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linux-next/arch/xtensa/kernel/entry.S
Max Filippov 09f8a6db20 xtensa: add support for call0 ABI in userspace 
Provide a Kconfig choice to select whether only the default ABI, only
call0 ABI or both are supported. The default for XEA2 is windowed, but
it may change for XEA3. Call0 only runs userspace with PS.WOE disabled.
Supporting both windowed and call0 ABIs is tricky, as there's no
indication in the ELF binaries which ABI they use. So it is done by
probing: each process is started with PS.WOE disabled, but the handler
of an illegal instruction exception taken with PS.WOE retries faulting
instruction after enabling PS.WOE. It must happen before any signal is
delivered to the process, otherwise it may be delivered incorrectly.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
2019-09-01 13:11:57 -07:00

2082 lines
48 KiB
ArmAsm
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/*
* 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/asmmacro.h>
#include <asm/processor.h>
#include <asm/coprocessor.h>
#include <asm/thread_info.h>
#include <asm/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
*/
.literal_position
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, NO_SYSCALL
rsr a3, excvaddr
s32i a2, a1, PT_SYSCALL
movi a2, 0
s32i a3, a1, PT_EXCVADDR
#if XCHAL_HAVE_LOOPS
xsr a2, lcount
s32i a2, a1, PT_LCOUNT
#endif
/* 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, PS_WOE_MASK
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, PS_WOE_MASK
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 */
#if XCHAL_HAVE_LOOPS
rsr a4, lbeg
rsr a3, lend
s32i a4, a1, PT_LBEG
s32i a3, a1, PT_LEND
#endif
/* 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
call4 trace_hardirqs_off
#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
call4 trace_hardirqs_on
#endif
rsil a2, 0
mov a6, a1
call4 do_notify_resume # int do_notify_resume(struct pt_regs*)
j 1b
3: /* Reschedule */
#ifdef CONFIG_TRACE_IRQFLAGS
call4 trace_hardirqs_on
#endif
rsil a2, 0
call4 schedule # void schedule (void)
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
call4 preempt_schedule_irq
j 1b
#endif
#if XTENSA_FAKE_NMI
.LNMIexit:
l32i a3, a1, PT_PS
_bbci.l a3, PS_UM_BIT, 4f
#endif
5:
#ifdef CONFIG_HAVE_HW_BREAKPOINT
_bbci.l a4, TIF_DB_DISABLED, 7f
call4 restore_dbreak
7:
#endif
#ifdef CONFIG_DEBUG_TLB_SANITY
l32i a4, a1, PT_DEPC
bgeui a4, VALID_DOUBLE_EXCEPTION_ADDRESS, 4f
call4 check_tlb_sanity
#endif
6:
4:
#ifdef CONFIG_TRACE_IRQFLAGS
extui a4, a3, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
bgei a4, LOCKLEVEL, 1f
call4 trace_hardirqs_on
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 */
#if XCHAL_HAVE_LOOPS
l32i a2, a1, PT_LBEG
l32i a3, a1, PT_LEND
wsr a2, lbeg
l32i a2, a1, PT_LCOUNT
wsr a3, lend
wsr a2, lcount
#endif
/* 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]
*/
.literal_position
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
wsr a2, ps
/* 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
3:
l32i a0, a3, DT_DEBUG_SAVE
s32i a1, a2, PT_AREG1
s32i a0, a2, PT_AREG0
movi a0, 0
s32i a0, a2, PT_DEPC # mark it as a regular exception
xsr a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
xsr a0, depc
s32i a3, a2, PT_AREG3
s32i a0, a2, PT_AREG2
mov a1, a2
/* Debug exception is handled as an exception, so interrupts will
* likely be enabled in the common exception handler. Disable
* preemption if we have HW breakpoints to preserve DEBUGCAUSE.DBNUM
* meaning.
*/
#if defined(CONFIG_PREEMPT_COUNT) && defined(CONFIG_HAVE_HW_BREAKPOINT)
GET_THREAD_INFO(a2, a1)
l32i a3, a2, TI_PRE_COUNT
addi a3, a3, 1
s32i a3, a2, TI_PRE_COUNT
#endif
rsr a2, ps
bbsi.l a2, PS_UM_BIT, _user_exception
j _kernel_exception
2: rsr a2, excsave1
l32i a2, a2, EXC_TABLE_KSTK # load kernel stack pointer
j 3b
#ifdef CONFIG_HAVE_HW_BREAKPOINT
/* Debug exception while in exception mode. This may happen when
* window overflow/underflow handler or fast exception handler hits
* data breakpoint, in which case save and disable all data
* breakpoints, single-step faulting instruction and restore data
* breakpoints.
