1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Process creation support for Hexagon 4 * 5 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved. 6 */ 7 8 #include <linux/sched.h> 9 #include <linux/sched/debug.h> 10 #include <linux/sched/task.h> 11 #include <linux/sched/task_stack.h> 12 #include <linux/types.h> 13 #include <linux/module.h> 14 #include <linux/tick.h> 15 #include <linux/uaccess.h> 16 #include <linux/slab.h> 17 #include <linux/resume_user_mode.h> 18 19 /* 20 * Program thread launch. Often defined as a macro in processor.h, 21 * but we're shooting for a small footprint and it's not an inner-loop 22 * performance-critical operation. 23 * 24 * The Hexagon ABI specifies that R28 is zero'ed before program launch, 25 * so that gets automatically done here. If we ever stop doing that here, 26 * we'll probably want to define the ELF_PLAT_INIT macro. 27 */ 28 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) 29 { 30 /* We want to zero all data-containing registers. Is this overkill? */ 31 memset(regs, 0, sizeof(*regs)); 32 /* We might want to also zero all Processor registers here */ 33 pt_set_usermode(regs); 34 pt_set_elr(regs, pc); 35 pt_set_rte_sp(regs, sp); 36 } 37 38 /* 39 * Spin, or better still, do a hardware or VM wait instruction 40 * If hardware or VM offer wait termination even though interrupts 41 * are disabled. 42 */ 43 void arch_cpu_idle(void) 44 { 45 __vmwait(); 46 /* interrupts wake us up, but irqs are still disabled */ 47 } 48 49 /* 50 * Copy architecture-specific thread state 51 */ 52 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) 53 { 54 unsigned long clone_flags = args->flags; 55 unsigned long usp = args->stack; 56 unsigned long tls = args->tls; 57 struct thread_info *ti = task_thread_info(p); 58 struct hexagon_switch_stack *ss; 59 struct pt_regs *childregs; 60 asmlinkage void ret_from_fork(void); 61 62 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) - 63 sizeof(*childregs)); 64 65 ti->regs = childregs; 66 67 /* 68 * Establish kernel stack pointer and initial PC for new thread 69 * Note that unlike the usual situation, we do not copy the 70 * parent's callee-saved here; those are in pt_regs and whatever 71 * we leave here will be overridden on return to userland. 72 */ 73 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs - 74 sizeof(*ss)); 75 ss->lr = (unsigned long)ret_from_fork; 76 p->thread.switch_sp = ss; 77 if (unlikely(args->fn)) { 78 memset(childregs, 0, sizeof(struct pt_regs)); 79 /* r24 <- fn, r25 <- arg */ 80 ss->r24 = (unsigned long)args->fn; 81 ss->r25 = (unsigned long)args->fn_arg; 82 pt_set_kmode(childregs); 83 return 0; 84 } 85 memcpy(childregs, current_pt_regs(), sizeof(*childregs)); 86 ss->r2524 = 0; 87 88 if (usp) 89 pt_set_rte_sp(childregs, usp); 90 91 /* Child sees zero return value */ 92 childregs->r00 = 0; 93 94 /* 95 * The clone syscall has the C signature: 96 * int [r0] clone(int flags [r0], 97 * void *child_frame [r1], 98 * void *parent_tid [r2], 99 * void *child_tid [r3], 100 * void *thread_control_block [r4]); 101 * ugp is used to provide TLS support. 102 */ 103 if (clone_flags & CLONE_SETTLS) 104 childregs->ugp = tls; 105 106 /* 107 * Parent sees new pid -- not necessary, not even possible at 108 * this point in the fork process 109 */ 110 111 return 0; 112 } 113 114 /* 115 * Some archs flush debug and FPU info here 116 */ 117 void flush_thread(void) 118 { 119 } 120 121 /* 122 * The "wait channel" terminology is archaic, but what we want 123 * is an identification of the point at which the scheduler 124 * was invoked by a blocked thread. 125 */ 126 unsigned long __get_wchan(struct task_struct *p) 127 { 128 unsigned long fp, pc; 129 unsigned long stack_page; 130 int count = 0; 131 132 stack_page = (unsigned long)task_stack_page(p); 133 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp; 134 do { 135 if (fp < (stack_page + sizeof(struct thread_info)) || 136 fp >= (THREAD_SIZE - 8 + stack_page)) 137 return 0; 138 pc = ((unsigned long *)fp)[1]; 139 if (!in_sched_functions(pc)) 140 return pc; 141 fp = *(unsigned long *) fp; 142 } while (count++ < 16); 143 144 return 0; 145 } 146 147 /* 148 * Called on the exit path of event entry; see vm_entry.S 149 * 150 * Interrupts will already be disabled. 151 * 152 * Returns 0 if there's no need to re-check for more work. 153 */ 154 155 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags) 156 { 157 if (!(thread_info_flags & _TIF_WORK_MASK)) { 158 return 0; 159 } /* shortcut -- no work to be done */ 160 161 local_irq_enable(); 162 163 if (thread_info_flags & _TIF_NEED_RESCHED) { 164 schedule(); 165 return 1; 166 } 167 168 if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) { 169 do_signal(regs); 170 return 1; 171 } 172 173 if (thread_info_flags & _TIF_NOTIFY_RESUME) { 174 resume_user_mode_work(regs); 175 return 1; 176 } 177 178 /* Should not even reach here */ 179 panic("%s: bad thread_info flags 0x%08x\n", __func__, 180 thread_info_flags); 181 } 182