- FPU context is stored only if conflict between 2 FPU users or while exporting context of a process to userspace while it is the active user of FPU - FPU has its owner (fpu_owner) which points to the process whose state is currently loaded in FPU - the FPU exception is only turned on when scheduling a process which is not the owner of FPU - FPU state is restored for the process that generated the FPU exception. This process runs immediately without letting scheduler to pick a new process to resolve the FPU conflict asap, to minimize the FPU thrashing and FPU exception hadler execution - faster all non-FPU-exception kernel entries as FPU state is not checked nor saved - removed MF_USED_FPU flag, only MF_FPU_INITIALIZED remains to signal that a process has used FPU in the past
669 lines
16 KiB
ArmAsm
669 lines
16 KiB
ArmAsm
/*
|
|
* This file is part of the lowest layer of the MINIX kernel. (The other part
|
|
* is "proc.c".) The lowest layer does process switching and message handling.
|
|
* Furthermore it contains the assembler startup code for Minix and the 32-bit
|
|
* interrupt handlers. It cooperates with the code in "start.c" to set up a
|
|
* good environment for main().
|
|
*
|
|
* Kernel is entered either because of kernel-calls, ipc-calls, interrupts or
|
|
* exceptions. TSS is set so that the kernel stack is loaded. The user cotext is
|
|
* saved to the proc table and the handler of the event is called. Once the
|
|
* handler is done, switch_to_user() function is called to pick a new process,
|
|
* finish what needs to be done for the next process to run, sets its context
|
|
* and switch to userspace.
|
|
*
|
|
* For communication with the boot monitor at startup time some constant
|
|
* data are compiled into the beginning of the text segment. This facilitates
|
|
* reading the data at the start of the boot process, since only the first
|
|
* sector of the file needs to be read.
|
|
*
|
|
* Some data storage is also allocated at the end of this file. This data
|
|
* will be at the start of the data segment of the kernel and will be read
|
|
* and modified by the boot monitor before the kernel starts.
|
|
*/
|
|
|
|
#include "kernel/kernel.h" /* configures the kernel */
|
|
|
|
/* sections */
|
|
|
|
#include <machine/vm.h>
|
|
|
|
#ifdef __ACK__
|
|
.text
|
|
begtext:
|
|
#ifdef __ACK__
|
|
.rom
|
|
#else
|
|
.data
|
|
#endif
|
|
begrom:
|
|
.data
|
|
begdata:
|
|
.bss
|
|
begbss:
|
|
#endif
|
|
|
|
|
|
#include <minix/config.h>
|
|
#include <minix/const.h>
|
|
#include <minix/com.h>
|
|
#include <machine/interrupt.h>
|
|
#include "archconst.h"
|
|
#include "kernel/const.h"
|
|
#include "kernel/proc.h"
|
|
#include "sconst.h"
|
|
|
|
/* Selected 386 tss offsets. */
|
|
#define TSS3_S_SP0 4
|
|
|
|
/*
|
|
* Exported functions
|
|
* Note: in assembly language the .define statement applied to a function name
|
|
* is loosely equivalent to a prototype in C code -- it makes it possible to
|
|
* link to an entity declared in the assembly code but does not create
|
|
* the entity.
