entry.s

linux 内核源代码

/*
 * File:         arch/blackfin/mach-common/entry.S
 * Based on:
 * Author:       Linus Torvalds
 *
 * Created:      ?
 * Description:  contains the system-call and fault low-level handling routines.
 *               This also contains the timer-interrupt handler, as well as all
 *               interrupts and faults that can result in a task-switch.
 *
 * Modified:
 *               Copyright 2004-2006 Analog Devices Inc.
 *
 * Bugs:         Enter bugs at http://blackfin.uclinux.org/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see the file COPYING, or write
 * to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

/* NOTE: This code handles signal-recognition, which happens every time
 * after a timer-interrupt and after each system call.
 */

#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/unistd.h>
#include <asm/blackfin.h>
#include <asm/errno.h>
#include <asm/thread_info.h>  /* TIF_NEED_RESCHED */
#include <asm/asm-offsets.h>
#include <asm/trace.h>

#include <asm/mach-common/context.S>

#if defined(CONFIG_BFIN_SCRATCH_REG_RETN)
# define EX_SCRATCH_REG RETN
#elif defined(CONFIG_BFIN_SCRATCH_REG_RETE)
# define EX_SCRATCH_REG RETE
#else
# define EX_SCRATCH_REG CYCLES
#endif

#if ANOMALY_05000281
ENTRY(_safe_speculative_execution)
	NOP;
	NOP;
	NOP;
	jump _safe_speculative_execution;
ENDPROC(_safe_speculative_execution)
#endif

#ifdef CONFIG_EXCPT_IRQ_SYSC_L1
.section .l1.text
#else
.text
#endif

/* Slightly simplified and streamlined entry point for CPLB misses.
 * This one does not lower the level to IRQ5, and thus can be used to
 * patch up CPLB misses on the kernel stack.
 */
#if ANOMALY_05000261
#define _ex_dviol _ex_workaround_261
#define _ex_dmiss _ex_workaround_261
#define _ex_dmult _ex_workaround_261

ENTRY(_ex_workaround_261)
	/*
	 * Work around an anomaly: if we see a new DCPLB fault, return
	 * without doing anything.  Then, if we get the same fault again,
	 * handle it.
	 */
	P4 = R7;	/* Store EXCAUSE */
	p5.l = _last_cplb_fault_retx;
	p5.h = _last_cplb_fault_retx;
	r7 = [p5];
	r6 = retx;
	[p5] = r6;
	cc = r6 == r7;
	if !cc jump _bfin_return_from_exception;
	/* fall through */
	R7 = P4;
	R6 = 0x26;	/* Data CPLB Miss */
	cc = R6 == R7;
	if cc jump _ex_dcplb_miss (BP);
	/* Handle 0x23 Data CPLB Protection Violation
	 * and Data CPLB Multiple Hits - Linux Trap Zero
	 */
	jump _ex_trap_c;
ENDPROC(_ex_workaround_261)

#else
#define _ex_dviol _ex_trap_c
#define _ex_dmiss _ex_dcplb_miss
#define _ex_dmult _ex_trap_c
#endif

ENTRY(_ex_dcplb_miss)
ENTRY(_ex_icplb_miss)
	(R7:6,P5:4) = [sp++];
	ASTAT = [sp++];
	SAVE_ALL_SYS
	call __cplb_hdr;
	DEBUG_START_HWTRACE(p5, r7)
	RESTORE_ALL_SYS
	SP = EX_SCRATCH_REG;
	rtx;
ENDPROC(_ex_icplb_miss)

ENTRY(_ex_syscall)
	DEBUG_START_HWTRACE(p5, r7)
	(R7:6,P5:4) = [sp++];
	ASTAT = [sp++];
	raise 15;		/* invoked by TRAP #0, for sys call */
	sp = EX_SCRATCH_REG;
	rtx
ENDPROC(_ex_syscall)

ENTRY(_ex_soft_bp)
	r7 = retx;
	r7 += -2;
	retx = r7;
	jump.s _ex_trap_c;
ENDPROC(_ex_soft_bp)

ENTRY(_ex_single_step)
	r7 = retx;
	r6 = reti;
	cc = r7 == r6;
	if cc jump _bfin_return_from_exception
	r7 = syscfg;
	bitclr (r7, 0);
	syscfg = R7;

	p5.l = lo(IPEND);
	p5.h = hi(IPEND);
	r6 = [p5];
	cc = bittst(r6, 5);
	if !cc jump _ex_trap_c;
	p4.l = lo(EVT5);
	p4.h = hi(EVT5);
	r6.h = _exception_to_level5;
	r6.l = _exception_to_level5;
	r7 = [p4];
	cc = r6 == r7;
	if !cc jump _ex_trap_c;
ENDPROC(_ex_single_step)

