entry.s

linux 内核源代码

	/* are we tracing syscalls?*/
	r7 = sp;
	r6.l = lo(ALIGN_PAGE_MASK);
	r6.h = hi(ALIGN_PAGE_MASK);
	r7 = r7 & r6;
	p2 = r7;
	r7 = [p2+TI_FLAGS];
	CC = BITTST(r7,TIF_SYSCALL_TRACE);
	if CC JUMP _sys_trace;

	/* Execute the appropriate system call */

	p4 = p0;
	p5.l = _sys_call_table;
	p5.h = _sys_call_table;
	p5 = p5 + (p4 << 2);
	r0 = [sp + PT_R0];
	r1 = [sp + PT_R1];
	r2 = [sp + PT_R2];
	p5 = [p5];

	[--sp] = r5;
	[--sp] = r4;
	[--sp] = r3;
	SP += -12;
	call (p5);
	SP += 24;
	[sp + PT_R0] = r0;

.Lresume_userspace:
	r7 = sp;
	r4.l = lo(ALIGN_PAGE_MASK);
	r4.h = hi(ALIGN_PAGE_MASK);
	r7 = r7 & r4;		/* thread_info->flags */
	p5 = r7;
.Lresume_userspace_1:
	/* Disable interrupts.  */
	[--sp] = reti;
	reti = [sp++];

	r7 = [p5 + TI_FLAGS];
	r4.l = lo(_TIF_WORK_MASK);
	r4.h = hi(_TIF_WORK_MASK);
	r7 =  r7 & r4;

.Lsyscall_resched:
	cc = BITTST(r7, TIF_NEED_RESCHED);
	if !cc jump .Lsyscall_sigpending;

	/* Reenable interrupts.  */
	[--sp] = reti;
	r0 = [sp++];

	SP += -12;
	call _schedule;
	SP += 12;

	jump .Lresume_userspace_1;

.Lsyscall_sigpending:
	cc = BITTST(r7, TIF_RESTORE_SIGMASK);
	if cc jump .Lsyscall_do_signals;
	cc = BITTST(r7, TIF_SIGPENDING);
	if !cc jump .Lsyscall_really_exit;
.Lsyscall_do_signals:
	/* Reenable interrupts.  */
	[--sp] = reti;
	r0 = [sp++];

	r0 = sp;
	SP += -12;
	call _do_signal;
	SP += 12;

.Lsyscall_really_exit:
	r5 = [sp + PT_RESERVED];
	rets = r5;
	rts;
ENDPROC(_system_call)

_sys_trace:
	call _syscall_trace;

	/* Execute the appropriate system call */

	p4 = [SP + PT_P0];
	p5.l = _sys_call_table;
	p5.h = _sys_call_table;
	p5 = p5 + (p4 << 2);
	r0 = [sp + PT_R0];
	r1 = [sp + PT_R1];
	r2 = [sp + PT_R2];
	r3 = [sp + PT_R3];
	r4 = [sp + PT_R4];
	r5 = [sp + PT_R5];
	p5 = [p5];

	[--sp] = r5;
	[--sp] = r4;
	[--sp] = r3;
	SP += -12;
	call (p5);
	SP += 24;
	[sp + PT_R0] = r0;

	call _syscall_trace;
	jump .Lresume_userspace;
ENDPROC(_sys_trace)

ENTRY(_resume)
	/*
	 * Beware - when entering resume, prev (the current task) is
	 * in r0, next (the new task) is in r1.
	 */
	p0 = r0;
	p1 = r1;
	[--sp] = rets;
	[--sp] = fp;
	[--sp] = (r7:4, p5:3);

	/* save usp */
	p2 = usp;
	[p0+(TASK_THREAD+THREAD_USP)] = p2;

	/* save current kernel stack pointer */
	[p0+(TASK_THREAD+THREAD_KSP)] = sp;

	/* save program counter */
	r1.l = _new_old_task;
	r1.h = _new_old_task;
	[p0+(TASK_THREAD+THREAD_PC)] = r1;

	/* restore the kernel stack pointer */
	sp = [p1+(TASK_THREAD+THREAD_KSP)];

	/* restore user stack pointer */
	p0 = [p1+(TASK_THREAD+THREAD_USP)];
	usp = p0;

	/* restore pc */
	p0 = [p1+(TASK_THREAD+THREAD_PC)];
	jump (p0);

	/*
	 * Following code actually lands up in a new (old) task.
	 */

_new_old_task:
	(r7:4, p5:3) = [sp++];
	fp = [sp++];
	rets = [sp++];

	/*
	 * When we come out of resume, r0 carries "old" task, becuase we are
	 * in "new" task.
	 */
	rts;
ENDPROC(_resume)

