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linux/arch/xtensa/kernel/entry.S
Max Filippov 38fef73c21 xtensa: implement fake NMI 
In case perf IRQ is the highest of the medium-level IRQs, and is alone
on its level, it may be treated as NMI:
- LOCKLEVEL is defined to be one level less than EXCM level,
- IRQ masking never lowers current IRQ level,
- new fake exception cause code, EXCCAUSE_MAPPED_NMI is assigned to that
  IRQ; new second level exception handler, do_nmi, assigned to it
  handles it as NMI,
- atomic operations in configurations without s32c1i still need to mask
  all interrupts.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
2015-08-17 07:33:39 +03:00

2003 lines
46 KiB
ArmAsm
Raw Blame History

/*
* Low-level exception handling
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2004 - 2008 by Tensilica Inc.
* Copyright (C) 2015 Cadence Design Systems Inc.
*
* Chris Zankel <chris@zankel.net>
*
*/
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/processor.h>
#include <asm/coprocessor.h>
#include <asm/thread_info.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/ptrace.h>
#include <asm/current.h>
#include <asm/pgtable.h>
#include <asm/page.h>
#include <asm/signal.h>
#include <asm/tlbflush.h>
#include <variant/tie-asm.h>
/* Unimplemented features. */
#undef KERNEL_STACK_OVERFLOW_CHECK
/* Not well tested.
*
* - fast_coprocessor
*/
/*
* Macro to find first bit set in WINDOWBASE from the left + 1
*
* 100....0 -> 1
* 010....0 -> 2
* 000....1 -> WSBITS
*/
.macro ffs_ws bit mask
#if XCHAL_HAVE_NSA
nsau \bit, \mask # 32-WSBITS ... 31 (32 iff 0)
addi \bit, \bit, WSBITS - 32 + 1 # uppest bit set -> return 1
#else
movi \bit, WSBITS
#if WSBITS > 16
_bltui \mask, 0x10000, 99f
addi \bit, \bit, -16
extui \mask, \mask, 16, 16
#endif
#if WSBITS > 8
99: _bltui \mask, 0x100, 99f
addi \bit, \bit, -8
srli \mask, \mask, 8
#endif
99: _bltui \mask, 0x10, 99f
addi \bit, \bit, -4
srli \mask, \mask, 4
99: _bltui \mask, 0x4, 99f
addi \bit, \bit, -2
srli \mask, \mask, 2
99: _bltui \mask, 0x2, 99f
addi \bit, \bit, -1
99:
#endif
.endm
.macro irq_save flags tmp
#if XTENSA_FAKE_NMI
#if defined(CONFIG_DEBUG_KERNEL) && (LOCKLEVEL | TOPLEVEL) >= XCHAL_DEBUGLEVEL
rsr \flags, ps
extui \tmp, \flags, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
bgei \tmp, LOCKLEVEL, 99f
rsil \tmp, LOCKLEVEL
99:
#else
movi \tmp, LOCKLEVEL
rsr \flags, ps
or \flags, \flags, \tmp
xsr \flags, ps
rsync
#endif
#else
rsil \flags, LOCKLEVEL
#endif
.endm
/* ----------------- DEFAULT FIRST LEVEL EXCEPTION HANDLERS ----------------- */
/*
* First-level exception handler for user exceptions.
* Save some special registers, extra states and all registers in the AR
* register file that were in use in the user task, and jump to the common
* exception code.
* We save SAR (used to calculate WMASK), and WB and WS (we don't have to
* save them for kernel exceptions).
*
* Entry condition for user_exception:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original value in depc
* a3: a3
* depc: a2, original value saved on stack (PT_DEPC)
* excsave1: dispatch table
*
* PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
* < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
*
* Entry condition for _user_exception:
*
* a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC
* excsave has been restored, and
* stack pointer (a1) has been set.
*
* Note: _user_exception might be at an odd address. Don't use call0..call12
*/
ENTRY(user_exception)
/* Save a1, a2, a3, and set SP. */
rsr a0, depc
s32i a1, a2, PT_AREG1
s32i a0, a2, PT_AREG2
s32i a3, a2, PT_AREG3
mov a1, a2
.globl _user_exception
_user_exception:
/* Save SAR and turn off single stepping */
movi a2, 0
wsr a2, depc # terminate user stack trace with 0
rsr a3, sar
xsr a2, icountlevel
s32i a3, a1, PT_SAR
s32i a2, a1, PT_ICOUNTLEVEL
#if XCHAL_HAVE_THREADPTR
rur a2, threadptr
s32i a2, a1, PT_THREADPTR
#endif
/* Rotate ws so that the current windowbase is at bit0. */
/* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */
rsr a2, windowbase
rsr a3, windowstart
ssr a2
s32i a2, a1, PT_WINDOWBASE
s32i a3, a1, PT_WINDOWSTART
slli a2, a3, 32-WSBITS
src a2, a3, a2
srli a2, a2, 32-WSBITS
s32i a2, a1, PT_WMASK # needed for restoring registers
/* Save only live registers. */
_bbsi.l a2, 1, 1f
s32i a4, a1, PT_AREG4
s32i a5, a1, PT_AREG5
s32i a6, a1, PT_AREG6
s32i a7, a1, PT_AREG7
_bbsi.l a2, 2, 1f
s32i a8, a1, PT_AREG8
s32i a9, a1, PT_AREG9
s32i a10, a1, PT_AREG10
s32i a11, a1, PT_AREG11
_bbsi.l a2, 3, 1f
s32i a12, a1, PT_AREG12
s32i a13, a1, PT_AREG13
s32i a14, a1, PT_AREG14
s32i a15, a1, PT_AREG15
_bnei a2, 1, 1f # only one valid frame?
/* Only one valid frame, skip saving regs. */
j 2f
/* Save the remaining registers.
* We have to save all registers up to the first '1' from
* the right, except the current frame (bit 0).
* Assume a2 is: 001001000110001
* All register frames starting from the top field to the marked '1'
* must be saved.
*/
1: addi a3, a2, -1 # eliminate '1' in bit 0: yyyyxxww0
neg a3, a3 # yyyyxxww0 -> YYYYXXWW1+1
and a3, a3, a2 # max. only one bit is set
/* Find number of frames to save */
ffs_ws a0, a3 # number of frames to the '1' from left
/* Store information into WMASK:
* bits 0..3: xxx1 masked lower 4 bits of the rotated windowstart,
* bits 4...: number of valid 4-register frames
*/
slli a3, a0, 4 # number of frames to save in bits 8..4
extui a2, a2, 0, 4 # mask for the first 16 registers
or a2, a3, a2
s32i a2, a1, PT_WMASK # needed when we restore the reg-file
/* Save 4 registers at a time */
1: rotw -1
s32i a0, a5, PT_AREG_END - 16
s32i a1, a5, PT_AREG_END - 12
s32i a2, a5, PT_AREG_END - 8
s32i a3, a5, PT_AREG_END - 4
addi a0, a4, -1
addi a1, a5, -16
_bnez a0, 1b
/* WINDOWBASE still in SAR! */
rsr a2, sar # original WINDOWBASE
movi a3, 1
ssl a2
sll a3, a3
wsr a3, windowstart # set corresponding WINDOWSTART bit
wsr a2, windowbase # and WINDOWSTART
rsync
/* We are back to the original stack pointer (a1) */
2: /* Now, jump to the common exception handler. */
j common_exception
ENDPROC(user_exception)
/*
* First-level exit handler for kernel exceptions
* Save special registers and the live window frame.
