[PATCH v2 09/29] nios2: Process management

Ley Foon Tan
2014-07-15T08:48:05Z

This patch adds support for thread creation and context switching.

Signed-off-by: Ley Foon Tan <lftan@altera.com>
---
arch/nios2/include/asm/mmu_context.h | 66 +++++++++
arch/nios2/include/asm/processor.h | 102 ++++++++++++++
arch/nios2/include/asm/switch_to.h | 31 +++++
arch/nios2/include/asm/thread_info.h | 120 ++++++++++++++++
arch/nios2/kernel/process.c | 262 +++++++++++++++++++++++++++++++++++
arch/nios2/mm/mmu_context.c | 116 ++++++++++++++++
6 files changed, 697 insertions(+)
create mode 100644 arch/nios2/include/asm/mmu_context.h
create mode 100644 arch/nios2/include/asm/processor.h
create mode 100644 arch/nios2/include/asm/switch_to.h
create mode 100644 arch/nios2/include/asm/thread_info.h
create mode 100644 arch/nios2/kernel/process.c
create mode 100644 arch/nios2/mm/mmu_context.c

diff --git a/arch/nios2/include/asm/mmu_context.h b/arch/nios2/include/asm/mmu_context.h
new file mode 100644
index 0000000..294b4b1
--- /dev/null
+++ b/arch/nios2/include/asm/mmu_context.h
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 1996, 1997, 1998, 1999 by Ralf Baechle
+ * Copyright (C) 1999 Silicon Graphics, Inc.
+ *
+ * based on MIPS asm/mmu_context.h
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _ASM_NIOS2_MMU_CONTEXT_H
+#define _ASM_NIOS2_MMU_CONTEXT_H
+
+#include <asm-generic/mm_hooks.h>
+
+extern void mmu_context_init(void);
+extern unsigned long get_pid_from_context(mm_context_t *ctx);
+
+/*
+ * For the fast tlb miss handlers, we keep a pointer to the current pgd.
+ * processor.
+ */
+extern pgd_t *pgd_current;
+
+static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+}
+
+/*
+ * Initialize the context related info for a new mm_struct instance.
+ *
+ * Set all new contexts to 0, that way the generation will never match
+ * the currently running generation when this context is switched in.
+ */
+static inline int init_new_context(struct task_struct *tsk,
+ struct mm_struct *mm)
+{
+ mm->context = 0;
+ return 0;
+}
+
+/*
+ * Destroy context related info for an mm_struct that is about
+ * to be put to rest.
+ */
+static inline void destroy_context(struct mm_struct *mm)
+{
+}
+
+void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+ struct task_struct *tsk);
+
+static inline void deactivate_mm(struct task_struct *tsk,
+ struct mm_struct *mm)
+{
+}
+
+/*
+ * After we have set current->mm to a new value, this activates
+ * the context for the new mm so we see the new mappings.
+ */
+void activate_mm(struct mm_struct *prev, struct mm_struct *next);
+
+#endif /* _ASM_NIOS2_MMU_CONTEXT_H */
diff --git a/arch/nios2/include/asm/processor.h b/arch/nios2/include/asm/processor.h
new file mode 100644
index 0000000..cff9b2d
--- /dev/null
+++ b/arch/nios2/include/asm/processor.h
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2013 Altera Corporation
+ * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2004 Microtronix Datacom Ltd
+ * Copyright (C) 2001 Ken Hill (khill@microtronix.com)
+ * Vic Phillips (vic@microtronix.com)
+ *
+ * based on SPARC asm/processor_32.h which is:
+ *
+ * Copyright (C) 1994 David S. Miller
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _ASM_NIOS2_PROCESSOR_H
+#define _ASM_NIOS2_PROCESSOR_H
+
+#include <asm/ptrace.h>
+#include <asm/registers.h>
+#include <asm/page.h>
+
+#define NIOS2_FLAG_KTHREAD 0x00000001 /* task is a kernel thread */
+
+#define NIOS2_OP_NOP 0x1883a
+#define NIOS2_OP_BREAK 0x3da03a
+
+#ifdef __KERNEL__
+
+#define STACK_TOP TASK_SIZE
+#define STACK_TOP_MAX STACK_TOP
+
+#endif /* __KERNEL__ */
+
+/* Kuser helpers is mapped to this user space address */
+#define KUSER_BASE 0x1000
+#define KUSER_SIZE (PAGE_SIZE)
+#ifndef __ASSEMBLY__
+
+/*
+ * Default implementation of macro that returns current
+ * instruction pointer ("program counter").
