/*
* Process creation support for Hexagon
*
* Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 and
* only version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/tick.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
/*
* Kernel thread creation. The desired kernel function is "wrapped"
* in the kernel_thread_helper function, which does cleanup
* afterwards.
*/
static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
{
do_exit(fn(arg));
}
int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
struct pt_regs regs;
memset(®s, 0, sizeof(regs));
/*
* Yes, we're exploting illicit knowledge of the ABI here.
*/
regs.r00 = (unsigned long) arg;
regs.r01 = (unsigned long) fn;
pt_set_elr(®s, (unsigned long)kernel_thread_helper);
pt_set_kmode(®s);
return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
}
EXPORT_SYMBOL(kernel_thread);
/*
* 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)
{
/* Set to run with user-mode data segmentation */
set_fs(USER_DS);
/* 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.
*/
static void default_idle(void)
{
__vmwait();
}
void (*idle_sleep)(void) = default_idle;
void cpu_idle(void)
{
while (1) {
tick_nohz_stop_sched_tick(1);
local_irq_disable();
while (!need_resched()) {
idle_sleep();
/* interrupts wake us up, but aren't serviced */
local_irq_enable(); /* service interrupt */
local_irq_disable();
}
local_irq_enable();
tick_nohz_restart_sched_tick();
schedule();
}
}
/*
* Return saved PC of a blocked thread
*/
unsigned long thread_saved_pc(struct task_struct *tsk)
{
return 0;
}
/*
* Copy architecture-specific thread state
*/
int copy_thread(unsigned long clone_flags, unsigned long usp,
unsigned long unused, struct task_struct *p,
struct pt_regs *regs)
{
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));
memcpy(childregs, regs, sizeof(*childregs));
ti->regs = childregs;
/*
* Establish kernel stack pointer and initial PC for new thread
*/
ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
sizeof(*ss));
ss->lr = (unsigned long)ret_from_fork;
p->thread.switch_sp = ss;
/* If User mode thread, set pt_reg stack pointer as per parameter */
if (user_mode(childregs)) {
pt_set_rte_sp(childregs, usp);
/* Child sees zero return value */
childregs->r00 = 0;
/*
* The clone syscall has the C signature:
* int [r0] clone(int flags [r0],
* void *child_frame [r1],
* void *parent_tid [r2],
* void *child_tid [r3],
* void *thread_control_block [r4]);
* ugp is used to provide TLS support.
*/
if (clone_flags & CLONE_SETTLS)
childregs->ugp = childregs->r04;
/*
* Parent sees new pid -- not necessary, not even possible at
* this point in the fork process
* Might also want to set things like ti->addr_limit
*/
} else {
/*
* If kernel thread, resume stack is kernel stack base.
* Note that this is pointer arithmetic on pt_regs *
*/
pt_set_rte_sp(childregs, (unsigned long)(childregs + 1));
/*
* We need the current thread_info fast path pointer
* set up in pt_regs. The register to be used is
* parametric for assembler code, but the mechanism
* doesn't drop neatly into C. Needs to be fixed.
*/
childregs->THREADINFO_REG = (unsigned long) ti;
}
/*
* thread_info pointer is pulled out of task_struct "stack"
* field on switch_to.
*/
p->stack = (void *)ti;
return 0;
}
/*
* Release any architecture-specific resources locked by thread
*/
void release_thread(struct task_struct *dead_task)
{
}
/*
* Free any architecture-specific thread data structures, etc.
*/
void exit_thread(void)
{
}
/*
* Some archs flush debug and FPU info here
*/
void flush_thread(void)
{
}
/*
* The "wait channel" terminology is archaic, but what we want
* is an identification of the point at which the scheduler
* was invoked by a blocked thread.
*/
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)task_stack_page(p);
fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
do {
if (fp < (stack_page + sizeof(struct thread_info)) ||
fp >= (THREAD_SIZE - 8 + stack_page))
return 0;
pc = ((unsigned long *)fp)[1];
if (!in_sched_functions(pc))
return pc;
fp = *(unsigned long *) fp;
} while (count++ < 16);
return 0;
}
/*
* Borrowed from PowerPC -- basically allow smaller kernel stacks if we
* go crazy with the page sizes.
*/
#if THREAD_SHIFT < PAGE_SHIFT
static struct kmem_cache *thread_info_cache;
struct thread_info *alloc_thread_info_node(struct task_struct *tsk, int node)
{
struct thread_info *ti;
ti = kmem_cache_alloc_node(thread_info_cache, GFP_KERNEL, node);
if (unlikely(ti == NULL))
return NULL;
#ifdef CONFIG_DEBUG_STACK_USAGE
memset(ti, 0, THREAD_SIZE);
#endif
return ti;
}
void free_thread_info(struct thread_info *ti)
{
kmem_cache_free(thread_info_cache, ti);
}
/* Weak symbol; called by init/main.c */
void thread_info_cache_init(void)
{
thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
THREAD_SIZE, 0, NULL);
BUG_ON(thread_info_cache == NULL);
}
#endif /* THREAD_SHIFT < PAGE_SHIFT */
/*
* Required placeholder.
*/
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
{
return 0;
}