* Note: Even though we changes the stack pointer, we don't have to do a
* MOVSP here, as we do that when we return from the exception.
* (See comment in the kernel exception exit code)
*
* Entry condition for kernel_exception:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in DEPC
* a3: a3
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: dispatch table
*
* PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
* < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
*
* Entry condition for _kernel_exception:
*
* a0-a3 and depc have been saved to PT_AREG0...PT_AREG3 and PT_DEPC
* excsave has been restored, and
* stack pointer (a1) has been set.
*
* Note: _kernel_exception might be at an odd address. Don't use call0..call12
*/
ENTRY(kernel_exception)
/* Save a1, a2, a3, and set SP. */
rsr a0, depc # get a2
s32i a1, a2, PT_AREG1
s32i a0, a2, PT_AREG2
s32i a3, a2, PT_AREG3
mov a1, a2
.globl _kernel_exception
_kernel_exception:
/* Save SAR and turn off single stepping */
movi a2, 0
rsr a3, sar
xsr a2, icountlevel
s32i a3, a1, PT_SAR
s32i a2, a1, PT_ICOUNTLEVEL
/* Rotate ws so that the current windowbase is at bit0. */
/* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */
rsr a2, windowbase # don't need to save these, we only
rsr a3, windowstart # need shifted windowstart: windowmask
ssr a2
slli a2, a3, 32-WSBITS
src a2, a3, a2
srli a2, a2, 32-WSBITS
s32i a2, a1, PT_WMASK # needed for kernel_exception_exit
/* Save only the live window-frame */
_bbsi.l a2, 1, 1f
s32i a4, a1, PT_AREG4
s32i a5, a1, PT_AREG5
s32i a6, a1, PT_AREG6
s32i a7, a1, PT_AREG7
_bbsi.l a2, 2, 1f
s32i a8, a1, PT_AREG8
s32i a9, a1, PT_AREG9
s32i a10, a1, PT_AREG10
s32i a11, a1, PT_AREG11
_bbsi.l a2, 3, 1f
s32i a12, a1, PT_AREG12
s32i a13, a1, PT_AREG13
s32i a14, a1, PT_AREG14
s32i a15, a1, PT_AREG15
_bnei a2, 1, 1f
/* Copy spill slots of a0 and a1 to imitate movsp
* in order to keep exception stack continuous
*/
l32i a3, a1, PT_SIZE
l32i a0, a1, PT_SIZE + 4
s32e a3, a1, -16
s32e a0, a1, -12
1:
l32i a0, a1, PT_AREG0 # restore saved a0
wsr a0, depc
#ifdef KERNEL_STACK_OVERFLOW_CHECK
/* Stack overflow check, for debugging */
extui a2, a1, TASK_SIZE_BITS,XX
movi a3, SIZE??
_bge a2, a3, out_of_stack_panic
#endif
/*
* This is the common exception handler.
* We get here from the user exception handler or simply by falling through
* from the kernel exception handler.
* Save the remaining special registers, switch to kernel mode, and jump
* to the second-level exception handler.
*
*/
common_exception:
/* Save some registers, disable loops and clear the syscall flag. */
rsr a2, debugcause
rsr a3, epc1
s32i a2, a1, PT_DEBUGCAUSE
s32i a3, a1, PT_PC
movi a2, -1
rsr a3, excvaddr
s32i a2, a1, PT_SYSCALL
movi a2, 0
s32i a3, a1, PT_EXCVADDR
xsr a2, lcount
s32i a2, a1, PT_LCOUNT
/* It is now save to restore the EXC_TABLE_FIXUP variable. */
rsr a2, exccause
movi a3, 0
rsr a0, excsave1
s32i a2, a1, PT_EXCCAUSE
s32i a3, a0, EXC_TABLE_FIXUP
/* All unrecoverable states are saved on stack, now, and a1 is valid.
* 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.
*
* Set PS(EXCM = 0, UM = 0, RING = 0, OWB = 0, WOE = 1, INTLEVEL = X)
*/
rsr a3, ps
s32i a3, a1, PT_PS # save ps
#if XTENSA_FAKE_NMI
/* Correct PS needs to be saved in the PT_PS:
* - in case of exception or level-1 interrupt it's in the PS,
* and is already saved.
* - in case of medium level interrupt it's in the excsave2.
*/
movi a0, EXCCAUSE_MAPPED_NMI
extui a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
beq a2, a0, .Lmedium_level_irq
bnei a2, EXCCAUSE_LEVEL1_INTERRUPT, .Lexception
beqz a3, .Llevel1_irq # level-1 IRQ sets ps.intlevel to 0
.Lmedium_level_irq:
rsr a0, excsave2
s32i a0, a1, PT_PS # save medium-level interrupt ps
bgei a3, LOCKLEVEL, .Lexception
.Llevel1_irq:
movi a3, LOCKLEVEL
.Lexception:
movi a0, 1 << PS_WOE_BIT
or a3, a3, a0
#else
addi a2, a2, -EXCCAUSE_LEVEL1_INTERRUPT
movi a0, LOCKLEVEL
extui a3, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
# a3 = PS.INTLEVEL
moveqz a3, a0, a2 # a3 = LOCKLEVEL iff interrupt
movi a2, 1 << PS_WOE_BIT
or a3, a3, a2
rsr a2, exccause
#endif
/* restore return address (or 0 if return to userspace) */
rsr a0, depc
wsr a3, ps
rsync # PS.WOE => rsync => overflow
/* Save lbeg, lend */
rsr a4, lbeg
rsr a3, lend
s32i a4, a1, PT_LBEG
s32i a3, a1, PT_LEND
/* Save SCOMPARE1 */
#if XCHAL_HAVE_S32C1I
rsr a3, scompare1
s32i a3, a1, PT_SCOMPARE1
#endif
/* Save optional registers. */
save_xtregs_opt a1 a3 a4 a5 a6 a7 PT_XTREGS_OPT
/* Go to second-level dispatcher. Set up parameters to pass to the
* exception handler and call the exception handler.