|
|
*/
|
|
|
|
.globl _restore_user_context
|
|
.globl _copr_not_available_handler
|
|
.globl _reload_cr3
|
|
|
|
.globl _divide_error
|
|
.globl _single_step_exception
|
|
.globl _nmi
|
|
.globl _breakpoint_exception
|
|
.globl _overflow
|
|
.globl _bounds_check
|
|
.globl _inval_opcode
|
|
.globl _copr_not_available
|
|
.globl _double_fault
|
|
.globl _copr_seg_overrun
|
|
.globl _inval_tss
|
|
.globl _segment_not_present
|
|
.globl _stack_exception
|
|
.globl _general_protection
|
|
.globl _page_fault
|
|
.globl _copr_error
|
|
.globl _alignment_check
|
|
.globl _machine_check
|
|
.globl _simd_exception
|
|
.globl _params_size
|
|
.globl _params_offset
|
|
.globl _mon_ds
|
|
.globl _switch_to_user
|
|
.globl _save_fpu
|
|
|
|
.globl _hwint00 /* handlers for hardware interrupts */
|
|
.globl _hwint01
|
|
.globl _hwint02
|
|
.globl _hwint03
|
|
.globl _hwint04
|
|
.globl _hwint05
|
|
.globl _hwint06
|
|
.globl _hwint07
|
|
.globl _hwint08
|
|
.globl _hwint09
|
|
.globl _hwint10
|
|
.globl _hwint11
|
|
.globl _hwint12
|
|
.globl _hwint13
|
|
.globl _hwint14
|
|
.globl _hwint15
|
|
|
|
/* Exported variables. */
|
|
.globl begbss
|
|
.globl begdata
|
|
|
|
.text
|
|
/*===========================================================================*/
|
|
/* MINIX */
|
|
/*===========================================================================*/
|
|
.globl MINIX
|
|
MINIX:
|
|
/* this is the entry point for the MINIX kernel */
|
|
jmp over_flags /* skip over the next few bytes */
|
|
.short CLICK_SHIFT /* for the monitor: memory granularity */
|
|
|
|
flags:
|
|
/* boot monitor flags:
|
|
* call in 386 mode, make bss, make stack,
|
|
* load high, don't patch, will return,
|
|
* uses generic INT, memory vector,
|
|
* new boot code return
|
|
*/
|
|
.short 0x01FD
|
|
nop /* extra byte to sync up disassembler */
|
|
over_flags:
|
|
|
|
/* Set up a C stack frame on the monitor stack. (The monitor sets cs and ds */
|
|
/* right. The ss descriptor still references the monitor data segment.) */
|
|
movzwl %sp, %esp /* monitor stack is a 16 bit stack */
|
|
push %ebp
|
|
mov %esp, %ebp
|
|
push %esi
|
|
push %edi
|
|
cmp $0, 4(%ebp) /* monitor return vector is */
|
|
je noret /* nonzero if return possible */
|
|
incl _mon_return
|
|
noret:
|
|
movl %esp, _mon_sp /* save stack pointer for later return */
|
|
|
|
/* Copy the monitor global descriptor table to the address space of kernel and */
|
|
/* switch over to it. Prot_init() can then update it with immediate effect. */
|
|
|
|
sgdt _gdt+GDT_SELECTOR /* get the monitor gdtr */
|
|
movl _gdt+GDT_SELECTOR+2, %esi /* absolute address of GDT */
|
|
mov $_gdt, %ebx /* address of kernel GDT */
|
|
mov $8*8, %ecx /* copying eight descriptors */
|
|
copygdt:
|
|
movb %es:(%esi), %al
|
|
movb %al, (%ebx)
|
|
inc %esi
|
|
inc %ebx
|
|
loop copygdt
|
|
movl _gdt+DS_SELECTOR+2, %eax /* base of kernel data */
|
|
and $0x00FFFFFF, %eax /* only 24 bits */
|
|
add $_gdt, %eax /* eax = vir2phys(gdt) */
|
|
movl %eax, _gdt+GDT_SELECTOR+2 /* set base of GDT */
|
|
lgdt _gdt+GDT_SELECTOR /* switch over to kernel GDT */
|
|
|
|
/* Locate boot parameters, set up kernel segment registers and stack. */
