Blackfin arch: add supporting for double fault debug handling (0c7a6b21) · Commits · github.com / kvm-riscv / linux

arch/blackfin/Kconfig.debug

+38 −0

Original line number	Diff line number	Diff line
		@@ -22,6 +22,44 @@ config DEBUG_HWERR
		hardware error interrupts and need to know where they are coming
		from.

		config DEBUG_DOUBLEFAULT
		bool "Debug Double Faults"
		default n
		help
		If an exception is caused while executing code within the exception
		handler, the NMI handler, the reset vector, or in emulator mode,
		a double fault occurs. On the Blackfin, this is a unrecoverable
		event. You have two options:
		- RESET exactly when double fault occurs. The excepting
		instruction address is stored in RETX, where the next kernel
		boot will print it out.
		- Print debug message. This is much more error prone, although
		easier to handle. It is error prone since:
		- The excepting instruction is not committed.
		- All writebacks from the instruction are prevented.
		- The generated exception is not taken.
		- The EXCAUSE field is updated with an unrecoverable event
		The only way to check this is to see if EXCAUSE contains the
		unrecoverable event value at every exception return. By selecting
		this option, you are skipping over the faulting instruction, and
		hoping things stay together enough to print out a debug message.

		This does add a little kernel code, but is the only method to debug
		double faults - if unsure say "Y"

		choice
		prompt "Double Fault Failure Method"
		default DEBUG_DOUBLEFAULT_PRINT
		depends on DEBUG_DOUBLEFAULT

		config DEBUG_DOUBLEFAULT_PRINT
		bool "Print"

		config DEBUG_DOUBLEFAULT_RESET
		bool "Reset"

		endchoice

		config DEBUG_ICACHE_CHECK
		bool "Check Instruction cache coherency"
		depends on DEBUG_KERNEL

arch/blackfin/kernel/setup.c

+20 −10

Original line number	Diff line number	Diff line
		@@ -52,7 +52,8 @@ EXPORT_SYMBOL(mtd_size);
		#endif

		char __initdata command_line[COMMAND_LINE_SIZE];
		unsigned int __initdata *__retx;
		void __initdata init_retx, init_saved_retx, *init_saved_seqstat,
		init_saved_icplb_fault_addr, init_saved_dcplb_fault_addr;

		/* boot memmap, for parsing "memmap=" */
		#define BFIN_MEMMAP_MAX 128 /* number of entries in bfin_memmap */
		@@ -782,16 +783,25 @@ void __init setup_arch(char **cmdline_p)

		_bfin_swrst = bfin_read_SWRST();

		/* If we double fault, reset the system - otherwise we hang forever */
		bfin_write_SWRST(DOUBLE_FAULT);
		#ifdef CONFIG_DEBUG_DOUBLEFAULT_PRINT
		bfin_write_SWRST(_bfin_swrst & ~DOUBLE_FAULT);
		#endif
		#ifdef CONFIG_DEBUG_DOUBLEFAULT_RESET
		bfin_write_SWRST(_bfin_swrst \| DOUBLE_FAULT);
		#endif

		if (_bfin_swrst & RESET_DOUBLE)
		/*
		* don't decode the address, since you don't know if this
		* kernel's symbol map is the same as the crashing kernel
		*/
		printk(KERN_INFO "Recovering from Double Fault event at %pF\n", __retx);
		else if (_bfin_swrst & RESET_WDOG)
		if (_bfin_swrst & RESET_DOUBLE) {
		printk(KERN_EMERG "Recovering from DOUBLE FAULT event\n");
		#ifdef CONFIG_DEBUG_DOUBLEFAULT
		/* We assume the crashing kernel, and the current symbol table match */
		printk(KERN_EMERG " While handling exception (EXCAUSE = 0x%x) at %pF\n",
		(int)init_saved_seqstat & SEQSTAT_EXCAUSE, init_saved_retx);
		printk(KERN_NOTICE " DCPLB_FAULT_ADDR: %pF\n", init_saved_dcplb_fault_addr);
		printk(KERN_NOTICE " ICPLB_FAULT_ADDR: %pF\n", init_saved_icplb_fault_addr);
		#endif
		printk(KERN_NOTICE " The instruction at %pF caused a double exception\n",
		init_retx);
		} else if (_bfin_swrst & RESET_WDOG)
		printk(KERN_INFO "Recovering from Watchdog event\n");
		else if (_bfin_swrst & RESET_SOFTWARE)
		printk(KERN_NOTICE "Reset caused by Software reset\n");