*/
rsr a4, excsave1
mov a6, a1 # pass stack frame
mov a7, a2 # pass EXCCAUSE
addx4 a4, a2, a4
l32i a4, a4, EXC_TABLE_DEFAULT # load handler
/* Call the second-level handler */
callx4 a4
/* Jump here for exception exit */
.global common_exception_return
common_exception_return:
#if XTENSA_FAKE_NMI
l32i a2, a1, PT_EXCCAUSE
movi a3, EXCCAUSE_MAPPED_NMI
beq a2, a3, .LNMIexit
#endif
1:
irq_save a2, a3
#ifdef CONFIG_TRACE_IRQFLAGS
movi a4, trace_hardirqs_off
callx4 a4
#endif
/* Jump if we are returning from kernel exceptions. */
l32i a3, a1, PT_PS
GET_THREAD_INFO(a2, a1)
l32i a4, a2, TI_FLAGS
_bbci.l a3, PS_UM_BIT, 6f
/* Specific to a user exception exit:
* We need to check some flags for signal handling and rescheduling,
* and have to restore WB and WS, extra states, and all registers
* in the register file that were in use in the user task.
* Note that we don't disable interrupts here.
*/
_bbsi.l a4, TIF_NEED_RESCHED, 3f
_bbsi.l a4, TIF_NOTIFY_RESUME, 2f
_bbci.l a4, TIF_SIGPENDING, 5f
2: l32i a4, a1, PT_DEPC
bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f
/* Call do_signal() */
#ifdef CONFIG_TRACE_IRQFLAGS
movi a4, trace_hardirqs_on
callx4 a4
#endif
rsil a2, 0
movi a4, do_notify_resume # int do_notify_resume(struct pt_regs*)
mov a6, a1
callx4 a4
j 1b
3: /* Reschedule */
#ifdef CONFIG_TRACE_IRQFLAGS
movi a4, trace_hardirqs_on
callx4 a4
#endif
rsil a2, 0
movi a4, schedule # void schedule (void)
callx4 a4
j 1b
#ifdef CONFIG_PREEMPT
6:
_bbci.l a4, TIF_NEED_RESCHED, 4f
/* Check current_thread_info->preempt_count */
l32i a4, a2, TI_PRE_COUNT
bnez a4, 4f
movi a4, preempt_schedule_irq
callx4 a4
j 1b
#endif
#if XTENSA_FAKE_NMI
.LNMIexit:
l32i a3, a1, PT_PS
_bbci.l a3, PS_UM_BIT, 4f
#endif
5:
#ifdef CONFIG_DEBUG_TLB_SANITY
l32i a4, a1, PT_DEPC
bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f
movi a4, check_tlb_sanity
callx4 a4
#endif
6:
4:
#ifdef CONFIG_TRACE_IRQFLAGS
extui a4, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
bgei a4, LOCKLEVEL, 1f
movi a4, trace_hardirqs_on
callx4 a4
1:
#endif
/* Restore optional registers. */
load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT
/* Restore SCOMPARE1 */
#if XCHAL_HAVE_S32C1I
l32i a2, a1, PT_SCOMPARE1
wsr a2, scompare1
#endif
wsr a3, ps /* disable interrupts */
_bbci.l a3, PS_UM_BIT, kernel_exception_exit
user_exception_exit:
/* Restore the state of the task and return from the exception. */
/* Switch to the user thread WINDOWBASE. Save SP temporarily in DEPC */
l32i a2, a1, PT_WINDOWBASE
l32i a3, a1, PT_WINDOWSTART
wsr a1, depc # use DEPC as temp storage
wsr a3, windowstart # restore WINDOWSTART
ssr a2 # preserve user's WB in the SAR
wsr a2, windowbase # switch to user's saved WB
rsync
rsr a1, depc # restore stack pointer
l32i a2, a1, PT_WMASK # register frames saved (in bits 4...9)
rotw -1 # we restore a4..a7
_bltui a6, 16, 1f # only have to restore current window?
/* The working registers are a0 and a3. We are restoring to
* a4..a7. Be careful not to destroy what we have just restored.
* Note: wmask has the format YYYYM:
* Y: number of registers saved in groups of 4
* M: 4 bit mask of first 16 registers
*/
mov a2, a6
mov a3, a5
2: rotw -1 # a0..a3 become a4..a7
addi a3, a7, -4*4 # next iteration
addi a2, a6, -16 # decrementing Y in WMASK
l32i a4, a3, PT_AREG_END + 0
l32i a5, a3, PT_AREG_END + 4
l32i a6, a3, PT_AREG_END + 8
l32i a7, a3, PT_AREG_END + 12
_bgeui a2, 16, 2b
/* Clear unrestored registers (don't leak anything to user-land */
1: rsr a0, windowbase
rsr a3, sar
sub a3, a0, a3
beqz a3, 2f
extui a3, a3, 0, WBBITS
1: rotw -1
addi a3, a7, -1
movi a4, 0
movi a5, 0
movi a6, 0
movi a7, 0
bgei a3, 1, 1b
/* We are back were we were when we started.
* Note: a2 still contains WMASK (if we've returned to the original
* frame where we had loaded a2), or at least the lower 4 bits
* (if we have restored WSBITS-1 frames).
*/
2:
#if XCHAL_HAVE_THREADPTR
l32i a3, a1, PT_THREADPTR
wur a3, threadptr
#endif
j common_exception_exit
/* This is the kernel exception exit.
* We avoided to do a MOVSP when we entered the exception, but we
* have to do it here.
*/
kernel_exception_exit:
/* Check if we have to do a movsp.
*
* We only have to do a movsp if the previous window-frame has
* been spilled to the *temporary* exception stack instead of the
* task's stack. This is the case if the corresponding bit in
* WINDOWSTART for the previous window-frame was set before
* (not spilled) but is zero now (spilled).
* If this bit is zero, all other bits except the one for the
* current window frame are also zero. So, we can use a simple test:
* 'and' WINDOWSTART and WINDOWSTART-1:
*
* (XXXXXX1[0]* - 1) AND XXXXXX1[0]* = XXXXXX0[0]*
*
* The result is zero only if one bit was set.
*
* (Note: We might have gone through several task switches before
* we come back to the current task, so WINDOWBASE might be
* different from the time the exception occurred.)
*/
/* Test WINDOWSTART before and after the exception.
* We actually have WMASK, so we only have to test if it is 1 or not.
*/
l32i a2, a1, PT_WMASK
_beqi a2, 1, common_exception_exit # Spilled before exception,jump
/* Test WINDOWSTART now. If spilled, do the movsp */
rsr a3, windowstart
addi a0, a3, -1
and a3, a3, a0
_bnez a3, common_exception_exit
/* Do a movsp (we returned from a call4, so we have at least a0..a7) */
addi a0, a1, -16
l32i a3, a0, 0
l32i a4, a0, 4
s32i a3, a1, PT_SIZE+0
s32i a4, a1, PT_SIZE+4
l32i a3, a0, 8
l32i a4, a0, 12
s32i a3, a1, PT_SIZE+8
s32i a4, a1, PT_SIZE+12
/* Common exception exit.
* We restore the special register and the current window frame, and
* return from the exception.