ENTRY(_bfin_return_from_exception)
	DEBUG_START_HWTRACE(p5, r7)
#if ANOMALY_05000257
	R7=LC0;
	LC0=R7;
	R7=LC1;
	LC1=R7;
#endif
	(R7:6,P5:4) = [sp++];
	ASTAT = [sp++];
	sp = EX_SCRATCH_REG;
	rtx;
ENDPROC(_bfin_return_from_exception)

ENTRY(_handle_bad_cplb)
	/* To get here, we just tried and failed to change a CPLB
	 * so, handle things in trap_c (C code), by lowering to
	 * IRQ5, just like we normally do. Since this is not a
	 * "normal" return path, we have a do alot of stuff to
	 * the stack to get ready so, we can fall through - we
	 * need to make a CPLB exception look like a normal exception
	 */

	DEBUG_START_HWTRACE(p5, r7)
	RESTORE_ALL_SYS
	[--sp] = ASTAT;
	[--sp] = (R7:6, P5:4);

ENTRY(_ex_replaceable)
	nop;

ENTRY(_ex_trap_c)
	/* Make sure we are not in a double fault */
	p4.l = lo(IPEND);
	p4.h = hi(IPEND);
	r7 = [p4];
	CC = BITTST (r7, 5);
	if CC jump _double_fault;

	/* Call C code (trap_c) to handle the exception, which most
	 * likely involves sending a signal to the current process.
	 * To avoid double faults, lower our priority to IRQ5 first.
	 */
	P5.h = _exception_to_level5;
	P5.l = _exception_to_level5;
	p4.l = lo(EVT5);
	p4.h = hi(EVT5);
	[p4] = p5;
	csync;

	/* Disable all interrupts, but make sure level 5 is enabled so
	 * we can switch to that level.  Save the old mask.  */
	cli r6;
	p4.l = _excpt_saved_imask;
	p4.h = _excpt_saved_imask;
	[p4] = r6;
	r6 = 0x3f;
	sti r6;

	/* Save the excause into a circular buffer, in case the instruction
	 * which caused this excecptions causes others.
	 */
	P5.l = _in_ptr_excause;
	P5.h = _in_ptr_excause;
	R7 = [P5];
	R7 += 4;
	R6 = 0xF;
	R7 = R7 & R6;
	[P5] = R7;
	R6.l = _excause_circ_buf;
	R6.h = _excause_circ_buf;
	R7 = R7 + R6;
	p5 = R7;
	R6 = SEQSTAT;
	[P5] = R6;

	DEBUG_START_HWTRACE(p5, r7)
	(R7:6,P5:4) = [sp++];
	ASTAT = [sp++];
	SP = EX_SCRATCH_REG;
	raise 5;
	rtx;
ENDPROC(_ex_trap_c)

/* We just realized we got an exception, while we were processing a different
 * exception. This is a unrecoverable event, so crash
 */
ENTRY(_double_fault)
        /* Turn caches & protection off, to ensure we don't get any more
         * double exceptions
         */

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

        R5 = [P4];              /* Control Register*/
        BITCLR(R5,ENICPLB_P);
        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;

        /* Fix up the stack */
        (R7:6,P5:4) = [sp++];
        ASTAT = [sp++];
        SP = EX_SCRATCH_REG;

        /* We should be out of the exception stack, and back down into
         * kernel or user space stack
         */
        SAVE_ALL_SYS

        r0 = sp;        /* stack frame pt_regs pointer argument ==> r0 */
        SP += -12;
        call _double_fault_c;
        SP += 12;
.L_double_fault_panic:
        JUMP .L_double_fault_panic

ENDPROC(_double_fault)

ENTRY(_exception_to_level5)
	SAVE_ALL_SYS

	/* Restore interrupt mask.  We haven't pushed RETI, so this
	 * doesn't enable interrupts until we return from this handler.  */
	p4.l = _excpt_saved_imask;
	p4.h = _excpt_saved_imask;
	r6 = [p4];
	sti r6;

	/* Restore the hardware error vector.  */
	P5.h = _evt_ivhw;
	P5.l = _evt_ivhw;
	p4.l = lo(EVT5);
	p4.h = hi(EVT5);
	[p4] = p5;
	csync;

	p2.l = lo(IPEND);
	p2.h = hi(IPEND);
	csync;
	r0 = [p2];              /* Read current IPEND */
	[sp + PT_IPEND] = r0;   /* Store IPEND */

