gdbstub, postmortem: clean up

- Move GDB stub hooks into a separate file, provide header for it
- Use syscall instruction raise user mode exception
- Remove unused code in postmortem.c

fixup

fixup

Author: igrr

cores/esp8266/core_esp8266_main.cpp

@@ -33,6 +33,7 @@ extern "C" {
 #include "cont.h"
 }
 #include <core_version.h>
+#include "gdb_hooks.h"
 
 #define LOOP_TASK_PRIORITY 1
 #define LOOP_QUEUE_SIZE    1
@@ -137,12 +138,6 @@ static void do_global_ctors(void) {
         (*--p)();
 }
 
-extern "C" void __gdb_init() {}
-extern "C" void gdb_init(void) __attribute__ ((weak, alias("__gdb_init")));
-
-extern "C" void __gdb_do_break(){}
-extern "C" void gdb_do_break(void) __attribute__ ((weak, alias("__gdb_do_break")));
-
 void init_done() {
     system_set_os_print(1);
     gdb_init();

cores/esp8266/core_esp8266_postmortem.c

@@ -28,26 +28,24 @@
 #include "esp8266_peri.h"
 #include "cont.h"
 #include "pgmspace.h"
+#include "gdb_hooks.h"
 
 extern void __real_system_restart_local();
-extern void gdb_do_break();
 
 extern cont_t g_cont;
 
 // These will be pointers to PROGMEM const strings
 static const char* s_panic_file = 0;
 static int s_panic_line = 0;
 static const char* s_panic_func = 0;
-
 static bool s_abort_called = false;
 
-void uart_write_char_d(char c);
+void abort() __attribute__((noreturn));
+static void uart_write_char_d(char c);
 static void uart0_write_char_d(char c);
 static void uart1_write_char_d(char c);
 static void print_stack(uint32_t start, uint32_t end);
-//static void print_pcs(uint32_t start, uint32_t end);
-
-bool __attribute((weak)) crash_for_gdb = 0;
+static void raise_exception() __attribute__((noreturn));
 
 extern void __custom_crash_callback( struct rst_info * rst_info, uint32_t stack, uint32_t stack_end ) {
     (void) rst_info;
@@ -66,9 +64,17 @@ static void ets_puts_P(const char *romString) {
 }
 
 void __wrap_system_restart_local() {
-    if (crash_for_gdb) *((int*)0) = 0;
     register uint32_t sp asm("a1");
 
+    if (gdb_present()) {
+        /* When GDBStub is present, exceptions are handled by GDBStub,
+           but Soft WDT will still call this function.
+           Trigger an exception to break into GDB.
+           TODO: check why gdb_do_break() or asm("break.n 0") do not
+           break into GDB here. */
+        raise_exception();
+    }
+
     struct rst_info rst_info = {0};
     system_rtc_mem_read(0, &rst_info, sizeof(rst_info));
     if (rst_info.reason != REASON_SOFT_WDT_RST &&
@@ -129,7 +135,6 @@ void __wrap_system_restart_local() {
 
     ets_printf("sp: %08x end: %08x offset: %04x\n", sp, stack_end, offset);
 
-    // print_pcs(sp + offset, stack_end);
     print_stack(sp + offset, stack_end);
 
     custom_crash_callback( &rst_info, sp + offset, stack_end );
@@ -153,24 +158,7 @@ static void print_stack(uint32_t start, uint32_t end) {
     ets_puts_P(PSTR("<<<stack<<<\n"));
 }
 
-/*
-static void print_pcs(uint32_t start, uint32_t end) {
-    uint32_t n = 0;
-    ets_printf("\n>>>pc>>>\n");
-    for (uint32_t pos = start; pos < end; pos += 16, ++n) {
-        uint32_t* sf = (uint32_t*) pos;
-
-        uint32_t pc_ret = sf[3];
-        uint32_t sp_ret = sf[2];
-        if (pc_ret < 0x40000000 || pc_ret > 0x40f00000 || sp_ret != pos + 16)
-            continue;
-        ets_printf("%08x\n", pc_ret);
-    }
-    ets_printf("<<<pc<<<\n");
-}
-*/
-
-void uart_write_char_d(char c) {
+static void uart_write_char_d(char c) {
     uart0_write_char_d(c);
     uart1_write_char_d(c);
 }
@@ -192,29 +180,30 @@ static void uart1_write_char_d(char c) {
     }
     USF(1) = c;
 }
-void abort() __attribute__((noreturn));
 