*
* Note: We expect a2 to hold PT_WMASK
*/
common_exception_exit:
/* Restore address registers. */
_bbsi.l a2, 1, 1f
l32i a4, a1, PT_AREG4
l32i a5, a1, PT_AREG5
l32i a6, a1, PT_AREG6
l32i a7, a1, PT_AREG7
_bbsi.l a2, 2, 1f
l32i a8, a1, PT_AREG8
l32i a9, a1, PT_AREG9
l32i a10, a1, PT_AREG10
l32i a11, a1, PT_AREG11
_bbsi.l a2, 3, 1f
l32i a12, a1, PT_AREG12
l32i a13, a1, PT_AREG13
l32i a14, a1, PT_AREG14
l32i a15, a1, PT_AREG15
/* Restore PC, SAR */
1: l32i a2, a1, PT_PC
l32i a3, a1, PT_SAR
wsr a2, epc1
wsr a3, sar
/* Restore LBEG, LEND, LCOUNT */
l32i a2, a1, PT_LBEG
l32i a3, a1, PT_LEND
wsr a2, lbeg
l32i a2, a1, PT_LCOUNT
wsr a3, lend
wsr a2, lcount
/* We control single stepping through the ICOUNTLEVEL register. */
l32i a2, a1, PT_ICOUNTLEVEL
movi a3, -2
wsr a2, icountlevel
wsr a3, icount
/* Check if it was double exception. */
l32i a0, a1, PT_DEPC
l32i a3, a1, PT_AREG3
l32i a2, a1, PT_AREG2
_bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f
/* Restore a0...a3 and return */
l32i a0, a1, PT_AREG0
l32i a1, a1, PT_AREG1
rfe
1: wsr a0, depc
l32i a0, a1, PT_AREG0
l32i a1, a1, PT_AREG1
rfde
ENDPROC(kernel_exception)
/*
* Debug exception handler.
*
* Currently, we don't support KGDB, so only user application can be debugged.
*
* When we get here, a0 is trashed and saved to excsave[debuglevel]
*/
ENTRY(debug_exception)
rsr a0, SREG_EPS + XCHAL_DEBUGLEVEL
bbsi.l a0, PS_EXCM_BIT, 1f # exception mode
/* Set EPC1 and EXCCAUSE */
wsr a2, depc # save a2 temporarily
rsr a2, SREG_EPC + XCHAL_DEBUGLEVEL
wsr a2, epc1
movi a2, EXCCAUSE_MAPPED_DEBUG
wsr a2, exccause
/* Restore PS to the value before the debug exc but with PS.EXCM set.*/
movi a2, 1 << PS_EXCM_BIT
or a2, a0, a2
movi a0, debug_exception # restore a3, debug jump vector
wsr a2, ps
xsr a0, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
/* Switch to kernel/user stack, restore jump vector, and save a0 */
bbsi.l a2, PS_UM_BIT, 2f # jump if user mode
addi a2, a1, -16-PT_SIZE # assume kernel stack
s32i a0, a2, PT_AREG0
movi a0, 0
s32i a1, a2, PT_AREG1
s32i a0, a2, PT_DEPC # mark it as a regular exception
xsr a0, depc
s32i a3, a2, PT_AREG3
s32i a0, a2, PT_AREG2
mov a1, a2
j _kernel_exception
2: rsr a2, excsave1
l32i a2, a2, EXC_TABLE_KSTK # load kernel stack pointer
s32i a0, a2, PT_AREG0
movi a0, 0
s32i a1, a2, PT_AREG1
s32i a0, a2, PT_DEPC
xsr a0, depc
s32i a3, a2, PT_AREG3
s32i a0, a2, PT_AREG2
mov a1, a2
j _user_exception
/* Debug exception while in exception mode. */
1: j 1b // FIXME!!
ENDPROC(debug_exception)
/*
* We get here in case of an unrecoverable exception.
* The only thing we can do is to be nice and print a panic message.
* We only produce a single stack frame for panic, so ???
*
*
* Entry conditions:
*
* - a0 contains the caller address; original value saved in excsave1.
* - the original a0 contains a valid return address (backtrace) or 0.
* - a2 contains a valid stackpointer
*
* Notes:
*
* - If the stack pointer could be invalid, the caller has to setup a
* dummy stack pointer (e.g. the stack of the init_task)
*
* - If the return address could be invalid, the caller has to set it
* to 0, so the backtrace would stop.
*
*/
.align 4
unrecoverable_text:
.ascii "Unrecoverable error in exception handler\0"
ENTRY(unrecoverable_exception)
movi a0, 1
movi a1, 0
wsr a0, windowstart
wsr a1, windowbase
rsync
movi a1, (1 << PS_WOE_BIT) | LOCKLEVEL
wsr a1, ps
rsync
movi a1, init_task
movi a0, 0
addi a1, a1, PT_REGS_OFFSET
movi a4, panic
movi a6, unrecoverable_text
callx4 a4
1: j 1b
ENDPROC(unrecoverable_exception)
/* -------------------------- FAST EXCEPTION HANDLERS ----------------------- */
/*
* Fast-handler for alloca exceptions
*
* The ALLOCA handler is entered when user code executes the MOVSP
* instruction and the caller's frame is not in the register file.
*
* 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:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in DEPC
* a3: a3
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: dispatch table
*
* PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
* < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
*/
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
_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)
/*
* fast system calls.
*
* WARNING: The kernel doesn't save the entire user context before
* handling a fast system call. These functions are small and short,
* usually offering some functionality not available to user tasks.
*
* BE CAREFUL TO PRESERVE THE USER'S CONTEXT.
*
* Entry condition:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in DEPC
* a3: a3
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: dispatch table
*/
ENTRY(fast_syscall_kernel)
/* Skip syscall. */
rsr a0, epc1
addi a0, a0, 3
wsr a0, epc1
l32i a0, a2, PT_DEPC
bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable
rsr a0, depc # get syscall-nr
_beqz a0, fast_syscall_spill_registers
_beqi a0, __NR_xtensa, fast_syscall_xtensa
j kernel_exception
ENDPROC(fast_syscall_kernel)
ENTRY(fast_syscall_user)
/* Skip syscall. */
rsr a0, epc1
addi a0, a0, 3
wsr a0, epc1
l32i a0, a2, PT_DEPC
bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, fast_syscall_unrecoverable
rsr a0, depc # get syscall-nr
_beqz a0, fast_syscall_spill_registers
_beqi a0, __NR_xtensa, fast_syscall_xtensa
j user_exception
ENDPROC(fast_syscall_user)
ENTRY(fast_syscall_unrecoverable)
/* Restore all states. */
l32i a0, a2, PT_AREG0 # restore a0
xsr a2, depc # restore a2, depc
wsr a0, excsave1
movi a0, unrecoverable_exception
callx0 a0
ENDPROC(fast_syscall_unrecoverable)
/*
* sysxtensa syscall handler
*
* int sysxtensa (SYS_XTENSA_ATOMIC_SET, ptr, val, unused);
* int sysxtensa (SYS_XTENSA_ATOMIC_ADD, ptr, val, unused);
* int sysxtensa (SYS_XTENSA_ATOMIC_EXG_ADD, ptr, val, unused);
* int sysxtensa (SYS_XTENSA_ATOMIC_CMP_SWP, ptr, oldval, newval);
* a2 a6 a3 a4 a5
*
* Entry condition:
*
* a0: a2 (syscall-nr), original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in a0 and DEPC
* a3: a3
* a4..a15: unchanged
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: dispatch table
*
* PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
* < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
*
* Note: we don't have to save a2; a2 holds the return value
*
* We use the two macros TRY and CATCH:
*
* TRY adds an entry to the __ex_table fixup table for the immediately
* following instruction.