	/* Pop the excause from the circular buffer and push it on the stack
	 * (in the right place - if you change the location of SEQSTAT, you
	 * must change this offset.
	 */
.L_excep_to_5_again:
	P5.l = _out_ptr_excause;
	P5.h = _out_ptr_excause;
	R7 = [P5];
	R7 += 4;
	R6 = 0xF;
	R7 = R7 & R6;
	[P5] = R7;
	R6.l = _excause_circ_buf;
	R6.h = _excause_circ_buf;
	R7 = R7 + R6;
	P5 = R7;
	R1 = [P5];
	[SP + 8] = r1;

	r0 = sp; 	/* stack frame pt_regs pointer argument ==> r0 */
	SP += -12;
	call _trap_c;
	SP += 12;

	/* See if anything else is in the exception buffer
	 * if there is, process it
	 */
	P5.l = _out_ptr_excause;
	P5.h = _out_ptr_excause;
	P4.l = _in_ptr_excause;
	P4.h = _in_ptr_excause;
	R6 = [P5];
	R7 = [P4];
	CC = R6 == R7;
	if ! CC JUMP .L_excep_to_5_again

	call _ret_from_exception;
	RESTORE_ALL_SYS
	rti;
ENDPROC(_exception_to_level5)

ENTRY(_trap) /* Exception: 4th entry into system event table(supervisor mode)*/
	/* Since the kernel stack can be anywhere, it's not guaranteed to be
	 * covered by a CPLB.  Switch to an exception stack; use RETN as a
	 * scratch register (for want of a better option).
	 */
	EX_SCRATCH_REG = sp;
	sp.l = _exception_stack_top;
	sp.h = _exception_stack_top;
	/* Try to deal with syscalls quickly.  */
	[--sp] = ASTAT;
	[--sp] = (R7:6, P5:4);
	DEBUG_STOP_HWTRACE(p5, r7)
	r7 = SEQSTAT;		/* reason code is in bit 5:0 */
	r6.l = lo(SEQSTAT_EXCAUSE);
	r6.h = hi(SEQSTAT_EXCAUSE);
	r7 = r7 & r6;
	p5.h = _ex_table;
	p5.l = _ex_table;
	p4 = r7;
	p5 = p5 + (p4 << 2);
	p4 = [p5];
	jump (p4);

.Lbadsys:
	r7 = -ENOSYS; 		/* signextending enough */
	[sp + PT_R0] = r7;	/* return value from system call */
	jump .Lsyscall_really_exit;
ENDPROC(_trap)

ENTRY(_kernel_execve)
	link SIZEOF_PTREGS;
	p0 = sp;
	r3 = SIZEOF_PTREGS / 4;
	r4 = 0(x);
0:
	[p0++] = r4;
	r3 += -1;
	cc = r3 == 0;
	if !cc jump 0b (bp);

	p0 = sp;
	sp += -16;
	[sp + 12] = p0;
	call _do_execve;
	SP += 16;
	cc = r0 == 0;
	if ! cc jump 1f;
	/* Success.  Copy our temporary pt_regs to the top of the kernel
	 * stack and do a normal exception return.
	 */
	r1 = sp;
	r0 = (-KERNEL_STACK_SIZE) (x);
	r1 = r1 & r0;
	p2 = r1;
	p3 = [p2];
	r0 = KERNEL_STACK_SIZE - 4 (z);
	p1 = r0;
	p1 = p1 + p2;

	p0 = fp;
	r4 = [p0--];
	r3 = SIZEOF_PTREGS / 4;
0:
	r4 = [p0--];
	[p1--] = r4;
	r3 += -1;
	cc = r3 == 0;
	if ! cc jump 0b (bp);

	r0 = (KERNEL_STACK_SIZE - SIZEOF_PTREGS) (z);
	p1 = r0;
	p1 = p1 + p2;
	sp = p1;
	r0 = syscfg;
	[SP + PT_SYSCFG] = r0;
	[p3 + (TASK_THREAD + THREAD_KSP)] = sp;

	RESTORE_CONTEXT;
	rti;
1:
	unlink;
	rts;
ENDPROC(_kernel_execve)

ENTRY(_system_call)
	/* Store IPEND */
	p2.l = lo(IPEND);
	p2.h = hi(IPEND);
	csync;
	r0 = [p2];
	[sp + PT_IPEND] = r0;

	/* Store RETS for now */
	r0 = rets;
	[sp + PT_RESERVED] = r0;
	/* Set the stack for the current process */
	r7 = sp;
	r6.l = lo(ALIGN_PAGE_MASK);
	r6.h = hi(ALIGN_PAGE_MASK);
	r7 = r7 & r6;  		/* thread_info */
	p2 = r7;
	p2 = [p2];

	[p2+(TASK_THREAD+THREAD_KSP)] = sp;

	/* Check the System Call */
	r7 = __NR_syscall;
	/* System call number is passed in P0 */
	r6 = p0;
	cc = r6 < r7;
	if ! cc jump .Lbadsys;