ENTRY(_ret_from_exception)
	p2.l = lo(IPEND);
	p2.h = hi(IPEND);

	csync;
	r0 = [p2];
	[sp + PT_IPEND] = r0;

1:
	r1 = 0x37(Z);
	r2 = ~r1;
	r2.h = 0;
	r0 = r2 & r0;
	cc = r0 == 0;
	if !cc jump 4f;	/* if not return to user mode, get out */

	/* Make sure any pending system call or deferred exception
	 * return in ILAT for this process to get executed, otherwise
	 * in case context switch happens, system call of
	 * first process (i.e in ILAT) will be carried
	 * forward to the switched process
	 */

	p2.l = lo(ILAT);
	p2.h = hi(ILAT);
	r0 = [p2];
	r1 = (EVT_IVG14 | EVT_IVG15) (z);
	r0 = r0 & r1;
	cc = r0 == 0;
	if !cc jump 5f;

	/* Set the stack for the current process */
	r7 = sp;
	r4.l = lo(ALIGN_PAGE_MASK);
	r4.h = hi(ALIGN_PAGE_MASK);
	r7 = r7 & r4;		/* thread_info->flags */
	p5 = r7;
	r7 = [p5 + TI_FLAGS];
	r4.l = lo(_TIF_WORK_MASK);
	r4.h = hi(_TIF_WORK_MASK);
	r7 =  r7 & r4;
	cc = r7 == 0;
	if cc jump 4f;

	p0.l = lo(EVT15);
	p0.h = hi(EVT15);
	p1.l = _schedule_and_signal;
	p1.h = _schedule_and_signal;
	[p0] = p1;
	csync;
	raise 15;		/* raise evt14 to do signal or reschedule */
4:
	r0 = syscfg;
	bitclr(r0, 0);
	syscfg = r0;
5:
	rts;
ENDPROC(_ret_from_exception)

ENTRY(_return_from_int)
	/* If someone else already raised IRQ 15, do nothing.  */
	csync;
	p2.l = lo(ILAT);
	p2.h = hi(ILAT);
	r0 = [p2];
	cc = bittst (r0, EVT_IVG15_P);
	if cc jump 2f;

	/* if not return to user mode, get out */
	p2.l = lo(IPEND);
	p2.h = hi(IPEND);
	r0 = [p2];
	r1 = 0x17(Z);
	r2 = ~r1;
	r2.h = 0;
	r0 = r2 & r0;
	r1 = 1;
	r1 = r0 - r1;
	r2 = r0 & r1;
	cc = r2 == 0;
	if !cc jump 2f;

	/* Lower the interrupt level to 15.  */
	p0.l = lo(EVT15);
	p0.h = hi(EVT15);
	p1.l = _schedule_and_signal_from_int;
	p1.h = _schedule_and_signal_from_int;
	[p0] = p1;
	csync;
#if ANOMALY_05000281
	r0.l = _safe_speculative_execution;
	r0.h = _safe_speculative_execution;
	reti = r0;
#endif
	r0 = 0x801f (z);
	STI r0;
	raise 15;	/* raise evt15 to do signal or reschedule */
	rti;
2:
	rts;
ENDPROC(_return_from_int)

ENTRY(_lower_to_irq14)
#if ANOMALY_05000281
	r0.l = _safe_speculative_execution;
	r0.h = _safe_speculative_execution;
	reti = r0;
#endif
	r0 = 0x401f;
	sti r0;
	raise 14;
	rti;
ENTRY(_evt14_softirq)
#ifdef CONFIG_DEBUG_HWERR
	r0 = 0x3f;
	sti r0;
#else
	cli r0;
#endif
	[--sp] = RETI;
	SP += 4;
	rts;

_schedule_and_signal_from_int:
	/* To end up here, vector 15 was changed - so we have to change it
	 * back.
	 */
	p0.l = lo(EVT15);
	p0.h = hi(EVT15);
	p1.l = _evt_system_call;
	p1.h = _evt_system_call;
	[p0] = p1;
	csync;

	/* Set orig_p0 to -1 to indicate this isn't the end of a syscall.  */
	r0 = -1 (x);
	[sp + PT_ORIG_P0] = r0;

	p1 = rets;
	[sp + PT_RESERVED] = p1;

	p0.l = _irq_flags;
	p0.h = _irq_flags;
	r0 = [p0];
	sti r0;

	r0 = sp;
	sp += -12;
	call _finish_atomic_sections;
	sp += 12;
	jump.s .Lresume_userspace;