+ */
+#define current_text_addr() ({ __label__ _l; _l: &&_l; })
+
+# define TASK_SIZE 0x7FFF0000UL
+# define TASK_UNMAPPED_BASE (PAGE_ALIGN(TASK_SIZE / 3))
+
+/* The Nios processor specific thread struct. */
+struct thread_struct {
+ struct pt_regs *kregs;
+
+ /* Context switch saved kernel state. */
+ unsigned long ksp;
+ unsigned long kpsr;
+};
+
+#define INIT_MMAP \
+ { &init_mm, (0), (0), __pgprot(0x0), VM_READ | VM_WRITE | VM_EXEC }
+
+# define INIT_THREAD { \
+ .kregs = NULL, \
+ .ksp = 0, \
+ .kpsr = 0, \
+}
+
+extern void start_thread(struct pt_regs *regs, unsigned long pc,
+ unsigned long sp);
+
+struct task_struct;
+
+/* Free all resources held by a thread. */
+static inline void release_thread(struct task_struct *dead_task)
+{
+}
+
+/* Free current thread data structures etc.. */
+static inline void exit_thread(void)
+{
+}
+
+/* Return saved PC of a blocked thread. */
+#define thread_saved_pc(tsk) ((tsk)->thread.kregs->ea)
+
+extern unsigned long get_wchan(struct task_struct *p);
+
+/* Prepare to copy thread state - unlazy all lazy status */
+#define prepare_to_copy(tsk) do { } while (0)
+
+#define task_pt_regs(p) \
+ ((struct pt_regs *)(THREAD_SIZE + task_stack_page(p)) - 1)
+
+/* Used by procfs */
+#define KSTK_EIP(tsk) ((tsk)->thread.kregs->ea)
+#define KSTK_ESP(tsk) ((tsk)->thread.kregs->sp)
+
+#define cpu_relax() barrier()
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_NIOS2_PROCESSOR_H */
diff --git a/arch/nios2/include/asm/switch_to.h b/arch/nios2/include/asm/switch_to.h
new file mode 100644
index 0000000..c47b3f4
--- /dev/null
+++ b/arch/nios2/include/asm/switch_to.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2004 Microtronix Datacom Ltd.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#ifndef _ASM_NIOS2_SWITCH_TO_H
+#define _ASM_NIOS2_SWITCH_TO_H
+
+/*
+ * switch_to(n) should switch tasks to task ptr, first checking that
+ * ptr isn't the current task, in which case it does nothing. This
+ * also clears the TS-flag if the task we switched to has used the
+ * math co-processor latest.
+ */
+#define switch_to(prev, next, last) \
+{ \
+ void *_last; \
+ __asm__ __volatile__ ( \
+ "mov r4, %1\n" \
+ "mov r5, %2\n" \
+ "call resume\n" \
+ "mov %0,r4\n" \
+ : "=r" (_last) \
+ : "r" (prev), "r" (next) \
+ : "r4", "r5", "r7", "r8", "ra"); \
+ (last) = _last; \
+}
+
+#endif /* _ASM_NIOS2_SWITCH_TO_H */
diff --git a/arch/nios2/include/asm/thread_info.h b/arch/nios2/include/asm/thread_info.h
new file mode 100644
index 0000000..1f26657
--- /dev/null
+++ b/arch/nios2/include/asm/thread_info.h
@@ -0,0 +1,120 @@
+/*
+ * NiosII low-level thread information
+ *
+ * Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2004 Microtronix Datacom Ltd.
+ *
+ * Based on asm/thread_info_no.h from m68k which is:
+ *
+ * Copyright (C) 2002 David Howells <dhowells@redhat.com>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _ASM_NIOS2_THREAD_INFO_H
+#define _ASM_NIOS2_THREAD_INFO_H
+
+#ifdef __KERNEL__
+
+/*
+ * Size of the kernel stack for each process.