-void abort(){
-    // cause exception
+static void raise_exception() {
+    __asm__ __volatile__ ("syscall");
+    while (1); // never reached, needed to satisfy "noreturn" attribute
+}
+
+void abort() {
     s_abort_called = true;
-    do {
-        *((int*)0) = 0;
-    } while(true);
+    raise_exception();
 }
 
 void __assert_func(const char *file, int line, const char *func, const char *what) {
     (void) what;
     s_panic_file = file;
     s_panic_line = line;
     s_panic_func = func;
-    gdb_do_break();
+    gdb_do_break();     /* if GDB is not present, this is a no-op */
 }
 
 void __panic_func(const char* file, int line, const char* func) {
     s_panic_file = file;
     s_panic_line = line;
     s_panic_func = func;
-    gdb_do_break();
-    abort();
+    gdb_do_break();     /* if GDB is not present, this is a no-op */
+    raise_exception();
 }
 

cores/esp8266/gdb_hooks.c

@@ -0,0 +1,36 @@
+/*
+ gdb_hooks.c - Default (no-op) hooks for GDB Stub library
+ Copyright (c) 2018 Ivan Grokhotkov.  All right reserved.
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#include "ets_sys.h"
+#include "gdb_hooks.h"
+
+
+/* gdb_init and gdb_do_break do not return anything, but since the return
+   value is in register, it doesn't hurt to return a bool, so that the
+   same stub can be used for gdb_present. */
+
+bool ICACHE_RAM_ATTR __gdb_no_op()
+{
+    return false;
+}
+
+extern void gdb_init(void) __attribute__ ((weak, alias("__gdb_no_op")));
+extern void gdb_do_break(void) __attribute__ ((weak, alias("__gdb_no_op")));
+extern bool gdb_present(void) __attribute__ ((weak, alias("__gdb_no_op")));
+

cores/esp8266/gdb_hooks.h

@@ -0,0 +1,57 @@
+/*
+ gdb_hooks.h - Hooks for GDB Stub library
+ Copyright (c) 2018 Ivan Grokhotkov.  All right reserved.
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Initialize GDB stub, if present
+ * 
+ * By default, this function is a no-op. When GDBStub library is linked,
+ * this function is overriden and does necessary initialization of that library.
+ * Called early at startup.
+ */
+void gdb_init(void);
+
+/**
+ * @brief Break into GDB, if present
+ * 
+ * By default, this function is a no-op. When GDBStub library is linked,
+ * this function is overriden and triggers entry into the debugger, which
+ * looks like a breakpoint hit.
+ */
+void gdb_do_break(void);
+
+/**
+ * @brief Check if GDB stub is present.
+ * 
+ * By default, this function returns false. When GDBStub library is linked,
+ * this function is overriden and returns true. Can be used to check whether
+ * GDB is used.
+ * 
+ * @return true if GDB stub is present
+ */
+bool gdb_present(void);
+
+#ifdef __cplusplus
+}
+#endif

libraries/GDBStub/src/GDBStub.h

@@ -3,6 +3,4 @@
 
 // this header is intentionally left blank
 
-bool crash_for_gdb = 1;
-
 #endif //GDBSTUB_H

libraries/GDBStub/src/internal/gdbstub.c

@@ -792,5 +792,11 @@ void ATTR_GDBFN gdbstub_do_break_wrapper() {
 	gdbstub_do_break();
 }
 
-extern void gdb_do_break() __attribute__((weak, alias("gdbstub_do_break_wrapper")));
-extern void gdb_init() __attribute__((weak, alias("gdbstub_init")));
+bool ATTR_GDBINIT gdb_present()
+{
+	return true;
+}
+
+extern void gdb_do_break() __attribute__((alias("gdbstub_do_break_wrapper")));
+extern void gdb_init() __attribute__((alias("gdbstub_init")));
+