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Date: Mon, 6 Jul 2015 16:32:43 +0300 From: Max Filippov <jcmvbkbc@...il.com> To: linux-xtensa@...ux-xtensa.org, linux-kernel@...r.kernel.org Cc: Chris Zankel <chris@...kel.net>, Marc Gauthier <marc@...ence.com>, Max Filippov <jcmvbkbc@...il.com> Subject: [PATCH 2/8] xtensa: keep exception/interrupt stack continuous Restore original a0 in the kernel exception stack frame. This way it looks like the frame that got interrupt/exception did alloca (copy a0 and a1 potentially spilled under old stack to the new location as well) to save registers and then did a call to handler. The point where interrupt/exception was taken is not in the stack chain, only in pt_regs (call4 from that address can be simulated to keep it in the stack trace). Signed-off-by: Max Filippov <jcmvbkbc@...il.com> --- arch/xtensa/kernel/entry.S | 60 +++++++++++++++++++++++++++------------------- 1 file changed, 35 insertions(+), 25 deletions(-) diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S index 82bbfa5..ab6a857 100644 --- a/arch/xtensa/kernel/entry.S +++ b/arch/xtensa/kernel/entry.S @@ -218,7 +218,7 @@ _user_exception: /* We are back to the original stack pointer (a1) */ 2: /* Now, jump to the common exception handler. */ - + movi a0, 0 # terminate user stack trace with 0 j common_exception ENDPROC(user_exception) @@ -264,6 +264,19 @@ ENTRY(kernel_exception) .globl _kernel_exception _kernel_exception: + /* Copy spill slots of a0 and a1 to imitate movsp + * in order to keep exception stack continuous + */ + l32i a0, a1, PT_AREG1 + addi a2, a1, -16 + addi a0, a0, -16 + l32i a3, a0, 0 + l32i a0, a0, 4 + s32i a3, a2, 0 + s32i a0, a2, 4 + + l32i a0, a1, PT_AREG0 # restore saved a0 + /* Save SAR and turn off single stepping */ movi a2, 0 @@ -338,52 +351,50 @@ common_exception: xsr a2, lcount s32i a2, a1, PT_LCOUNT - /* It is now save to restore the EXC_TABLE_FIXUP variable. */ + /* It is now safe to restore the EXC_TABLE_FIXUP variable. */ - rsr a0, exccause movi a3, 0 rsr a2, excsave1 - s32i a0, a1, PT_EXCCAUSE s32i a3, a2, EXC_TABLE_FIXUP - /* All unrecoverable states are saved on stack, now, and a1 is valid, - * so we can allow exceptions and interrupts (*) again. - * Set PS(EXCM = 0, UM = 0, RING = 0, OWB = 0, WOE = 1, INTLEVEL = X) + /* Save remaining unrecoverable states (exccause, ps) on stack. + * Now we can allow exceptions again. In case we've got an interrupt + * PS.INTLEVEL is set to LOCKLEVEL disabling furhter interrupts, + * otherwise it's left unchanged. * - * (*) We only allow interrupts if they were previously enabled and - * we're not handling an IRQ + * Set PS(EXCM = 0, UM = 0, RING = 0, OWB = 0, WOE = 1, INTLEVEL = X) */ rsr a3, ps - addi a0, a0, -EXCCAUSE_LEVEL1_INTERRUPT - movi a2, LOCKLEVEL + movi a2, (1 << PS_WOE_BIT) extui a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH - # a3 = PS.INTLEVEL - moveqz a3, a2, a0 # a3 = LOCKLEVEL iff interrupt - movi a2, 1 << PS_WOE_BIT or a3, a3, a2 - rsr a0, exccause - xsr a3, ps + rsr a2, exccause + bnei a2, EXCCAUSE_LEVEL1_INTERRUPT, 1f + movi a3, (1 << PS_WOE_BIT) | LOCKLEVEL +1: + xsr a3, ps + s32i a2, a1, PT_EXCCAUSE s32i a3, a1, PT_PS # save ps /* Save lbeg, lend */ - rsr a2, lbeg + rsr a4, lbeg rsr a3, lend - s32i a2, a1, PT_LBEG + s32i a4, a1, PT_LBEG s32i a3, a1, PT_LEND /* Save SCOMPARE1 */ #if XCHAL_HAVE_S32C1I - rsr a2, scompare1 - s32i a2, a1, PT_SCOMPARE1 + rsr a3, scompare1 + s32i a3, a1, PT_SCOMPARE1 #endif /* Save optional registers. */ - save_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT + save_xtregs_opt a1 a3 a4 a5 a6 a7 PT_XTREGS_OPT #ifdef CONFIG_TRACE_IRQFLAGS l32i a4, a1, PT_DEPC @@ -391,8 +402,7 @@ common_exception: * while PS.EXCM was set, i.e. interrupts disabled. */ bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f - l32i a4, a1, PT_EXCCAUSE - bnei a4, EXCCAUSE_LEVEL1_INTERRUPT, 1f + bnei a2, EXCCAUSE_LEVEL1_INTERRUPT, 1f /* We came here with an interrupt means interrupts were enabled * and we've just disabled them. */ @@ -407,8 +417,8 @@ common_exception: rsr a4, excsave1 mov a6, a1 # pass stack frame - mov a7, a0 # pass EXCCAUSE - addx4 a4, a0, a4 + mov a7, a2 # pass EXCCAUSE + addx4 a4, a2, a4 l32i a4, a4, EXC_TABLE_DEFAULT # load handler /* Call the second-level handler */ -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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