[PATCH v2 0/3] Add KGDB support to PA-RISC

[PATCH v2 0/3] Add KGDB support to PA-RISC

[Sven Schnelle]

Hi,

this is v2 of the patch set. Changes compared to v1:

- add a missing #ifdef CONFIG_KGDB in traps.c, to fix a compile error
  when CONFIG_KGDB is not enabled.
- call __patch_text() in kgdb, as kgdb already stops all CPUs.

Sven Schnelle (3):
  parisc: add set_fixmap()/clear_fixmap()
  parisc: add parisc code patching
  parisc: add KGDB support

 arch/parisc/Kconfig              |   1 +
 arch/parisc/include/asm/fixmap.h |  19 ++-
 arch/parisc/include/asm/kgdb.h   |  68 ++++++++++
 arch/parisc/include/asm/patch.h  |  11 ++
 arch/parisc/kernel/Makefile      |   4 +-
 arch/parisc/kernel/kgdb.c        | 210 +++++++++++++++++++++++++++++++
 arch/parisc/kernel/patch.c       |  78 ++++++++++++
 arch/parisc/kernel/traps.c       |  17 +++
 arch/parisc/mm/Makefile          |   2 +-
 arch/parisc/mm/fixmap.c          |  43 +++++++
 arch/parisc/mm/init.c            |  14 ++-
 11 files changed, 459 insertions(+), 8 deletions(-)
 create mode 100644 arch/parisc/include/asm/kgdb.h
 create mode 100644 arch/parisc/include/asm/patch.h
 create mode 100644 arch/parisc/kernel/kgdb.c
 create mode 100644 arch/parisc/kernel/patch.c
 create mode 100644 arch/parisc/mm/fixmap.c

-- 
2.20.1

[PATCH v2 1/3] parisc: add set_fixmap()/clear_fixmap()

[Sven Schnelle]

These functions will be used for adding code patching
functions later.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
---
 arch/parisc/include/asm/fixmap.h | 19 +++++++++++++-
 arch/parisc/mm/Makefile          |  2 +-
 arch/parisc/mm/fixmap.c          | 43 ++++++++++++++++++++++++++++++++
 arch/parisc/mm/init.c            | 14 +++++++----
 4 files changed, 71 insertions(+), 7 deletions(-)
 create mode 100644 arch/parisc/mm/fixmap.c

diff --git a/arch/parisc/include/asm/fixmap.h b/arch/parisc/include/asm/fixmap.h
index f7c3a0905de4..288da73d4cc0 100644
--- a/arch/parisc/include/asm/fixmap.h
+++ b/arch/parisc/include/asm/fixmap.h
@@ -15,17 +15,34 @@
  * from areas congruently mapped with user space.  It is 8MB large
  * and must be 16MB aligned */
 #define TMPALIAS_MAP_START	((__PAGE_OFFSET) - 16*1024*1024)
+
+#define FIXMAP_SIZE		(FIX_BITMAP_COUNT << PAGE_SHIFT)
+#define FIXMAP_START		(TMPALIAS_MAP_START - FIXMAP_SIZE)
 /* This is the kernel area for all maps (vmalloc, dma etc.)  most
  * usually, it extends up to TMPALIAS_MAP_START.  Virtual addresses
  * 0..GATEWAY_PAGE_SIZE are reserved for the gateway page */
 #define KERNEL_MAP_START	(GATEWAY_PAGE_SIZE)
-#define KERNEL_MAP_END		(TMPALIAS_MAP_START)
+#define KERNEL_MAP_END		(FIXMAP_START)
 
 #ifndef __ASSEMBLY__
+
+
+enum fixed_addresses {
+	/* Support writing RO kernel text via kprobes, jump labels, etc. */
+	FIX_TEXT_POKE0,
+	FIX_BITMAP_COUNT
+};
+
 extern void *parisc_vmalloc_start;
 #define PCXL_DMA_MAP_SIZE	(8*1024*1024)
 #define VMALLOC_START		((unsigned long)parisc_vmalloc_start)
 #define VMALLOC_END		(KERNEL_MAP_END)
+
+#define __fix_to_virt(_x) (FIXMAP_START + ((_x) << PAGE_SHIFT))
+
+void set_fixmap(enum fixed_addresses idx, phys_addr_t phys);
+void clear_fixmap(enum fixed_addresses idx);
+
 #endif /*__ASSEMBLY__*/
 
