243 lines
6.2 KiB
C
243 lines
6.2 KiB
C
/*
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* Process creation support for Hexagon
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*
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* Copyright (c) 2010-2012, Code Aurora Forum. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 and
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* only version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*/
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#include <linux/sched.h>
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#include <linux/types.h>
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#include <linux/module.h>
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#include <linux/tick.h>
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#include <linux/uaccess.h>
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#include <linux/slab.h>
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/*
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* Kernel thread creation. The desired kernel function is "wrapped"
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* in the kernel_thread_helper function, which does cleanup
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* afterwards.
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*/
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static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
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{
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do_exit(fn(arg));
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}
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int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
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{
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struct pt_regs regs;
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memset(®s, 0, sizeof(regs));
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/*
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* Yes, we're exploting illicit knowledge of the ABI here.
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*/
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regs.r00 = (unsigned long) arg;
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regs.r01 = (unsigned long) fn;
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pt_set_elr(®s, (unsigned long)kernel_thread_helper);
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pt_set_kmode(®s);
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return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
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}
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EXPORT_SYMBOL(kernel_thread);
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/*
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* Program thread launch. Often defined as a macro in processor.h,
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* but we're shooting for a small footprint and it's not an inner-loop
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* performance-critical operation.
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*
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* The Hexagon ABI specifies that R28 is zero'ed before program launch,
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* so that gets automatically done here. If we ever stop doing that here,
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* we'll probably want to define the ELF_PLAT_INIT macro.
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*/
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void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
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{
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/* Set to run with user-mode data segmentation */
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set_fs(USER_DS);
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/* We want to zero all data-containing registers. Is this overkill? */
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memset(regs, 0, sizeof(*regs));
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/* We might want to also zero all Processor registers here */
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pt_set_usermode(regs);
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pt_set_elr(regs, pc);
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pt_set_rte_sp(regs, sp);
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}
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/*
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* Spin, or better still, do a hardware or VM wait instruction
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* If hardware or VM offer wait termination even though interrupts
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* are disabled.
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*/
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static void default_idle(void)
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{
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__vmwait();
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}
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void (*idle_sleep)(void) = default_idle;
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void cpu_idle(void)
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{
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while (1) {
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tick_nohz_idle_enter();
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local_irq_disable();
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while (!need_resched()) {
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idle_sleep();
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/* interrupts wake us up, but aren't serviced */
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local_irq_enable(); /* service interrupt */
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local_irq_disable();
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}
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local_irq_enable();
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tick_nohz_idle_exit();
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schedule();
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}
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}
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/*
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* Return saved PC of a blocked thread
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*/
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unsigned long thread_saved_pc(struct task_struct *tsk)
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{
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return 0;
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}
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/*
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* Copy architecture-specific thread state
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*/
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int copy_thread(unsigned long clone_flags, unsigned long usp,
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unsigned long unused, struct task_struct *p,
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struct pt_regs *regs)
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{
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struct thread_info *ti = task_thread_info(p);
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struct hexagon_switch_stack *ss;
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struct pt_regs *childregs;
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asmlinkage void ret_from_fork(void);
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childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
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sizeof(*childregs));
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memcpy(childregs, regs, sizeof(*childregs));
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ti->regs = childregs;
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/*
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* Establish kernel stack pointer and initial PC for new thread
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*/
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ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
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sizeof(*ss));
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ss->lr = (unsigned long)ret_from_fork;
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p->thread.switch_sp = ss;
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/* If User mode thread, set pt_reg stack pointer as per parameter */
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if (user_mode(childregs)) {
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pt_set_rte_sp(childregs, usp);
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/* Child sees zero return value */
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childregs->r00 = 0;
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/*
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* The clone syscall has the C signature:
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* int [r0] clone(int flags [r0],
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* void *child_frame [r1],
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* void *parent_tid [r2],
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* void *child_tid [r3],
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* void *thread_control_block [r4]);
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* ugp is used to provide TLS support.
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*/
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if (clone_flags & CLONE_SETTLS)
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childregs->ugp = childregs->r04;
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/*
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* Parent sees new pid -- not necessary, not even possible at
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* this point in the fork process
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* Might also want to set things like ti->addr_limit
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*/
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} else {
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/*
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* If kernel thread, resume stack is kernel stack base.
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* Note that this is pointer arithmetic on pt_regs *
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*/
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pt_set_rte_sp(childregs, (unsigned long)(childregs + 1));
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/*
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* We need the current thread_info fast path pointer
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* set up in pt_regs. The register to be used is
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* parametric for assembler code, but the mechanism
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* doesn't drop neatly into C. Needs to be fixed.
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*/
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childregs->THREADINFO_REG = (unsigned long) ti;
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}
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/*
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* thread_info pointer is pulled out of task_struct "stack"
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* field on switch_to.
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*/
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p->stack = (void *)ti;
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return 0;
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}
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/*
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* Release any architecture-specific resources locked by thread
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*/
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void release_thread(struct task_struct *dead_task)
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{
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}
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/*
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* Free any architecture-specific thread data structures, etc.
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*/
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void exit_thread(void)
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{
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}
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/*
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* Some archs flush debug and FPU info here
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*/
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void flush_thread(void)
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{
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}
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/*
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* The "wait channel" terminology is archaic, but what we want
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* is an identification of the point at which the scheduler
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* was invoked by a blocked thread.
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*/
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unsigned long get_wchan(struct task_struct *p)
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{
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unsigned long fp, pc;
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unsigned long stack_page;
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int count = 0;
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if (!p || p == current || p->state == TASK_RUNNING)
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return 0;
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stack_page = (unsigned long)task_stack_page(p);
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fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
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do {
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if (fp < (stack_page + sizeof(struct thread_info)) ||
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fp >= (THREAD_SIZE - 8 + stack_page))
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return 0;
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pc = ((unsigned long *)fp)[1];
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if (!in_sched_functions(pc))
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return pc;
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fp = *(unsigned long *) fp;
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} while (count++ < 16);
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return 0;
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}
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/*
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* Required placeholder.
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*/
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int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
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{
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return 0;
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}
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