This patch adds a vector for debug events along with a hook similar to
the exception framework. The debug vector generates an exception frame
for use by libdebugger.
---
 .../start/_debug_sw_break_handler.S           | 106 ++++++++++++++++++
 bsps/microblaze/shared/start/start.S          |   7 +-
 cpukit/score/cpu/microblaze/cpu.c             |  26 +++++
 .../cpu/microblaze/include/rtems/score/cpu.h  |   9 ++
 .../bsps/microblaze/microblaze_fpga/obj.yml   |   1 +
 5 files changed, 148 insertions(+), 1 deletion(-)
 create mode 100644 
bsps/microblaze/microblaze_fpga/start/_debug_sw_break_handler.S

diff --git a/bsps/microblaze/microblaze_fpga/start/_debug_sw_break_handler.S 
b/bsps/microblaze/microblaze_fpga/start/_debug_sw_break_handler.S
new file mode 100644
index 0000000000..872f488889
--- /dev/null
+++ b/bsps/microblaze/microblaze_fpga/start/_debug_sw_break_handler.S
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+
+/**
+ * @file
+ *
+ * @ingroup RTEMSBSPsMicroBlaze
+ *
+ * @brief MicroBlaze debug trap handler implementation
+ */
+
+/*
+ * Copyright (C) 2022 On-Line Applications Research Corporation (OAR)
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <rtems/score/cpu.h>
+
+       .text
+       .globl _debug_sw_break_handler    # HW Exception Handler Label
+       .extern _MicroBlaze_Debug_handle
+       .align 2
+
+       _debug_sw_break_handler:
+       /* The stack used here does not matter since debug cannot recurse */
+
+       /* Subtract exception frame */
+       addik r1, r1, -(CPU_EXCEPTION_FRAME_SIZE)
+
+       /* Store program state */
+       swi  r2, r1, MICROBLAZE_EXCEPTION_FRAME_R2
+       swi  r3, r1, MICROBLAZE_EXCEPTION_FRAME_R3
+       swi  r4, r1, MICROBLAZE_EXCEPTION_FRAME_R4
+       swi  r5, r1, MICROBLAZE_EXCEPTION_FRAME_R5
+       swi  r6, r1, MICROBLAZE_EXCEPTION_FRAME_R6
+       swi  r7, r1, MICROBLAZE_EXCEPTION_FRAME_R7
+       swi  r8, r1, MICROBLAZE_EXCEPTION_FRAME_R8
+       swi  r9, r1, MICROBLAZE_EXCEPTION_FRAME_R9
+       swi r10, r1, MICROBLAZE_EXCEPTION_FRAME_R10
+       swi r11, r1, MICROBLAZE_EXCEPTION_FRAME_R11
+       swi r12, r1, MICROBLAZE_EXCEPTION_FRAME_R12
+       swi r13, r1, MICROBLAZE_EXCEPTION_FRAME_R13
+       swi r14, r1, MICROBLAZE_EXCEPTION_FRAME_R14
+       swi r15, r1, MICROBLAZE_EXCEPTION_FRAME_R15
+       swi r16, r1, MICROBLAZE_EXCEPTION_FRAME_R16
+       swi r17, r1, MICROBLAZE_EXCEPTION_FRAME_R17
+       swi r18, r1, MICROBLAZE_EXCEPTION_FRAME_R18
+       swi r19, r1, MICROBLAZE_EXCEPTION_FRAME_R19
+       swi r20, r1, MICROBLAZE_EXCEPTION_FRAME_R20
+       swi r21, r1, MICROBLAZE_EXCEPTION_FRAME_R21
+       swi r22, r1, MICROBLAZE_EXCEPTION_FRAME_R22
+       swi r23, r1, MICROBLAZE_EXCEPTION_FRAME_R23
+       swi r24, r1, MICROBLAZE_EXCEPTION_FRAME_R24
+       swi r25, r1, MICROBLAZE_EXCEPTION_FRAME_R25
+       swi r26, r1, MICROBLAZE_EXCEPTION_FRAME_R26
+       swi r27, r1, MICROBLAZE_EXCEPTION_FRAME_R27
+       swi r28, r1, MICROBLAZE_EXCEPTION_FRAME_R28
+       swi r29, r1, MICROBLAZE_EXCEPTION_FRAME_R29
+       swi r30, r1, MICROBLAZE_EXCEPTION_FRAME_R30
+       swi r31, r1, MICROBLAZE_EXCEPTION_FRAME_R31
+
+       /* Retrieve and store MSR */
+       mfs r3, rmsr
+       swi r3, r1, MICROBLAZE_EXCEPTION_FRAME_MSR
+
+       /* Retrieve and store EAR */
+       mfs r3, rear
+       swi r3, r1, MICROBLAZE_EXCEPTION_FRAME_EAR
+
+       /* Retrieve and store ESR */
+       mfs r3, resr
+       swi r3, r1, MICROBLAZE_EXCEPTION_FRAME_ESR
+
+       /* Retrieve and store BTR */
+       mfs r3, rbtr
+       swi r3, r1, MICROBLAZE_EXCEPTION_FRAME_BTR
+
+       /* Calculate and store original stack pointer */
+       addik r3, r1, CPU_EXCEPTION_FRAME_SIZE
+       swi r3, r1, MICROBLAZE_EXCEPTION_FRAME_R1
+
+       /* set parameter 1 to CPU Exception frame */
+       addi r5, r1, 0
+
+       /* call into the debug framework */
+       braid _MicroBlaze_Debug_handle
+       nop
diff --git a/bsps/microblaze/shared/start/start.S 
b/bsps/microblaze/shared/start/start.S
index bd50fe0d24..e9aaa706e5 100644
--- a/bsps/microblaze/shared/start/start.S
+++ b/bsps/microblaze/shared/start/start.S
@@ -46,7 +46,7 @@
                # 0x14 #                                Hardware Interrupt      
    _interrupt_handler
 
