entry.s

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

/*
 *  arch/s390/kernel/entry.S
 *    S390 low-level entry points.
 *
 *  S390 version
 *    Copyright (C) 1999,2000 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Martin Schwidefsky ([e-mail]),
 *               Hartmut Penner ([e-mail]),
 *               Denis Joseph Barrow ([e-mail],[e-mail]),
 */

#include <linux/sys.h>
#include <linux/linkage.h>
#include <linux/config.h>
#include <asm/cache.h>
#include <asm/lowcore.h>
#include <asm/errno.h>
#include <asm/smp.h>
#include <asm/ptrace.h>

/*
 * Stack layout for the system_call stack entry.
 * The first few entries are identical to the user_regs_struct.
 */
SP_PTREGS    =  STACK_FRAME_OVERHEAD 
SP_PSW       =  STACK_FRAME_OVERHEAD + PT_PSWMASK
SP_R0        =  STACK_FRAME_OVERHEAD + PT_GPR0
SP_R1        =  STACK_FRAME_OVERHEAD + PT_GPR1
SP_R2        =  STACK_FRAME_OVERHEAD + PT_GPR2
SP_R3        =  STACK_FRAME_OVERHEAD + PT_GPR3
SP_R4        =  STACK_FRAME_OVERHEAD + PT_GPR4
SP_R5        =  STACK_FRAME_OVERHEAD + PT_GPR5
SP_R6        =  STACK_FRAME_OVERHEAD + PT_GPR6
SP_R7        =  STACK_FRAME_OVERHEAD + PT_GPR7
SP_R8        =  STACK_FRAME_OVERHEAD + PT_GPR8
SP_R9        =  STACK_FRAME_OVERHEAD + PT_GPR9
SP_R10       =  STACK_FRAME_OVERHEAD + PT_GPR10
SP_R11       =  STACK_FRAME_OVERHEAD + PT_GPR11
SP_R12       =  STACK_FRAME_OVERHEAD + PT_GPR12
SP_R13       =  STACK_FRAME_OVERHEAD + PT_GPR13
SP_R14       =  STACK_FRAME_OVERHEAD + PT_GPR14
SP_R15       =  STACK_FRAME_OVERHEAD + PT_GPR15
SP_AREGS     =  STACK_FRAME_OVERHEAD + PT_ACR0
SP_ORIG_R2   =  STACK_FRAME_OVERHEAD + PT_ORIGGPR2
/* Now the additional entries */
SP_TRAP      =  (SP_ORIG_R2+GPR_SIZE)
#if CONFIG_REMOTE_DEBUG
SP_CRREGS    =  (SP_TRAP+4)
/* fpu registers are saved & restored by the gdb stub itself */
SP_FPC       =  (SP_CRREGS+(NUM_CRS*CR_SIZE))
SP_FPRS      =  (SP_FPC+FPC_SIZE+FPC_PAD_SIZE)
SP_PGM_OLD_ILC= (SP_FPRS+(NUM_FPRS*FPR_SIZE))
#else
SP_PGM_OLD_ILC= (SP_TRAP+4)
#endif
SP_SIZE      =  (SP_PGM_OLD_ILC+4)
/*
 * these defines are offsets into the thread_struct
 */
_TSS_PTREGS  = 0
_TSS_FPRS    = (_TSS_PTREGS+8)
_TSS_AR2     = (_TSS_FPRS+136)
_TSS_AR4     = (_TSS_AR2+4)
_TSS_KSP     = (_TSS_AR4+4)
_TSS_USERSEG = (_TSS_KSP+4)
_TSS_ERROR   = (_TSS_USERSEG+4)
_TSS_PROT    = (_TSS_ERROR+4)
_TSS_TRAP    = (_TSS_PROT+4)
_TSS_MM      = (_TSS_TRAP+4)
_TSS_PER     = (_TSS_MM+8)
_TSS_IEEE    = (_TSS_PER+36)
_TSS_FLAGS   = (_TSS_IEEE+4)

/*
 * these are offsets into the task-struct.
 */
state        =  0
flags        =  4
sigpending   =  8
need_resched = 24
tsk_ptrace   = 28
processor    = 52

/*
 * Base Address of this Module --- saved in __LC_ENTRY_BASE
 */
       .globl entry_base
entry_base:

#define BASED(name) name-entry_base(%r13)

/*
 * Register usage in interrupt handlers:
 *    R9  - pointer to current task structure
 *    R13 - pointer to literal pool
 *    R14 - return register for function calls
 *    R15 - kernel stack pointer
 */

