, scr2) },
> + { "scr3", GDB_SIZEOF_REG, offsetof(struct loongarch_lbt, scr3) },
> +};
> +
> +int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
> +{
> + int reg_offset, reg_size;
> +
> + if (regno < 0 || regno >= DBG_MAX_REG_NUM)
> + return -EINVAL;
> +
> + reg_offset = dbg_reg_def[regno].offset;
> + reg_size = dbg_reg_def[regno].size;
> +
> + if (reg_offset == -1)
> + return 0;
> +
> + /* Handle general-purpose/orig_a0/pc/badv registers */
> + if (regno <= DBG_PT_REGS_END) {
> + memcpy((void *)regs + reg_offset, mem, reg_size);
> + return 0;
> + }
> +
> + if (!current || !(regs->csr_euen & CSR_EUEN_FPEN))
> + return 0;
> +
> + /* Handle FP registers */
> + switch (regno) {
> + case DBG_FCSR: /* Process the fcsr/fsr */
> + memcpy((void *)&current->thread.fpu.fcsr, mem, reg_size);
> + break;
> + case DBG_FCC_BASE ... DBG_FCC_END: /* Process the fcc */
> + memcpy((char *)&current->thread.fpu.fcc + reg_offset, mem, reg_size);
> + break;
> + case DBG_SCR_BASE ... DBG_SCR_END: /* Process the scr */
> + memcpy((void *)&current->thread.lbt.scr0 + reg_offset, mem, reg_size);
> + break;
> + default:
> + memcpy((void *)&current->thread.fpu.fpr[reg_offset], mem, reg_size);
> + }
> +
> + restore_fp(current);
> + return 0;
> +}
> +
> +char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
> +{
> + int reg_offset, reg_size;
> +
> + if (regno < 0 || regno >= DBG_MAX_REG_NUM)
> + return NULL;
> +
> + reg_offset = dbg_reg_def[regno].offset;
> + reg_size = dbg_reg_def[regno].size;
> +
> + if (reg_offset == -1)
> + goto out;
> +
> + /* Handle general-purpose/orig_a0/pc/badv registers */
> + if (regno <= DBG_PT_REGS_END) {
> + memcpy(mem, (void *)regs + reg_offset, reg_size);
> + goto out;
> + }
> +
> + if (!current || !(regs->csr_euen & CSR_EUEN_FPEN))
> + goto out;
> +
> + save_fp(current);
> +
> + /* Handle FP registers */
> + switch (regno) {
> + case DBG_FCSR: /* Process the fcsr/fsr */
> + memcpy(mem, (void *)&current->thread.fpu.fcsr, reg_size);
> + break;
> + case DBG_FCC_BASE ... DBG_FCC_END: /* Process the fcc */
> + memcpy(mem, (char *)&current->thread.fpu.fcc + reg_offset, reg_size);
> + break;
> + case DBG_SCR_BASE ... DBG_SCR_END: /* Process the scr */
> + memcpy(mem, (void *)&current->thread.lbt.scr0 + reg_offset, reg_size);
> + break;
> + default:
> + memcpy(mem, (void *)&current->thread.fpu.fpr[reg_offset], reg_size);
> + }
> +
> +out:
> + return dbg_reg_def[regno].name;
> +}
> +
> +/*
> + * Similar to regs_to_gdb_regs() except that process is sleeping and so
> + * we may not be able to get all the info.