 #endif /*_ASM_FIXMAP_H*/
diff --git a/arch/parisc/mm/Makefile b/arch/parisc/mm/Makefile
index 134393de69d2..20e39b043a60 100644
--- a/arch/parisc/mm/Makefile
+++ b/arch/parisc/mm/Makefile
@@ -2,5 +2,5 @@
 # Makefile for arch/parisc/mm
 #
 
-obj-y	 := init.o fault.o ioremap.o
+obj-y	 := init.o fault.o ioremap.o fixmap.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
diff --git a/arch/parisc/mm/fixmap.c b/arch/parisc/mm/fixmap.c
new file mode 100644
index 000000000000..6f9744c688ae
--- /dev/null
+++ b/arch/parisc/mm/fixmap.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fixmaps for parisc
+ *
+ * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+ */
+
+#include <linux/kprobes.h>
+#include <linux/mm.h>
+#include <asm/cacheflush.h>
+#include <asm/fixmap.h>
+
+void set_fixmap(enum fixed_addresses idx, phys_addr_t phys)
+{
+	unsigned long vaddr = __fix_to_virt(idx);
+	pgd_t *pgd = pgd_offset_k(vaddr);
+	pmd_t *pmd = pmd_offset(pgd, vaddr);
+	pte_t *pte;
+
+	if (pmd_none(*pmd))
+		pmd = pmd_alloc(NULL, pgd, vaddr);
+
+	pte = pte_offset_kernel(pmd, vaddr);
+	if (pte_none(*pte))
+		pte = pte_alloc_kernel(pmd, vaddr);
+
+	set_pte_at(&init_mm, vaddr, pte, __mk_pte(phys, PAGE_KERNEL_RWX));
+	flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
+}
+
+void clear_fixmap(enum fixed_addresses idx)
+{
+	unsigned long vaddr = __fix_to_virt(idx);
+	pgd_t *pgd = pgd_offset_k(vaddr);
+	pmd_t *pmd = pmd_offset(pgd, vaddr);
+	pte_t *pte = pte_offset_kernel(pmd, vaddr);
+
+	pte_clear(&init_mm, vaddr, pte);
+
+	flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
+}
+
+
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index d0b166256f1a..b2b52de2b82b 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -622,15 +622,19 @@ void __init mem_init(void)
 	 * But keep code for debugging purposes.
 	 */
 	printk("virtual kernel memory layout:\n"
-	       "    vmalloc : 0x%px - 0x%px   (%4ld MB)\n"
-	       "    memory  : 0x%px - 0x%px   (%4ld MB)\n"
-	       "      .init : 0x%px - 0x%px   (%4ld kB)\n"
-	       "      .data : 0x%px - 0x%px   (%4ld kB)\n"
-	       "      .text : 0x%px - 0x%px   (%4ld kB)\n",
+	       "     vmalloc : 0x%px - 0x%px   (%4ld MB)\n"
+	       "     fixmap  : 0x%px - 0x%px   (%4ld kB)\n"
+	       "     memory  : 0x%px - 0x%px   (%4ld MB)\n"
+	       "       .init : 0x%px - 0x%px   (%4ld kB)\n"
+	       "       .data : 0x%px - 0x%px   (%4ld kB)\n"
+	       "       .text : 0x%px - 0x%px   (%4ld kB)\n",
 
 	       (void*)VMALLOC_START, (void*)VMALLOC_END,
 	       (VMALLOC_END - VMALLOC_START) >> 20,
 
+	       (void *)FIXMAP_START, (void *)(FIXMAP_START + FIXMAP_SIZE),
+	       (unsigned long)(FIXMAP_SIZE / 1024),
+
 	       __va(0), high_memory,
 	       ((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,
 
