process.c

一个2.4.21版本的嵌入式linux内核

/*
 *  linux/arch/ppc/kernel/process.c
 *
 *  Derived from "arch/i386/kernel/process.c"
 *    Copyright (C) 1995  Linus Torvalds
 *
 *  Updated and modified by Cort Dougan ([e-mail]) and
 *  Paul Mackerras ([e-mail])
 *
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas ([e-mail])
 *
 *  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.
 *
 */

#include <linux/config.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/init.h>
#include <linux/prctl.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/mmu.h>
#include <asm/prom.h>

int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpregs);
extern unsigned long _get_SP(void);

struct task_struct *last_task_used_math = NULL;
struct task_struct *last_task_used_altivec = NULL;
static struct fs_struct init_fs = INIT_FS;
static struct files_struct init_files = INIT_FILES;
static struct signal_struct init_signals = INIT_SIGNALS;
struct mm_struct init_mm = INIT_MM(init_mm);
/* this is 16-byte aligned because it has a stack in it */
union task_union __attribute((aligned(16))) init_task_union = {
	INIT_TASK(init_task_union.task)
};
/* only used to get secondary processor up */
struct task_struct *current_set[NR_CPUS] = {&init_task, };

#undef SHOW_TASK_SWITCHES
#undef CHECK_STACK

#if defined(CHECK_STACK)
unsigned long
kernel_stack_top(struct task_struct *tsk)
{
	return ((unsigned long)tsk) + sizeof(union task_union);
}

unsigned long
task_top(struct task_struct *tsk)
{
	return ((unsigned long)tsk) + sizeof(struct task_struct);
}

/* check to make sure the kernel stack is healthy */
int check_stack(struct task_struct *tsk)
{
	unsigned long stack_top = kernel_stack_top(tsk);
	unsigned long tsk_top = task_top(tsk);
	int ret = 0;

#if 0	
	/* check thread magic */
	if ( tsk->thread.magic != THREAD_MAGIC )
	{
		ret |= 1;
		printk("thread.magic bad: %08x\n", tsk->thread.magic);
	}
#endif

	if ( !tsk )
		printk("check_stack(): tsk bad tsk %p\n",tsk);
	
	/* check if stored ksp is bad */
	if ( (tsk->thread.ksp > stack_top) || (tsk->thread.ksp < tsk_top) )
	{
		printk("stack out of bounds: %s/%d\n"
		       " tsk_top %08lx ksp %08lx stack_top %08lx\n",
		       tsk->comm,tsk->pid,
		       tsk_top, tsk->thread.ksp, stack_top);
		ret |= 2;
	}
	
	/* check if stack ptr RIGHT NOW is bad */
	if ( (tsk == current) && ((_get_SP() > stack_top ) || (_get_SP() < tsk_top)) )
	{
		printk("current stack ptr out of bounds: %s/%d\n"
		       " tsk_top %08lx sp %08lx stack_top %08lx\n",
		       current->comm,current->pid,
		       tsk_top, _get_SP(), stack_top);
		ret |= 4;
	}

#if 0	
	/* check amount of free stack */
	for ( i = (unsigned long *)task_top(tsk) ; i < kernel_stack_top(tsk) ; i++ )
	{
		if ( !i )
			printk("check_stack(): i = %p\n", i);
		if ( *i != 0 )
		{
			/* only notify if it's less than 900 bytes */
			if ( (i - (unsigned long *)task_top(tsk))  < 900 )
				printk("%d bytes free on stack\n",
				       i - task_top(tsk));
			break;
		}
	}
#endif

	if (ret)
	{
		panic("bad kernel stack");
	}
	return(ret);
}
#endif /* defined(CHECK_STACK) */

#ifdef CONFIG_ALTIVEC
int
dump_altivec(struct pt_regs *regs, elf_vrregset_t *vrregs)
{
	if (regs->msr & MSR_VEC)
		giveup_altivec(current);
	memcpy(vrregs, &current->thread.vr[0], sizeof(*vrregs));
	return 1;
}

void 
enable_kernel_altivec(void)
{
#ifdef CONFIG_SMP
	if (current->thread.regs && (current->thread.regs->msr & MSR_VEC))
		giveup_altivec(current);
	else
		giveup_altivec(NULL);	/* just enable AltiVec for kernel - force */
#else
	giveup_altivec(last_task_used_altivec);
#endif /* __SMP __ */
}
#endif /* CONFIG_ALTIVEC */

void
enable_kernel_fp(void)
{
#ifdef CONFIG_SMP
	if (current->thread.regs && (current->thread.regs->msr & MSR_FP))
		giveup_fpu(current);
	else
		giveup_fpu(NULL);	/* just enables FP for kernel */
#else
	giveup_fpu(last_task_used_math);
#endif /* CONFIG_SMP */
}

int
dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpregs)
{
	if (regs->msr & MSR_FP)
		giveup_fpu(current);
	memcpy(fpregs, &current->thread.fpr[0], sizeof(*fpregs));
	return 1;
}

void
_switch_to(struct task_struct *prev, struct task_struct *new,
	  struct task_struct **last)
{
	struct thread_struct *new_thread, *old_thread;
	unsigned long s;
	
