CONT stack overflow postmortem

check in cont_run() and cont_suspend() whether a1 points after cont_t::stack[0]
in case a1 is broken, postmortem will still report proper context in proper stack boundaries. previously it used sys ctx values

additionally

as suggested in https://github.com/esp8266/Arduino/issues/9069, change stack smashing to a single line that does not mention any Exceptions
reduce overall stack dump length when there are know garbage values i.e. cont stackguard
decoder.py addr search regexp should no longer skip stack lines ending with ' <'
update decoder.py parsing so it notices both stack smashing and alloc errors

Noticed in esp-idf cfg as CONFIG_FREERTOS_CHECK_STACKOVERFLOW_PTRVAL=y, where Freertos it is a so called 'Method 1' of overflow checking happening right before ctx switch https://www.freertos.org/Stacks-and-stack-overflow-checking.html (also ref. #8666)

simple example like this one usually already offsets a1 when yield() happens, so the newly added check would cause a reset

#include <Arduino.h>

void setup() {
  Serial.begin(115200);
}

void loop() {
  int buf[1048]; // oops
  yield();
  printf("%p %p %p %p\n",
    &buf[0], &buf[1], &buf[2], &buf[3]);
}

and it should generate more useful info as the result

Stack overflow detected
sp: 3fffef28 end: 3fffffd0 offset: 0000

ctx: cont
0x4010015c: ets_post at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/core_esp8266_main.cpp:243
0x402017f5: esp_suspend_within_cont at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/core_esp8266_main.cpp:121
(inlined by) __yield at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/core_esp8266_main.cpp:193
0x40201052: loop at /home/runner/dev/stack_overflow_test/src/main.cpp:10
0x402016da: loop_task(ETSEventTag*) at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/core_esp8266_main.cpp:279
0x40105245: call_user_start_local at ??:?
0x4010524b: call_user_start_local at ??:?
0x4010000d: call_user_start at ??:?
0x401000ab: app_entry_redefinable at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/core_esp8266_main.cpp:391
0x40225e1e: cont_ret at cont.S.o:?
0x40202761: uart_flush at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/uart.cpp:583
0x401009d8: malloc at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/umm_malloc/umm_malloc.cpp:914
0x40202ab0: uart_init at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/uart.cpp:715
0x402029d6: uart_init at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/uart.cpp:707
0x40202c2c: uart_set_debug at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/uart.cpp:989
0x402012b0: HardwareSerial::begin(unsigned long, SerialConfig, SerialMode, unsigned char, bool) at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/HardwareSerial.cpp:56
0x402018b0: loop_wrapper() at /home/runner/.platformio/packages/framework-arduinoespressif8266@src-31d658a59f41540201fc3726a1394910/cores/esp8266/core_esp8266_main.cpp:263
0x40100d4d: cont_wrapper at ??:?

0x40201052: loop at /home/runner/dev/stack_overflow_test/src/main.cpp:10

> sed -ne 10p src/main.cpp
  printf("%p %p %p %p\n",

esp8266 / Arduino

CONT stack overflow postmortem #9083