-- 
2.20.1

[PATCH v2 2/3] parisc: add parisc code patching

[Sven Schnelle]

Instead of re-mapping the whole kernel text with RWX rights
add a patch_text() which can be used to replace instructions
in the kernel .text section. Based on the ARM implementation.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
---
 arch/parisc/include/asm/patch.h | 11 +++++
 arch/parisc/kernel/Makefile     |  3 +-
 arch/parisc/kernel/patch.c      | 78 +++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+), 1 deletion(-)
 create mode 100644 arch/parisc/include/asm/patch.h
 create mode 100644 arch/parisc/kernel/patch.c

diff --git a/arch/parisc/include/asm/patch.h b/arch/parisc/include/asm/patch.h
new file mode 100644
index 000000000000..685b58a13968
--- /dev/null
+++ b/arch/parisc/include/asm/patch.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PARISC_KERNEL_PATCH_H
+#define _PARISC_KERNEL_PATCH_H
+
+/* stop machine and patch kernel text */
+void patch_text(void *addr, unsigned int insn);
+
+/* patch kernel text with machine already stopped (e.g. in kgdb) */
+void __patch_text(void *addr, unsigned int insn);
+
+#endif
diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index 8e5f1ab65c68..d29bbd1a73b2 100644
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -9,7 +9,8 @@ obj-y	     	:= cache.o pacache.o setup.o pdt.o traps.o time.o irq.o \
 		   pa7300lc.o syscall.o entry.o sys_parisc.o firmware.o \
 		   ptrace.o hardware.o inventory.o drivers.o alternative.o \
 		   signal.o hpmc.o real2.o parisc_ksyms.o unaligned.o \
-		   process.o processor.o pdc_cons.o pdc_chassis.o unwind.o
+		   process.o processor.o pdc_cons.o pdc_chassis.o unwind.o \
+		   patch.o
 
 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities
diff --git a/arch/parisc/kernel/patch.c b/arch/parisc/kernel/patch.c
new file mode 100644
index 000000000000..4a3bff87b177
--- /dev/null
+++ b/arch/parisc/kernel/patch.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+ /*
+  * functions to patch RO kernel text during runtime
+  *
+  * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+  */
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/kprobes.h>
+#include <linux/mm.h>
+#include <linux/stop_machine.h>
+
+#include <asm/cacheflush.h>
+#include <asm/fixmap.h>
+#include <asm/patch.h>
+
+struct patch {
+	void *addr;
+	unsigned int insn;
+};
+
+static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
+{
+	unsigned int uintaddr = (uintptr_t) addr;
+	bool module = !core_kernel_text(uintaddr);
+	struct page *page;
+
+	if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		page = vmalloc_to_page(addr);
+	else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
+		page = virt_to_page(addr);
+	else
+		return addr;
+
+	set_fixmap(fixmap, page_to_phys(page));
+
+	return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
+}
+
+static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
+{
+	clear_fixmap(fixmap);
+}
+
+void __kprobes __patch_text(void *addr, unsigned int insn)
+{
+	unsigned long flags;
+	void *waddr = addr;
+	int size;
+
+	waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
+	*(u32 *)waddr = insn;
+	size = sizeof(u32);
+	flush_kernel_vmap_range(waddr, size);
+	patch_unmap(FIX_TEXT_POKE0, &flags);
+	flush_icache_range((uintptr_t)(addr),
+			   (uintptr_t)(addr) + size);
+}
+
+static int __kprobes patch_text_stop_machine(void *data)
+{
+	struct patch *patch = data;
+
+	__patch_text(patch->addr, patch->insn);
+
+	return 0;
+}
+
+void __kprobes patch_text(void *addr, unsigned int insn)
+{
+	struct patch patch = {
+		.addr = addr,
+		.insn = insn,
+	};
+
+	stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
+}
-- 
2.20.1

[PATCH v2 3/3] parisc: add KGDB support

[Sven Schnelle]

