Re: [RFC PATCH] LoongArch: KGDB: Add Basic KGDB support

From: Binbin Zhou
Date: Wed Jun 21 2023 - 02:25:10 EST

Hi Qing:

On Tue, Jun 20, 2023 at 9:13 PM Qing Zhang <zhangqing@xxxxxxxxxxx> wrote:
>
> Add Kgdb debug support for LoongArch kernel debugging, more support
> and testing is working in progress.
>
> Kgdb is intended to be used as a source level debugger for thekernel,
> It is used along with gdb to debug a kernel. The expectation is that
> gdb can be used to "break in" to the kernel to inspect memory, variables
> and look through call stack information similar to the way an application
> developer would use gdb to debug an application.
>
> Signed-off-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 79412304a01f..dd823823b7fc 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -85,6 +85,7 @@ config LOONGARCH
> select GPIOLIB
> select HAS_IOPORT
> select HAVE_ARCH_AUDITSYSCALL
> + select HAVE_ARCH_KGDB

Please list the Kconfig options in alphabetical order.
> select HAVE_ARCH_JUMP_LABEL
> select HAVE_ARCH_JUMP_LABEL_RELATIVE
> select HAVE_ARCH_MMAP_RND_BITS if MMU
> diff --git a/arch/loongarch/include/asm/kgdb.h b/arch/loongarch/include/asm/kgdb.h
> new file mode 100644
> index 000000000000..35ef7a46beb5
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kgdb.h
> @@ -0,0 +1,23 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_LOONGARCH_KGDB_H
> +#define _ASM_LOONGARCH_KGDB_H
> +
> +#define KGDB_GDB_REG_SIZE 64
> +#define GDB_SIZEOF_REG sizeof(u64)
> +
> +#define BUFMAX 2048
> +#define DBG_ALL_REG_NUM 78
> +#define DBG_MAX_REG_NUM 33
> +#define NUMREGBYTES (DBG_MAX_REG_NUM * sizeof(GDB_SIZEOF_REG))
> +#define NUMCRITREGBYTES (12 * sizeof(GDB_SIZEOF_REG))
> +#define BREAK_INSTR_SIZE 4
> +#define CACHE_FLUSH_IS_SAFE 0
> +
> +extern void arch_kgdb_breakpoint(void);
> +extern void *saved_vectors[32];
> +extern void handle_exception(struct pt_regs *regs);
> +extern void breakinst(void);
> +extern int kgdb_ll_trap(int cmd, const char *str,
> + struct pt_regs *regs, long err, int trap, int sig);
> +
> +#endif /* __ASM_KGDB_H_ */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 8e279f04f9e7..cbe109cd93ba 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -60,4 +60,6 @@ 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/kgdb.c b/arch/loongarch/kernel/kgdb.c
> new file mode 100755
> index 000000000000..ecd9ec873cf7
> --- /dev/null
> +++ b/arch/loongarch/kernel/kgdb.c
> @@ -0,0 +1,584 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2023 Loongson Technology Corporation Limited
> + */
> +
> +#include <linux/module.h>
> +#include <linux/ptrace.h> /* for linux pt_regs struct */
> +#include <linux/hw_breakpoint.h>
> +#include <linux/kgdb.h>
> +#include <linux/kdebug.h>
> +#include <linux/sched.h>
> +#include <linux/smp.h>
> +#include <asm/inst.h>
> +#include <asm/fpu.h>
> +#include <asm/cacheflush.h>
> +#include <asm/processor.h>
> +#include <asm/sigcontext.h>
> +#include <asm/irq_regs.h>
> +#include <asm/ptrace.h>
> +#include <asm/hw_breakpoint.h>
> +int kgdb_watch_activated;
> +
> +struct dbg_reg_def_t dbg_reg_def[DBG_ALL_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]) },
> + { "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, csr_era) },
> + { "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", GDB_SIZEOF_REG, 0 },
> + { "scr0", GDB_SIZEOF_REG, offsetof(struct thread_struct, scr0) },
> + { "scr1", GDB_SIZEOF_REG, offsetof(struct thread_struct, scr1) },
> + { "scr2", GDB_SIZEOF_REG, offsetof(struct thread_struct, scr2) },
> + { "scr3", GDB_SIZEOF_REG, offsetof(struct thread_struct, scr2) },
> +};
> +
> +int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
> +{
> + int fp_reg;
> +
> + if (regno < 0 || regno >= DBG_ALL_REG_NUM)
> + return -EINVAL;
> +
> + if (dbg_reg_def[regno].offset != -1 && regno < 33) {
> + memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
> + dbg_reg_def[regno].size);
> + } else if (current && dbg_reg_def[regno].offset != -1 && regno < 78) {
> + /* FP registers 32 -> 77 */
> + if (!(regs->csr_euen & CSR_EUEN_FPEN))
> + return 0;
> + if (regno == 72) {
> + /* Process the fcsr/fsr (register 70) */
> + memcpy((void *)&current->thread.fpu.fcsr, mem,
> + dbg_reg_def[regno].size);
> + } else if (regno >= 64 && regno < 72) {
> + /* Process the fcc */
> + fp_reg = dbg_reg_def[regno].offset;
> + memcpy((char *)&current->thread.fpu.fcc + fp_reg, mem,
> + dbg_reg_def[regno].size);
> + } else if (regno >= 73 && regno < 77) {
> + /* Process the scr */
> + memcpy((void *)&current->thread + dbg_reg_def[regno].offset, mem,
> + dbg_reg_def[regno].size);
> + } else {
> + fp_reg = dbg_reg_def[regno].offset;
> + memcpy((void *)&current->thread.fpu.fpr[fp_reg], mem, dbg_reg_def[regno].size);
> + }
> + restore_fp(current);
> + }

