From ae4f073c40bf677b03826262e6022b4a251fe437 Mon Sep 17 00:00:00 2001 From: Robin Getz Date: Mon, 22 Jun 2009 02:02:16 +0000 Subject: 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: Robin Getz Signed-off-by: Mike Frysinger --- arch/blackfin/mach-common/entry.S | 86 ++++++++++++++++++++++++--------------- 1 file changed, 54 insertions(+), 32 deletions(-) (limited to 'arch/blackfin/mach-common/entry.S') diff --git a/arch/blackfin/mach-common/entry.S b/arch/blackfin/mach-common/entry.S index fb1795d5be2..4c07fcb356a 100644 --- a/arch/blackfin/mach-common/entry.S +++ b/arch/blackfin/mach-common/entry.S @@ -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 -- cgit v1.2.3-70-g09d2