+ */
+#define THREAD_SIZE_ORDER 1
+#define THREAD_SIZE 8192 /* 2 * PAGE_SIZE */
+
+#ifndef __ASSEMBLY__
+
+typedef struct {
+ unsigned long seg;
+} mm_segment_t;
+
+/*
+ * low level task data that entry.S needs immediate access to
+ * - this struct should fit entirely inside of one cache line
+ * - this struct shares the supervisor stack pages
+ * - if the contents of this structure are changed, the assembly constants
+ * must also be changed
+ */
+struct thread_info {
+ struct task_struct *task; /* main task structure */
+ struct exec_domain *exec_domain; /* execution domain */
+ unsigned long flags; /* low level flags */
+ __u32 cpu; /* current CPU */
+ int preempt_count; /* 0 => preemptable,<0 => BUG */
+ mm_segment_t addr_limit; /* thread address space:
+ 0-0x7FFFFFFF for user-thead
+ 0-0xFFFFFFFF for kernel-thread
+ */
+ struct restart_block restart_block;
+ struct pt_regs *regs;
+};
+
+/*
+ * macros/functions for gaining access to the thread information structure
+ *
+ * preempt_count needs to be 1 initially, until the scheduler is functional.
+ */
+#define INIT_THREAD_INFO(tsk) \
+{ \
+ .task = &tsk, \
+ .exec_domain = &default_exec_domain, \
+ .flags = 0, \
+ .cpu = 0, \
+ .preempt_count = INIT_PREEMPT_COUNT, \
+ .addr_limit = KERNEL_DS, \
+ .restart_block = { \
+ .fn = do_no_restart_syscall, \
+ }, \
+}
+
+#define init_thread_info (init_thread_union.thread_info)
+#define init_stack (init_thread_union.stack)
+
+/* how to get the thread information struct from C */
+static inline struct thread_info *current_thread_info(void)
+{
+ register unsigned long sp asm("sp");
+
+ return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
+}
+#endif /* !__ASSEMBLY__ */
+
+/*
+ * thread information flags
+ * - these are process state flags that various assembly files may need to
+ * access
+ * - pending work-to-be-done flags are in LSW
+ * - other flags in MSW
+ */
+#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
+#define TIF_NOTIFY_RESUME 1 /* resumption notification requested */
+#define TIF_SIGPENDING 2 /* signal pending */
+#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
+#define TIF_MEMDIE 4 /* is terminating due to OOM killer */
+#define TIF_SECCOMP 5 /* secure computing */
+#define TIF_SYSCALL_AUDIT 6 /* syscall auditing active */
+#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal() */
+
+#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling
+ TIF_NEED_RESCHED */
+
+#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
+#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
+#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
+#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
+#define _TIF_SECCOMP (1 << TIF_SECCOMP)
+#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
+#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
+#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
+
+/* work to do on interrupt/exception return */
+#define _TIF_WORK_MASK 0x0000FFFE
+
+/* work to do on any return to u-space */
+# define _TIF_ALLWORK_MASK 0x0000FFFF
+
+#endif /* __KERNEL__ */
+
+#endif /* _ASM_NIOS2_THREAD_INFO_H */
diff --git a/arch/nios2/kernel/process.c b/arch/nios2/kernel/process.c
new file mode 100644
index 0000000..162b3f0
--- /dev/null
+++ b/arch/nios2/kernel/process.c
@@ -0,0 +1,262 @@
+/*
+ * Architecture-dependent parts of process handling.
+ *
+ * Copyright (C) 2013 Altera Corporation
+ * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2009 Wind River Systems Inc
+ * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ * Copyright (C) 2004 Microtronix Datacom Ltd
+ *
+ * based on arch/m68knommu/kernel/process.c which is:
+ *
+ * Copyright (C) 2000-2002 David McCullough <davidm@snapgear.com>
+ * Copyright (C) 1995 Hamish Macdonald
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/tick.h>
+#include <linux/uaccess.h>
+
+#include <asm/unistd.h>
+#include <asm/traps.h>
+#include <asm/cpuinfo.h>
+
+asmlinkage void ret_from_fork(void);
+asmlinkage void ret_from_kernel_thread(void);
+
+void (*pm_power_off)(void) = NULL;
+EXPORT_SYMBOL(pm_power_off);
+
+void arch_cpu_idle(void)
+{
+ local_irq_enable();
+}
+
+/*
+ * The development boards have no way to pull a board reset. Just jump to the
+ * cpu reset address and let the boot loader or the code in head.S take care of
+ * resetting peripherals.