*
* CATCH catches any exception that occurred at one of the preceding TRY
* statements and continues from there
*
* Usage TRY l32i a0, a1, 0
* <other code>
* done: rfe
* CATCH <set return code>
* j done
*/
#ifdef CONFIG_FAST_SYSCALL_XTENSA
#define TRY \
.section __ex_table, "a"; \
.word 66f, 67f; \
.text; \
66:
#define CATCH \
67:
ENTRY(fast_syscall_xtensa)
s32i a7, a2, PT_AREG7 # we need an additional register
movi a7, 4 # sizeof(unsigned int)
access_ok a3, a7, a0, a2, .Leac # a0: scratch reg, a2: sp
_bgeui a6, SYS_XTENSA_COUNT, .Lill
_bnei a6, SYS_XTENSA_ATOMIC_CMP_SWP, .Lnswp
/* Fall through for ATOMIC_CMP_SWP. */
.Lswp: /* Atomic compare and swap */
TRY l32i a0, a3, 0 # read old value
bne a0, a4, 1f # same as old value? jump
TRY s32i a5, a3, 0 # different, modify value
l32i a7, a2, PT_AREG7 # restore a7
l32i a0, a2, PT_AREG0 # restore a0
movi a2, 1 # and return 1
rfe
1: l32i a7, a2, PT_AREG7 # restore a7
l32i a0, a2, PT_AREG0 # restore a0
movi a2, 0 # return 0 (note that we cannot set
rfe
.Lnswp: /* Atomic set, add, and exg_add. */
TRY l32i a7, a3, 0 # orig
addi a6, a6, -SYS_XTENSA_ATOMIC_SET
add a0, a4, a7 # + arg
moveqz a0, a4, a6 # set
addi a6, a6, SYS_XTENSA_ATOMIC_SET
TRY s32i a0, a3, 0 # write new value
mov a0, a2
mov a2, a7
l32i a7, a0, PT_AREG7 # restore a7
l32i a0, a0, PT_AREG0 # restore a0
rfe
CATCH
.Leac: l32i a7, a2, PT_AREG7 # restore a7
l32i a0, a2, PT_AREG0 # restore a0
movi a2, -EFAULT
rfe
.Lill: l32i a7, a2, PT_AREG7 # restore a7
l32i a0, a2, PT_AREG0 # restore a0
movi a2, -EINVAL
rfe
ENDPROC(fast_syscall_xtensa)
#else /* CONFIG_FAST_SYSCALL_XTENSA */
ENTRY(fast_syscall_xtensa)
l32i a0, a2, PT_AREG0 # restore a0
movi a2, -ENOSYS
rfe
ENDPROC(fast_syscall_xtensa)
#endif /* CONFIG_FAST_SYSCALL_XTENSA */
/* fast_syscall_spill_registers.
*
* Entry condition:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in DEPC
* a3: a3
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: dispatch table
*
* Note: We assume the stack pointer is EXC_TABLE_KSTK in the fixup handler.
*/
#ifdef CONFIG_FAST_SYSCALL_SPILL_REGISTERS
ENTRY(fast_syscall_spill_registers)
/* Register a FIXUP handler (pass current wb as a parameter) */
xsr a3, excsave1
movi a0, fast_syscall_spill_registers_fixup
s32i a0, a3, EXC_TABLE_FIXUP
rsr a0, windowbase
s32i a0, a3, EXC_TABLE_PARAM
xsr a3, excsave1 # restore a3 and excsave_1
/* Save a3, a4 and SAR on stack. */
rsr a0, sar
s32i a3, a2, PT_AREG3
s32i a0, a2, PT_SAR
/* The spill routine might clobber a4, a7, a8, a11, a12, and a15. */
s32i a4, a2, PT_AREG4
s32i a7, a2, PT_AREG7
s32i a8, a2, PT_AREG8
s32i a11, a2, PT_AREG11
s32i a12, a2, PT_AREG12
s32i a15, a2, PT_AREG15
/*
* Rotate ws so that the current windowbase is at bit 0.
* Assume ws = xxxwww1yy (www1 current window frame).
* Rotate ws right so that a4 = yyxxxwww1.
*/
rsr a0, windowbase
rsr a3, windowstart # a3 = xxxwww1yy
ssr a0 # holds WB
slli a0, a3, WSBITS
or a3, a3, a0 # a3 = xxxwww1yyxxxwww1yy
srl a3, a3 # a3 = 00xxxwww1yyxxxwww1
/* We are done if there are no more than the current register frame. */
extui a3, a3, 1, WSBITS-1 # a3 = 0yyxxxwww
movi a0, (1 << (WSBITS-1))
_beqz a3, .Lnospill # only one active frame? jump
/* We want 1 at the top, so that we return to the current windowbase */
or a3, a3, a0 # 1yyxxxwww
/* Skip empty frames - get 'oldest' WINDOWSTART-bit. */
wsr a3, windowstart # save shifted windowstart
neg a0, a3
and a3, a0, a3 # first bit set from right: 000010000
ffs_ws a0, a3 # a0: shifts to skip empty frames
movi a3, WSBITS
sub a0, a3, a0 # WSBITS-a0:number of 0-bits from right
ssr a0 # save in SAR for later.
rsr a3, windowbase
add a3, a3, a0
wsr a3, windowbase
rsync
rsr a3, windowstart
srl a3, a3 # shift windowstart
/* WB is now just one frame below the oldest frame in the register
window. WS is shifted so the oldest frame is in bit 0, thus, WB
and WS differ by one 4-register frame. */
/* Save frames. Depending what call was used (call4, call8, call12),
* we have to save 4,8. or 12 registers.
