process.c

底层驱动开发

/*
 *  linux/arch/ppc64/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/module.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/slab.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/init.h>
#include <linux/init_task.h>
#include <linux/prctl.h>
#include <linux/ptrace.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/utsname.h>
#include <linux/kprobes.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/mmu_context.h>
#include <asm/prom.h>
#include <asm/ppcdebug.h>
#include <asm/machdep.h>
#include <asm/iSeries/HvCallHpt.h>
#include <asm/cputable.h>
#include <asm/firmware.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/time.h>
#include <asm/plpar_wrappers.h>

#ifndef CONFIG_SMP
struct task_struct *last_task_used_math = NULL;
struct task_struct *last_task_used_altivec = NULL;
#endif

/*
 * Make sure the floating-point register state in the
 * the thread_struct is up to date for task tsk.
 */
void flush_fp_to_thread(struct task_struct *tsk)
{
	if (tsk->thread.regs) {
		/*
		 * We need to disable preemption here because if we didn't,
		 * another process could get scheduled after the regs->msr
		 * test but before we have finished saving the FP registers
		 * to the thread_struct.  That process could take over the
		 * FPU, and then when we get scheduled again we would store
		 * bogus values for the remaining FP registers.
		 */
		preempt_disable();
		if (tsk->thread.regs->msr & MSR_FP) {
#ifdef CONFIG_SMP
			/*
			 * This should only ever be called for current or
			 * for a stopped child process.  Since we save away
			 * the FP register state on context switch on SMP,
			 * there is something wrong if a stopped child appears
			 * to still have its FP state in the CPU registers.
			 */
			BUG_ON(tsk != current);
#endif
			giveup_fpu(current);
		}
		preempt_enable();
	}
}

void enable_kernel_fp(void)
{
	WARN_ON(preemptible());

#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 */
}
EXPORT_SYMBOL(enable_kernel_fp);

int dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
{
	if (!tsk->thread.regs)
		return 0;
	flush_fp_to_thread(current);

	memcpy(fpregs, &tsk->thread.fpr[0], sizeof(*fpregs));

	return 1;
}

#ifdef CONFIG_ALTIVEC

void enable_kernel_altivec(void)
{
	WARN_ON(preemptible());

#ifdef CONFIG_SMP
	if (current->thread.regs && (current->thread.regs->msr & MSR_VEC))
		giveup_altivec(current);
	else
		giveup_altivec(NULL);	/* just enables FP for kernel */
#else
	giveup_altivec(last_task_used_altivec);
#endif /* CONFIG_SMP */
}
EXPORT_SYMBOL(enable_kernel_altivec);

/*
 * Make sure the VMX/Altivec register state in the
 * the thread_struct is up to date for task tsk.
 */
void flush_altivec_to_thread(struct task_struct *tsk)
{
	if (tsk->thread.regs) {
		preempt_disable();
		if (tsk->thread.regs->msr & MSR_VEC) {
#ifdef CONFIG_SMP
			BUG_ON(tsk != current);
#endif
			giveup_altivec(current);
		}
		preempt_enable();
	}
}

int dump_task_altivec(struct pt_regs *regs, elf_vrregset_t *vrregs)
{
	flush_altivec_to_thread(current);
	memcpy(vrregs, &current->thread.vr[0], sizeof(*vrregs));
	return 1;
}

#endif /* CONFIG_ALTIVEC */

static void set_dabr_spr(unsigned long val)
{
	mtspr(SPRN_DABR, val);
}

int set_dabr(unsigned long dabr)
{
	int ret = 0;

	if (firmware_has_feature(FW_FEATURE_XDABR)) {
		/* We want to catch accesses from kernel and userspace */
		unsigned long flags = H_DABRX_KERNEL|H_DABRX_USER;
		ret = plpar_set_xdabr(dabr, flags);
	} else if (firmware_has_feature(FW_FEATURE_DABR)) {
		ret = plpar_set_dabr(dabr);
	} else {
		set_dabr_spr(dabr);
	}

	return ret;
}

DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
static DEFINE_PER_CPU(unsigned long, current_dabr);

struct task_struct *__switch_to(struct task_struct *prev,
				struct task_struct *new)
{
	struct thread_struct *new_thread, *old_thread;
	unsigned long flags;
	struct task_struct *last;