                # 0x18 #                                (-- IMM --)
-               # 0x1C #                                Breakpoint Exception    
    (-- Don't Care --)
+               # 0x1C #                                Breakpoint Exception    
    _debug_sw_break_handler
 
                # 0x20 #                                (-- IMM --)
                # 0x24 #                                Hardware Exception      
    _hw_exception_handler
@@ -73,6 +73,11 @@ _vector_sw_exception:
 _vector_interrupt:
        brai _interrupt_handler
 
+       .section .vectors.debug_sw_break, "ax"
+       .align 2
+_vector_debug_sw_break:
+       brai _debug_sw_break_handler
+
        .section .vectors.hw_exception, "ax"
        .align 2
 _vector_hw_exception:
diff --git a/cpukit/score/cpu/microblaze/cpu.c 
b/cpukit/score/cpu/microblaze/cpu.c
index 7ff8ca3071..fe55ef5546 100644
--- a/cpukit/score/cpu/microblaze/cpu.c
+++ b/cpukit/score/cpu/microblaze/cpu.c
@@ -203,3 +203,29 @@ void _MicroBlaze_Exception_handle( CPU_Exception_frame *ef 
)
 
   rtems_fatal( RTEMS_FATAL_SOURCE_EXCEPTION, (rtems_fatal_code) ef );
 }
+
+MicroBlaze_Exception_handler installed_debug_handler = NULL;
+
+void _MicroBlaze_Debug_install_handler(
+  MicroBlaze_Exception_handler  new_handler,
+  MicroBlaze_Exception_handler *old_handler
+)
+{
+  if ( old_handler != NULL ) {
+    *old_handler = installed_debug_handler;
+  }
+
+  installed_debug_handler = new_handler;
+}
+
+void _MicroBlaze_Debug_handle( CPU_Exception_frame *ef )
+{
+  /* BiP is not set for software debug events, set it here */
+  ef->msr |= MICROBLAZE_MSR_BIP;
+
+  if ( installed_debug_handler != NULL ) {
+    installed_debug_handler( ef );
+  }
+
+  rtems_fatal( RTEMS_FATAL_SOURCE_EXCEPTION, (rtems_fatal_code) ef );
+}
diff --git a/cpukit/score/cpu/microblaze/include/rtems/score/cpu.h 
b/cpukit/score/cpu/microblaze/include/rtems/score/cpu.h
index a9c5066399..fe0d9a8996 100644
--- a/cpukit/score/cpu/microblaze/include/rtems/score/cpu.h
+++ b/cpukit/score/cpu/microblaze/include/rtems/score/cpu.h
@@ -344,6 +344,15 @@ void _MicroBlaze_Exception_handle(
   CPU_Exception_frame *ef
 );
 
+void _MicroBlaze_Debug_install_handler(
+  MicroBlaze_Exception_handler  new_handler,
+  MicroBlaze_Exception_handler *old_handler
+);
+
+void _MicroBlaze_Debug_handle(
+  CPU_Exception_frame *ef
+);
+
 void _CPU_Context_switch(
   Context_Control  *run,
   Context_Control  *heir
diff --git a/spec/build/bsps/microblaze/microblaze_fpga/obj.yml 
b/spec/build/bsps/microblaze/microblaze_fpga/obj.yml
index 0757fe2d53..37096cdc84 100644
--- a/spec/build/bsps/microblaze/microblaze_fpga/obj.yml
+++ b/spec/build/bsps/microblaze/microblaze_fpga/obj.yml
@@ -25,6 +25,7 @@ source:
 - bsps/microblaze/microblaze_fpga/console/debug-io.c
 - bsps/microblaze/microblaze_fpga/fdt/bsp_fdt.c
 - bsps/microblaze/microblaze_fpga/irq/irq.c
+- bsps/microblaze/microblaze_fpga/start/_debug_sw_break_handler.S
 - bsps/microblaze/microblaze_fpga/start/_exception_handler.S
 - bsps/microblaze/microblaze_fpga/start/_interrupt_handler.S
 - bsps/microblaze/microblaze_fpga/start/bspreset.c
-- 
2.30.2

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