*/
.Lloop: _bbsi.l a3, 1, .Lc4
_bbci.l a3, 2, .Lc12
.Lc8: s32e a4, a13, -16
l32e a4, a5, -12
s32e a8, a4, -32
s32e a5, a13, -12
s32e a6, a13, -8
s32e a7, a13, -4
s32e a9, a4, -28
s32e a10, a4, -24
s32e a11, a4, -20
srli a11, a3, 2 # shift windowbase by 2
rotw 2
_bnei a3, 1, .Lloop
j .Lexit
.Lc4: s32e a4, a9, -16
s32e a5, a9, -12
s32e a6, a9, -8
s32e a7, a9, -4
srli a7, a3, 1
rotw 1
_bnei a3, 1, .Lloop
j .Lexit
.Lc12: _bbci.l a3, 3, .Linvalid_mask # bit 2 shouldn't be zero!
/* 12-register frame (call12) */
l32e a0, a5, -12
s32e a8, a0, -48
mov a8, a0
s32e a9, a8, -44
s32e a10, a8, -40
s32e a11, a8, -36
s32e a12, a8, -32
s32e a13, a8, -28
s32e a14, a8, -24
s32e a15, a8, -20
srli a15, a3, 3
/* The stack pointer for a4..a7 is out of reach, so we rotate the
* window, grab the stackpointer, and rotate back.
* Alternatively, we could also use the following approach, but that
* makes the fixup routine much more complicated:
* rotw 1
* s32e a0, a13, -16
* ...
* rotw 2
*/
rotw 1
mov a4, a13
rotw -1
s32e a4, a8, -16
s32e a5, a8, -12
s32e a6, a8, -8
s32e a7, a8, -4
rotw 3
_beqi a3, 1, .Lexit
j .Lloop
.Lexit:
/* Done. Do the final rotation and set WS */
rotw 1
rsr a3, windowbase
ssl a3
movi a3, 1
sll a3, a3
wsr a3, windowstart
.Lnospill:
/* Advance PC, restore registers and SAR, and return from exception. */
l32i a3, a2, PT_SAR
l32i a0, a2, PT_AREG0
wsr a3, sar
l32i a3, a2, PT_AREG3
/* Restore clobbered registers. */
l32i a4, a2, PT_AREG4
l32i a7, a2, PT_AREG7
l32i a8, a2, PT_AREG8
l32i a11, a2, PT_AREG11
l32i a12, a2, PT_AREG12
l32i a15, a2, PT_AREG15
movi a2, 0
rfe
.Linvalid_mask:
/* We get here because of an unrecoverable error in the window
* registers, so set up a dummy frame and kill the user application.
* Note: We assume EXC_TABLE_KSTK contains a valid stack pointer.
*/
movi a0, 1
movi a1, 0
wsr a0, windowstart
wsr a1, windowbase
rsync
movi a0, 0
rsr a3, excsave1
l32i a1, a3, EXC_TABLE_KSTK
movi a4, (1 << PS_WOE_BIT) | LOCKLEVEL
wsr a4, ps
rsync
movi a6, SIGSEGV
movi a4, do_exit
callx4 a4
/* shouldn't return, so panic */
wsr a0, excsave1
movi a0, unrecoverable_exception
callx0 a0 # should not return
1: j 1b
ENDPROC(fast_syscall_spill_registers)
/* Fixup handler.
*
* We get here if the spill routine causes an exception, e.g. tlb miss.
* We basically restore WINDOWBASE and WINDOWSTART to the condition when
* we entered the spill routine and jump to the user exception handler.
*
* Note that we only need to restore the bits in windowstart that have not
* been spilled yet by the _spill_register routine. Luckily, a3 contains a
* rotated windowstart with only those bits set for frames that haven't been
* spilled yet. Because a3 is rotated such that bit 0 represents the register
* frame for the current windowbase - 1, we need to rotate a3 left by the
* value of the current windowbase + 1 and move it to windowstart.
*
* a0: value of depc, original value in depc
* a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE
* a3: exctable, original value in excsave1
*/
ENTRY(fast_syscall_spill_registers_fixup)
rsr a2, windowbase # get current windowbase (a2 is saved)
xsr a0, depc # restore depc and a0
ssl a2 # set shift (32 - WB)
/* We need to make sure the current registers (a0-a3) are preserved.
* To do this, we simply set the bit for the current window frame
* in WS, so that the exception handlers save them to the task stack.
*
* Note: we use a3 to set the windowbase, so we take a special care
* of it, saving it in the original _spill_registers frame across
* the exception handler call.
*/
xsr a3, excsave1 # get spill-mask
slli a3, a3, 1 # shift left by one
addi a3, a3, 1 # set the bit for the current window frame
slli a2, a3, 32-WSBITS
src a2, a3, a2 # a2 = xxwww1yyxxxwww1yy......
wsr a2, windowstart # set corrected windowstart
srli a3, a3, 1
rsr a2, excsave1
l32i a2, a2, EXC_TABLE_DOUBLE_SAVE # restore a2
xsr a2, excsave1
s32i a3, a2, EXC_TABLE_DOUBLE_SAVE # save a3
l32i a3, a2, EXC_TABLE_PARAM # original WB (in user task)
xsr a2, excsave1
/* Return to the original (user task) WINDOWBASE.
* We leave the following frame behind:
* a0, a1, a2 same
* a3: trashed (saved in EXC_TABLE_DOUBLE_SAVE)
* depc: depc (we have to return to that address)
* excsave_1: exctable
*/
wsr a3, windowbase
rsync
/* We are now in the original frame when we entered _spill_registers:
* a0: return address
* a1: used, stack pointer
* a2: kernel stack pointer
* a3: available
* depc: exception address
* excsave: exctable
* Note: This frame might be the same as above.
*/
/* Setup stack pointer. */
addi a2, a2, -PT_USER_SIZE
s32i a0, a2, PT_AREG0
/* Make sure we return to this fixup handler. */
movi a3, fast_syscall_spill_registers_fixup_return
s32i a3, a2, PT_DEPC # setup depc
/* Jump to the exception handler. */
rsr a3, excsave1
rsr a0, exccause
addx4 a0, a0, a3 # find entry in table
l32i a0, a0, EXC_TABLE_FAST_USER # load handler
l32i a3, a3, EXC_TABLE_DOUBLE_SAVE
jx a0
ENDPROC(fast_syscall_spill_registers_fixup)
ENTRY(fast_syscall_spill_registers_fixup_return)
/* When we return here, all registers have been restored (a2: DEPC) */
wsr a2, depc # exception address
/* Restore fixup handler. */
rsr a2, excsave1
s32i a3, a2, EXC_TABLE_DOUBLE_SAVE
movi a3, fast_syscall_spill_registers_fixup
s32i a3, a2, EXC_TABLE_FIXUP
rsr a3, windowbase
s32i a3, a2, EXC_TABLE_PARAM
l32i a2, a2, EXC_TABLE_KSTK
/* Load WB at the time the exception occurred. */
rsr a3, sar # WB is still in SAR
neg a3, a3
wsr a3, windowbase
rsync
rsr a3, excsave1
l32i a3, a3, EXC_TABLE_DOUBLE_SAVE
rfde
ENDPROC(fast_syscall_spill_registers_fixup_return)
#else /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */
ENTRY(fast_syscall_spill_registers)
l32i a0, a2, PT_AREG0 # restore a0
movi a2, -ENOSYS
rfe
ENDPROC(fast_syscall_spill_registers)
#endif /* CONFIG_FAST_SYSCALL_SPILL_REGISTERS */
#ifdef CONFIG_MMU
/*
* We should never get here. Bail out!
