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 void arch_cpu_idle(void) 55 { 56 __vmwait(); 57 /* interrupts wake us up, but irqs are still disabled */ 58 local_irq_enable(); 59 } 60 61 /* 62 * Return saved PC of a blocked thread 63 */ 64 unsigned long thread_saved_pc(struct task_struct *tsk) 65 { 66 return 0; 67 } 68 69 /* 70 * Copy architecture-specific thread state 71 */ 72 int copy_thread(unsigned long clone_flags, unsigned long usp, 73 unsigned long arg, struct task_struct *p) 74 { 75 struct thread_info *ti = task_thread_info(p); 76 struct hexagon_switch_stack *ss; 77 struct pt_regs *childregs; 78 asmlinkage void ret_from_fork(void); 79 80 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) - 81 sizeof(*childregs)); 82 83 ti->regs = childregs; 84 85 /* 86 * Establish kernel stack pointer and initial PC for new thread 87 * Note that unlike the usual situation, we do not copy the 88 * parent's callee-saved here; those are in pt_regs and whatever 89 * we leave here will be overridden on return to userland. 90 */ 91 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs - 92 sizeof(*ss)); 93 ss->lr = (unsigned long)ret_from_fork; 94 p->thread.switch_sp = ss; 95 if (unlikely(p->flags & PF_KTHREAD)) { 96 memset(childregs, 0, sizeof(struct pt_regs)); 97 /* r24 <- fn, r25 <- arg */ 98 ss->r2524 = usp | ((u64)arg << 32); 99 pt_set_kmode(childregs); 100 return 0; 101 } 102 memcpy(childregs, current_pt_regs(), sizeof(*childregs)); 103 ss->r2524 = 0; 104 105 if (usp) 106 pt_set_rte_sp(childregs, usp); 107 108 /* Child sees zero return value */ 109 childregs->r00 = 0; 110 111 /* 112 * The clone syscall has the C signature: 113 * int [r0] clone(int flags [r0], 114 * void *child_frame [r1], 115 * void *parent_tid [r2], 116 * void *child_tid [r3], 117 * void *thread_control_block [r4]); 118 * ugp is used to provide TLS support. 119 */ 120 if (clone_flags & CLONE_SETTLS) 121 childregs->ugp = childregs->r04; 122 123 /* 124 * Parent sees new pid -- not necessary, not even possible at 125 * this point in the fork process 126 * Might also want to set things like ti->addr_limit 127 */ 128 129 return 0; 130 } 131 132 /* 133 * Release any architecture-specific resources locked by thread 134 */ 135 void release_thread(struct task_struct *dead_task) 136 { 137 } 138 139 /* 140 * Free any architecture-specific thread data structures, etc. 141 */ 142 void exit_thread(void) 143 { 144 } 145 146 /* 147 * Some archs flush debug and FPU info here 148 */ 149 void flush_thread(void) 150 { 151 } 152 153 /* 154 * The "wait channel" terminology is archaic, but what we want 155 * is an identification of the point at which the scheduler 156 * was invoked by a blocked thread. 157 */ 158 unsigned long get_wchan(struct task_struct *p) 159 { 160 unsigned long fp, pc; 161 unsigned long stack_page; 162 int count = 0; 163 if (!p || p == current || p->state == TASK_RUNNING) 164 return 0; 165 166 stack_page = (unsigned long)task_stack_page(p); 167 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp; 168 do { 169 if (fp < (stack_page + sizeof(struct thread_info)) || 170 fp >= (THREAD_SIZE - 8 + stack_page)) 171 return 0; 172 pc = ((unsigned long *)fp)[1]; 173 if (!in_sched_functions(pc)) 174 return pc; 175 fp = *(unsigned long *) fp; 176 } while (count++ < 16); 177 178 return 0; 179 } 180 181 /* 182 * Required placeholder. 183 */ 184 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu) 185 { 186 return 0; 187 } 188