	__save_flags(s);
	__cli();
#if CHECK_STACK
	check_stack(prev);
	check_stack(new);
#endif

#ifdef CONFIG_SMP
	/* avoid complexity of lazy save/restore of fpu
	 * by just saving it every time we switch out if
	 * this task used the fpu during the last quantum.
	 * 
	 * If it tries to use the fpu again, it'll trap and
	 * reload its fp regs.  So we don't have to do a restore
	 * every switch, just a save.
	 *  -- Cort
	 */
	if ( prev->thread.regs && (prev->thread.regs->msr & MSR_FP) )
		giveup_fpu(prev);
#ifdef CONFIG_ALTIVEC	
	/*
	 * If the previous thread used altivec in the last quantum
	 * (thus changing altivec regs) then save them.
	 * We used to check the VRSAVE register but not all apps
	 * set it, so we don't rely on it now (and in fact we need
	 * to save & restore VSCR even if VRSAVE == 0).  -- paulus
	 *
	 * On SMP we always save/restore altivec regs just to avoid the
	 * complexity of changing processors.
	 *  -- Cort
	 */
	if ((prev->thread.regs && (prev->thread.regs->msr & MSR_VEC)))
		giveup_altivec(prev);
#endif /* CONFIG_ALTIVEC */	
#endif /* CONFIG_SMP */

	current_set[smp_processor_id()] = new;

	/* Avoid the trap.  On smp this this never happens since
	 * we don't set last_task_used_altivec -- Cort
	 */
	if (new->thread.regs && last_task_used_altivec == new)
		new->thread.regs->msr |= MSR_VEC;
	new_thread = &new->thread;
	old_thread = &current->thread;
	*last = _switch(old_thread, new_thread);
	__restore_flags(s);
}

void show_regs(struct pt_regs * regs)
{
	int i;

	printk("NIP: %08lX XER: %08lX LR: %08lX SP: %08lX REGS: %p TRAP: %04lx    %s\n",
	       regs->nip, regs->xer, regs->link, regs->gpr[1], regs,regs->trap, print_tainted());
	printk("MSR: %08lx EE: %01x PR: %01x FP: %01x ME: %01x IR/DR: %01x%01x\n",
	       regs->msr, regs->msr&MSR_EE ? 1 : 0, regs->msr&MSR_PR ? 1 : 0,
	       regs->msr & MSR_FP ? 1 : 0,regs->msr&MSR_ME ? 1 : 0,
	       regs->msr&MSR_IR ? 1 : 0,
	       regs->msr&MSR_DR ? 1 : 0);
	if (regs->trap == 0x300 || regs->trap == 0x600)
		printk("DAR: %08lX, DSISR: %08lX\n", regs->dar, regs->dsisr);
	printk("TASK = %p[%d] '%s' ",
	       current, current->pid, current->comm);
	printk("Last syscall: %ld ", current->thread.last_syscall);
	printk("\nlast math %p last altivec %p", last_task_used_math,
	       last_task_used_altivec);

#ifdef CONFIG_4xx
	printk("\nPLB0: bear= 0x%8.8x acr=   0x%8.8x besr=  0x%8.8x\n",
	    mfdcr(DCRN_POB0_BEAR), mfdcr(DCRN_PLB0_ACR),
	    mfdcr(DCRN_PLB0_BESR));
	printk("PLB0 to OPB: bear= 0x%8.8x besr0= 0x%8.8x besr1= 0x%8.8x\n",
	    mfdcr(DCRN_PLB0_BEAR), mfdcr(DCRN_POB0_BESR0),
	    mfdcr(DCRN_POB0_BESR1));
#endif
	
#ifdef CONFIG_SMP
	printk(" CPU: %d", current->processor);
#endif /* CONFIG_SMP */
	
	printk("\n");
	for (i = 0;  i < 32;  i++)
	{
		long r;
		if ((i % 8) == 0)
		{
			printk("GPR%02d: ", i);
		}

		if ( __get_user(r, &(regs->gpr[i])) )
		    goto out;
		printk("%08lX ", r);
		if ((i % 8) == 7)
		{
			printk("\n");
		}
	}
out:
	print_backtrace((unsigned long *)regs->gpr[1]);
}

void exit_thread(void)
{
	if (last_task_used_math == current)
		last_task_used_math = NULL;
	if (last_task_used_altivec == current)
		last_task_used_altivec = NULL;
}

void flush_thread(void)
{
	if (last_task_used_math == current)
		last_task_used_math = NULL;
	if (last_task_used_altivec == current)
		last_task_used_altivec = NULL;
}

void
release_thread(struct task_struct *t)
{
}

/*
 * Copy a thread..
 */
int
copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
	    unsigned long unused,
	    struct task_struct *p, struct pt_regs *regs)
{
	struct pt_regs *childregs, *kregs;