Commit57fa6cd

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Soft WDT: detect deliberate infinite loop at Postmortem (esp8266#8918)

A popular method of handling an unrecoverable state is to reboot. The SDK does this in many places by printing a cryptic debug message followed by something equivalent to while(true){}, which compiles down to loop: j loop, creating a Soft WDT reset.

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cores/esp8266
- core_esp8266_postmortem.cpp

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`‎cores/esp8266/core_esp8266_postmortem.cpp‎`

Lines changed: 7 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -181,7 +181,13 @@ static void postmortem_report(uint32_t sp_dump) {`
`181`	`181`	`exccause, epc1, rst_info.epc2, rst_info.epc3, rst_info.excvaddr, rst_info.depc);`
`182`	`182`	`}`
`183`	`183`	`elseif (rst_info.reason == REASON_SOFT_WDT_RST) {`
`184`		`-ets_printf_P(PSTR("\nSoft WDT reset\n"));`
	`184`	`+ets_printf_P(PSTR("\nSoft WDT reset"));`
	`185`	`+constchar infinite_loop[] = {0x06,0xff,0xff };// loop: j loop`
	`186`	`+if (0 ==memcmp_P(infinite_loop, (PGM_VOID_P)rst_info.epc1,3u)) {`
	`187`	`+// The SDK is riddled with these. They are usually preceded by an ets_printf.`
	`188`	`+ets_printf_P(PSTR(" - deliberate infinite loop detected"));`
	`189`	`+ }`
	`190`	`+ets_putc('\n');`
`185`	`191`	`ets_printf_P(PSTR("\nException (%d):\nepc1=0x%08x epc2=0x%08x epc3=0x%08x excvaddr=0x%08x depc=0x%08x\n"),`
`186`	`192`	`rst_info.exccause,/* Address executing at time of Soft WDT level-1 interrupt*/ rst_info.epc1,0,0,0,0);`
`187`	`193`	`}`

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Commit57fa6cd

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`‎cores/esp8266/core_esp8266_postmortem.cpp‎`

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