        .macro  SAVE_ALL psworg,sync      # system entry macro
        stm     %r13,%r15,__LC_SAVE_AREA
        basr    %r13,0                    #  temp base pointer
        l       %r13,.Lentry_base-.(%r13) # load &entry_base to %r13 
        tm      \psworg+1,0x01            # test problem state bit
        stam    %a2,%a4,__LC_SAVE_AREA+12
	.if	\sync
        bz      BASED(1f)                 # skip stack setup save
	.else
        bnz     BASED(0f)                 # from user -> load kernel stack
	l	%r14,__LC_ASYNC_STACK	  # are we already on the async stack ?
	slr     %r14,%r15
	sra	%r14,13
	be	BASED(1f)
        l       %r15,__LC_ASYNC_STACK     # load async. stack
	b	BASED(1f)
	.endif
0:      l       %r15,__LC_KERNEL_STACK    # problem state -> load ksp
	lam	%a2,%a4,BASED(.Lc_ac)	  # set ac.reg. 2 to primary space
					  # and ac.reg. 4 to home space
1:      s       %r15,BASED(.Lc_spsize)    # make room for registers & psw
        n       %r15,BASED(.Lc0xfffffff8) # align stack pointer to 8
        stm     %r0,%r12,SP_R0(%r15)      # store gprs 0-12 to kernel stack
        st      %r2,SP_ORIG_R2(%r15)      # store original content of gpr 2
        mvc     SP_R13(12,%r15),__LC_SAVE_AREA  # move R13-R15 to stack
        stam    %a0,%a15,SP_AREGS(%r15)   # store access registers to kst.
        mvc     SP_AREGS+8(12,%r15),__LC_SAVE_AREA+12 # store ac. regs
        mvc     SP_PSW(8,%r15),\psworg    # move user PSW to stack
        la      %r0,\psworg               # store trap indication
        st      %r0,SP_TRAP(%r15)
        xc      0(4,%r15),0(%r15)         # clear back chain
        .endm

        .macro  RESTORE_ALL sync          # system exit macro
        mvc     __LC_RETURN_PSW(8),SP_PSW(%r15)  # move user PSW to lowcore
        lam     %a0,%a15,SP_AREGS(%r15)   # load the access registers
        lm      %r0,%r15,SP_R0(%r15)      # load gprs 0-15 of user
        ni      __LC_RETURN_PSW+1,0xfd    # clear wait state bit
        lpsw    __LC_RETURN_PSW           # back to caller
        .endm

        .macro  GET_CURRENT
	l	%r9,BASED(.Lc0xffffe000)  # load pointer to task_struct to %r9
	al	%r9,__LC_KERNEL_STACK
        .endm


/*
 * Scheduler resume function, called by switch_to
 *  grp2 = (thread_struct *) prev->tss
 *  grp3 = (thread_struct *) next->tss
 * Returns:
 *  gpr2 = prev
 */
        .globl  resume
resume:
        basr    %r1,0
resume_base:
        l       %r4,_TSS_PTREGS(%r3)
        tm      SP_PSW-SP_PTREGS(%r4),0x40 # is the new process using per ?
        bz      resume_noper-resume_base(%r1) # if not we're fine
        stctl   %c9,%c11,24(%r15)             # We are using per stuff
        clc     _TSS_PER(12,%r3),24(%r15)
        be      resume_noper-resume_base(%r1) # we got away w/o bashing TLB's
        lctl    %c9,%c11,_TSS_PER(%r3)        # Nope we didn't
resume_noper:
        stm     %r6,%r15,24(%r15)       # store resume registers of prev task
        st      %r15,_TSS_KSP(%r2) # store kernel stack ptr to prev->tss.ksp
        lr      %r0,%r15
        n       %r0,.Lc0xffffe000-resume_base(%r1)
        l       %r15,_TSS_KSP(%r3) # load kernel stack ptr from next->tss.ksp
        l       %r1,.Lc8191-resume_base(%r1)
        or      %r1,%r15
        la      %r1,1(%r1)
        st      %r1,__LC_KERNEL_STACK   # __LC_KERNEL_STACK = new kernel stack
        stam    %a2,%a2,_TSS_AR2(%r2)   # store kernel access reg. 2
        stam    %a4,%a4,_TSS_AR4(%r2)   # store kernel access reg. 4
        lam     %a2,%a2,_TSS_AR2(%r3)   # load kernel access reg. 2
        lam     %a4,%a4,_TSS_AR4(%r3)   # load kernel access reg. 4
        lr      %r2,%r0                 # return task_struct of last task
        lm      %r6,%r15,24(%r15)       # load resume registers of next task
        br      %r14