+ */
+void machine_restart(char *__unused)
+{
+ pr_notice("Machine restart (%08x)...\n", cpuinfo.reset_addr);
+ local_irq_disable();
+ __asm__ __volatile__ (
+ "jmp %0\n\t"
+ :
+ : "r" (cpuinfo.reset_addr)
+ : "r4");
+}
+
+void machine_halt(void)
+{
+ pr_notice("Machine halt...\n");
+ local_irq_disable();
+ for (;;)
+ ;
+}
+
+/*
+ * There is no way to power off the development boards. So just spin for now. If
+ * we ever have a way of resetting a board using a GPIO we should add that here.
+ */
+void machine_power_off(void)
+{
+ pr_notice("Machine power off...\n");
+ local_irq_disable();
+ for (;;)
+ ;
+}
+
+void show_regs(struct pt_regs *regs)
+{
+ pr_notice("\n");
+ show_regs_print_info(KERN_DEFAULT);
+
+ pr_notice("r1: %08lx r2: %08lx r3: %08lx r4: %08lx\n",
+ regs->r1, regs->r2, regs->r3, regs->r4);
+
+ pr_notice("r5: %08lx r6: %08lx r7: %08lx r8: %08lx\n",
+ regs->r5, regs->r6, regs->r7, regs->r8);
+
+ pr_notice("r9: %08lx r10: %08lx r11: %08lx r12: %08lx\n",
+ regs->r9, regs->r10, regs->r11, regs->r12);
+
+ pr_notice("r13: %08lx r14: %08lx r15: %08lx\n",
+ regs->r13, regs->r14, regs->r15);
+
+ pr_notice("ra: %08lx fp: %08lx sp: %08lx gp: %08lx\n",
+ regs->ra, regs->fp, regs->sp, regs->gp);
+
+ pr_notice("ea: %08lx estatus: %08lx\n",
+ regs->ea, regs->estatus);
+}
+
+void flush_thread(void)
+{
+ set_fs(USER_DS);
+}
+
+int copy_thread(unsigned long clone_flags,
+ unsigned long usp, unsigned long arg, struct task_struct *p)
+{
+ struct pt_regs *childregs = task_pt_regs(p);
+ struct pt_regs *regs;
+ struct switch_stack *stack;
+ struct switch_stack *childstack =
+ ((struct switch_stack *)childregs) - 1;
+
+ if (unlikely(p->flags & PF_KTHREAD)) {
+ memset(childstack, 0,
+ sizeof(struct switch_stack) + sizeof(struct pt_regs));
+
+ childstack->r16 = usp; /* fn */
+ childstack->r17 = arg;
+ childstack->ra = (unsigned long) ret_from_kernel_thread;
+ childregs->estatus = STATUS_PIE;
+ childregs->sp = (unsigned long) childstack;
+
+ p->thread.ksp = (unsigned long) childstack;
+ p->thread.kregs = childregs;
+ return 0;
+ }
+
+ regs = current_pt_regs();
+ *childregs = *regs;
+ childregs->r2 = 0; /* Set the return value for the child. */
+ childregs->r7 = 0;
+
+ stack = ((struct switch_stack *) regs) - 1;
+ *childstack = *stack;
+ childstack->ra = (unsigned long)ret_from_fork;
+ p->thread.kregs = childregs;
+ p->thread.ksp = (unsigned long) childstack;
+
+ if (usp)
+ childregs->sp = usp;
+
+ /* Initialize tls register. */
+ if (clone_flags & CLONE_SETTLS)
+ childstack->r23 = regs->r8;
+
+ return 0;
+}
+
+/*
+ * Generic dumping code. Used for panic and debug.
