Instead of emulating movsp instruction in the kernel use window underflow handler to load missing register window and retry failed movsp. Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx> --- arch/xtensa/kernel/entry.S | 192 +++++++++---------------------------------- 1 files changed, 40 insertions(+), 152 deletions(-) diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S index ab025c1..de1dfa1 100644 --- a/arch/xtensa/kernel/entry.S +++ b/arch/xtensa/kernel/entry.S @@ -31,7 +31,6 @@ /* Unimplemented features. */ #undef KERNEL_STACK_OVERFLOW_CHECK -#undef ALLOCA_EXCEPTION_IN_IRAM /* Not well tested. * @@ -819,11 +818,27 @@ ENDPROC(unrecoverable_exception) * * The ALLOCA handler is entered when user code executes the MOVSP * instruction and the caller's frame is not in the register file. - * In this case, the caller frame's a0..a3 are on the stack just - * below sp (a1), and this handler moves them. * - * For "MOVSP <ar>,<as>" without destination register a1, this routine - * simply moves the value from <as> to <ar> without moving the save area. + * This algorithm was taken from the Ross Morley's RTOS Porting Layer: + * + * /home/ross/rtos/porting/XtensaRTOS-PortingLayer-20090507/xtensa_vectors.S + * + * It leverages the existing window spill/fill routines and their support for + * double exceptions. The 'movsp' instruction will only cause an exception if + * the next window needs to be loaded. In fact this ALLOCA exception may be + * replaced at some point by changing the hardware to do a underflow exception + * of the proper size instead. + * + * This algorithm simply backs out the register changes started by the user + * excpetion handler, makes it appear that we have started a window underflow + * by rotating the window back and then setting the old window base (OWB) in + * the 'ps' register with the rolled back window base. The 'movsp' instruction + * will be re-executed and this time since the next window frames is in the + * active AR registers it won't cause an exception. + * + * If the WindowUnderflow code gets a TLB miss the page will get mapped + * the the partial windeowUnderflow will be handeled in the double exception + * handler. * * Entry condition: * @@ -838,155 +853,28 @@ ENDPROC(unrecoverable_exception) * < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception */ -#if XCHAL_HAVE_BE -#define _EXTUI_MOVSP_SRC(ar) extui ar, ar, 4, 4 -#define _EXTUI_MOVSP_DST(ar) extui ar, ar, 0, 4 -#else -#define _EXTUI_MOVSP_SRC(ar) extui ar, ar, 0, 4 -#define _EXTUI_MOVSP_DST(ar) extui ar, ar, 4, 4 -#endif - ENTRY(fast_alloca) + rsr a0, windowbase + rotw -1 + rsr a2, ps + extui a3, a2, PS_OWB_SHIFT, PS_OWB_WIDTH + xor a3, a3, a4 + l32i a4, a6, PT_AREG0 + l32i a1, a6, PT_DEPC + rsr a6, depc + wsr a1, depc + slli a3, a3, PS_OWB_SHIFT + xor a2, a2, a3 + wsr a2, ps + rsync - /* We shouldn't be in a double exception. */ - - l32i a0, a2, PT_DEPC - _bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lunhandled_double - - rsr a0, depc # get a2 - s32i a4, a2, PT_AREG4 # save a4 and - s32i a3, a2, PT_AREG3 - s32i a0, a2, PT_AREG2 # a2 to stack - - /* Exit critical section. */ - - movi a0, 0 - rsr a3, excsave1 - s32i a0, a3, EXC_TABLE_FIXUP - - rsr a4, epc1 # get exception address - -#ifdef ALLOCA_EXCEPTION_IN_IRAM -#error iram not supported -#else - /* Note: l8ui not allowed in IRAM/IROM!! */ - l8ui a0, a4, 1 # read as(src) from