> + */
> +void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
> +{
> + /* Initialize to zero */
> + memset((char *)gdb_regs, 0, NUMREGBYTES);
> +
> + gdb_regs[DBG_LOONGARCH_RA] = p->thread.reg01;
> + gdb_regs[DBG_LOONGARCH_TP] = (long)p;
> + gdb_regs[DBG_LOONGARCH_SP] = p->thread.reg03;
> +
> + /* S0 - S8 */
> + gdb_regs[DBG_LOONGARCH_S0] = p->thread.reg23;
> + gdb_regs[DBG_LOONGARCH_S1] = p->thread.reg24;
> + gdb_regs[DBG_LOONGARCH_S2] = p->thread.reg25;
> + gdb_regs[DBG_LOONGARCH_S3] = p->thread.reg26;
> + gdb_regs[DBG_LOONGARCH_S4] = p->thread.reg27;
> + gdb_regs[DBG_LOONGARCH_S5] = p->thread.reg28;
> + gdb_regs[DBG_LOONGARCH_S6] = p->thread.reg29;
> + gdb_regs[DBG_LOONGARCH_S7] = p->thread.reg30;
> + gdb_regs[DBG_LOONGARCH_S8] = p->thread.reg31;
> +
> + /*
> + * PC
> + * use return address (RA), i.e. the moment after return from resume()
> + */
> + gdb_regs[DBG_LOONGARCH_PC] = p->thread.reg01;
> +
> + gdb_regs[DBG_LOONGARCH_SCR0] = p->thread.lbt.scr0;
> + gdb_regs[DBG_LOONGARCH_SCR1] = p->thread.lbt.scr1;
> + gdb_regs[DBG_LOONGARCH_SCR2] = p->thread.lbt.scr2;
> + gdb_regs[DBG_LOONGARCH_SCR3] = p->thread.lbt.scr3;
> +}
> +
> +void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
> +{
> + regs->csr_era = pc;
> +}
> +
> +void arch_kgdb_breakpoint(void)
> +{
> + __asm__ __volatile__ ( \
> + ".globl kgdb_compiled_break\n\t" \
> + "nop\n" \
> + "kgdb_compiled_break:\tbreak 2\n\t");
> +}
> +
> +/*
> + * Calls linux_debug_hook before the kernel dies. If KGDB is enabled,
> + * then try to fall into the debugger
> + */
> +static int kgdb_loongarch_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
> +{
> + struct die_args *args = (struct die_args *)ptr;
> + struct pt_regs *regs = args->regs;
> +
> + /* Userspace events, ignore. */
> + if (user_mode(regs))
> + return NOTIFY_DONE;
> +
> + if (!kgdb_io_module_registered)
> + return NOTIFY_DONE;
> +
> + if (atomic_read(&kgdb_active) != -1)
> + kgdb_nmicallback(smp_processor_id(), regs);
> +
> + if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
> + return NOTIFY_DONE;
> +
> + if (atomic_read(&kgdb_setting_breakpoint))
> + if (regs->csr_era == (unsigned long)&kgdb_compiled_break)
> + regs->csr_era += LOONGARCH_INSN_SIZE;
> +
> + return NOTIFY_STOP;
> +}
> +
> +bool kgdb_breakpoint_handler(struct pt_regs *regs)
> +{
> + struct die_args args = {
> + .regs = regs,
> + .str = "Break",
> + .err = BRK_KDB,
> + .trapnr = read_csr_excode(),
> + .signr = SIGTRAP,
> +
> + };
> +
> + return (kgdb_loongarch_notify(NULL, DIE_TRAP, &args) == NOTIFY_STOP) ? true : false;
> +}
> +
> +static struct notifier_block kgdb_notifier = {
> + .notifier_call = kgdb_loongarch_notify,
> +};
> +
> +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->csr_era = addr;
> +}
> +
> +/* Calculate the new address for after a step */
> +static int get_step_address(struct pt_regs *regs, unsigned long *next_addr)
> +{
> + unsigned int si, si_l, si_h, rd, rj, cj;
> + char cj_val;
> + unsigned long pc = instruction_pointer(regs);
> + union loongarch_instruction *ip = (union loongarch_instruction *)pc;
> +
> + if (pc & 3) {
> + pr_warn("%s: invalid pc 0x%lx\n", __func__, pc);
> + return -EINVAL;
> + }
> +
> + *next_addr = pc + LOONGARCH_INSN_SIZE;
> +
> + si_h = ip->reg0i26_format.immediate_h;
> + si_l = ip->reg0i26_format.immediate_l;
> + switch (ip->reg0i26_format.opcode) {
> + case b_op:
> + *next_addr = pc + sign_extend64((si_h << 16 | si_l) << 2, 27);
> + return 0;
> + case bl_op:
> + *next_addr = pc + sign_extend64((si_h << 16 | si_l) << 2, 27);
> + regs->regs[1] = pc + LOONGARCH_INSN_SIZE;
> + return 0;
> + }
> +
> + si_l = ip->reg1i21_format.immediate_l;
> + si_h = ip->reg1i21_format.immediate_h;
> + rj = ip->reg1i21_format.rj;
> + switch (ip->reg1i21_format.opcode) {
> + case beqz_op:
> + if (regs->regs[rj] == 0)
> + *next_addr = pc + sign_extend64((si_h << 16 | si_l) << 2, 22);
> + return 0;
> + case bnez_op:
> + if (regs->regs[rj] != 0)
> + *next_addr = pc + sign_extend64((si_h << 16 | si_l) << 2, 22);
> + return 0;
> + /* bceqz_op = bcnez_op */
> + case bceqz_op:
> + /* bceqz */
> + if ((rj & 0x18) == 0x00)
> + if (cj_val == 0)
> + *next_addr = pc + sign_extend64((si_h << 16 | si_l) << 2, 22);
> + /* bcnez */
