Blackfin arch: add supporting for double fault debug handling
Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
diff --git a/arch/blackfin/Kconfig.debug b/arch/blackfin/Kconfig.debug
index c468624..0afa898 100644
--- a/arch/blackfin/Kconfig.debug
+++ b/arch/blackfin/Kconfig.debug
@@ -22,6 +22,44 @@
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
diff --git a/arch/blackfin/kernel/setup.c b/arch/blackfin/kernel/setup.c
index 7a82d10..8e639dc 100644
--- a/arch/blackfin/kernel/setup.c
+++ b/arch/blackfin/kernel/setup.c
@@ -52,7 +52,8 @@
#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 @@
_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");
diff --git a/arch/blackfin/kernel/traps.c b/arch/blackfin/kernel/traps.c
index fd24e04..bd41fca 100644
--- a/arch/blackfin/kernel/traps.c
+++ b/arch/blackfin/kernel/traps.c
@@ -68,7 +68,15 @@
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 @@
console_verbose();
oops_in_progress = 1;
printk(KERN_EMERG "\n" KERN_EMERG "Double Fault\n");
- dump_bfin_process(fp);
- dump_bfin_mem(fp);
- show_regs(fp);
+#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");
}
diff --git a/arch/blackfin/mach-common/entry.S b/arch/blackfin/mach-common/entry.S
index 847c172..90c7397 100644
--- a/arch/blackfin/mach-common/entry.S
+++ b/arch/blackfin/mach-common/entry.S
@@ -129,6 +129,18 @@
#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 @@
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 @@
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 @@
[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 @@
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);
@@ -327,59 +366,56 @@
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
* exception. This is a unrecoverable event, so crash
*/
ENTRY(_double_fault)
- /* Turn caches & protection off, to ensure we don't get any more
- * double exceptions
- */
+ /* Turn caches & protection off, to ensure we don't get any more
+ * double exceptions
+ */
- P4.L = LO(IMEM_CONTROL);
- P4.H = HI(IMEM_CONTROL);
+ P4.L = LO(IMEM_CONTROL);
+ P4.H = HI(IMEM_CONTROL);
- R5 = [P4]; /* Control Register*/
- BITCLR(R5,ENICPLB_P);
- SSYNC; /* SSYNC required before writing to IMEM_CONTROL. */
- .align 8;
- [P4] = R5;
- SSYNC;
+ R5 = [P4]; /* Control Register*/
+ BITCLR(R5,ENICPLB_P);
+ SSYNC; /* SSYNC required before writing to IMEM_CONTROL. */
+ .align 8;
+ [P4] = R5;
+ SSYNC;
- P4.L = LO(DMEM_CONTROL);
- P4.H = HI(DMEM_CONTROL);
- R5 = [P4];
- BITCLR(R5,ENDCPLB_P);
- SSYNC; /* SSYNC required before writing to DMEM_CONTROL. */
- .align 8;
- [P4] = R5;
- SSYNC;
+ P4.L = LO(DMEM_CONTROL);
+ P4.H = HI(DMEM_CONTROL);
+ R5 = [P4];
+ BITCLR(R5,ENDCPLB_P);
+ SSYNC; /* SSYNC required before writing to DMEM_CONTROL. */
+ .align 8;
+ [P4] = R5;
+ SSYNC;
- /* Fix up the stack */
- (R7:6,P5:4) = [sp++];
- ASTAT = [sp++];
- SP = EX_SCRATCH_REG;
+ /* Fix up the stack */
+ (R7:6,P5:4) = [sp++];
+ ASTAT = [sp++];
+ SP = EX_SCRATCH_REG;
- /* We should be out of the exception stack, and back down into
- * kernel or user space stack
- */
- SAVE_ALL_SYS
+ /* We should be out of the exception stack, and back down into
+ * kernel or user space stack
+ */
+ SAVE_ALL_SYS
/* The dumping functions expect the return address in the RETI
* slot. */
r6 = retx;
[sp + PT_PC] = r6;
- r0 = sp; /* stack frame pt_regs pointer argument ==> r0 */
- SP += -12;
- call _double_fault_c;
- SP += 12;
+ r0 = sp; /* stack frame pt_regs pointer argument ==> r0 */
+ SP += -12;
+ call _double_fault_c;
+ SP += 12;
.L_double_fault_panic:
JUMP .L_double_fault_panic
@@ -388,8 +424,8 @@
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 @@
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 @@
/* 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 @@
.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
diff --git a/arch/blackfin/mach-common/head.S b/arch/blackfin/mach-common/head.S
index 191b4e9..7cb21cf 100644
--- a/arch/blackfin/mach-common/head.S
+++ b/arch/blackfin/mach-common/head.S
@@ -90,12 +90,46 @@
[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);