|
|
mov 8(%ebp), %ebx /* boot parameters offset */
|
|
mov 12(%ebp), %edx /* boot parameters length */
|
|
mov 16(%ebp), %eax /* address of a.out headers */
|
|
movl %eax, _aout
|
|
mov %ds, %ax /* kernel data */
|
|
mov %ax, %es
|
|
mov %ax, %fs
|
|
mov %ax, %gs
|
|
mov %ax, %ss
|
|
mov $_k_boot_stktop, %esp /* set sp to point to the top of kernel stack */
|
|
|
|
/* Save boot parameters into these global variables for i386 code */
|
|
movl %edx, _params_size
|
|
movl %ebx, _params_offset
|
|
movl $SS_SELECTOR, _mon_ds
|
|
|
|
/* Call C startup code to set up a proper environment to run main(). */
|
|
push %edx
|
|
push %ebx
|
|
push $SS_SELECTOR
|
|
push $DS_SELECTOR
|
|
push $CS_SELECTOR
|
|
call _cstart /* cstart(cs, ds, mds, parmoff, parmlen) */
|
|
add $5*4, %esp
|
|
|
|
/* Reload gdtr, idtr and the segment registers to global descriptor table set */
|
|
/* up by prot_init(). */
|
|
|
|
lgdt _gdt+GDT_SELECTOR
|
|
lidt _gdt+IDT_SELECTOR
|
|
|
|
ljmp $CS_SELECTOR, $csinit
|
|
csinit:
|
|
movw $DS_SELECTOR, %ax
|
|
mov %ax, %ds
|
|
mov %ax, %es
|
|
mov %ax, %fs
|
|
mov %ax, %gs
|
|
mov %ax, %ss
|
|
movw $TSS_SELECTOR, %ax /* no other TSS is used */
|
|
ltr %ax
|
|
push $0 /* set flags to known good state */
|
|
popf /* esp, clear nested task and int enable */
|
|
jmp _main /* main() */
|
|
|
|
|
|
/*===========================================================================*/
|
|
/* interrupt handlers */
|
|
/* interrupt handlers for 386 32-bit protected mode */
|
|
/*===========================================================================*/
|
|
|
|
#define PIC_IRQ_HANDLER(irq) \
|
|
push $irq ;\
|
|
call _irq_handle /* intr_handle(irq_handlers[irq]) */ ;\
|
|
add $4, %esp ;
|
|
|
|
/*===========================================================================*/
|
|
/* hwint00 - 07 */
|
|
/*===========================================================================*/
|
|
/* Note this is a macro, it just looks like a subroutine. */
|
|
|
|
#define hwint_master(irq) \
|
|
TEST_INT_IN_KERNEL(4, 0f) ;\
|
|
\
|
|
SAVE_PROCESS_CTX(0) ;\
|
|
push %ebp ;\
|
|
movl $0, %ebp /* for stack trace */ ;\
|
|
call _context_stop ;\
|
|
add $4, %esp ;\
|
|
PIC_IRQ_HANDLER(irq) ;\
|
|
movb $END_OF_INT, %al ;\
|
|
outb $INT_CTL /* reenable interrupts in master pic */ ;\
|
|
jmp _switch_to_user ;\
|
|
\
|
|
0: \
|
|
pusha ;\
|
|
call _context_stop_idle ;\
|
|
PIC_IRQ_HANDLER(irq) ;\
|
|
movb $END_OF_INT, %al ;\
|
|
outb $INT_CTL /* reenable interrupts in master pic */ ;\
|
|
CLEAR_IF(10*4(%esp)) ;\
|
|
popa ;\
|
|
iret ;
|
|
|
|
/* Each of these entry points is an expansion of the hwint_master macro */
|
|
.balign 16
|
|
_hwint00:
|
|
/* Interrupt routine for irq 0 (the clock). */
|
|
hwint_master(0)
|
|
|
|
.balign 16
|
|
_hwint01:
|
|
/* Interrupt routine for irq 1 (keyboard) */
|
|
hwint_master(1)
|
|
|
|
.balign 16
|
|
_hwint02:
|
|
/* Interrupt routine for irq 2 (cascade!) */
|
|
hwint_master(2)
|
|
|
|
.balign 16
|
|
_hwint03:
|
|
/* Interrupt routine for irq 3 (second serial) */
|
|
hwint_master(3)
|
|
|
|
.balign 16
|
|
_hwint04:
|
|
/* Interrupt routine for irq 4 (first serial) */
|
|
hwint_master(4)
|
|
|
|
.balign 16
|
|