arch/blackfin/kernel/traps.c

+30 −4

Original line number	Diff line number	Diff line
		@@ -68,7 +68,15 @@ void __init trap_init(void)
		CSYNC();
		}

		unsigned long saved_icplb_fault_addr, saved_dcplb_fault_addr;
		/*
		* Used to save the RETX, SEQSTAT, I/D CPLB FAULT ADDR
		* values across the transition from exception to IRQ5.
		* We put these in L1, so they are going to be in a valid
		* location during exception context
		*/
		__attribute__((l1_data))
		unsigned long saved_retx, saved_seqstat,
		saved_icplb_fault_addr, saved_dcplb_fault_addr;

		static void decode_address(char *buf, unsigned long address)
		{
		@@ -186,9 +194,27 @@ asmlinkage void double_fault_c(struct pt_regs *fp)
		console_verbose();
		oops_in_progress = 1;
		printk(KERN_EMERG "\n" KERN_EMERG "Double Fault\n");
		#ifdef CONFIG_DEBUG_DOUBLEFAULT_PRINT
		if (((long)fp->seqstat & SEQSTAT_EXCAUSE) == VEC_UNCOV) {
		char buf[150];
		decode_address(buf, saved_retx);
		printk(KERN_EMERG "While handling exception (EXCAUSE = 0x%x) at %s:\n",
		(int)saved_seqstat & SEQSTAT_EXCAUSE, buf);
		decode_address(buf, saved_dcplb_fault_addr);
		printk(KERN_NOTICE " DCPLB_FAULT_ADDR: %s\n", buf);
		decode_address(buf, saved_icplb_fault_addr);
		printk(KERN_NOTICE " ICPLB_FAULT_ADDR: %s\n", buf);

		decode_address(buf, fp->retx);
		printk(KERN_NOTICE "The instruction at %s caused a double exception\n",
		buf);
		} else
		#endif
		{
		dump_bfin_process(fp);
		dump_bfin_mem(fp);
		show_regs(fp);
		}
		panic("Double Fault - unrecoverable event\n");

		}

arch/blackfin/mach-common/entry.S

+130 −59

Original line number	Diff line number	Diff line
		@@ -129,6 +129,18 @@ ENTRY(_ex_icplb_miss)
		#else
		call __cplb_hdr;
		#endif

		#ifdef CONFIG_DEBUG_DOUBLEFAULT
		/* While we were processing this, did we double fault? */
		r7 = SEQSTAT; /* reason code is in bit 5:0 */
		r6.l = lo(SEQSTAT_EXCAUSE);
		r6.h = hi(SEQSTAT_EXCAUSE);
		r7 = r7 & r6;
		r6 = 0x25;
		CC = R7 == R6;
		if CC JUMP _double_fault;
		#endif

		DEBUG_HWTRACE_RESTORE(p5, r7)
		RESTORE_ALL_SYS
		SP = EX_SCRATCH_REG;
		@@ -136,11 +148,8 @@ ENTRY(_ex_icplb_miss)
		ENDPROC(_ex_icplb_miss)

		ENTRY(_ex_syscall)
		(R7:6,P5:4) = [sp++];
		ASTAT = [sp++];
		raise 15; /* invoked by TRAP #0, for sys call */
		sp = EX_SCRATCH_REG;
		rtx
		jump.s _bfin_return_from_exception;
		ENDPROC(_ex_syscall)