#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 (prev->thread.regs && (prev->thread.regs->msr & MSR_VEC))
		giveup_altivec(prev);
#endif /* CONFIG_ALTIVEC */
#endif /* CONFIG_SMP */

#if defined(CONFIG_ALTIVEC) && !defined(CONFIG_SMP)
	/* 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;
#endif /* CONFIG_ALTIVEC */

	if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr)) {
		set_dabr(new->thread.dabr);
		__get_cpu_var(current_dabr) = new->thread.dabr;
	}

	flush_tlb_pending();

	new_thread = &new->thread;
	old_thread = &current->thread;

	/* Collect purr utilization data per process and per processor
	 * wise purr is nothing but processor time base
	 */
	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
		struct cpu_usage *cu = &__get_cpu_var(cpu_usage_array);
		long unsigned start_tb, current_tb;
		start_tb = old_thread->start_tb;
		cu->current_tb = current_tb = mfspr(SPRN_PURR);
		old_thread->accum_tb += (current_tb - start_tb);
		new_thread->start_tb = current_tb;
	}

	local_irq_save(flags);
	last = _switch(old_thread, new_thread);

	local_irq_restore(flags);

	return last;
}

static int instructions_to_print = 16;

static void show_instructions(struct pt_regs *regs)
{
	int i;
	unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
			sizeof(int));

	printk("Instruction dump:");

	for (i = 0; i < instructions_to_print; i++) {
		int instr;

		if (!(i % 8))
			printk("\n");

		if (((REGION_ID(pc) != KERNEL_REGION_ID) &&
		     (REGION_ID(pc) != VMALLOC_REGION_ID)) ||
		     __get_user(instr, (unsigned int *)pc)) {
			printk("XXXXXXXX ");
		} else {
			if (regs->nip == pc)
				printk("<%08x> ", instr);
			else
				printk("%08x ", instr);
		}

		pc += sizeof(int);
	}

	printk("\n");
}

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

	printk("NIP: %016lX XER: %08X LR: %016lX CTR: %016lX\n",
	       regs->nip, (unsigned int)regs->xer, regs->link, regs->ctr);
	printk("REGS: %p TRAP: %04lx   %s  (%s)\n",
	       regs, regs->trap, print_tainted(), system_utsname.release);
	printk("MSR: %016lx EE: %01x PR: %01x FP: %01x ME: %01x "
	       "IR/DR: %01x%01x CR: %08X\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,
	       (unsigned int)regs->ccr);
	trap = TRAP(regs);
	printk("DAR: %016lx DSISR: %016lx\n", regs->dar, regs->dsisr);
	printk("TASK: %p[%d] '%s' THREAD: %p",
	       current, current->pid, current->comm, current->thread_info);

#ifdef CONFIG_SMP
	printk(" CPU: %d", smp_processor_id());
#endif /* CONFIG_SMP */

	for (i = 0; i < 32; i++) {
		if ((i % 4) == 0) {
			printk("\n" KERN_INFO "GPR%02d: ", i);
		}

		printk("%016lX ", regs->gpr[i]);
		if (i == 13 && !FULL_REGS(regs))
			break;
	}
	printk("\n");
	/*
	 * Lookup NIP late so we have the best change of getting the
	 * above info out without failing
	 */
	printk("NIP [%016lx] ", regs->nip);
	print_symbol("%s\n", regs->nip);
	printk("LR [%016lx] ", regs->link);
	print_symbol("%s\n", regs->link);
	show_stack(current, (unsigned long *)regs->gpr[1]);
	if (!user_mode(regs))
		show_instructions(regs);
}

void exit_thread(void)
{
	kprobe_flush_task(current);

#ifndef CONFIG_SMP
	if (last_task_used_math == current)
		last_task_used_math = NULL;
#ifdef CONFIG_ALTIVEC
	if (last_task_used_altivec == current)
		last_task_used_altivec = NULL;
#endif /* CONFIG_ALTIVEC */
#endif /* CONFIG_SMP */
}

void flush_thread(void)
{
	struct thread_info *t = current_thread_info();

	kprobe_flush_task(current);
	if (t->flags & _TIF_ABI_PENDING)
		t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT);