Fix exception handler, add assert, reduce RAM (esp8266#4187)

Move all exception strings to IRAM and out of both PMEM (illegal) and add
output of any assert() failinf conditions.

The exception handler may be called while the SPI interface is in a bad
state.  This means no PROGMEM reads are allowed, and all data and functions
used must be in system RAM or IRAM.

Add a new helper macro, ets_printf_P(), which places a constant string in
IRAM and copies it to the stack before calling the real ets_printf().
This makes the code simpler to read as no unwieldy combinations of
ets_putc/ets_printf/... are required to output anything.

The old handler also mistakenly used PSTR() strings in some places, so
fix those with this patch as well.

Gives back ~180 bytes of heap to every sketch built as the exception handler
is always included an application.

cores/esp8266/core_esp8266_postmortem.c

@@ -38,6 +38,8 @@ extern cont_t g_cont;
 static const char* s_panic_file = 0;
 static int s_panic_line = 0;
 static const char* s_panic_func = 0;
+static const char* s_panic_what = 0;
+
 static bool s_abort_called = false;
 
 void abort() __attribute__((noreturn));
@@ -60,12 +62,28 @@ extern void __custom_crash_callback( struct rst_info * rst_info, uint32_t stack,
 
 extern void custom_crash_callback( struct rst_info * rst_info, uint32_t stack, uint32_t stack_end ) __attribute__ ((weak, alias("__custom_crash_callback")));
 
-static void ets_puts_P(const char *romString) {
-    char c = pgm_read_byte(romString++);
-    while (c) {
-        ets_putc(c);
-        c = pgm_read_byte(romString++);
-    }
+// Single, non-inlined copy of pgm_read_byte to save IRAM space (as this is not timing critical)
+static char ICACHE_RAM_ATTR iram_read_byte (const char *addr) {
+    return pgm_read_byte(addr);
+}
+
+// Required to output the s_panic_file, it's stored in PMEM
+#define ets_puts_P(pstr) \
+{ \
+    char c; \
+    do { \
+        c = iram_read_byte(pstr++); \
+        if (c) ets_putc(c); \
+    } while (c); \
+}
+
+// Place these strings in .text because the SPI interface may be in bad shape during an exception.
+#define ets_printf_P(str, ...) \
+{ \
+    static const char istr[] ICACHE_RAM_ATTR = (str); \
+    char mstr[sizeof(str)]; \
+    for (size_t i=0; i < sizeof(str); i++) mstr[i] = iram_read_byte(&istr[i]); \
+    ets_printf(mstr, ##__VA_ARGS__); \
 }
 
 void __wrap_system_restart_local() {
@@ -92,21 +110,25 @@ void __wrap_system_restart_local() {
     ets_install_putc1(&uart_write_char_d);
 
     if (s_panic_line) {
-        ets_puts_P(PSTR("\nPanic "));
-        ets_puts_P(s_panic_file);
-        ets_printf(":%d ", s_panic_line);
-        ets_puts_P(s_panic_func);
-        ets_puts_P(PSTR("\n"));
+        ets_printf_P("\nPanic ");
+        ets_puts_P(s_panic_file); // This is in PROGMEM, need special output because ets_printf can't handle ROM parameters
+        ets_printf_P(":%d %s", s_panic_line, s_panic_func);
+        if (s_panic_what) {
+            ets_printf_P(": Assertion '");
+            ets_puts_P(s_panic_what); // This is also in PMEM
+            ets_printf_P("' failed.");
+        }
+        ets_putc('\n');
     }
     else if (s_abort_called) {
-        ets_puts_P(PSTR("Abort called\n"));
+        ets_printf_P("\nAbort called\n");
     }
     else if (rst_info.reason == REASON_EXCEPTION_RST) {
-        ets_printf("\nException (%d):\nepc1=0x%08x epc2=0x%08x epc3=0x%08x excvaddr=0x%08x depc=0x%08x\n",
+        ets_printf_P("\nException (%d):\nepc1=0x%08x epc2=0x%08x epc3=0x%08x excvaddr=0x%08x depc=0x%08x\n",
             rst_info.exccause, rst_info.epc1, rst_info.epc2, rst_info.epc3, rst_info.excvaddr, rst_info.depc);
     }
     else if (rst_info.reason == REASON_SOFT_WDT_RST) {
-        ets_puts_P(PSTR("\nSoft WDT reset\n"));
+        ets_printf_P("\nSoft WDT reset\n");
     }
 
     uint32_t cont_stack_start = (uint32_t) &(g_cont.stack);
@@ -128,17 +150,17 @@ void __wrap_system_restart_local() {
     }
 
     if (sp > cont_stack_start && sp < cont_stack_end) {
-        ets_puts_P(PSTR("\nctx: cont \n"));
+        ets_printf_P("\nctx: cont \n");
         stack_end = cont_stack_end;
     }
     else {
-        ets_puts_P(("\nctx: sys \n"));
+        ets_printf_P("\nctx: sys \n");
         stack_end = 0x3fffffb0;
         // it's actually 0x3ffffff0, but the stuff below ets_run
         // is likely not really relevant to the crash
     }
 
-    ets_printf("sp: %08x end: %08x offset: %04x\n", sp, stack_end, offset);
+    ets_printf_P("sp: %08x end: %08x offset: %04x\n", sp, stack_end, offset);
 
     print_stack(sp + offset, stack_end);
 
@@ -154,18 +176,18 @@ void __wrap_system_restart_local() {
 }
 
 
-static void print_stack(uint32_t start, uint32_t end) {
-    ets_puts_P(PSTR("\n>>>stack>>>\n"));
+static void ICACHE_RAM_ATTR print_stack(uint32_t start, uint32_t end) {
+    ets_printf_P("\n>>>stack>>>\n");
     for (uint32_t pos = start; pos < end; pos += 0x10) {
         uint32_t* values = (uint32_t*)(pos);
 
         // rough indicator: stack frames usually have SP saved as the second word
         bool looksLikeStackFrame = (values[2] == pos + 0x10);
 
-        ets_printf("%08x:  %08x %08x %08x %08x %c\n",
+        ets_printf_P("%08x:  %08x %08x %08x %08x %c\n",
             pos, values[0], values[1], values[2], values[3], (looksLikeStackFrame)?'<':' ');
     }
-    ets_puts_P(PSTR("<<<stack<<<\n"));
+    ets_printf_P("<<<stack<<<\n");
 }
 
 static void uart_write_char_d(char c) {
@@ -202,10 +224,10 @@ void abort() {
 }
 
 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;
+    s_panic_what = what;
     gdb_do_break();     /* if GDB is not present, this is a no-op */
     raise_exception();
 }
@@ -214,6 +236,7 @@ void __panic_func(const char* file, int line, const char* func) {
     s_panic_file = file;
     s_panic_line = line;
     s_panic_func = func;
+    s_panic_what = 0;
     gdb_do_break();     /* if GDB is not present, this is a no-op */
     raise_exception();
 }

tools/sdk/libc/xtensa-lx106-elf/include/assert.h

@@ -15,7 +15,7 @@ extern "C" {
 # define assert(__e) ((void)0)
 #else
 # define assert(__e) ((__e) ? (void)0 : __assert_func (PSTR(__FILE__), __LINE__, \
-						       __ASSERT_FUNC, #__e))
+						       __ASSERT_FUNC, PSTR(#__e)))
 
 # ifndef __ASSERT_FUNC
   /* Use g++'s demangled names in C++.  */