/*
 * do_softirq calling function. We want to run the softirq functions on the
 * asynchronous interrupt stack.
 */
	.global do_call_softirq
do_call_softirq:
	stm	%r12,%r15,24(%r15)
	lr	%r12,%r15
        basr    %r13,0
do_call_base:
	l	%r0,__LC_ASYNC_STACK
	slr     %r0,%r15
	sra	%r0,13
	be	0f-do_call_base(%r13)
	l	%r15,__LC_ASYNC_STACK
0:	sl	%r15,.Lc_overhead-do_call_base(%r13)
        st	%r12,0(%r15)	# store backchain
	l	%r1,.Ldo_softirq-do_call_base(%r13)
	basr	%r14,%r1
	lm	%r12,%r15,24(%r12)
	br	%r14
	
/*
 * SVC interrupt handler routine. System calls are synchronous events and
 * are executed with interrupts enabled.
 */

	.globl  system_call
system_call:
        SAVE_ALL __LC_SVC_OLD_PSW,1
	mvi     SP_PGM_OLD_ILC(%r15),1  # mark PGM_OLD_ILC as invalid
pgm_system_call:	
        GET_CURRENT               # load pointer to task_struct to R9
        slr     %r8,%r8           # gpr 8 is call save (-> tracesys)
        ic      %r8,0x8B          # get svc number from lowcore
        stosm   24(%r15),0x03     # reenable interrupts
        sll     %r8,2
        l       %r8,sys_call_table-entry_base(8,%r13) # get address of system call
        tm      tsk_ptrace+3(%r9),0x02 # PT_TRACESYS
        bnz     BASED(sysc_tracesys)
        basr    %r14,%r8          # call sys_xxxx
        st      %r2,SP_R2(%r15)   # store return value (change R2 on stack)
                                  # ATTENTION: check sys_execve_glue before
                                  # changing anything here !!

sysc_return:
        tm      SP_PSW+1(%r15),0x01 # returning to user ?
        bno     BASED(sysc_leave) # no-> skip resched & signal
#
# check, if reschedule is needed
#
        icm     %r0,15,need_resched(%r9) # get need_resched from task_struct
        bnz     BASED(sysc_reschedule)
        icm     %r0,15,sigpending(%r9)   # get sigpending from task_struct
        bnz     BASED(sysc_signal_return)
sysc_leave:
	tm      SP_PGM_OLD_ILC(%r15),0xff
        bz      BASED(pgm_svcret)
	stnsm   24(%r15),0xfc            # disable I/O and ext. interrupts
        RESTORE_ALL 1

#
# call do_signal before return
#
sysc_signal_return:     
        la      %r2,SP_PTREGS(%r15) # load pt_regs
        sr      %r3,%r3           # clear *oldset
        l       %r1,BASED(.Ldo_signal)
	la      %r14,BASED(sysc_leave)
        br      %r1               # return point is sysc_leave

#
# call trace before and after sys_call
#
sysc_tracesys:
        l       %r1,BASED(.Ltrace)
	l       %r7,BASED(.Lc_ENOSYS)
	st      %r7,SP_R2(%r15)   # give sysc_trace an -ENOSYS retval
        basr    %r14,%r1
	l       %r2,SP_R2(%r15)
	cr      %r2,%r7 # compare with saved -ENOSYS
	be      BASED(sysc_tracesys_dn1)
	# strace wants to change the syscall
	sll     %r2,24
	srl     %r2,22
        l       %r8,sys_call_table-entry_base(2,%r13) # get address of system call    
sysc_tracesys_dn1:		
	lm      %r3,%r6,SP_R3(%r15)
	l       %r2,SP_ORIG_R2(%r15)
        basr    %r14,%r8          # call sys_xxx
        st      %r2,SP_R2(%r15)   # store return value
        l       %r1,BASED(.Ltrace)
	la      %r14,BASED(sysc_return)
        br      %r1               # return point is sysc_return


#
# call schedule with sysc_return as return-address
#
sysc_reschedule:        
        l       %r1,BASED(.Lschedule)
	la      %r14,BASED(sysc_return)
        br      %r1               # call scheduler, return to sysc_return

#
# a new process exits the kernel with ret_from_fork
#
        .globl  ret_from_fork
ret_from_fork:  
        basr    %r13,0
        l       %r13,.Lentry_base-.(%r13)  # setup base pointer to &entry_base
        GET_CURRENT               # load pointer to task_struct to R9
        stosm   24(%r15),0x03     # reenable interrupts
        sr      %r0,%r0           # child returns 0
        st      %r0,SP_R2(%r15)   # store return value (change R2 on stack)
#ifdef CONFIG_SMP
        l       %r1,BASED(.Lschedtail)
	la      %r14,BASED(sysc_return)
        br      %r1               # call schedule_tail, return to sysc_return