MOVSP instruction -#endif - movi a3, .Lmovsp_src - _EXTUI_MOVSP_SRC(a0) # extract source register number - addx8 a3, a0, a3 - jx a3 - -.Lunhandled_double: - wsr a0, excsave1 - movi a0, unrecoverable_exception - callx0 a0 - - .align 8 -.Lmovsp_src: - l32i a3, a2, PT_AREG0; _j 1f; .align 8 - mov a3, a1; _j 1f; .align 8 - l32i a3, a2, PT_AREG2; _j 1f; .align 8 - l32i a3, a2, PT_AREG3; _j 1f; .align 8 - l32i a3, a2, PT_AREG4; _j 1f; .align 8 - mov a3, a5; _j 1f; .align 8 - mov a3, a6; _j 1f; .align 8 - mov a3, a7; _j 1f; .align 8 - mov a3, a8; _j 1f; .align 8 - mov a3, a9; _j 1f; .align 8 - mov a3, a10; _j 1f; .align 8 - mov a3, a11; _j 1f; .align 8 - mov a3, a12; _j 1f; .align 8 - mov a3, a13; _j 1f; .align 8 - mov a3, a14; _j 1f; .align 8 - mov a3, a15; _j 1f; .align 8 - -1: - -#ifdef ALLOCA_EXCEPTION_IN_IRAM -#error iram not supported -#else - l8ui a0, a4, 0 # read ar(dst) from MOVSP instruction -#endif - addi a4, a4, 3 # step over movsp - _EXTUI_MOVSP_DST(a0) # extract destination register - wsr a4, epc1 # save new epc_1 - - _bnei a0, 1, 1f # no 'movsp a1, ax': jump - - /* Move the save area. This implies the use of the L32E - * and S32E instructions, because this move must be done with - * the user's PS.RING privilege levels, not with ring 0 - * (kernel's) privileges currently active with PS.EXCM - * set. Note that we have stil registered a fixup routine with the - * double exception vector in case a double exception occurs. - */ - - /* a0,a4:avail a1:old user stack a2:exc. stack a3:new user stack. */ - - l32e a0, a1, -16 - l32e a4, a1, -12 - s32e a0, a3, -16 - s32e a4, a3, -12 - l32e a0, a1, -8 - l32e a4, a1, -4 - s32e a0, a3, -8 - s32e a4, a3, -4 - - /* Restore stack-pointer and all the other saved registers. */ - - mov a1, a3 - - l32i a4, a2, PT_AREG4 - l32i a3, a2, PT_AREG3 - l32i a0, a2, PT_AREG0 - l32i a2, a2, PT_AREG2 - rfe - - /* MOVSP <at>,<as> was invoked with <at> != a1. - * Because the stack pointer is not being modified, - * we should be able to just modify the pointer - * without moving any save area. - * The processor only traps these occurrences if the - * caller window isn't live, so unfortunately we can't - * use this as an alternate trap mechanism. - * So we just do the move. This requires that we - * resolve the destination register, not just the source, - * so there's some extra work. - * (PERHAPS NOT REALLY NEEDED, BUT CLEANER...) - */ - - /* a0 dst-reg, a1 user-stack, a2 stack, a3 value of src reg. */ - -1: movi a4, .Lmovsp_dst - addx8 a4, a0, a4 - jx a4 - - .align 8 -.Lmovsp_dst: - s32i a3, a2, PT_AREG0; _j 1f; .align 8 - mov a1, a3; _j 1f; .align 8 - s32i a3, a2, PT_AREG2; _j 1f; .align 8 - s32i a3, a2, PT_AREG3; _j 1f; .align 8 - s32i a3, a2, PT_AREG4; _j 1f; .align 8 - mov a5, a3; _j 1f; .align 8 - mov a6, a3; _j 1f; .align 8 - mov a7, a3; _j 1f; .align 8 - mov a8, a3; _j 1f; .align 8 - mov a9, a3; _j 1f; .align 8 - mov a10, a3; _j 1f; .align 8 - mov a11, a3; _j 1f; .align 8 - mov a12, a3; _j 1f; .align 8 - mov a13, a3; _j 1f; .align 8 - mov a14, a3; _j 1f; .align 8 - mov a15, a3; _j 1f; .align 8 - -1: l32i a4, a2, PT_AREG4 - l32i a3, a2, PT_AREG3 - l32i a0, a2, PT_AREG0 - l32i a2, a2, PT_AREG2 - rfe - + _bbci.l a4, 31, 4f + rotw -1 + _bbci.l a8, 30, 8f + rotw -1 + j _WindowUnderflow12 +8: j _WindowUnderflow8 +4: j _WindowUnderflow4 ENDPROC(fast_alloca) /* -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