_hwint05:
|
|
/* Interrupt routine for irq 5 (XT winchester) */
|
|
hwint_master(5)
|
|
|
|
.balign 16
|
|
_hwint06:
|
|
/* Interrupt routine for irq 6 (floppy) */
|
|
hwint_master(6)
|
|
|
|
.balign 16
|
|
_hwint07:
|
|
/* Interrupt routine for irq 7 (printer) */
|
|
hwint_master(7)
|
|
|
|
/*===========================================================================*/
|
|
/* hwint08 - 15 */
|
|
/*===========================================================================*/
|
|
/* Note this is a macro, it just looks like a subroutine. */
|
|
#define hwint_slave(irq) \
|
|
TEST_INT_IN_KERNEL(4, 0f) ;\
|
|
\
|
|
SAVE_PROCESS_CTX(0) ;\
|
|
push %ebp ;\
|
|
movl $0, %ebp /* for stack trace */ ;\
|
|
call _context_stop ;\
|
|
add $4, %esp ;\
|
|
PIC_IRQ_HANDLER(irq) ;\
|
|
movb $END_OF_INT, %al ;\
|
|
outb $INT_CTL /* reenable interrupts in master pic */ ;\
|
|
outb $INT2_CTL /* reenable slave 8259 */ ;\
|
|
jmp _switch_to_user ;\
|
|
\
|
|
0: \
|
|
pusha ;\
|
|
call _context_stop_idle ;\
|
|
PIC_IRQ_HANDLER(irq) ;\
|
|
movb $END_OF_INT, %al ;\
|
|
outb $INT_CTL /* reenable interrupts in master pic */ ;\
|
|
outb $INT2_CTL /* reenable slave 8259 */ ;\
|
|
CLEAR_IF(10*4(%esp)) ;\
|
|
popa ;\
|
|
iret ;
|
|
|
|
/* Each of these entry points is an expansion of the hwint_slave macro */
|
|
.balign 16
|
|
_hwint08:
|
|
/* Interrupt routine for irq 8 (realtime clock) */
|
|
hwint_slave(8)
|
|
|
|
.balign 16
|
|
_hwint09:
|
|
/* Interrupt routine for irq 9 (irq 2 redirected) */
|
|
hwint_slave(9)
|
|
|
|
.balign 16
|
|
_hwint10:
|
|
/* Interrupt routine for irq 10 */
|
|
hwint_slave(10)
|
|
|
|
.balign 16
|
|
_hwint11:
|
|
/* Interrupt routine for irq 11 */
|
|
hwint_slave(11)
|
|
|
|
.balign 16
|
|
_hwint12:
|
|
/* Interrupt routine for irq 12 */
|
|
hwint_slave(12)
|
|
|
|
.balign 16
|
|
_hwint13:
|
|
/* Interrupt routine for irq 13 (FPU exception) */
|
|
hwint_slave(13)
|
|
|
|
.balign 16
|
|
_hwint14:
|
|
/* Interrupt routine for irq 14 (AT winchester) */
|
|
hwint_slave(14)
|
|
|
|
.balign 16
|
|
_hwint15:
|
|
/* Interrupt routine for irq 15 */
|
|
hwint_slave(15)
|
|
|
|
/*
|
|
* IPC is only from a process to kernel
|
|
*/
|
|
.balign 16
|
|
.globl _ipc_entry
|
|
_ipc_entry:
|
|
|
|
SAVE_PROCESS_CTX(0)
|
|
|
|
/* save the pointer to the current process */
|
|
push %ebp
|
|
|
|
/*
|
|
* pass the syscall arguments from userspace to the handler.
|
|
* SAVE_PROCESS_CTX() does not clobber these registers, they are still
|
|
* set as the userspace have set them
|
|
*/
|
|
push %ebx
|
|
push %eax
|
|
push %ecx
|
|
|
|
/* stop user process cycles */
|
|
push %ebp
|
|
/* for stack trace */
|
|
movl $0, %ebp
|
|
call _context_stop
|
|
add $4, %esp
|
|
|
|
call _do_ipc
|
|
|
|
/* restore the current process pointer and save the return value */
|
|
add $3 * 4, %esp
|
|
pop %esi
|
|
mov %eax, AXREG(%esi)
|
|
|
|
jmp _switch_to_user
|
|
|
|
|
|
/*
|
|
* kernel call is only from a process to kernel
|
|
*/
|
|
.balign 16
|
|
.globl _kernel_call_entry
|
|
_kernel_call_entry:
|
|
|
|
SAVE_PROCESS_CTX(0)
|
|
|
|
/* save the pointer to the current process */
|
|
push %ebp
|
|
|
|
/*
|
|
* pass the syscall arguments from userspace to the handler.