		ENTRY(_ex_soft_bp)
		@@ -250,6 +259,29 @@ ENTRY(_bfin_return_from_exception)
		R7=LC1;
		LC1=R7;
		#endif

		#ifdef CONFIG_DEBUG_DOUBLEFAULT
		/* While we were processing the current exception,
		* did we cause another, and double fault?
		*/
		r7 = SEQSTAT; /* reason code is in bit 5:0 */
		r6.l = lo(SEQSTAT_EXCAUSE);
		r6.h = hi(SEQSTAT_EXCAUSE);
		r7 = r7 & r6;
		r6 = 0x25;
		CC = R7 == R6;
		if CC JUMP _double_fault;

		/* Did we cause a HW error? */
		p5.l = lo(ILAT);
		p5.h = hi(ILAT);
		r6 = [p5];
		r7 = 0x20; /* Did I just cause anther HW error? */
		r7 = r7 & r1;
		CC = R7 == R6;
		if CC JUMP _double_fault;
		#endif

		(R7:6,P5:4) = [sp++];
		ASTAT = [sp++];
		sp = EX_SCRATCH_REG;
		@@ -292,6 +324,14 @@ ENTRY(_ex_trap_c)
		[p4] = p5;
		csync;

		#ifndef CONFIG_DEBUG_DOUBLEFAULT
		/*
		* Save these registers, as they are only valid in exception context
		* (where we are now - as soon as we defer to IRQ5, they can change)
		* DCPLB_STATUS and ICPLB_STATUS are also only valid in EVT3,
		* but they are not very interesting, so don't save them
		*/

		p4.l = lo(DCPLB_FAULT_ADDR);
		p4.h = hi(DCPLB_FAULT_ADDR);
		r7 = [p4];
		@@ -304,12 +344,11 @@ ENTRY(_ex_trap_c)
		p5.l = _saved_icplb_fault_addr;
		[p5] = r7;

		p4.l = _excpt_saved_stuff;
		p4.h = _excpt_saved_stuff;

		r6 = retx;
		p4.l = _saved_retx;
		p4.h = _saved_retx;
		[p4] = r6;

		#endif
		r6 = SYSCFG;
		[p4 + 4] = r6;
		BITCLR(r6, 0);
		@@ -327,11 +366,8 @@ ENTRY(_ex_trap_c)
		r6 = 0x3f;
		sti r6;

		(R7:6,P5:4) = [sp++];
		ASTAT = [sp++];
		SP = EX_SCRATCH_REG;
		raise 5;
		rtx;
		jump.s _bfin_return_from_exception;
		ENDPROC(_ex_trap_c)

		/* We just realized we got an exception, while we were processing a different
		@@ -388,8 +424,8 @@ ENDPROC(_double_fault)
		ENTRY(_exception_to_level5)
		SAVE_ALL_SYS

		p4.l = _excpt_saved_stuff;
		p4.h = _excpt_saved_stuff;
		p4.l = _saved_retx;
		p4.h = _saved_retx;
		r6 = [p4];
		[sp + PT_PC] = r6;

		@@ -420,6 +456,17 @@ ENTRY(_exception_to_level5)
		call _trap_c;
		SP += 12;

		#ifdef CONFIG_DEBUG_DOUBLEFAULT
		/* Grab ILAT */
		p2.l = lo(ILAT);
		p2.h = hi(ILAT);
		r0 = [p2];
		r1 = 0x20; /* Did I just cause anther HW error? */
		r0 = r0 & r1;
		CC = R0 == R1;
		if CC JUMP _double_fault;
		#endif

		call _ret_from_exception;
		RESTORE_ALL_SYS
		rti;
		@@ -436,7 +483,39 @@ ENTRY(_trap) /* Exception: 4th entry into system event table(supervisor mode)*/
		/* Try to deal with syscalls quickly. */
		[--sp] = ASTAT;
		[--sp] = (R7:6,P5:4);

