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linux/arch/xtensa/kernel/align.S

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/*
* arch/xtensa/kernel/align.S
*
* Handle unalignment exceptions in kernel space.
*
* 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) 2001 - 2005 Tensilica, Inc.
*
* Rewritten by Chris Zankel <chris@zankel.net>
*
* Based on work from Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
* and Marc Gauthier <marc@tensilica.com, marc@alimni.uwaterloo.ca>
*/
#include <linux/linkage.h>
#include <asm/current.h>
#include <asm/asm-offsets.h>
#include <asm/processor.h>
#if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION
/* First-level exception handler for unaligned exceptions.
*
* Note: This handler works only for kernel exceptions. Unaligned user
* access should get a seg fault.
*/
/* Big and little endian 16-bit values are located in
* different halves of a register. HWORD_START helps to
* abstract the notion of extracting a 16-bit value from a
* register.
* We also have to define new shifting instructions because
* lsb and msb are on 'opposite' ends in a register for
* different endian machines.
*
* Assume a memory region in ascending address:
* 0 1 2 3|4 5 6 7
*
* When loading one word into a register, the content of that register is:
* LE 3 2 1 0, 7 6 5 4
* BE 0 1 2 3, 4 5 6 7
*
* Masking the bits of the higher/lower address means:
* LE X X 0 0, 0 0 X X
* BE 0 0 X X, X X 0 0
*
* Shifting to higher/lower addresses, means:
* LE shift left / shift right
* BE shift right / shift left
*
* Extracting 16 bits from a 32 bit reg. value to higher/lower address means:
* LE mask 0 0 X X / shift left
* BE shift left / mask 0 0 X X
*/
#define UNALIGNED_USER_EXCEPTION
#if XCHAL_HAVE_BE
#define HWORD_START 16
#define INSN_OP0 28
#define INSN_T 24
#define INSN_OP1 16
.macro __src_b r, w0, w1; src \r, \w0, \w1; .endm
.macro __ssa8 r; ssa8b \r; .endm
.macro __ssa8r r; ssa8l \r; .endm
.macro __sh r, s; srl \r, \s; .endm
.macro __sl r, s; sll \r, \s; .endm
.macro __exth r, s; extui \r, \s, 0, 16; .endm
.macro __extl r, s; slli \r, \s, 16; .endm
#else
#define HWORD_START 0
#define INSN_OP0 0
#define INSN_T 4
#define INSN_OP1 12
.macro __src_b r, w0, w1; src \r, \w1, \w0; .endm
.macro __ssa8 r; ssa8l \r; .endm
.macro __ssa8r r; ssa8b \r; .endm
.macro __sh r, s; sll \r, \s; .endm
.macro __sl r, s; srl \r, \s; .endm
.macro __exth r, s; slli \r, \s, 16; .endm
.macro __extl r, s; extui \r, \s, 0, 16; .endm
#endif
/*
* xxxx xxxx = imm8 field
* yyyy = imm4 field
* ssss = s field
* tttt = t field
*
* 16 0
* -------------------
* L32I.N yyyy ssss tttt 1000
* S32I.N yyyy ssss tttt 1001
*
* 23 0
* -----------------------------
* res 0000 0010
* L16UI xxxx xxxx 0001 ssss tttt 0010
* L32I xxxx xxxx 0010 ssss tttt 0010
* XXX 0011 ssss tttt 0010
* XXX 0100 ssss tttt 0010
* S16I xxxx xxxx 0101 ssss tttt 0010
* S32I xxxx xxxx 0110 ssss tttt 0010
* XXX 0111 ssss tttt 0010
* XXX 1000 ssss tttt 0010
* L16SI xxxx xxxx 1001 ssss tttt 0010
* XXX 1010 0010
* **L32AI xxxx xxxx 1011 ssss tttt 0010 unsupported
* XXX 1100 0010
* XXX 1101 0010
* XXX 1110 0010
* **S32RI xxxx xxxx 1111 ssss tttt 0010 unsupported
* -----------------------------
* ^ ^ ^
* sub-opcode (NIBBLE_R) -+ | |
* t field (NIBBLE_T) -----------+ |
* major opcode (NIBBLE_OP0) --------------+
*/
#define OP0_L32I_N 0x8 /* load immediate narrow */
#define OP0_S32I_N 0x9 /* store immediate narrow */
#define OP1_SI_MASK 0x4 /* OP1 bit set for stores */
#define OP1_SI_BIT 2 /* OP1 bit number for stores */
#define OP1_L32I 0x2
#define OP1_L16UI 0x1
#define OP1_L16SI 0x9
#define OP1_L32AI 0xb
#define OP1_S32I 0x6
#define OP1_S16I 0x5
#define OP1_S32RI 0xf
/*
* Entry condition:
*
* a0: trashed, original value saved on stack (PT_AREG0)
* a1: a1
* a2: new stack pointer, original in DEPC
* a3: dispatch table
* depc: a2, original value saved on stack (PT_DEPC)
* excsave_1: a3
*
* PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
* < VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
*/
ENTRY(fast_unaligned)
/* Note: We don't expect the address to be aligned on a word
* boundary. After all, the processor generated that exception
* and it would be a hardware fault.
*/
/* Save some working register */
s32i a4, a2, PT_AREG4
s32i a5, a2, PT_AREG5
s32i a6, a2, PT_AREG6
s32i a7, a2, PT_AREG7
s32i a8, a2, PT_AREG8
rsr a0, DEPC
xsr a3, EXCSAVE_1
s32i a0, a2, PT_AREG2
s32i a3, a2, PT_AREG3
/* Keep value of SAR in a0 */
rsr a0, SAR
rsr a8, EXCVADDR # load unaligned memory address
/* Now, identify one of the following load/store instructions.
*
* The only possible danger of a double exception on the
* following l32i instructions is kernel code in vmalloc
* memory. The processor was just executing at the EPC_1
* address, and indeed, already fetched the instruction. That
* guarantees a TLB mapping, which hasn't been replaced by
* this unaligned exception handler that uses only static TLB
* mappings. However, high-level interrupt handlers might
* modify TLB entries, so for the generic case, we register a
* TABLE_FIXUP handler here, too.
*/
/* a3...a6 saved on stack, a2 = SP */
/* Extract the instruction that caused the unaligned access. */
rsr a7, EPC_1 # load exception address
movi a3, ~3
and a3, a3, a7 # mask lower bits
l32i a4, a3, 0 # load 2 words
l32i a5, a3, 4
__ssa8 a7
__src_b a4, a4, a5 # a4 has the instruction
/* Analyze the instruction (load or store?). */
extui a5, a4, INSN_OP0, 4 # get insn.op0 nibble
#if XCHAL_HAVE_DENSITY
_beqi a5, OP0_L32I_N, .Lload # L32I.N, jump
addi a6, a5, -OP0_S32I_N
_beqz a6, .Lstore # S32I.N, do a store
#endif
/* 'store indicator bit' not set, jump */
_bbci.l a4, OP1_SI_BIT + INSN_OP1, .Lload
/* Store: Jump to table entry to get the value in the source register.*/
.Lstore:movi a5, .Lstore_table # table
extui a6, a4, INSN_T, 4 # get source register
addx8 a5, a6, a5
jx a5 # jump into table
/* Invalid instruction, CRITICAL! */
.Linvalid_instruction_load:
j .Linvalid_instruction
/* Load: Load memory address. */
.Lload: movi a3, ~3
and a3, a3, a8 # align memory address
__ssa8 a8
#ifdef UNALIGNED_USER_EXCEPTION
addi a3, a3, 8
l32e a5, a3, -8
l32e a6, a3, -4
#else
l32i a5, a3, 0
l32i a6, a3, 4
#endif
__src_b a3, a5, a6 # a3 has the data word
#if XCHAL_HAVE_DENSITY
addi a7, a7, 2 # increment PC (assume 16-bit insn)
extui a5, a4, INSN_OP0, 4
_beqi a5, OP0_L32I_N, 1f # l32i.n: jump
addi a7, a7, 1
#else
addi a7, a7, 3
#endif
extui a5, a4, INSN_OP1, 4
_beqi a5, OP1_L32I, 1f # l32i: jump
extui a3, a3, 0, 16 # extract lower 16 bits
_beqi a5, OP1_L16UI, 1f
addi a5, a5, -OP1_L16SI
_bnez a5, .Linvalid_instruction_load
/* sign extend value */
slli a3, a3, 16
srai a3, a3, 16
/* Set target register. */
1:
#if XCHAL_HAVE_LOOPS
rsr a5, LEND # check if we reached LEND
bne a7, a5, 1f
rsr a5, LCOUNT # and LCOUNT != 0
beqz a5, 1f
addi a5, a5, -1 # decrement LCOUNT and set
rsr a7, LBEG # set PC to LBEGIN
wsr a5, LCOUNT
#endif
1: wsr a7, EPC_1 # skip load instruction
extui a4, a4, INSN_T, 4 # extract target register
movi a5, .Lload_table
addx8 a4, a4, a5
jx a4 # jump to entry for target register
.align 8
.Lload_table:
s32i a3, a2, PT_AREG0; _j .Lexit; .align 8
mov a1, a3; _j .Lexit; .align 8 # fishy??
s32i a3, a2, PT_AREG2; _j .Lexit; .align 8
s32i a3, a2, PT_AREG3; _j .Lexit; .align 8
s32i a3, a2, PT_AREG4; _j .Lexit; .align 8
s32i a3, a2, PT_AREG5; _j .Lexit; .align 8
s32i a3, a2, PT_AREG6; _j .Lexit; .align 8
s32i a3, a2, PT_AREG7; _j .Lexit; .align 8
s32i a3, a2, PT_AREG8; _j .Lexit; .align 8
mov a9, a3 ; _j .Lexit; .align 8
mov a10, a3 ; _j .Lexit; .align 8
mov a11, a3 ; _j .Lexit; .align 8
mov a12, a3 ; _j .Lexit; .align 8
mov a13, a3 ; _j .Lexit; .align 8
mov a14, a3 ; _j .Lexit; .align 8
mov a15, a3 ; _j .Lexit; .align 8
.Lstore_table:
l32i a3, a2, PT_AREG0; _j 1f; .align 8
mov a3, a1; _j 1f; .align 8 # fishy??
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
l32i a3, a2, PT_AREG5; _j 1f; .align 8
l32i a3, a2, PT_AREG6; _j 1f; .align 8
l32i a3, a2, PT_AREG7; _j 1f; .align 8
l32i a3, a2, PT_AREG8; _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: # a7: instruction pointer, a4: instruction, a3: value
movi a6, 0 # mask: ffffffff:00000000
#if XCHAL_HAVE_DENSITY
addi a7, a7, 2 # incr. PC,assume 16-bit instruction
extui a5, a4, INSN_OP0, 4 # extract OP0
addi a5, a5, -OP0_S32I_N
_beqz a5, 1f # s32i.n: jump
addi a7, a7, 1 # increment PC, 32-bit instruction
#else
addi a7, a7, 3 # increment PC, 32-bit instruction
#endif
extui a5, a4, INSN_OP1, 4 # extract OP1
_beqi a5, OP1_S32I, 1f # jump if 32 bit store
_bnei a5, OP1_S16I, .Linvalid_instruction_store
movi a5, -1
__extl a3, a3 # get 16-bit value
__exth a6, a5 # get 16-bit mask ffffffff:ffff0000
/* Get memory address */
1:
#if XCHAL_HAVE_LOOPS
rsr a4, LEND # check if we reached LEND
bne a7, a4, 1f
rsr a4, LCOUNT # and LCOUNT != 0
beqz a4, 1f
addi a4, a4, -1 # decrement LCOUNT and set
rsr a7, LBEG # set PC to LBEGIN
wsr a4, LCOUNT
#endif
1: wsr a7, EPC_1 # skip store instruction
movi a4, ~3
and a4, a4, a8 # align memory address
/* Insert value into memory */
movi a5, -1 # mask: ffffffff:XXXX0000
#ifdef UNALIGNED_USER_EXCEPTION
addi a4, a4, 8
#endif
__ssa8r a8
__src_b a7, a5, a6 # lo-mask F..F0..0 (BE) 0..0F..F (LE)
__src_b a6, a6, a5 # hi-mask 0..0F..F (BE) F..F0..0 (LE)
#ifdef UNALIGNED_USER_EXCEPTION
l32e a5, a4, -8
#else
l32i a5, a4, 0 # load lower address word
#endif
and a5, a5, a7 # mask
__sh a7, a3 # shift value
or a5, a5, a7 # or with original value
#ifdef UNALIGNED_USER_EXCEPTION
s32e a5, a4, -8
l32e a7, a4, -4
#else
s32i a5, a4, 0 # store
l32i a7, a4, 4 # same for upper address word
#endif
__sl a5, a3
and a6, a7, a6
or a6, a6, a5
#ifdef UNALIGNED_USER_EXCEPTION
s32e a6, a4, -4
#else
s32i a6, a4, 4
#endif
/* Done. restore stack and return */
.Lexit:
movi a4, 0
rsr a3, EXCSAVE_1
s32i a4, a3, EXC_TABLE_FIXUP
/* Restore working register */
l32i a8, a2, PT_AREG8
l32i a7, a2, PT_AREG7
l32i a6, a2, PT_AREG6
l32i a5, a2, PT_AREG5
l32i a4, a2, PT_AREG4
l32i a3, a2, PT_AREG3
/* restore SAR and return */
wsr a0, SAR
l32i a0, a2, PT_AREG0
l32i a2, a2, PT_AREG2
rfe
/* We cannot handle this exception. */
.extern _kernel_exception
.Linvalid_instruction_store:
.Linvalid_instruction:
/* Restore a4...a8 and SAR, set SP, and jump to default exception. */
l32i a8, a2, PT_AREG8
l32i a7, a2, PT_AREG7
l32i a6, a2, PT_AREG6
l32i a5, a2, PT_AREG5
l32i a4, a2, PT_AREG4
wsr a0, SAR
mov a1, a2
rsr a0, PS
bbsi.l a2, PS_UM_BIT, 1f # jump if user mode
movi a0, _kernel_exception
jx a0
1: movi a0, _user_exception
jx a0
#endif /* XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION */
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