+ */
+void dump(struct pt_regs *fp)
+{
+ unsigned long *sp;
+ unsigned char *tp;
+ int i;
+
+ pr_emerg("\nCURRENT PROCESS:\n\n");
+ pr_emerg("COMM=%s PID=%d\n", current->comm, current->pid);
+
+ if (current->mm) {
+ pr_emerg("TEXT=%08x-%08x DATA=%08x-%08x BSS=%08x-%08x\n",
+ (int) current->mm->start_code,
+ (int) current->mm->end_code,
+ (int) current->mm->start_data,
+ (int) current->mm->end_data,
+ (int) current->mm->end_data,
+ (int) current->mm->brk);
+ pr_emerg("USER-STACK=%08x KERNEL-STACK=%08x\n\n",
+ (int) current->mm->start_stack,
+ (int)(((unsigned long) current) + THREAD_SIZE));
+ }
+
+ pr_emerg("PC: %08lx\n", fp->ea);
+ pr_emerg(KERN_EMERG "SR: %08lx SP: %08lx\n",
+ (long) fp->estatus, (long) fp);
+
+ pr_emerg("r1: %08lx r2: %08lx r3: %08lx\n",
+ fp->r1, fp->r2, fp->r3);
+
+ pr_emerg("r4: %08lx r5: %08lx r6: %08lx r7: %08lx\n",
+ fp->r4, fp->r5, fp->r6, fp->r7);
+ pr_emerg("r8: %08lx r9: %08lx r10: %08lx r11: %08lx\n",
+ fp->r8, fp->r9, fp->r10, fp->r11);
+ pr_emerg("r12: %08lx r13: %08lx r14: %08lx r15: %08lx\n",
+ fp->r12, fp->r13, fp->r14, fp->r15);
+ pr_emerg("or2: %08lx ra: %08lx fp: %08lx sp: %08lx\n",
+ fp->orig_r2, fp->ra, fp->fp, fp->sp);
+ pr_emerg("\nUSP: %08x TRAPFRAME: %08x\n",
+ (unsigned int) fp->sp, (unsigned int) fp);
+
+ pr_emerg("\nCODE:");
+ tp = ((unsigned char *) fp->ea) - 0x20;
+ for (sp = (unsigned long *) tp, i = 0; (i < 0x40); i += 4) {
+ if ((i % 0x10) == 0)
+ pr_emerg("\n%08x: ", (int) (tp + i));
+ pr_emerg("%08x ", (int) *sp++);
+ }
+ pr_emerg("\n");
+
+ pr_emerg("\nKERNEL STACK:");
+ tp = ((unsigned char *) fp) - 0x40;
+ for (sp = (unsigned long *) tp, i = 0; (i < 0xc0); i += 4) {
+ if ((i % 0x10) == 0)
+ pr_emerg("\n%08x: ", (int) (tp + i));
+ pr_emerg("%08x ", (int) *sp++);
+ }
+ pr_emerg("\n");
+ pr_emerg("\n");
+
+ pr_emerg("\nUSER STACK:");
+ tp = (unsigned char *) (fp->sp - 0x10);
+ for (sp = (unsigned long *) tp, i = 0; (i < 0x80); i += 4) {
+ if ((i % 0x10) == 0)
+ pr_emerg("\n%08x: ", (int) (tp + i));
+ pr_emerg("%08x ", (int) *sp++);
+ }
+ pr_emerg("\n\n");
+}
+
+unsigned long get_wchan(struct task_struct *p)
+{
+ unsigned long fp, pc;
+ unsigned long stack_page;
+ int count = 0;
+ if (!p || p == current || p->state == TASK_RUNNING)
+ return 0;
+
+ stack_page = (unsigned long)p;
+ fp = ((struct switch_stack *)p->thread.ksp)->fp; /* ;dgt2 */
+ do {
+ if (fp < stack_page+sizeof(struct task_struct) ||
+ fp >= 8184+stack_page) /* ;dgt2;tmp */
+ return 0;
+ pc = ((unsigned long *)fp)[1];
+ if (!in_sched_functions(pc))
+ return pc;
+ fp = *(unsigned long *) fp;
+ } while (count++ < 16); /* ;dgt2;tmp */
+ return 0;
+}
+
+/*
+ * Do necessary setup to start up a newly executed thread.