Would it be better to change if-else to switch-case?
> +
> + return 0;
> +}
> +
> +char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
> +{
> + int fp_reg;
> +
> + if (regno >= DBG_ALL_REG_NUM || regno < 0)
> + return NULL;
> +
> + if (dbg_reg_def[regno].offset != -1 && regno < 33) {
> + /* First 32 registers */
> + memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
> + dbg_reg_def[regno].size);
> + } else if (current && dbg_reg_def[regno].offset != -1 && regno < 78) {
> + /* FP registers 32 -> 77 */
> + if (!(regs->csr_euen & CSR_EUEN_FPEN))
> + goto out;
> + save_fp(current);
> + if (regno == 72) {
> + /* Process the fcsr/fsr (register 70) */
> + memcpy(mem, (void *)&current->thread.fpu.fcsr,
> + dbg_reg_def[regno].size);
> + } else if (regno >= 64 && regno < 72) {
> + /* Process the fcc */
> + fp_reg = dbg_reg_def[regno].offset;
> + memcpy(mem, (char *)&current->thread.fpu.fcc + fp_reg,
> + dbg_reg_def[regno].size);
> + } else if (regno >= 73 && regno < 77) {
> + /* Process the scr */
> + memcpy(mem, (void *)&current->thread + dbg_reg_def[regno].offset,
> + dbg_reg_def[regno].size);
> + } else {
> + fp_reg = dbg_reg_def[regno].offset;
> + memcpy(mem, (void *)&current->thread.fpu.fpr[fp_reg], dbg_reg_def[regno].size);
> + }
> + }

Ditto.