*/
ENTRY(fast_second_level_miss_double_kernel)
1: movi a0, unrecoverable_exception
callx0 a0 # should not return
1: j 1b
ENDPROC(fast_second_level_miss_double_kernel)
/* First-level entry handler for user, kernel, and double 2nd-level
* TLB miss exceptions. Note that for now, user and kernel miss
* exceptions share the same entry point and are handled identically.
*
* An old, less-efficient C version of this function used to exist.
* We include it below, interleaved as comments, for reference.
*
* Entry condition:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in DEPC
* a3: a3
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: dispatch table
*
* PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
* < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
*/
ENTRY(fast_second_level_miss)
/* Save a1 and a3. Note: we don't expect a double exception. */
s32i a1, a2, PT_AREG1
s32i a3, a2, PT_AREG3
/* We need to map the page of PTEs for the user task. Find
* the pointer to that page. Also, it's possible for tsk->mm
* to be NULL while tsk->active_mm is nonzero if we faulted on
* a vmalloc address. In that rare case, we must use
* active_mm instead to avoid a fault in this handler. See
*
* http://mail.nl.linux.org/linux-mm/2002-08/msg00258.html
* (or search Internet on "mm vs. active_mm")
*
* if (!mm)
* mm = tsk->active_mm;
* pgd = pgd_offset (mm, regs->excvaddr);
* pmd = pmd_offset (pgd, regs->excvaddr);
* pmdval = *pmd;
*/
GET_CURRENT(a1,a2)
l32i a0, a1, TASK_MM # tsk->mm
beqz a0, 9f
8: rsr a3, excvaddr # fault address
_PGD_OFFSET(a0, a3, a1)
l32i a0, a0, 0 # read pmdval
beqz a0, 2f
/* Read ptevaddr and convert to top of page-table page.
*
* vpnval = read_ptevaddr_register() & PAGE_MASK;
* vpnval += DTLB_WAY_PGTABLE;
* pteval = mk_pte (virt_to_page(pmd_val(pmdval)), PAGE_KERNEL);
* write_dtlb_entry (pteval, vpnval);
*
* The messy computation for 'pteval' above really simplifies
* into the following:
*
* pteval = ((pmdval - PAGE_OFFSET) & PAGE_MASK) | PAGE_DIRECTORY
*/
movi a1, (-PAGE_OFFSET) & 0xffffffff
add a0, a0, a1 # pmdval - PAGE_OFFSET
extui a1, a0, 0, PAGE_SHIFT # ... & PAGE_MASK
xor a0, a0, a1
movi a1, _PAGE_DIRECTORY
or a0, a0, a1 # ... | PAGE_DIRECTORY
/*
* We utilize all three wired-ways (7-9) to hold pmd translations.
* Memory regions are mapped to the DTLBs according to bits 28 and 29.
* This allows to map the three most common regions to three different
* DTLBs:
* 0,1 -> way 7 program (0040.0000) and virtual (c000.0000)
* 2 -> way 8 shared libaries (2000.0000)
* 3 -> way 0 stack (3000.0000)
*/
extui a3, a3, 28, 2 # addr. bit 28 and 29 0,1,2,3
rsr a1, ptevaddr
addx2 a3, a3, a3 # -> 0,3,6,9
srli a1, a1, PAGE_SHIFT
extui a3, a3, 2, 2 # -> 0,0,1,2
slli a1, a1, PAGE_SHIFT # ptevaddr & PAGE_MASK
addi a3, a3, DTLB_WAY_PGD
add a1, a1, a3 # ... + way_number
3: wdtlb a0, a1
dsync
/* Exit critical section. */
4: rsr a3, excsave1
movi a0, 0
s32i a0, a3, EXC_TABLE_FIXUP
/* Restore the working registers, and return. */
l32i a0, a2, PT_AREG0
l32i a1, a2, PT_AREG1
l32i a3, a2, PT_AREG3
l32i a2, a2, PT_DEPC
bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f
/* Restore excsave1 and return. */
rsr a2, depc
rfe
/* Return from double exception. */
1: xsr a2, depc
esync
rfde
9: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0
bnez a0, 8b
/* Even more unlikely case active_mm == 0.
* We can get here with NMI in the middle of context_switch that
* touches vmalloc area.
*/
movi a0, init_mm
j 8b
#if (DCACHE_WAY_SIZE > PAGE_SIZE)
2: /* Special case for cache aliasing.
* We (should) only get here if a clear_user_page, copy_user_page
* or the aliased cache flush functions got preemptively interrupted
* by another task. Re-establish temporary mapping to the
* TLBTEMP_BASE areas.
*/
/* We shouldn't be in a double exception */
l32i a0, a2, PT_DEPC
bgeui a0, VALID_DOUBLE_EXCEPTION_ADDRESS, 2f
/* Make sure the exception originated in the special functions */
movi a0, __tlbtemp_mapping_start
rsr a3, epc1
bltu a3, a0, 2f
movi a0, __tlbtemp_mapping_end
bgeu a3, a0, 2f
/* Check if excvaddr was in one of the TLBTEMP_BASE areas. */
movi a3, TLBTEMP_BASE_1
rsr a0, excvaddr
bltu a0, a3, 2f
addi a1, a0, -TLBTEMP_SIZE
bgeu a1, a3, 2f
/* Check if we have to restore an ITLB mapping. */
movi a1, __tlbtemp_mapping_itlb
rsr a3, epc1
sub a3, a3, a1
/* Calculate VPN */
movi a1, PAGE_MASK
and a1, a1, a0
/* Jump for ITLB entry */
bgez a3, 1f
/* We can use up to two TLBTEMP areas, one for src and one for dst. */
extui a3, a0, PAGE_SHIFT + DCACHE_ALIAS_ORDER, 1
add a1, a3, a1
/* PPN is in a6 for the first TLBTEMP area and in a7 for the second. */
mov a0, a6
movnez a0, a7, a3
j 3b
/* ITLB entry. We only use dst in a6. */
1: witlb a6, a1
isync
j 4b
#endif // DCACHE_WAY_SIZE > PAGE_SIZE
2: /* Invalid PGD, default exception handling */
rsr a1, depc
s32i a1, a2, PT_AREG2
mov a1, a2
rsr a2, ps
bbsi.l a2, PS_UM_BIT, 1f
j _kernel_exception
1: j _user_exception
ENDPROC(fast_second_level_miss)
/*
* StoreProhibitedException
*
* Update the pte and invalidate the itlb mapping for this pte.