> + if ((rj & 0x18) == 0x08)
> + if (cj_val != 0)
> + *next_addr = pc + sign_extend64((si_h << 16 | si_l) << 2, 22);
> + return 0;
> + }
> +
> + si = ip->reg2i16_format.immediate;
> + rj = ip->reg2i16_format.rj;
> + rd = ip->reg2i16_format.rd;
> + switch (ip->reg2i16_format.opcode) {
> + case beq_op:
> + if (regs->regs[rj] == regs->regs[rd])
> + *next_addr = pc + sign_extend64(si << 2, 17);
> + return 0;
> + case bne_op:
> + if (regs->regs[rj] != regs->regs[rd])
> + *next_addr = pc + sign_extend64(si << 2, 17);
> + return 0;
> + case blt_op:
> + if ((long)regs->regs[rj] < (long)regs->regs[rd])
> + *next_addr = pc + sign_extend64(si << 2, 17);
> + return 0;
> + case bge_op:
> + if ((long)regs->regs[rj] >= (long)regs->regs[rd])
> + *next_addr = pc + sign_extend64(si << 2, 17);
> + return 0;
> + case bltu_op:
> + if (regs->regs[rj] < regs->regs[rd])
> + *next_addr = pc + sign_extend64(si << 2, 17);
> + return 0;
> + case bgeu_op:
> + if (regs->regs[rj] >= regs->regs[rd])
> + *next_addr = pc + sign_extend64(si << 2, 17);
> + return 0;
> + case jirl_op:
> + regs->regs[rd] = pc + LOONGARCH_INSN_SIZE;
> + *next_addr = regs->regs[rj] + sign_extend64(si << 2, 17);
> + return 0;
> + }
> +
> + return 0;
> +}
> +
> +static int do_single_step(struct pt_regs *regs)
> +{
> + /* Determine where the target instruction will send us to */
> + unsigned long addr = 0;
> + int error = 0;
> +
> + if (!dbg_kdb_mode)
> + return 0;
> +
> + error = get_step_address(regs, &addr);
> + if (error)
> + return error;
> +
> + /* Store the opcode in the stepped address */
> + error = get_kernel_nofault(stepped_opcode, (void *)addr);
> + if (error)
> + return error;
> +
> + stepped_address = addr;
> +
> + /* Replace the opcode with the break instruction */
> + error = copy_to_kernel_nofault((void *)stepped_address,
> + arch_kgdb_ops.gdb_bpt_instr,
> + BREAK_INSTR_SIZE);
> +
> + /* Flush and return */
> + if (!error) {
> + flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
> + kgdb_single_step = 1;
> + atomic_set(&kgdb_cpu_doing_single_step, raw_smp_processor_id());
> + } else {
> + stepped_address = 0;
> + stepped_opcode = 0;
> + }
> +
> + return error;
> +}
> +
> +/* Undo a single step */
> +static void undo_single_step(struct pt_regs *regs)
> +{
> + if (!dbg_kdb_mode)
> + return;
> +
> + if (stepped_opcode != 0) {
> + copy_to_kernel_nofault((void *)stepped_address,
> + (void *)&stepped_opcode, BREAK_INSTR_SIZE);
> + flush_icache_range(stepped_address,
> + stepped_address + BREAK_INSTR_SIZE);
> + }
> +
> + stepped_address = 0;
> + stepped_opcode = 0;
> + kgdb_single_step = 0;
> + atomic_set(&kgdb_cpu_doing_single_step, -1);
> +}
> +
> +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 ret = 0;
> +
> + undo_single_step(regs);
> +
> + regs->csr_prmd |= CSR_PRMD_PWE;
> + switch (remcom_in_buffer[0]) {
> + case 'D':
> + case 'k':
> + regs->csr_prmd &= ~CSR_PRMD_PWE;
> + fallthrough;
> + case 'c':
> + kgdb_arch_update_addr(regs, remcom_in_buffer);
> + break;
> + case 's':
> + kgdb_arch_update_addr(regs, remcom_in_buffer);
> + ret = do_single_step(regs);
> + break;
> + default:
> + ret = -1;
> + }
> +
> + return ret;
> +}
> +
> +static struct hw_breakpoint {
> + unsigned int enabled;
> + unsigned long addr;
> + int len;
> + int type;
> + struct perf_event * __percpu *pev;
> +} breakinfo[LOONGARCH_MAX_BRP];
> +
> +static int hw_break_reserve_slot(int breakno)
> +{
> + int cpu;
> + int cnt = 0;
> + struct perf_event **pevent;
> +
> + for_each_online_cpu(cpu) {
> + cnt++;
> + pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
> + if (dbg_reserve_bp_slot(*pevent))
> + goto fail;
> + }
> +
> + return 0;
> +
> +fail:
> + for_each_online_cpu(cpu) {
> + cnt--;
> + if (!cnt)
> + break;
> + pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
> + dbg_release_bp_slot(*pevent);
> + }
> +
> + return -1;
> +}
> +
> +static int hw_break_release_slot(int breakno)
> +{
> + struct perf_event **pevent;
> + int cpu;
> +
> + if (dbg_is_early)
> + return 0;
> +
> + for_each_online_cpu(cpu) {
> + pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
> + if (dbg_release_bp_slot(*pevent))
> + /*
> + * The debugger is responsible for handing the retry on
> + * remove failure.
