arch/hexagon/kernel/process.c

Source file repositories/reference/linux-study-clean/arch/hexagon/kernel/process.c

File Facts

System
Linux kernel
Corpus path
arch/hexagon/kernel/process.c
Extension
.c
Size
4777 bytes
Lines
184
Domain
Architecture Layer
Bucket
arch/hexagon
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Process creation support for Hexagon
 *
 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
 */

#include <linux/cpu.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/tick.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/resume_user_mode.h>

/*
 * Program thread launch.  Often defined as a macro in processor.h,
 * but we're shooting for a small footprint and it's not an inner-loop
 * performance-critical operation.
 *
 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
 * so that gets automatically done here.  If we ever stop doing that here,
 * we'll probably want to define the ELF_PLAT_INIT macro.
 */
void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
	/* We want to zero all data-containing registers. Is this overkill? */
	memset(regs, 0, sizeof(*regs));
	/* We might want to also zero all Processor registers here */
	pt_set_usermode(regs);
	pt_set_elr(regs, pc);
	pt_set_rte_sp(regs, sp);
}

/*
 *  Spin, or better still, do a hardware or VM wait instruction
 *  If hardware or VM offer wait termination even though interrupts
 *  are disabled.
 */
void arch_cpu_idle(void)
{
	__vmwait();
	/*  interrupts wake us up, but irqs are still disabled */
}

/*
 * Copy architecture-specific thread state
 */
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
	u64 clone_flags = args->flags;
	unsigned long usp = args->stack;
	unsigned long tls = args->tls;
	struct thread_info *ti = task_thread_info(p);
	struct hexagon_switch_stack *ss;
	struct pt_regs *childregs;
	asmlinkage void ret_from_fork(void);

	childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
					sizeof(*childregs));

	ti->regs = childregs;

	/*
	 * Establish kernel stack pointer and initial PC for new thread
	 * Note that unlike the usual situation, we do not copy the
	 * parent's callee-saved here; those are in pt_regs and whatever
	 * we leave here will be overridden on return to userland.
	 */
	ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
						    sizeof(*ss));
	ss->lr = (unsigned long)ret_from_fork;
	p->thread.switch_sp = ss;
	if (unlikely(args->fn)) {
		memset(childregs, 0, sizeof(struct pt_regs));
		/* r24 <- fn, r25 <- arg */
		ss->r24 = (unsigned long)args->fn;
		ss->r25 = (unsigned long)args->fn_arg;
		pt_set_kmode(childregs);
		return 0;
	}
	memcpy(childregs, current_pt_regs(), sizeof(*childregs));
	ss->r2524 = 0;

	if (usp)
		pt_set_rte_sp(childregs, usp);

Annotation

Implementation Notes