From 12d0da0c5866c71bc11124e3058d0b2926b69fa6 Mon Sep 17 00:00:00 2001
From: Vlad Ivanov <vlad-mbx@ya.ru>
Date: Thu, 15 Sep 2016 09:26:38 +0300
Subject: [PATCH] core: exception_vectors: initial esp-gdbstub support (#205)
---
core/exception_vectors.S | 52 +++++++++++++++++++++++++++++++++-----
core/include/debug_dumps.h | 2 ++
2 files changed, 47 insertions(+), 7 deletions(-)
diff --git a/core/exception_vectors.S b/core/exception_vectors.S
index 000e742..df04ab3 100644
--- a/core/exception_vectors.S
+++ b/core/exception_vectors.S
@@ -45,6 +45,15 @@ LoadStoreErrorHandlerStack:
.word 0 # a3
.word 0 # a4
+ .balign 4
+ .global debug_saved_ctx
+debug_saved_ctx:
+ .word 0 # a0
+ .word 0 # a1
+ .word 0 # a2
+ .word 0 # a3
+ .word 0 # a4
+
/***************************** Exception Vectors *****************************/
.section .vecbase.text, "x"
@@ -66,12 +75,7 @@ VecBase:
.org VecBase + 0x10
DebugExceptionVector:
.type DebugExceptionVector, @function
-
- wsr a0, excsave2
- mov a2, a1
- movi a3, 0
- call0 fatal_exception_handler
- rfi 2
+ j DebugExceptionHandler
.org VecBase + 0x20
NMIExceptionVector:
@@ -362,6 +366,32 @@ LoadStoreErrorHandler:
rsr a1, excsave1
rfe
+/*************************** Debug exception handler *************************/
+
+ .section .vecbase.text, "x"
+ .literal_position
+ .balign 4
+
+DebugExceptionHandler:
+ wsr a0, excsave2
+ // Save context in case an actual debugger is running
+ movi a0, debug_saved_ctx
+ // Save a1 - a4 as we are going to use them later
+ s32i a1, a0, 0x04
+ s32i a2, a0, 0x08
+ s32i a3, a0, 0x0C
+ s32i a4, a0, 0x10
+ // Save a0
+ rsr a4, excsave2
+ s32i a4, a0, 0x00
+ // Default handler is fatal_exception_handler(uint32_t * sp, bool registers_saved_on_stack)
+ // sp
+ mov a2, a1
+ // registers_saved_on_stack
+ movi a3, 0
+ call0 debug_exception_handler
+ rfi 2
+
/****************************** call_user_start ******************************/
.section .vecbase.text, "x"
@@ -491,7 +521,15 @@ NMIExceptionHandler:
.balign 4
UserExceptionHandler:
.type UserExceptionHandler, @function
- xsr a0, excsave1 # a0 now contains sp
+ // save a0, a1 to debug_saved_ctx before stack pointer is affected
+ // excsave1 contains a1
+ // a1 was changed earlier
+ movi a1, debug_saved_ctx
+ // store a0
+ s32i a0, a1, 0x00
+ xsr a0, excsave1
+ // store a1
+ s32i a0, a1, 0x04
mov sp, a0
addi sp, sp, -0x50
s32i a0, sp, 0x10
diff --git a/core/include/debug_dumps.h b/core/include/debug_dumps.h
index ab3c972..8b82b84 100644
--- a/core/include/debug_dumps.h
+++ b/core/include/debug_dumps.h
@@ -21,5 +21,7 @@ void dump_heapinfo(void);
Probably not useful to be called in other contexts.
*/
void __attribute__((noreturn)) fatal_exception_handler(uint32_t *sp, bool registers_saved_on_stack);
+void __attribute__((weak, alias("fatal_exception_handler")))
+ debug_exception_handler(uint32_t *sp, bool registers_saved_on_stack);
#endif