|
|
* SAVE_PROCESS_CTX() does not clobber these registers, they are still
|
|
* set as the userspace have set them
|
|
*/
|
|
push %eax
|
|
|
|
/* stop user process cycles */
|
|
push %ebp
|
|
/* for stack trace */
|
|
movl $0, %ebp
|
|
call _context_stop
|
|
add $4, %esp
|
|
|
|
call _kernel_call
|
|
|
|
/* restore the current process pointer and save the return value */
|
|
add $8, %esp
|
|
|
|
jmp _switch_to_user
|
|
|
|
|
|
.balign 16
|
|
/*
|
|
* called by the exception interrupt vectors. If the exception does not push
|
|
* errorcode, we assume that the vector handler pushed 0 instead. Next pushed
|
|
* thing is the vector number. From this point on we can continue as if every
|
|
* exception pushes an error code
|
|
*/
|
|
exception_entry:
|
|
/*
|
|
* check if it is a nested trap by comparing the saved code segment
|
|
* descriptor with the kernel CS first
|
|
*/
|
|
TEST_INT_IN_KERNEL(12, exception_entry_nested)
|
|
|
|
exception_entry_from_user:
|
|
SAVE_PROCESS_CTX(8)
|
|
|
|
/* stop user process cycles */
|
|
push %ebp
|
|
/* for stack trace clear %ebp */
|
|
movl $0, %ebp
|
|
call _context_stop
|
|
add $4, %esp
|
|
|
|
/*
|
|
* push a pointer to the interrupt state pushed by the cpu and the
|
|
* vector number pushed by the vector handler just before calling
|
|
* exception_entry and call the exception handler.
|
|
*/
|
|
push %esp
|
|
push $0 /* it's not a nested exception */
|
|
call _exception_handler
|
|
|
|
jmp _switch_to_user
|
|
|
|
exception_entry_nested:
|
|
|
|
pusha
|
|
mov %esp, %eax
|
|
add $(8 * 4), %eax
|
|
push %eax
|
|
pushl $1 /* it's a nested exception */
|
|
call _exception_handler
|
|
add $8, %esp
|
|
popa
|
|
|
|
/* clear the error code and the exception number */
|
|
add $8, %esp
|
|
/* resume execution at the point of exception */
|
|
iret
|
|
|
|
/*===========================================================================*/
|
|
/* restart */
|
|
/*===========================================================================*/
|
|
_restore_user_context:
|
|
mov 4(%esp), %ebp /* will assume P_STACKBASE == 0 */
|
|
|
|
/* reconstruct the stack for iret */
|
|
movl SSREG(%ebp), %eax
|
|
push %eax
|
|
movl SPREG(%ebp), %eax
|
|
push %eax
|
|
movl PSWREG(%ebp), %eax
|
|
push %eax
|
|
movl CSREG(%ebp), %eax
|
|
push %eax
|
|
movl PCREG(%ebp), %eax
|
|
push %eax
|
|
|
|
RESTORE_GP_REGS(%ebp)
|
|
|
|
RESTORE_SEGS(%ebp)
|
|
|
|
movl %ss:BPREG(%ebp), %ebp
|
|
|
|
iret /* continue process */
|
|
|
|
/*===========================================================================*/
|
|
/* exception handlers */
|
|
/*===========================================================================*/
|
|
|
|
#define EXCEPTION_ERR_CODE(vector) \
|
|
push $vector ;\
|
|
jmp exception_entry
|
|
|
|
#define EXCEPTION_NO_ERR_CODE(vector) \
|
|
pushl $0 ;\
|
|
EXCEPTION_ERR_CODE(vector)
|
|
|
|
_divide_error:
|
|
EXCEPTION_NO_ERR_CODE(DIVIDE_VECTOR)
|
|
|
|
_single_step_exception:
|
|
EXCEPTION_NO_ERR_CODE(DEBUG_VECTOR)
|
|
|
|
_nmi:
|
|
#ifndef CONFIG_WATCHDOG
|
|
EXCEPTION_NO_ERR_CODE(NMI_VECTOR)
|
|
#else
|
|
/*
|
|
* We have to be very careful as this interrupt can occur anytime. On
|
|
* the other hand, if it interrupts a user process, we will resume the
|
|
* same process which makes things a little simpler. We know that we are
|
|
* already on kernel stack whenever it happened and we can be
|
|
* conservative and save everything as we don't need to be extremely
|
|
* efficient as the interrupt is infrequent and some overhead is already
|
|
* expected.
