1 /* 2 * Process creation support for Hexagon 3 * 4 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved. 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 and 8 * only version 2 as published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 18 * 02110-1301, USA. 19 */ 20 21 #include <linux/sched.h> 22 #include <linux/types.h> 23 #include <linux/module.h> 24 #include <linux/tick.h> 25 #include <linux/uaccess.h> 26 #include <linux/slab.h> 27 28 /* 29 * Program thread launch. Often defined as a macro in processor.h, 30 * but we're shooting for a small footprint and it's not an inner-loop 31 * performance-critical operation. 32 * 33 * The Hexagon ABI specifies that R28 is zero'ed before program launch, 34 * so that gets automatically done here. If we ever stop doing that here, 35 * we'll probably want to define the ELF_PLAT_INIT macro. 36 */ 37 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) 38 { 39 /* Set to run with user-mode data segmentation */ 40 set_fs(USER_DS); 41 /* We want to zero all data-containing registers. Is this overkill? */ 42 memset(regs, 0, sizeof(*regs)); 43 /* We might want to also zero all Processor registers here */ 44 pt_set_usermode(regs); 45 pt_set_elr(regs, pc); 46 pt_set_rte_sp(regs, sp); 47 } 48 49 /* 50 * Spin, or better still, do a hardware or VM wait instruction 51 * If hardware or VM offer wait termination even though interrupts 52 * are disabled. 53 */ 54 static void default_idle(void) 55 { 56 __vmwait(); 57 } 58 59 void (*idle_sleep)(void) = default_idle; 60 61 void cpu_idle(void) 62 { 63 while (1) { 64 tick_nohz_idle_enter(); 65 local_irq_disable(); 66 while (!need_resched()) { 67 idle_sleep(); 68 /* interrupts wake us up, but aren't serviced */ 69 local_irq_enable(); /* service interrupt */ 70 local_irq_disable(); 71 } 72 local_irq_enable(); 73 tick_nohz_idle_exit(); 74 schedule(); 75 } 76 } 77 78 /* 79 * Return saved PC of a blocked thread 80 */ 81 unsigned long thread_saved_pc(struct task_struct *tsk) 82 { 83 return 0; 84 } 85 86 /* 87 * Copy architecture-specific thread state 88 */ 89 int copy_thread(unsigned long clone_flags, unsigned long usp, 90 unsigned long arg, struct task_struct *p) 91 { 92 struct thread_info *ti = task_thread_info(p); 93 struct hexagon_switch_stack *ss; 94 struct pt_regs *childregs; 95 asmlinkage void ret_from_fork(void); 96 97 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) - 98 sizeof(*childregs)); 99 100 ti->regs = childregs; 101 102 /* 103 * Establish kernel stack pointer and initial PC for new thread 104 * Note that unlike the usual situation, we do not copy the 105 * parent's callee-saved here; those are in pt_regs and whatever 106 * we leave here will be overridden on return to userland. 107 */ 108 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs - 109 sizeof(*ss)); 110 ss->lr = (unsigned long)ret_from_fork; 111 p->thread.switch_sp = ss; 112 if (unlikely(p->flags & PF_KTHREAD)) { 113 memset(childregs, 0, sizeof(struct pt_regs)); 114 /* r24 <- fn, r25 <- arg */ 115 ss->r2524 = usp | ((u64)arg << 32); 116 pt_set_kmode(childregs); 117 return 0; 118 } 119 memcpy(childregs, current_pt_regs(), sizeof(*childregs)); 120 ss->r2524 = 0; 121 122 if (usp) 123 pt_set_rte_sp(childregs, usp); 124 125 /* Child sees zero return value */ 126 childregs->r00 = 0; 127 128 /* 129 * The clone syscall has the C signature: 130 * int [r0] clone(int flags [r0], 131 * void *child_frame [r1], 132 * void *parent_tid [r2], 133 * void *child_tid [r3], 134 * void *thread_control_block [r4]); 135 * ugp is used to provide TLS support. 136 */ 137 if (clone_flags & CLONE_SETTLS) 138 childregs->ugp = childregs->r04; 139 140 /* 141 * Parent sees new pid -- not necessary, not even possible at 142 * this point in the fork process 143 * Might also want to set things like ti->addr_limit 144 */ 145 146 return 0; 147 } 148 149 /* 150 * Release any architecture-specific resources locked by thread 151 */ 152 void release_thread(struct task_struct *dead_task) 153 { 154 } 155 156 /* 157 * Free any architecture-specific thread data structures, etc. 158 */ 159 void exit_thread(void) 160 { 161 } 162 163 /* 164 * Some archs flush debug and FPU info here 165 */ 166 void flush_thread(void) 167 { 168 } 169 170 /* 171 * The "wait channel" terminology is archaic, but what we want 172 * is an identification of the point at which the scheduler 173 * was invoked by a blocked thread. 174 */ 175 unsigned long get_wchan(struct task_struct *p) 176 { 177 unsigned long fp, pc; 178 unsigned long stack_page; 179 int count = 0; 180 if (!p || p == current || p->state == TASK_RUNNING) 181 return 0; 182 183 stack_page = (unsigned long)task_stack_page(p); 184 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp; 185 do { 186 if (fp < (stack_page + sizeof(struct thread_info)) || 187 fp >= (THREAD_SIZE - 8 + stack_page)) 188 return 0; 189 pc = ((unsigned long *)fp)[1]; 190 if (!in_sched_functions(pc)) 191 return pc; 192 fp = *(unsigned long *) fp; 193 } while (count++ < 16); 194 195 return 0; 196 } 197 198 /* 199 * Required placeholder. 200 */ 201 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu) 202 { 203 return 0; 204 } 205