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/sched/debug.h> 23 #include <linux/sched/task.h> 24 #include <linux/sched/task_stack.h> 25 #include <linux/types.h> 26 #include <linux/module.h> 27 #include <linux/tick.h> 28 #include <linux/uaccess.h> 29 #include <linux/slab.h> 30 #include <linux/tracehook.h> 31 32 /* 33 * Program thread launch. Often defined as a macro in processor.h, 34 * but we're shooting for a small footprint and it's not an inner-loop 35 * performance-critical operation. 36 * 37 * The Hexagon ABI specifies that R28 is zero'ed before program launch, 38 * so that gets automatically done here. If we ever stop doing that here, 39 * we'll probably want to define the ELF_PLAT_INIT macro. 40 */ 41 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) 42 { 43 /* We want to zero all data-containing registers. Is this overkill? */ 44 memset(regs, 0, sizeof(*regs)); 45 /* We might want to also zero all Processor registers here */ 46 pt_set_usermode(regs); 47 pt_set_elr(regs, pc); 48 pt_set_rte_sp(regs, sp); 49 } 50 51 /* 52 * Spin, or better still, do a hardware or VM wait instruction 53 * If hardware or VM offer wait termination even though interrupts 54 * are disabled. 55 */ 56 void arch_cpu_idle(void) 57 { 58 __vmwait(); 59 /* interrupts wake us up, but irqs are still disabled */ 60 local_irq_enable(); 61 } 62 63 /* 64 * Return saved PC of a blocked thread 65 */ 66 unsigned long thread_saved_pc(struct task_struct *tsk) 67 { 68 return 0; 69 } 70 71 /* 72 * Copy architecture-specific thread state 73 */ 74 int copy_thread(unsigned long clone_flags, unsigned long usp, 75 unsigned long arg, struct task_struct *p) 76 { 77 struct thread_info *ti = task_thread_info(p); 78 struct hexagon_switch_stack *ss; 79 struct pt_regs *childregs; 80 asmlinkage void ret_from_fork(void); 81 82 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) - 83 sizeof(*childregs)); 84 85 ti->regs = childregs; 86 87 /* 88 * Establish kernel stack pointer and initial PC for new thread 89 * Note that unlike the usual situation, we do not copy the 90 * parent's callee-saved here; those are in pt_regs and whatever 91 * we leave here will be overridden on return to userland. 92 */ 93 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs - 94 sizeof(*ss)); 95 ss->lr = (unsigned long)ret_from_fork; 96 p->thread.switch_sp = ss; 97 if (unlikely(p->flags & PF_KTHREAD)) { 98 memset(childregs, 0, sizeof(struct pt_regs)); 99 /* r24 <- fn, r25 <- arg */ 100 ss->r24 = usp; 101 ss->r25 = arg; 102 pt_set_kmode(childregs); 103 return 0; 104 } 105 memcpy(childregs, current_pt_regs(), sizeof(*childregs)); 106 ss->r2524 = 0; 107 108 if (usp) 109 pt_set_rte_sp(childregs, usp); 110 111 /* Child sees zero return value */ 112 childregs->r00 = 0; 113 114 /* 115 * The clone syscall has the C signature: 116 * int [r0] clone(int flags [r0], 117 * void *child_frame [r1], 118 * void *parent_tid [r2], 119 * void *child_tid [r3], 120 * void *thread_control_block [r4]); 121 * ugp is used to provide TLS support. 122 */ 123 if (clone_flags & CLONE_SETTLS) 124 childregs->ugp = childregs->r04; 125 126 /* 127 * Parent sees new pid -- not necessary, not even possible at 128 * this point in the fork process 129 * Might also want to set things like ti->addr_limit 130 */ 131 132 return 0; 133 } 134 135 /* 136 * Release any architecture-specific resources locked by thread 137 */ 138 void release_thread(struct task_struct *dead_task) 139 { 140 } 141 142 /* 143 * Some archs flush debug and FPU info here 144 */ 145 void flush_thread(void) 146 { 147 } 148 149 /* 150 * The "wait channel" terminology is archaic, but what we want 151 * is an identification of the point at which the scheduler 152 * was invoked by a blocked thread. 153 */ 154 unsigned long get_wchan(struct task_struct *p) 155 { 156 unsigned long fp, pc; 157 unsigned long stack_page; 158 int count = 0; 159 if (!p || p == current || p->state == TASK_RUNNING) 160 return 0; 161 162 stack_page = (unsigned long)task_stack_page(p); 163 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp; 164 do { 165 if (fp < (stack_page + sizeof(struct thread_info)) || 166 fp >= (THREAD_SIZE - 8 + stack_page)) 167 return 0; 168 pc = ((unsigned long *)fp)[1]; 169 if (!in_sched_functions(pc)) 170 return pc; 171 fp = *(unsigned long *) fp; 172 } while (count++ < 16); 173 174 return 0; 175 } 176 177 /* 178 * Required placeholder. 179 */ 180 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu) 181 { 182 return 0; 183 } 184 185 186 /* 187 * Called on the exit path of event entry; see vm_entry.S 188 * 189 * Interrupts will already be disabled. 190 * 191 * Returns 0 if there's no need to re-check for more work. 192 */ 193 194 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags) 195 { 196 if (!(thread_info_flags & _TIF_WORK_MASK)) { 197 return 0; 198 } /* shortcut -- no work to be done */ 199 200 local_irq_enable(); 201 202 if (thread_info_flags & _TIF_NEED_RESCHED) { 203 schedule(); 204 return 1; 205 } 206 207 if (thread_info_flags & _TIF_SIGPENDING) { 208 do_signal(regs); 209 return 1; 210 } 211 212 if (thread_info_flags & _TIF_NOTIFY_RESUME) { 213 clear_thread_flag(TIF_NOTIFY_RESUME); 214 tracehook_notify_resume(regs); 215 return 1; 216 } 217 218 /* Should not even reach here */ 219 panic("%s: bad thread_info flags 0x%08x\n", __func__, 220 thread_info_flags); 221 } 222