_schedule_and_signal:
	SAVE_CONTEXT_SYSCALL
	/* To end up here, vector 15 was changed - so we have to change it
	 * back.
	 */
	p0.l = lo(EVT15);
	p0.h = hi(EVT15);
	p1.l = _evt_system_call;
	p1.h = _evt_system_call;
	[p0] = p1;
	csync;
	p0.l = 1f;
	p0.h = 1f;
	[sp + PT_RESERVED] = P0;
	call .Lresume_userspace;
1:
	RESTORE_CONTEXT
	rti;
ENDPROC(_lower_to_irq14)

/* Make sure when we start, that the circular buffer is initialized properly
 * R0 and P0 are call clobbered, so we can use them here.
 */
ENTRY(_init_exception_buff)
	r0 = 0;
	p0.h = _in_ptr_excause;
	p0.l = _in_ptr_excause;
	[p0] = r0;
	p0.h = _out_ptr_excause;
	p0.l = _out_ptr_excause;
	[p0] = r0;
	rts;
ENDPROC(_init_exception_buff)

/* We handle this 100% in exception space - to reduce overhead
 * Only potiential problem is if the software buffer gets swapped out of the
 * CPLB table - then double fault. - so we don't let this happen in other places
 */
#ifdef CONFIG_DEBUG_BFIN_HWTRACE_EXPAND
ENTRY(_ex_trace_buff_full)
	[--sp] = P3;
	[--sp] = P2;
	[--sp] = LC0;
	[--sp] = LT0;
	[--sp] = LB0;
	P5.L = _trace_buff_offset;
	P5.H = _trace_buff_offset;
	P3 = [P5];              /* trace_buff_offset */
	P5.L = lo(TBUFSTAT);
	P5.H = hi(TBUFSTAT);
	R7 = [P5];
	R7 <<= 1;               /* double, since we need to read twice */
	LC0 = R7;
	R7 <<= 2;               /* need to shift over again,
				 * to get the number of bytes */
	P5.L = lo(TBUF);
	P5.H = hi(TBUF);
	R6 = ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN)*1024) - 1;

	P2 = R7;
	P3 = P3 + P2;
	R7 = P3;
	R7 = R7 & R6;
	P3 = R7;
	P2.L = _trace_buff_offset;
	P2.H = _trace_buff_offset;
	[P2] = P3;

	P2.L = _software_trace_buff;
	P2.H = _software_trace_buff;

	LSETUP (.Lstart, .Lend) LC0;
.Lstart:
	R7 = [P5];      /* read TBUF */
	P4 = P3 + P2;
	[P4] = R7;
	P3 += -4;
	R7 = P3;
	R7 = R7 & R6;
.Lend:
	P3 = R7;

	LB0 = [sp++];
	LT0 = [sp++];
	LC0 = [sp++];
	P2 = [sp++];
	P3 = [sp++];
	jump _bfin_return_from_exception;
ENDPROC(_ex_trace_buff_full)

#if CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN == 4
.data
#else
.section .l1.data.B
#endif /* CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN */
ENTRY(_trace_buff_offset)
        .long 0;
ALIGN
ENTRY(_software_trace_buff)
	.rept ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN)*256);
	.long 0
	.endr
#endif /* CONFIG_DEBUG_BFIN_HWTRACE_EXPAND */

#if CONFIG_EARLY_PRINTK
__INIT
ENTRY(_early_trap)
	SAVE_ALL_SYS
	trace_buffer_stop(p0,r0);

	/* Turn caches off, to ensure we don't get double exceptions */

	P4.L = LO(IMEM_CONTROL);
	P4.H = HI(IMEM_CONTROL);

	R5 = [P4];              /* Control Register*/
	BITCLR(R5,ENICPLB_P);
	CLI R1;
	SSYNC;          /* SSYNC required before writing to IMEM_CONTROL. */
	.align 8;
	[P4] = R5;
	SSYNC;

	P4.L = LO(DMEM_CONTROL);
	P4.H = HI(DMEM_CONTROL);
	R5 = [P4];
	BITCLR(R5,ENDCPLB_P);
	SSYNC;          /* SSYNC required before writing to DMEM_CONTROL. */
	.align 8;
	[P4] = R5;
	SSYNC;
	STI R1;

	r0 = sp;        /* stack frame pt_regs pointer argument ==> r0 */
	r1 = RETX;

	SP += -12;
	call _early_trap_c;
	SP += 12;
ENDPROC(_early_trap)
__FINIT
#endif /* CONFIG_EARLY_PRINTK */

/*
 * Put these in the kernel data section - that should always be covered by
 * a CPLB. This is needed to ensure we don't get double fault conditions
 */

#ifdef CONFIG_SYSCALL_TAB_L1
.section .l1.data
#else
.data
#endif