Commit ae4f073c authored by Robin Getz's avatar Robin Getz Committed by Mike Frysinger
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Blackfin: make EVT3->EVT5 lowering more robust wrt IPEND[4] 



We handle many exceptions at EVT5 (hardware error level) so that we can
catch exceptions in our exception handling code.  Today - if the global
interrupt enable bit (IPEND[4]) is set (interrupts disabled) our trap
handling code goes into a infinite loop, since we need interrupts to be
on to defer things to EVT5.

Normal kernel code should not trigger this for any reason as IPEND[4] gets
cleared early (when doing an interrupt context save) and the kernel stack
there should be sane (or something much worse is happening in the system).
But there have been a few times where this has happened, so this change
makes sure we dump a proper crash message even when things have gone south.

Signed-off-by: default avatarRobin Getz <robin.getz@analog.com>
Signed-off-by: default avatarMike Frysinger <vapier@gentoo.org>
parent d4b834c1

arch/blackfin/include/asm/pda.h

+1 −0
Original line number Diff line number Diff line
@@ -50,6 +50,7 @@ struct blackfin_pda { /* Per-processor Data Area */ 
	unsigned long ex_optr;

	unsigned long ex_buf[4];

	unsigned long ex_imask;		/* Saved imask from exception */

	unsigned long ex_ipend;		/* Saved IPEND from exception */

	unsigned long *ex_stack;	/* Exception stack space */



#ifdef ANOMALY_05000261

arch/blackfin/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -145,6 +145,7 @@ int main(void) 
	DEFINE(PDA_EXBUF, offsetof(struct blackfin_pda, ex_buf));

	DEFINE(PDA_EXIMASK, offsetof(struct blackfin_pda, ex_imask));

	DEFINE(PDA_EXSTACK, offsetof(struct blackfin_pda, ex_stack));

	DEFINE(PDA_EXIPEND, offsetof(struct blackfin_pda, ex_ipend));

#ifdef ANOMALY_05000261

	DEFINE(PDA_LFRETX, offsetof(struct blackfin_pda, last_cplb_fault_retx));

#endif

arch/blackfin/kernel/traps.c

+10 −9
Original line number Diff line number Diff line
@@ -267,11 +267,6 @@ asmlinkage void trap_c(struct pt_regs *fp) 
	 * double faults if the stack has become corrupt

	 */



#ifndef CONFIG_KGDB

	/* IPEND is skipped if KGDB isn't enabled (see entry code) */

	fp->ipend = bfin_read_IPEND();

#endif



	/* trap_c() will be called for exceptions. During exceptions

	 * processing, the pc value should be set with retx value.

	 * With this change we can cleanup some code in signal.c- TODO
@@ -1116,10 +1111,16 @@ void show_regs(struct pt_regs *fp) 


	verbose_printk(KERN_NOTICE "%s", linux_banner);



	verbose_printk(KERN_NOTICE "\nSEQUENCER STATUS:\t\t%s\n",

		       print_tainted());

	verbose_printk(KERN_NOTICE " SEQSTAT: %08lx  IPEND: %04lx  SYSCFG: %04lx\n",

		       (long)fp->seqstat, fp->ipend, fp->syscfg);

	verbose_printk(KERN_NOTICE "\nSEQUENCER STATUS:\t\t%s\n", print_tainted());

	verbose_printk(KERN_NOTICE " SEQSTAT: %08lx  IPEND: %04lx  IMASK: %04lx  SYSCFG: %04lx\n",

		(long)fp->seqstat, fp->ipend, cpu_pda[smp_processor_id()].ex_imask, fp->syscfg);

	if (fp->ipend & EVT_IRPTEN)

		verbose_printk(KERN_NOTICE "  Global Interrupts Disabled (IPEND[4])\n");

	if (!(cpu_pda[smp_processor_id()].ex_imask & (EVT_IVG13 | EVT_IVG12 | EVT_IVG11 |

			EVT_IVG10 | EVT_IVG9 | EVT_IVG8 | EVT_IVG7 | EVT_IVTMR)))

		verbose_printk(KERN_NOTICE "  Peripheral interrupts masked off\n");

	if (!(cpu_pda[smp_processor_id()].ex_imask & (EVT_IVG15 | EVT_IVG14)))

		verbose_printk(KERN_NOTICE "  Kernel interrupts masked off\n");

	if ((fp->seqstat & SEQSTAT_EXCAUSE) == VEC_HWERR) {

		verbose_printk(KERN_NOTICE "  HWERRCAUSE: 0x%lx\n",

			(fp->seqstat & SEQSTAT_HWERRCAUSE) >> 14);

arch/blackfin/mach-common/entry.S

+54 −32
Original line number Diff line number Diff line
@@ -301,25 +301,31 @@ ENTRY(_ex_replaceable) 
	nop;



ENTRY(_ex_trap_c)

	/* The only thing that has been saved in this context is

	 * (R7:6,P5:4), ASTAT & SP - don't use anything else

	 */



	GET_PDA(p5, r6);



	/* Make sure we are not in a double fault */

	p4.l = lo(IPEND);

	p4.h = hi(IPEND);

	r7 = [p4];

	CC = BITTST (r7, 5);

	if CC jump _double_fault;

	[p5 + PDA_EXIPEND] = r7;



	/* Call C code (trap_c) to handle the exception, which most

	 * likely involves sending a signal to the current process.