|
|
*/
|
|
|
|
/*
|
|
* save the important registers. We don't save %cs and %ss and they are
|
|
* saved and restored by CPU
|
|
*/
|
|
pushw %ds
|
|
pushw %es
|
|
pushw %fs
|
|
pushw %gs
|
|
pusha
|
|
|
|
/*
|
|
* We cannot be sure about the state of the kernel segment register,
|
|
* however, we always set %ds and %es to the same as %ss
|
|
*/
|
|
mov %ss, %si
|
|
mov %si, %ds
|
|
mov %si, %es
|
|
|
|
push %esp
|
|
call _nmi_watchdog_handler
|
|
add $4, %esp
|
|
|
|
/* restore all the important registers as they were before the trap */
|
|
popa
|
|
popw %gs
|
|
popw %fs
|
|
popw %es
|
|
popw %ds
|
|
|
|
iret
|
|
#endif
|
|
|
|
_breakpoint_exception:
|
|
EXCEPTION_NO_ERR_CODE(BREAKPOINT_VECTOR)
|
|
|
|
_overflow:
|
|
EXCEPTION_NO_ERR_CODE(OVERFLOW_VECTOR)
|
|
|
|
_bounds_check:
|
|
EXCEPTION_NO_ERR_CODE(BOUNDS_VECTOR)
|
|
|
|
_inval_opcode:
|
|
EXCEPTION_NO_ERR_CODE(INVAL_OP_VECTOR)
|
|
|
|
_copr_not_available:
|
|
TEST_INT_IN_KERNEL(4, copr_not_available_in_kernel)
|
|
cld /* set direction flag to a known value */
|
|
SAVE_PROCESS_CTX(0)
|
|
/* stop user process cycles */
|
|
push %ebp
|
|
mov $0, %ebp
|
|
call _context_stop
|
|
jmp _copr_not_available_handler
|
|
|
|
copr_not_available_in_kernel:
|
|
pushl $0
|
|
pushl $COPROC_NOT_VECTOR
|
|
jmp exception_entry_nested
|
|
|
|
_double_fault:
|
|
EXCEPTION_ERR_CODE(DOUBLE_FAULT_VECTOR)
|
|
|
|
_copr_seg_overrun:
|
|
EXCEPTION_NO_ERR_CODE(COPROC_SEG_VECTOR)
|
|
|
|
_inval_tss:
|
|
EXCEPTION_ERR_CODE(INVAL_TSS_VECTOR)
|
|
|
|
_segment_not_present:
|
|
EXCEPTION_ERR_CODE(SEG_NOT_VECTOR)
|
|
|
|
_stack_exception:
|
|
EXCEPTION_ERR_CODE(STACK_FAULT_VECTOR)
|
|
|
|
_general_protection:
|
|
EXCEPTION_ERR_CODE(PROTECTION_VECTOR)
|
|
|
|
_page_fault:
|
|
EXCEPTION_ERR_CODE(PAGE_FAULT_VECTOR)
|
|
|
|
_copr_error:
|
|
EXCEPTION_NO_ERR_CODE(COPROC_ERR_VECTOR)
|
|
|
|
_alignment_check:
|
|
EXCEPTION_NO_ERR_CODE(ALIGNMENT_CHECK_VECTOR)
|
|
|
|
_machine_check:
|
|
EXCEPTION_NO_ERR_CODE(MACHINE_CHECK_VECTOR)
|
|
|
|
_simd_exception:
|
|
EXCEPTION_NO_ERR_CODE(SIMD_EXCEPTION_VECTOR)
|
|
|
|
/*===========================================================================*/
|
|
/* reload_cr3 */
|
|
/*===========================================================================*/
|
|
/* PUBLIC void reload_cr3(void); */
|
|
_reload_cr3:
|
|
push %ebp
|
|
mov %esp, %ebp
|
|
mov %cr3, %eax
|
|
mov %eax, %cr3
|
|
pop %ebp
|
|
ret
|
|
|
|
/*===========================================================================*/
|
|
/* data */
|
|
/*===========================================================================*/
|
|
|
|
#ifdef __ACK__
|
|
.rom /* Before the string table please */
|
|
#else
|
|
.data
|
|
#endif
|
|
.short 0x526F /* this must be the first data entry (magic #) */
|
|
|
|
.bss
|
|
/*
|
|
* the kernel stack
|
|
*/
|
|
.globl _k_boot_stktop
|
|
k_boot_stack:
|
|
.space 4096 /* kernel stack */ /* FIXME use macro here */
|
|
_k_boot_stktop: /* top of kernel stack */
|