		#ifdef CONFIG_DEBUG_DOUBLEFAULT
		/*
		* Save these registers, as they are only valid in exception context
		* (where we are now - as soon as we defer to IRQ5, they can change)
		* DCPLB_STATUS and ICPLB_STATUS are also only valid in EVT3,
		* but they are not very interesting, so don't save them
		*/

		p4.l = lo(DCPLB_FAULT_ADDR);
		p4.h = hi(DCPLB_FAULT_ADDR);
		r7 = [p4];
		p5.h = _saved_dcplb_fault_addr;
		p5.l = _saved_dcplb_fault_addr;
		[p5] = r7;

		r7 = [p4 + (ICPLB_FAULT_ADDR - DCPLB_FAULT_ADDR)];
		p5.h = _saved_icplb_fault_addr;
		p5.l = _saved_icplb_fault_addr;
		[p5] = r7;

		p4.l = _saved_retx;
		p4.h = _saved_retx;
		r6 = retx;
		[p4] = r6;

		r7 = SEQSTAT; /* reason code is in bit 5:0 */
		p4.l = _saved_seqstat;
		p4.h = _saved_seqstat;
		[p4] = r7;
		#else
		r7 = SEQSTAT; /* reason code is in bit 5:0 */
		#endif
		r6.l = lo(SEQSTAT_EXCAUSE);
		r6.h = hi(SEQSTAT_EXCAUSE);
		r7 = r7 & r6;
		@@ -1432,15 +1511,7 @@ ENTRY(_sys_call_table)
		.rept NR_syscalls-(.-_sys_call_table)/4
		.long _sys_ni_syscall
		.endr

		/*
		* Used to save the real RETX, IMASK and SYSCFG when temporarily
		* storing safe values across the transition from exception to IRQ5.
		*/
		_excpt_saved_stuff:
		.long 0;
		.long 0;
		.long 0;
		END(_sys_call_table)

		_exception_stack:
		.rept 1024

arch/blackfin/mach-common/head.S

+37 −3

Original line number	Diff line number	Diff line
		@@ -90,12 +90,46 @@ ENTRY(__start)
		[p0] = R0;
		SSYNC;

		/* Save RETX, in case of doublefault */
		p0.l = ___retx;
		p0.h = ___retx;
		/* in case of double faults, save a few things */
		p0.l = _init_retx;
		p0.h = _init_retx;
		R0 = RETX;
		[P0] = R0;

		#ifdef CONFIG_DEBUG_DOUBLEFAULT
		/* Only save these if we are storing them,
		* This happens here, since L1 gets clobbered
		* below
		*/
		p0.l = _saved_retx;
		p0.h = _saved_retx;
		p1.l = _init_saved_retx;
		p1.h = _init_saved_retx;
		r0 = [p0];
		[p1] = r0;

		p0.l = _saved_dcplb_fault_addr;
		p0.h = _saved_dcplb_fault_addr;
		p1.l = _init_saved_dcplb_fault_addr;
		p1.h = _init_saved_dcplb_fault_addr;
		r0 = [p0];
		[p1] = r0;

		p0.l = _saved_icplb_fault_addr;
		p0.h = _saved_icplb_fault_addr;
		p1.l = _init_saved_icplb_fault_addr;
		p1.h = _init_saved_icplb_fault_addr;
		r0 = [p0];
		[p1] = r0;

		p0.l = _saved_seqstat;
		p0.h = _saved_seqstat;
		p1.l = _init_saved_seqstat;
		p1.h = _init_saved_seqstat;
		r0 = [p0];
		[p1] = r0;
		#endif

		/* Initialize stack pointer */
		sp.l = lo(INITIAL_STACK);
		sp.h = hi(INITIAL_STACK);