> + */
> + return -1;
> + }
> + return 0;
> +}
> +
> +static int kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
> +{
> + int i;
> +
> + for (i = 0; i < LOONGARCH_MAX_BRP; i++)
> + if (!breakinfo[i].enabled)
> + break;
> +
> + if (i == LOONGARCH_MAX_BRP)
> + return -1;
> +
> + switch (bptype) {
> + case BP_HARDWARE_BREAKPOINT:
> + breakinfo[i].type = HW_BREAKPOINT_X;
> + break;
> + case BP_READ_WATCHPOINT:
> + breakinfo[i].type = HW_BREAKPOINT_R;
> + break;
> + case BP_WRITE_WATCHPOINT:
> + breakinfo[i].type = HW_BREAKPOINT_W;
> + break;
> + case BP_ACCESS_WATCHPOINT:
> + breakinfo[i].type = HW_BREAKPOINT_RW;
> + break;
> + default:
> + return -1;
> + }
> +
> + switch (len) {
> + case 1:
> + breakinfo[i].len = HW_BREAKPOINT_LEN_1;
> + break;
> + case 2:
> + breakinfo[i].len = HW_BREAKPOINT_LEN_2;
> + break;
> + case 4:
> + breakinfo[i].len = HW_BREAKPOINT_LEN_4;
> + break;
> + case 8:
> + breakinfo[i].len = HW_BREAKPOINT_LEN_8;
> + break;
> + default:
> + return -1;
> + }
> +
> + breakinfo[i].addr = addr;
> + if (hw_break_reserve_slot(i)) {
> + breakinfo[i].addr = 0;
> + return -1;
> + }
> + breakinfo[i].enabled = 1;
> +
> + return 0;
> +}
> +
> +static int kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
> +{
> + int i;
> +
> + for (i = 0; i < LOONGARCH_MAX_BRP; i++)
> + if (breakinfo[i].addr == addr && breakinfo[i].enabled)
> + break;
> +
> + if (i == LOONGARCH_MAX_BRP)
> + return -1;
> +
> + if (hw_break_release_slot(i)) {
> + pr_err("Cannot remove hw breakpoint at %lx\n", addr);
> + return -1;
> + }
> + breakinfo[i].enabled = 0;
> +
> + return 0;
> +}
> +
> +static void kgdb_disable_hw_break(struct pt_regs *regs)
> +{
> + int i;
> + int cpu = raw_smp_processor_id();
> + struct perf_event *bp;
> +
> + for (i = 0; i < LOONGARCH_MAX_BRP; i++) {
> + if (!breakinfo[i].enabled)
> + continue;
> +
> + bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
> + if (bp->attr.disabled == 1)
> + continue;
> +
> + arch_uninstall_hw_breakpoint(bp);
> + bp->attr.disabled = 1;
> + }
> +
> + /* Disable hardware debugging while we are in kgdb: */
> + csr_xchg32(0, CSR_CRMD_WE, LOONGARCH_CSR_CRMD);
> + regs->csr_prmd &= ~CSR_PRMD_PWE;
> +}
> +
> +static void kgdb_remove_all_hw_break(void)
> +{
> + int i;
> + int cpu = raw_smp_processor_id();
> + struct perf_event *bp;
> +
> + for (i = 0; i < LOONGARCH_MAX_BRP; i++) {
> + if (!breakinfo[i].enabled)
> + continue;
> +
> + bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
> + if (!bp->attr.disabled) {
> + arch_uninstall_hw_breakpoint(bp);
> + bp->attr.disabled = 1;
> + continue;
> + }
> +
> + if (hw_break_release_slot(i))
> + pr_err("KGDB: hw bpt remove failed %lx\n", breakinfo[i].addr);
> + breakinfo[i].enabled = 0;
> + }
> +
> + csr_xchg32(0, CSR_CRMD_WE, LOONGARCH_CSR_CRMD);
> + kgdb_watch_activated = 0;
> +}
> +
> +static void kgdb_correct_hw_break(void)
> +{
> + int i, activated = 0;
> +
> + for (i = 0; i < LOONGARCH_MAX_BRP; i++) {
> + struct perf_event *bp;
> + struct arch_hw_breakpoint *info;
> + int val;
> + int cpu = raw_smp_processor_id();
> +
> + if (!breakinfo[i].enabled)
> + continue;