*/
1:
bbci.l a0, PS_UM_BIT, 1b # jump if kernel mode
rsr a0, debugcause
bbsi.l a0, DEBUGCAUSE_DBREAK_BIT, .Ldebug_save_dbreak
.set _index, 0
.rept XCHAL_NUM_DBREAK
l32i a0, a3, DT_DBREAKC_SAVE + _index * 4
wsr a0, SREG_DBREAKC + _index
.set _index, _index + 1
.endr
l32i a0, a3, DT_ICOUNT_LEVEL_SAVE
wsr a0, icountlevel
l32i a0, a3, DT_ICOUNT_SAVE
xsr a0, icount
l32i a0, a3, DT_DEBUG_SAVE
xsr a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
rfi XCHAL_DEBUGLEVEL
.Ldebug_save_dbreak:
.set _index, 0
.rept XCHAL_NUM_DBREAK
movi a0, 0
xsr a0, SREG_DBREAKC + _index
s32i a0, a3, DT_DBREAKC_SAVE + _index * 4
.set _index, _index + 1
.endr
movi a0, XCHAL_EXCM_LEVEL + 1
xsr a0, icountlevel
s32i a0, a3, DT_ICOUNT_LEVEL_SAVE
movi a0, 0xfffffffe
xsr a0, icount
s32i a0, a3, DT_ICOUNT_SAVE
l32i a0, a3, DT_DEBUG_SAVE
xsr a3, SREG_EXCSAVE + XCHAL_DEBUGLEVEL
rfi XCHAL_DEBUGLEVEL
#else
/* Debug exception while in exception mode. Should not happen. */
1: j 1b // FIXME!!
#endif
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"
.literal_position
ENTRY(unrecoverable_exception)
movi a0, 1
movi a1, 0
wsr a0, windowstart
wsr a1, windowbase
rsync
movi a1, PS_WOE_MASK | LOCKLEVEL
wsr a1, ps
rsync
movi a1, init_task
movi a0, 0
addi a1, a1, PT_REGS_OFFSET
movi a6, unrecoverable_text
call4 panic
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)
#ifdef CONFIG_USER_ABI_CALL0_PROBE
/*
* fast illegal instruction handler.
*
* This is used to fix up user PS.WOE on the exception caused
* by the first opcode related to register window. If PS.WOE is
* already set it goes directly to the common user 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
*/
ENTRY(fast_illegal_instruction_user)
rsr a0, ps
bbsi.l a0, PS_WOE_BIT, user_exception
s32i a3, a2, PT_AREG3
movi a3, PS_WOE_MASK
or a0, a0, a3
wsr a0, ps
l32i a3, a2, PT_AREG3
l32i a0, a2, PT_AREG0
rsr a2, depc
rfe
ENDPROC(fast_illegal_instruction_user)
#endif
/*
* 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_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
call0 unrecoverable_exception
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
*/
.literal_position
#ifdef CONFIG_FAST_SYSCALL_XTENSA
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 */
EX(.Leac) l32i a0, a3, 0 # read old value
bne a0, a4, 1f # same as old value? jump
EX(.Leac) 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. */
EX(.Leac) 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
EX(.Leac) 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
.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, PS_WOE_MASK | LOCKLEVEL
wsr a4, ps
rsync
movi a6, SIGSEGV
call4 do_exit
/* shouldn't return, so panic */
wsr a0, excsave1
call0 unrecoverable_exception # 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:
call0 unrecoverable_exception # 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 + PHYS_OFFSET) & PAGE_MASK)
* | PAGE_DIRECTORY
*/
movi a1, (PHYS_OFFSET - 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
*/
.literal_position
ENTRY(system_call)
/* reserve 4 bytes on stack for function parameter */
abi_entry(4)
/* regs->syscall = regs->areg[2] */
l32i a7, a2, PT_AREG2
s32i a7, a2, PT_SYSCALL
GET_THREAD_INFO(a4, a1)
l32i a3, a4, TI_FLAGS
movi a4, _TIF_WORK_MASK
and a3, a3, a4
beqz a3, 1f
mov a6, a2
call4 do_syscall_trace_enter
l32i a7, a2, PT_SYSCALL
1:
s32i a7, a1, 4
/* syscall = sys_call_table[syscall_nr] */
movi a4, sys_call_table
movi a5, __NR_syscalls
movi a6, -ENOSYS
bgeu a7, a5, 1f
addx4 a4, a7, 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
bnez a3, 1f
abi_ret(4)
1:
l32i a4, a1, 4
l32i a3, a2, PT_SYSCALL
s32i a4, a2, PT_SYSCALL
mov a6, a2
call4 do_syscall_trace_leave
s32i a3, a2, PT_SYSCALL
abi_ret(4)
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)
abi_entry(XTENSA_SPILL_STACK_RESERVE)
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
#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)
movi a6, __stack_chk_guard
l32i a8, a3, TASK_STACK_CANARY
s32i a8, a6, 0
#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
abi_ret(XTENSA_SPILL_STACK_RESERVE)
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)
*/
call4 schedule_tail
mov a6, a1
call4 do_syscall_trace_leave
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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