*
* Entry condition:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in DEPC
* a3: a3
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: dispatch table
*
* PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
* < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
*/
ENTRY(fast_store_prohibited)
/* Save a1 and a3. */
s32i a1, a2, PT_AREG1
s32i a3, a2, PT_AREG3
GET_CURRENT(a1,a2)
l32i a0, a1, TASK_MM # tsk->mm
beqz a0, 9f
8: rsr a1, excvaddr # fault address
_PGD_OFFSET(a0, a1, a3)
l32i a0, a0, 0
beqz a0, 2f
/*
* Note that we test _PAGE_WRITABLE_BIT only if PTE is present
* and is not PAGE_NONE. See pgtable.h for possible PTE layouts.
*/
_PTE_OFFSET(a0, a1, a3)
l32i a3, a0, 0 # read pteval
movi a1, _PAGE_CA_INVALID
ball a3, a1, 2f
bbci.l a3, _PAGE_WRITABLE_BIT, 2f
movi a1, _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_HW_WRITE
or a3, a3, a1
rsr a1, excvaddr
s32i a3, a0, 0
/* We need to flush the cache if we have page coloring. */
#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
dhwb a0, 0
#endif
pdtlb a0, a1
wdtlb a3, a0
/* Exit critical section. */
movi a0, 0
rsr a3, excsave1
s32i a0, a3, EXC_TABLE_FIXUP
/* Restore the working registers, and return. */
l32i a3, a2, PT_AREG3
l32i a1, a2, PT_AREG1
l32i a0, a2, PT_AREG0
l32i a2, a2, PT_DEPC
bgeui a2, VALID_DOUBLE_EXCEPTION_ADDRESS, 1f
rsr a2, depc
rfe
/* Double exception. Restore FIXUP handler and return. */
1: xsr a2, depc
esync
rfde
9: l32i a0, a1, TASK_ACTIVE_MM # unlikely case mm == 0
j 8b
2: /* If there was a problem, handle fault in C */
rsr a3, depc # still holds a2
s32i a3, a2, PT_AREG2
mov a1, a2
rsr a2, ps
bbsi.l a2, PS_UM_BIT, 1f
j _kernel_exception
1: j _user_exception
ENDPROC(fast_store_prohibited)
#endif /* CONFIG_MMU */
/*
* System Calls.
*
* void system_call (struct pt_regs* regs, int exccause)
* a2 a3
*/
ENTRY(system_call)
entry a1, 32
/* regs->syscall = regs->areg[2] */
l32i a3, a2, PT_AREG2
mov a6, a2
movi a4, do_syscall_trace_enter
s32i a3, a2, PT_SYSCALL
callx4 a4
/* syscall = sys_call_table[syscall_nr] */
movi a4, sys_call_table;
movi a5, __NR_syscall_count
movi a6, -ENOSYS
bgeu a3, a5, 1f
addx4 a4, a3, a4
l32i a4, a4, 0
movi a5, sys_ni_syscall;
beq a4, a5, 1f
/* Load args: arg0 - arg5 are passed via regs. */
l32i a6, a2, PT_AREG6
l32i a7, a2, PT_AREG3
l32i a8, a2, PT_AREG4
l32i a9, a2, PT_AREG5
l32i a10, a2, PT_AREG8
l32i a11, a2, PT_AREG9
/* Pass one additional argument to the syscall: pt_regs (on stack) */
s32i a2, a1, 0
callx4 a4
1: /* regs->areg[2] = return_value */
s32i a6, a2, PT_AREG2
movi a4, do_syscall_trace_leave
mov a6, a2
callx4 a4
retw
ENDPROC(system_call)
/*
* Spill live registers on the kernel stack macro.
*
* Entry condition: ps.woe is set, ps.excm is cleared
* Exit condition: windowstart has single bit set
* May clobber: a12, a13
*/
.macro spill_registers_kernel
#if XCHAL_NUM_AREGS > 16
call12 1f
_j 2f
retw
.align 4
1:
_entry a1, 48
addi a12, a0, 3
#if XCHAL_NUM_AREGS > 32
.rept (XCHAL_NUM_AREGS - 32) / 12
_entry a1, 48
mov a12, a0
.endr
#endif
_entry a1, 16
#if XCHAL_NUM_AREGS % 12 == 0
mov a8, a8
#elif XCHAL_NUM_AREGS % 12 == 4
mov a12, a12
#elif XCHAL_NUM_AREGS % 12 == 8
mov a4, a4
#endif
retw
2:
#else
mov a12, a12
#endif
.endm
/*
* Task switch.
*
* struct task* _switch_to (struct task* prev, struct task* next)
* a2 a2 a3
*/
ENTRY(_switch_to)
entry a1, 48
mov a11, a3 # and 'next' (a3)
l32i a4, a2, TASK_THREAD_INFO
l32i a5, a3, TASK_THREAD_INFO
save_xtregs_user a4 a6 a8 a9 a12 a13 THREAD_XTREGS_USER
#if THREAD_RA > 1020 || THREAD_SP > 1020
addi a10, a2, TASK_THREAD
s32i a0, a10, THREAD_RA - TASK_THREAD # save return address
s32i a1, a10, THREAD_SP - TASK_THREAD # save stack pointer
#else
s32i a0, a2, THREAD_RA # save return address
s32i a1, a2, THREAD_SP # save stack pointer
#endif
/* Disable ints while we manipulate the stack pointer. */
irq_save a14, a3
rsync
/* Switch CPENABLE */
#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
l32i a3, a5, THREAD_CPENABLE
xsr a3, cpenable
s32i a3, a4, THREAD_CPENABLE
#endif
/* Flush register file. */
spill_registers_kernel
/* Set kernel stack (and leave critical section)
* Note: It's save to set it here. The stack will not be overwritten
* because the kernel stack will only be loaded again after
* we return from kernel space.
*/
rsr a3, excsave1 # exc_table
addi a7, a5, PT_REGS_OFFSET
s32i a7, a3, EXC_TABLE_KSTK
/* restore context of the task 'next' */
l32i a0, a11, THREAD_RA # restore return address
l32i a1, a11, THREAD_SP # restore stack pointer
load_xtregs_user a5 a6 a8 a9 a12 a13 THREAD_XTREGS_USER
wsr a14, ps
rsync
retw
ENDPROC(_switch_to)
ENTRY(ret_from_fork)
/* void schedule_tail (struct task_struct *prev)
* Note: prev is still in a6 (return value from fake call4 frame)
*/
movi a4, schedule_tail
callx4 a4
movi a4, do_syscall_trace_leave
mov a6, a1
callx4 a4
j common_exception_return
ENDPROC(ret_from_fork)
/*
* Kernel thread creation helper
* On entry, set up by copy_thread: a2 = thread_fn, a3 = thread_fn arg
* left from _switch_to: a6 = prev
*/
ENTRY(ret_from_kernel_thread)
call4 schedule_tail
mov a6, a3
callx4 a2
j common_exception_return
ENDPROC(ret_from_kernel_thread)
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