	 * To avoid double faults, lower our priority to IRQ5 first.

	 */

	P5.h = _exception_to_level5;

	P5.l = _exception_to_level5;

	r7.h = _exception_to_level5;

	r7.l = _exception_to_level5;

	p4.l = lo(EVT5);

	p4.h = hi(EVT5);

	[p4] = p5;

	[p4] = r7;

	csync;



	GET_PDA(p5, r6);

#ifndef CONFIG_DEBUG_DOUBLEFAULT



	/*
@@ -349,8 +355,7 @@ ENTRY(_ex_trap_c) 
	BITCLR(r6, SYSCFG_SSSTEP_P);

	SYSCFG = r6;



	/* Disable all interrupts, but make sure level 5 is enabled so

	 * we can switch to that level.  Save the old mask.  */

	/* Save the current IMASK, since we change in order to jump to level 5 */

	cli r6;

	[p5 + PDA_EXIMASK] = r6;
@@ -358,9 +363,21 @@ ENTRY(_ex_trap_c) 
	p4.h = hi(SAFE_USER_INSTRUCTION);

	retx = p4;



	/* Disable all interrupts, but make sure level 5 is enabled so

	 * we can switch to that level.

	 */

	r6 = 0x3f;

	sti r6;



	/* In case interrupts are disabled IPEND[4] (global interrupt disable bit)

	 * clear it (re-enabling interrupts again) by the special sequence of pushing

	 * RETI onto the stack.  This way we can lower ourselves to IVG5 even if the

	 * exception was taken after the interrupt handler was called but before it

	 * got a chance to enable global interrupts itself.

	 */

	[--sp] = reti;

	sp += 4;



	raise 5;

	jump.s _bfin_return_from_exception;

ENDPROC(_ex_trap_c)
@@ -420,47 +437,52 @@ ENDPROC(_double_fault) 
ENTRY(_exception_to_level5)

	SAVE_ALL_SYS



	GET_PDA(p4, r7);        /* Fetch current PDA */

	r6 = [p4 + PDA_RETX];

	GET_PDA(p5, r7);        /* Fetch current PDA */

	r6 = [p5 + PDA_RETX];

	[sp + PT_PC] = r6;



	r6 = [p4 + PDA_SYSCFG];

	r6 = [p5 + PDA_SYSCFG];

	[sp + PT_SYSCFG] = r6;



	/* Restore interrupt mask.  We haven't pushed RETI, so this

	 * doesn't enable interrupts until we return from this handler.  */

	r6 = [p4 + PDA_EXIMASK];

	sti r6;



	/* Restore the hardware error vector.  */

	P5.h = _evt_ivhw;

	P5.l = _evt_ivhw;

	r7.h = _evt_ivhw;

	r7.l = _evt_ivhw;

	p4.l = lo(EVT5);

	p4.h = hi(EVT5);

	[p4] = p5;

	[p4] = r7;

	csync;



	p2.l = lo(IPEND);

	p2.h = hi(IPEND);

	csync;

	r0 = [p2];              /* Read current IPEND */

	[sp + PT_IPEND] = r0;   /* Store IPEND */

#ifdef CONFIG_DEBUG_DOUBLEFAULT

	/* Now that we have the hardware error vector programmed properly

	 * we can re-enable interrupts (IPEND[4]), so if the _trap_c causes

	 * another hardware error, we can catch it (self-nesting).

	 */

	[--sp] = reti;

	sp += 4;

#endif



	r7 = [p5 + PDA_EXIPEND]	/* Read the IPEND from the Exception state */

	[sp + PT_IPEND] = r7;   /* Store IPEND onto the stack */



	r0 = sp; 	/* stack frame pt_regs pointer argument ==> r0 */

	SP += -12;

	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

	/* If interrupts were off during the exception (IPEND[4] = 1), turn them off

	 * before we return.

	 */

	CC = BITTST(r7, EVT_IRPTEN_P)

	if !CC jump 1f;

	/* this will load a random value into the reti register - but that is OK,

	 * since we do restore it to the correct value in the 'RESTORE_ALL_SYS' macro

	 */

	sp += -4;

	reti = [sp++];

1:

	/* restore the interrupt mask (IMASK) */

	r6 = [p5 + PDA_EXIMASK];

	sti r6;



	call _ret_from_exception;

	RESTORE_ALL_SYS

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