+ * Will startup in user mode (status_extension = 0).
+ */
+void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
+{
+ memset((void *) regs, 0, sizeof(struct pt_regs));
+ regs->estatus = ESTATUS_EPIE | ESTATUS_EU;
+ regs->ea = pc;
+ regs->sp = sp;
+}
+
+#include <linux/elfcore.h>
+
+/* Fill in the FPU structure for a core dump. */
+int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
+{
+ return 0; /* Nios2 has no FPU and thus no FPU registers */
+}
diff --git a/arch/nios2/mm/mmu_context.c b/arch/nios2/mm/mmu_context.c
new file mode 100644
index 0000000..45d6b9c
--- /dev/null
+++ b/arch/nios2/mm/mmu_context.c
@@ -0,0 +1,116 @@
+/*
+ * MMU context handling.
+ *
+ * Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2009 Wind River Systems Inc
+ * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/mm.h>
+
+#include <asm/cpuinfo.h>
+#include <asm/mmu_context.h>
+#include <asm/tlb.h>
+
+/* The pids position and mask in context */
+#define PID_SHIFT 0
+#define PID_BITS (cpuinfo.tlb_pid_num_bits)
+#define PID_MASK ((1UL << PID_BITS) - 1)
+
+/* The versions position and mask in context */
+#define VERSION_BITS (32 - PID_BITS)
+#define VERSION_SHIFT (PID_SHIFT + PID_BITS)
+#define VERSION_MASK ((1UL << VERSION_BITS) - 1)
+
+/* Return the version part of a context */
+#define CTX_VERSION(c) (((c) >> VERSION_SHIFT) & VERSION_MASK)
+
+/* Return the pid part of a context */
+#define CTX_PID(c) (((c) >> PID_SHIFT) & PID_MASK)
+
+/* Value of the first context (version 1, pid 0) */
+#define FIRST_CTX ((1UL << VERSION_SHIFT) | (0 << PID_SHIFT))
+
+static mm_context_t next_mmu_context;
+
+/*
+ * Initialize MMU context management stuff.
+ */
+void __init mmu_context_init(void)
+{
+ /* We need to set this here because the value depends on runtime data
+ * from cpuinfo */
+ next_mmu_context = FIRST_CTX;
+}
+
+/*
+ * Set new context (pid), keep way
+ */
+static void set_context(mm_context_t context)
+{
+ set_mmu_pid(CTX_PID(context));
+}
+
+static mm_context_t get_new_context(void)
+{
+ /* Return the next pid */
+ next_mmu_context += (1UL << PID_SHIFT);
+
+ /* If the pid field wraps around we increase the version and
+ * flush the tlb */
+ if (unlikely(CTX_PID(next_mmu_context) == 0)) {
+ /* Version is incremented since the pid increment above
+ * overflows info version */
+ flush_cache_all();
+ flush_tlb_all();
+ }
+
+ /* If the version wraps we start over with the first generation, we do
+ * not need to flush the tlb here since it's always done above */
+ if (unlikely(CTX_VERSION(next_mmu_context) == 0))
+ next_mmu_context = FIRST_CTX;
+
+ return next_mmu_context;
+}
+
+void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+ struct task_struct *tsk)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+
+ /* If the process context we are swapping in has a different context
+ * generation then we have it should get a new generation/pid */
+ if (unlikely(CTX_VERSION(next->context) !=
+ CTX_VERSION(next_mmu_context)))
+ next->context = get_new_context();
+
+ /* Save the current pgd so the fast tlb handler can find it */
+ pgd_current = next->pgd;
+
+ /* Set the current context */
+ set_context(next->context);
+
+ local_irq_restore(flags);
+}
+
+/*
+ * After we have set current->mm to a new value, this activates
+ * the context for the new mm so we see the new mappings.
+ */
+void activate_mm(struct mm_struct *prev, struct mm_struct *next)
+{
+ next->context = get_new_context();
+ set_context(next->context);
+ pgd_current = next->pgd;
+}
+
+unsigned long get_pid_from_context(mm_context_t *context)
+{
+ return CTX_PID((*context));
+}
--
1.8.2.1