This patch add KGDB support to PA-RISC. It also implements
single-stepping utilizing the recovery counter.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
---
 arch/parisc/Kconfig            |   1 +
 arch/parisc/include/asm/kgdb.h |  68 +++++++++++
 arch/parisc/kernel/Makefile    |   1 +
 arch/parisc/kernel/kgdb.c      | 210 +++++++++++++++++++++++++++++++++
 arch/parisc/kernel/traps.c     |  17 +++
 5 files changed, 297 insertions(+)
 create mode 100644 arch/parisc/include/asm/kgdb.h
 create mode 100644 arch/parisc/kernel/kgdb.c

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index c8e621296092..a80c19c7fc0e 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -54,6 +54,7 @@ config PARISC
 	select CPU_NO_EFFICIENT_FFS
 	select NEED_DMA_MAP_STATE
 	select NEED_SG_DMA_LENGTH
+	select HAVE_ARCH_KGDB
 
 	help
 	  The PA-RISC microprocessor is designed by Hewlett-Packard and used
diff --git a/arch/parisc/include/asm/kgdb.h b/arch/parisc/include/asm/kgdb.h
new file mode 100644
index 000000000000..f23e7f8f13a5
--- /dev/null
+++ b/arch/parisc/include/asm/kgdb.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * PA-RISC KGDB support
+ *
+ * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+ *
+ */
+
+#ifndef __PARISC_KGDB_H__
+#define __PARISC_KGDB_H__
+
+#define BREAK_INSTR_SIZE		4
+#define PARISC_KGDB_COMPILED_BREAK_INSN	0x3ffc01f
+#define PARISC_KGDB_BREAK_INSN		0x3ffa01f
+
+
+#define NUMREGBYTES			sizeof(struct parisc_gdb_regs)
+#define BUFMAX				4096
+
+#define CACHE_FLUSH_IS_SAFE		1
+
+#ifndef __ASSEMBLY__
+
+static inline void arch_kgdb_breakpoint(void)
+{
+	asm(".word %0" : : "i"(PARISC_KGDB_COMPILED_BREAK_INSN) : "memory");
+}
+
+struct parisc_gdb_regs {
+	unsigned long gpr[32];
+	unsigned long sar;
+	unsigned long iaoq_f;
+	unsigned long iasq_f;
+	unsigned long iaoq_b;
+	unsigned long iasq_b;
+	unsigned long eiem;
+	unsigned long iir;
+	unsigned long isr;
+	unsigned long ior;
+	unsigned long ipsw;
+	unsigned long __unused0;
+	unsigned long sr4;
+	unsigned long sr0;
+	unsigned long sr1;
+	unsigned long sr2;
+	unsigned long sr3;
+	unsigned long sr5;
+	unsigned long sr6;
+	unsigned long sr7;
+	unsigned long cr0;
+	unsigned long pid1;
+	unsigned long pid2;
+	unsigned long scrccr;
+	unsigned long pid3;
+	unsigned long pid4;
+	unsigned long cr24;
+	unsigned long cr25;
+	unsigned long cr26;
+	unsigned long cr27;
+	unsigned long cr28;
+	unsigned long cr29;
+	unsigned long cr30;
+
+	u64 fr[32];
+};
+
+#endif
+#endif
diff --git a/arch/parisc/kernel/Makefile b/arch/parisc/kernel/Makefile
index d29bbd1a73b2..5012da96c196 100644
--- a/arch/parisc/kernel/Makefile
+++ b/arch/parisc/kernel/Makefile
@@ -33,3 +33,4 @@ obj-$(CONFIG_64BIT)	+= perf.o perf_asm.o $(obj64-y)
 obj-$(CONFIG_PARISC_CPU_TOPOLOGY)	+= topology.o
 obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o
+obj-$(CONFIG_KGDB)			+= kgdb.o
diff --git a/arch/parisc/kernel/kgdb.c b/arch/parisc/kernel/kgdb.c
new file mode 100644
index 000000000000..30f6a7653356
--- /dev/null
+++ b/arch/parisc/kernel/kgdb.c
@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * PA-RISC KGDB support
+ *
+ * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+ *
+ */
+
+#include <linux/kgdb.h>
+#include <linux/string.h>
+#include <linux/sched.h>
+#include <linux/notifier.h>
+#include <linux/kdebug.h>
+#include <linux/uaccess.h>
+#include <asm/ptrace.h>
+#include <asm/traps.h>
+#include <asm/processor.h>
+#include <asm/patch.h>
+#include <asm/cacheflush.h>
+
+const struct kgdb_arch arch_kgdb_ops = {
+	.gdb_bpt_instr = { 0x03, 0xff, 0xa0, 0x1f }
+};
+
+static int __kgdb_notify(struct die_args *args, unsigned long cmd)
+{
+	struct pt_regs *regs = args->regs;
+
+	if (kgdb_handle_exception(1, args->signr, cmd, regs))
+		return NOTIFY_DONE;
+	return NOTIFY_STOP;
+}
+
+static int kgdb_notify(struct notifier_block *self,
+		       unsigned long cmd, void *ptr)
+{
+	unsigned long flags;
+	int ret;
+
+	local_irq_save(flags);
+	ret = __kgdb_notify(ptr, cmd);
+	local_irq_restore(flags);
+
+	return ret;
+}
+
+static struct notifier_block kgdb_notifier = {
+	.notifier_call	= kgdb_notify,
+	.priority	= -INT_MAX,
+};
+
+int kgdb_arch_init(void)
+{
+	return register_die_notifier(&kgdb_notifier);
+}
+
+void kgdb_arch_exit(void)
+{
+	unregister_die_notifier(&kgdb_notifier);
+}
+
+void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+	struct parisc_gdb_regs *gr = (struct parisc_gdb_regs *)gdb_regs;
+
+	memset(gr, 0, sizeof(struct parisc_gdb_regs));
+
+	memcpy(gr->gpr, regs->gr, sizeof(gr->gpr));
+	memcpy(gr->fr, regs->fr, sizeof(gr->fr));
+
+	gr->sr0 = regs->sr[0];
+	gr->sr1 = regs->sr[1];
+	gr->sr2 = regs->sr[2];
+	gr->sr3 = regs->sr[3];
+	gr->sr4 = regs->sr[4];
+	gr->sr5 = regs->sr[5];
+	gr->sr6 = regs->sr[6];
+	gr->sr7 = regs->sr[7];
+
+	gr->sar = regs->sar;
+	gr->iir = regs->iir;
+	gr->isr = regs->isr;
+	gr->ior = regs->ior;
+	gr->ipsw = regs->ipsw;
+	gr->cr27 = regs->cr27;
+
+	gr->iaoq_f = regs->iaoq[0];
+	gr->iasq_f = regs->iasq[0];
+
+	gr->iaoq_b = regs->iaoq[1];
+	gr->iasq_b = regs->iasq[1];
+}
+
+void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+	struct parisc_gdb_regs *gr = (struct parisc_gdb_regs *)gdb_regs;
+
+
+	memcpy(regs->gr, gr->gpr, sizeof(regs->gr));
+	memcpy(regs->fr, gr->fr, sizeof(regs->fr));
+
+	regs->sr[0] = gr->sr0;
+	regs->sr[1] = gr->sr1;
+	regs->sr[2] = gr->sr2;
+	regs->sr[3] = gr->sr3;
+	regs->sr[4] = gr->sr4;
+	regs->sr[5] = gr->sr5;
+	regs->sr[6] = gr->sr6;
+	regs->sr[7] = gr->sr7;
+
+	regs->sar = gr->sar;
+	regs->iir = gr->iir;
+	regs->isr = gr->isr;
+	regs->ior = gr->ior;
+	regs->ipsw = gr->ipsw;
+	regs->cr27 = gr->cr27;
+
+	regs->iaoq[0] = gr->iaoq_f;
+	regs->iasq[0] = gr->iasq_f;
+
+	regs->iaoq[1] = gr->iaoq_b;
+	regs->iasq[1] = gr->iasq_b;
+}
+
+void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs,
+				struct task_struct *task)
+{
+	struct pt_regs *regs = task_pt_regs(task);
+	unsigned long gr30, iaoq;
+
+	gr30 = regs->gr[30];
+	iaoq = regs->iaoq[0];
+
+	regs->gr[30] = regs->ksp;
+	regs->iaoq[0] = regs->kpc;
+	pt_regs_to_gdb_regs(gdb_regs, regs);
+
+	regs->gr[30] = gr30;
+	regs->iaoq[0] = iaoq;
+
+}
+
+static void step_instruction_queue(struct pt_regs *regs)
+{
+	regs->iaoq[0] = regs->iaoq[1];
+	regs->iaoq[1] += 4;
+}
+
+void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
+{
+	regs->iaoq[0] = ip;
+	regs->iaoq[1] = ip + 4;
+}
+
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+	int ret = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
+				BREAK_INSTR_SIZE);
+	if (ret)
+		return ret;
+
+	__patch_text((void *)bpt->bpt_addr,
+			*(unsigned int *)&arch_kgdb_ops.gdb_bpt_instr);
+	return ret;
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+	__patch_text((void *)bpt->bpt_addr, *(unsigned int *)&bpt->saved_instr);
+	return 0;
+}
+
+int kgdb_arch_handle_exception(int trap, int signo,
+		int err_code, char *inbuf, char *outbuf,
+		struct pt_regs *regs)
+{
+	unsigned long addr;
+	char *p = inbuf + 1;
+
+	switch (inbuf[0]) {
+	case 'D':
+	case 'c':
+	case 'k':
+		kgdb_contthread = NULL;
+		kgdb_single_step = 0;
+
+		if (kgdb_hex2long(&p, &addr))
+			kgdb_arch_set_pc(regs, addr);
+		else if (trap == 9 && regs->iir ==
+				PARISC_KGDB_COMPILED_BREAK_INSN)
+			step_instruction_queue(regs);
+		return 0;
+	case 's':
+		kgdb_single_step = 1;
+		if (kgdb_hex2long(&p, &addr)) {
+			kgdb_arch_set_pc(regs, addr);
+		} else if (trap == 9 && regs->iir ==
+				PARISC_KGDB_COMPILED_BREAK_INSN) {
+			step_instruction_queue(regs);
+			mtctl(-1, 0);
+		} else {
+			mtctl(0, 0);
+		}
+		regs->gr[0] |= PSW_R;
+		return 0;
+
+	}
+	return -1;
+}
+
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 7e1ccafadf57..4a0516524f2a 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -42,6 +42,7 @@
 #include <asm/unwind.h>
 #include <asm/tlbflush.h>
 #include <asm/cacheflush.h>
+#include <linux/kgdb.h>
 
 #include "../math-emu/math-emu.h"	/* for handle_fpe() */
 
@@ -293,6 +294,14 @@ static void handle_break(struct pt_regs *regs)
 			(tt == BUG_TRAP_TYPE_NONE) ? 9 : 0);
 	}
 
+#ifdef CONFIG_KGDB
+	if (unlikely(iir == PARISC_KGDB_COMPILED_BREAK_INSN ||
+		iir == PARISC_KGDB_BREAK_INSN)) {
+		kgdb_handle_exception(9, SIGTRAP, 0, regs);
+		return;
+	}
+#endif
+
 	if (unlikely(iir != GDB_BREAK_INSN))
 		parisc_printk_ratelimited(0, regs,
 			KERN_DEBUG "break %d,%d: pid=%d command='%s'\n",
@@ -518,6 +527,14 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
 	case  3:
 		/* Recovery counter trap */
 		regs->gr[0] &= ~PSW_R;
+
+#ifdef CONFIG_KGDB
+		if (kgdb_single_step) {
+			kgdb_handle_exception(0, SIGTRAP, 0, regs);
+			return;
+		}
+#endif
+
 		if (user_space(regs))
 			handle_gdb_break(regs, TRAP_TRACE);
 		/* else this must be the start of a syscall - just let it run */
-- 
2.20.1