> +out:
> + return dbg_reg_def[regno].name;
> +
> +}
> +
> +void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
> +{
> + int reg;
> + u64 *ptr = (u64 *)gdb_regs, *gdbregs = ptr;
> +
> + *(ptr++) = 0;
> + *(ptr++) = p->thread.reg01;
> + *(ptr++) = (long)p;
> + *(ptr++) = p->thread.reg03;
> + for (reg = 4; reg < 23; reg++)
> + *(ptr++) = 0;
> +
> + /* S0 - S8 */
> + *(ptr++) = p->thread.reg23;
> + *(ptr++) = p->thread.reg24;
> + *(ptr++) = p->thread.reg25;
> + *(ptr++) = p->thread.reg26;
> + *(ptr++) = p->thread.reg27;
> + *(ptr++) = p->thread.reg28;
> + *(ptr++) = p->thread.reg29;
> + *(ptr++) = p->thread.reg30;
> + *(ptr++) = p->thread.reg31;
> +
> + /*
> + * PC
> + * use return address (RA), i.e. the moment after return from resume()
> + */
> + *(ptr++) = p->thread.reg01;
> +
> + ptr = gdbregs + 73;
> + *(ptr++) = p->thread.scr0;
> + *(ptr++) = p->thread.scr1;
> + *(ptr++) = p->thread.scr2;
> + *(ptr++) = p->thread.scr3;
> +}
> +
> +void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
> +{
> + regs->csr_era = 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->csr_era = addr;
> +}
> +
> +static struct hw_breakpoint {
> + unsigned 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:
> + len = 1;
> + breakinfo[i].type = LOONGARCH_BREAKPOINT_EXECUTE;
> + break;
> + case BP_WRITE_WATCHPOINT:
> + breakinfo[i].type = LOONGARCH_BREAKPOINT_STORE;
> + break;
> + case BP_ACCESS_WATCHPOINT:
> + breakinfo[i].type = LOONGARCH_BREAKPOINT_LOAD && LOONGARCH_BREAKPOINT_STORE;
> + break;
> + default:
> + return -1;
> + }
> + switch (len) {
> + case 1:
> + breakinfo[i].len = LOONGARCH_BREAKPOINT_LEN_1;
> + break;
> + case 2:
> + breakinfo[i].len = LOONGARCH_BREAKPOINT_LEN_2;
> + break;
> + case 4:
> + breakinfo[i].len = LOONGARCH_BREAKPOINT_LEN_4;
> + break;
> + case 8:
> + breakinfo[i].len = LOONGARCH_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)) {
> + printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
> + return -1;
> + }
> + breakinfo[i].enabled = 0;
> +
> + return 0;
> +}
> +
> +static void kgdb_disable_hw_debug(struct pt_regs *regs)
> +{
> + int i;
> + int cpu = raw_smp_processor_id();
> + struct perf_event *bp;
> +
> + /* Disable hardware debugging while we are in kgdb: */
> + csr_xchg32(0, CSR_CRMD_WE, LOONGARCH_CSR_CRMD);
> + regs->csr_prmd &= ~CSR_PRMD_PWE;
> +
> + 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;
> + }
> +}
> +
> +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))
> + printk(KERN_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 breakno, activated = 0;
> +
> + for (breakno = 0; breakno < LOONGARCH_MAX_BRP; breakno++) {
> + struct perf_event *bp;
> + struct arch_hw_breakpoint *info;
> + int val;
> + int cpu = raw_smp_processor_id();
> +
> + if (!breakinfo[breakno].enabled)
> + continue;
> + bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
> + info = counter_arch_bp(bp);
> + if (bp->attr.disabled != 1)
> + continue;
> + bp->attr.bp_addr = breakinfo[breakno].addr;
> + bp->attr.bp_len = breakinfo[breakno].len;
> + bp->attr.bp_type = breakinfo[breakno].type;
> + info->address = breakinfo[breakno].addr;
> + info->ctrl.len = breakinfo[breakno].len;
> + info->ctrl.type = breakinfo[breakno].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 = {0x00, 0x00, break_op, 0x00},

Unlike our internal code repository:
.gdb_bpt_instr = { 0x00, 0x00, break_op >> 1, 0x00 },