> +
> + bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
> + info = counter_arch_bp(bp);
> + if (bp->attr.disabled != 1)
> + continue;
> +
> + bp->attr.bp_addr = breakinfo[i].addr;
> + bp->attr.bp_len = breakinfo[i].len;
> + bp->attr.bp_type = breakinfo[i].type;
> + info->address = breakinfo[i].addr;
> + info->ctrl.len = breakinfo[i].len;
> + info->ctrl.type = breakinfo[i].type;
> + val = arch_install_hw_breakpoint(bp);
> + if (!val)
> + bp->attr.disabled = 0;
> + activated = 1;
> + }
> +
> + csr_xchg32(activated ? CSR_CRMD_WE : 0, CSR_CRMD_WE, LOONGARCH_CSR_CRMD);
> + kgdb_watch_activated = activated;
> +}
> +
> +const struct kgdb_arch arch_kgdb_ops = {
> + .gdb_bpt_instr = {0x02, 0x00, break_op >> 1, 0x00},
> + .flags = KGDB_HW_BREAKPOINT,
> + .set_hw_breakpoint = kgdb_set_hw_break,
> + .remove_hw_breakpoint = kgdb_remove_hw_break,
> + .disable_hw_break = kgdb_disable_hw_break,
> + .remove_all_hw_break = kgdb_remove_all_hw_break,
> + .correct_hw_break = kgdb_correct_hw_break,
> +};
> +
> +int kgdb_arch_init(void)
> +{
> + return register_die_notifier(&kgdb_notifier);
> +}
> +
> +void kgdb_arch_late(void)
> +{
> + int i, cpu;
> + struct perf_event_attr attr;
> + struct perf_event **pevent;
> +
> + hw_breakpoint_init(&attr);
> +
> + attr.bp_addr = (unsigned long)kgdb_arch_init;
> + attr.bp_len = HW_BREAKPOINT_LEN_4;
> + attr.bp_type = HW_BREAKPOINT_W;
> + attr.disabled = 1;
> +
> + for (i = 0; i < LOONGARCH_MAX_BRP; i++) {
> + if (breakinfo[i].pev)
> + continue;
> +
> + breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL, NULL);
> + if (IS_ERR((void * __force)breakinfo[i].pev)) {
> + pr_err("kgdb: Could not allocate hw breakpoints.\n");
> + breakinfo[i].pev = NULL;
> + return;
> + }
> +
> + for_each_online_cpu(cpu) {
> + pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
> + if (pevent[0]->destroy) {
> + pevent[0]->destroy = NULL;
> + release_bp_slot(*pevent);
> + }
> + }
> + }
> +}
> +
> +void kgdb_arch_exit(void)
> +{
> + int i;
> +
> + for (i = 0; i < LOONGARCH_MAX_BRP; i++) {
> + if (breakinfo[i].pev) {
> + unregister_wide_hw_breakpoint(breakinfo[i].pev);
> + breakinfo[i].pev = NULL;
> + }
> + }
> +
> + unregister_die_notifier(&kgdb_notifier);
> +}
> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> index 6838bea5ab64..c70370a94f61 100644
> --- a/arch/loongarch/kernel/traps.c
> +++ b/arch/loongarch/kernel/traps.c
> @@ -720,6 +720,11 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
> goto out;
> else
> break;
> + case BRK_KDB:
> + if (kgdb_breakpoint_handler(regs))
> + goto out;
> + else
> + break;
> default:
> current->thread.trap_nr = read_csr_excode();
> if (notify_die(DIE_TRAP, "Break", regs, bcode,
> @@ -766,6 +771,9 @@ asmlinkage void noinstr do_watch(struct pt_regs *regs)
> #ifndef CONFIG_HAVE_HW_BREAKPOINT
> pr_warn("Hardware watch point handler not implemented!\n");
> #else
> + if (kgdb_breakpoint_handler(regs))
> + goto out;
> +
> if (test_tsk_thread_flag(current, TIF_SINGLESTEP)) {
> int llbit = (csr_read32(LOONGARCH_CSR_LLBCTL) & 0x1);
> unsigned long pc = instruction_pointer(regs);
> --
> 2.38.1
>