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 #include <linux/tracehook.h> 28 29 /* 30 * Program thread launch. Often defined as a macro in processor.h, 31 * but we're shooting for a small footprint and it's not an inner-loop 32 * performance-critical operation. 33 * 34 * The Hexagon ABI specifies that R28 is zero'ed before program launch, 35 * so that gets automatically done here. If we ever stop doing that here, 36 * we'll probably want to define the ELF_PLAT_INIT macro. 37 */ 38 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) 39 { 40 /* We want to zero all data-containing registers. Is this overkill? */ 41 memset(regs, 0, sizeof(*regs)); 42 /* We might want to also zero all Processor registers here */ 43 pt_set_usermode(regs); 44 pt_set_elr(regs, pc); 45 pt_set_rte_sp(regs, sp); 46 } 47 48 /* 49 * Spin, or better still, do a hardware or VM wait instruction 50 * If hardware or VM offer wait termination even though interrupts 51 * are disabled. 52 */ 53 void arch_cpu_idle(void) 54 { 55 __vmwait(); 56 /* interrupts wake us up, but irqs are still disabled */ 57 local_irq_enable(); 58 } 59 60 /* 61 * Return saved PC of a blocked thread 62 */ 63 unsigned long thread_saved_pc(struct task_struct *tsk) 64 { 65 return 0; 66 } 67 68 /* 69 * Copy architecture-specific thread state 70 */ 71 int copy_thread(unsigned long clone_flags, unsigned long usp, 72 unsigned long arg, struct task_struct *p) 73 { 74 struct thread_info *ti = task_thread_info(p); 75 struct hexagon_switch_stack *ss; 76 struct pt_regs *childregs; 77 asmlinkage void ret_from_fork(void); 78 79 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) - 80 sizeof(*childregs)); 81 82 ti->regs = childregs; 83 84 /* 85 * Establish kernel stack pointer and initial PC for new thread 86 * Note that unlike the usual situation, we do not copy the 87 * parent's callee-saved here; those are in pt_regs and whatever 88 * we leave here will be overridden on return to userland. 89 */ 90 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs - 91 sizeof(*ss)); 92 ss->lr = (unsigned long)ret_from_fork; 93 p->thread.switch_sp = ss; 94 if (unlikely(p->flags & PF_KTHREAD)) { 95 memset(childregs, 0, sizeof(struct pt_regs)); 96 /* r24 <- fn, r25 <- arg */ 97 ss->r24 = usp; 98 ss->r25 = arg; 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 * Some archs flush debug and FPU info here 141 */ 142 void flush_thread(void) 143 { 144 } 145 146 /* 147 * The "wait channel" terminology is archaic, but what we want 148 * is an identification of the point at which the scheduler 149 * was invoked by a blocked thread. 150 */ 151 unsigned long get_wchan(struct task_struct *p) 152 { 153 unsigned long fp, pc; 154 unsigned long stack_page; 155 int count = 0; 156 if (!p || p == current || p->state == TASK_RUNNING) 157 return 0; 158 159 stack_page = (unsigned long)task_stack_page(p); 160 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp; 161 do { 162 if (fp < (stack_page + sizeof(struct thread_info)) || 163 fp >= (THREAD_SIZE - 8 + stack_page)) 164 return 0; 165 pc = ((unsigned long *)fp)[1]; 166 if (!in_sched_functions(pc)) 167 return pc; 168 fp = *(unsigned long *) fp; 169 } while (count++ < 16); 170 171 return 0; 172 } 173 174 /* 175 * Required placeholder. 176 */ 177 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu) 178 { 179 return 0; 180 } 181 182 183 /* 184 * Called on the exit path of event entry; see vm_entry.S 185 * 186 * Interrupts will already be disabled. 187 * 188 * Returns 0 if there's no need to re-check for more work. 189 */ 190 191 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags) 192 { 193 if (!(thread_info_flags & _TIF_WORK_MASK)) { 194 return 0; 195 } /* shortcut -- no work to be done */ 196 197 local_irq_enable(); 198 199 if (thread_info_flags & _TIF_NEED_RESCHED) { 200 schedule(); 201 return 1; 202 } 203 204 if (thread_info_flags & _TIF_SIGPENDING) { 205 do_signal(regs); 206 return 1; 207 } 208 209 if (thread_info_flags & _TIF_NOTIFY_RESUME) { 210 clear_thread_flag(TIF_NOTIFY_RESUME); 211 tracehook_notify_resume(regs); 212 return 1; 213 } 214 215 /* Should not even reach here */ 216 panic("%s: bad thread_info flags 0x%08x\n", __func__, 217 thread_info_flags); 218 } 219