Why？

> + .flags = KGDB_HW_BREAKPOINT,
> + .set_hw_breakpoint = kgdb_set_hw_break,
> + .remove_hw_breakpoint = kgdb_remove_hw_break,
> + .disable_hw_break = kgdb_disable_hw_debug,
> + .remove_all_hw_break = kgdb_remove_all_hw_break,
> + .correct_hw_break = kgdb_correct_hw_break,
> +};
> +
> +int kgdb_arch_handle_exception(int vector, int signo, int err_code,
> + char *remcom_in_buffer, char *remcom_out_buffer,
> + struct pt_regs *regs)
> +{
> + regs->csr_prmd |= CSR_PRMD_PWE;
> +
> + switch (remcom_in_buffer[0]) {
> + case 'c':
> + kgdb_arch_update_addr(regs, remcom_in_buffer);
> + return 0;
> + }
> +
> + return -1;
> +}
> +
> +static struct hard_trap_info {
> + unsigned char tt; /* Trap type code for LoongArch */
> + unsigned char signo; /* Signal that we map this trap into */
> +} hard_trap_info[] = {
> + { 1, SIGBUS },
> + { 2, SIGBUS },
> + { 3, SIGBUS },
> + { 4, SIGBUS },
> + { 5, SIGBUS },
> + { 6, SIGBUS },
> + { 7, SIGBUS },
> + { 8, SIGBUS },
> + { 9, SIGBUS },
> + { 10, SIGBUS },
> + { 12, SIGTRAP }, /* break */
> + { 13, SIGBUS },
> + { 14, SIGBUS },
> + { 15, SIGFPE },
> + { 16, SIGFPE },
> + { 17, SIGFPE },
> + { 18, SIGFPE },
> + { 0, 0} /* Must be last */
> +};
> +
> +void arch_kgdb_breakpoint(void)
> +{
> + __asm__ __volatile__(
> + ".globl breakinst\n\t"
> + "nop\n"
> + "breakinst:\tbreak 0\n\t");
> +}
> +
> +void kgdb_call_nmi_hook(void *ignored)
> +{
> + kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
> +}
> +
> +void kgdb_roundup_cpus(void)
> +{
> + local_irq_enable();
> + smp_call_function(kgdb_call_nmi_hook, NULL, 0);
> + local_irq_disable();
> +}
> +
> +static int compute_signal(int tt)
> +{
> + struct hard_trap_info *ht;
> +
> + for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
> + if (ht->tt == tt)
> + return ht->signo;
> +
> + return SIGTRAP; /* default for things we don't know about */
> +}
> +
> +/*
> + * 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;
> + int trap = read_csr_excode();
> +
> + /* Userspace events, ignore. */
> + if (user_mode(regs))
> + return NOTIFY_DONE;
> +
> + if (atomic_read(&kgdb_active) != -1)
> + kgdb_nmicallback(smp_processor_id(), regs);
> +
> + if (kgdb_handle_exception(trap, compute_signal(trap), cmd, regs))
> + return NOTIFY_DONE;
> +
> + if (atomic_read(&kgdb_setting_breakpoint))
> + if ((regs->csr_era == (unsigned long)breakinst))
> + regs->csr_era += 4;
> +
> + /* In SMP mode, __flush_cache_all does IPI */
> + local_irq_enable();
> + flush_cache_all();
> +
> + return NOTIFY_STOP;
> +}
> +
> +#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
> +int kgdb_ll_trap(int cmd, const char *str,
> + struct pt_regs *regs, long err, int trap, int sig)
> +{
> + struct die_args args = {
> + .regs = regs,
> + .str = str,
> + .err = err,
> + .trapnr = trap,
> + .signr = sig,
> +
> + };
> +
> + if (!kgdb_io_module_registered)
> + return NOTIFY_DONE;
> +
> + return kgdb_loongarch_notify(NULL, cmd, &args);
> +}
> +#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
> +
> +static struct notifier_block kgdb_notifier = {
> + .notifier_call = kgdb_loongarch_notify,
> +};
> +
> +int kgdb_arch_init(void)
> +{
> + register_die_notifier(&kgdb_notifier);

I noticed that we have the following codes in our internal code repository:
dbcn = csr_read32(LOONGARCH_CSR_MWPC) & 0x3f.
ibcn = csr_read32(LOONGARCH_CSR_FWPC) & 0x3f.
boot_cpu_data.watch_dreg_count = dbcn - kgdb_watch_dcount.
boot_cpu_data.watch_ireg_count = ibcn - kgdb_watch_icount.

Why is it not needed here?

> + return 0;
> +}
> +
> +/*
> + * kgdb_arch_exit - Perform any architecture specific uninitalization.
> + *
> + * This function will handle the uninitalization of any architecture
> + * specific callbacks, for dynamic registration and unregistration.
> + */
Incorrect comment indentation, one space is fine.

And, there are also several differences from our internal code
repository as follows:

1.
arch/loongarch/include/asm/stackframe.h
@@ -159,6 +159,10 @@
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
UNWIND_HINT_REGS
.endm

2.
arch/loongarch/kernel/entry.S
@@ -59,6 +59,10 @@ SYM_FUNC_START(handle_syscall)

SAVE_STATIC

+#ifdef CONFIG_KGDB
+ li.w t1, CSR_CRMD_WE
+ csrxchg t1, t1, LOONGARCH_CSR_CRMD
+#endif
UNWIND_HINT_REGS

move u0, t0

Are these two changes being missed?

Thanks.
Binbin

> +void kgdb_arch_exit(void)
> +{
> + unregister_die_notifier(&kgdb_notifier);
> +}
> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> index 22179cf6f33c..a2a220375a8a 100644
> --- a/arch/loongarch/kernel/traps.c
> +++ b/arch/loongarch/kernel/traps.c
> @@ -695,6 +695,12 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
>
> bcode = (opcode & 0x7fff);
>
> +#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
> + if (kgdb_ll_trap(DIE_TRAP, "Break", regs, code, current->thread.trap_nr,
> + SIGTRAP) == NOTIFY_STOP)
> + return;
> +#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
> +
> /*
> * notify the kprobe handlers, if instruction is likely to
> * pertain to them.
> --
> 2.36.0
>
>