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 raw_local_irq_enable(); 48 } 49 50 /* 51 * Copy architecture-specific thread state 52 */ 53 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) 54 { 55 unsigned long clone_flags = args->flags; 56 unsigned long usp = args->stack; 57 unsigned long tls = args->tls; 58 struct thread_info *ti = task_thread_info(p); 59 struct hexagon_switch_stack *ss; 60 struct pt_regs *childregs; 61 asmlinkage void ret_from_fork(void); 62 63 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) - 64 sizeof(*childregs)); 65 66 ti->regs = childregs; 67 68 /* 69 * Establish kernel stack pointer and initial PC for new thread 70 * Note that unlike the usual situation, we do not copy the 71 * parent's callee-saved here; those are in pt_regs and whatever 72 * we leave here will be overridden on return to userland. 73 */ 74 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs - 75 sizeof(*ss)); 76 ss->lr = (unsigned long)ret_from_fork; 77 p->thread.switch_sp = ss; 78 if (unlikely(args->fn)) { 79 memset(childregs, 0, sizeof(struct pt_regs)); 80 /* r24 <- fn, r25 <- arg */ 81 ss->r24 = (unsigned long)args->fn; 82 ss->r25 = (unsigned long)args->fn_arg; 83 pt_set_kmode(childregs); 84 return 0; 85 } 86 memcpy(childregs, current_pt_regs(), sizeof(*childregs)); 87 ss->r2524 = 0; 88 89 if (usp) 90 pt_set_rte_sp(childregs, usp); 91 92 /* Child sees zero return value */ 93 childregs->r00 = 0; 94 95 /* 96 * The clone syscall has the C signature: 97 * int [r0] clone(int flags [r0], 98 * void *child_frame [r1], 99 * void *parent_tid [r2], 100 * void *child_tid [r3], 101 * void *thread_control_block [r4]); 102 * ugp is used to provide TLS support. 103 */ 104 if (clone_flags & CLONE_SETTLS) 105 childregs->ugp = tls; 106 107 /* 108 * Parent sees new pid -- not necessary, not even possible at 109 * this point in the fork process 110 */ 111 112 return 0; 113 } 114 115 /* 116 * Some archs flush debug and FPU info here 117 */ 118 void flush_thread(void) 119 { 120 } 121 122 /* 123 * The "wait channel" terminology is archaic, but what we want 124 * is an identification of the point at which the scheduler 125 * was invoked by a blocked thread. 126 */ 127 unsigned long __get_wchan(struct task_struct *p) 128 { 129 unsigned long fp, pc; 130 unsigned long stack_page; 131 int count = 0; 132 133 stack_page = (unsigned long)task_stack_page(p); 134 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp; 135 do { 136 if (fp < (stack_page + sizeof(struct thread_info)) || 137 fp >= (THREAD_SIZE - 8 + stack_page)) 138 return 0; 139 pc = ((unsigned long *)fp)[1]; 140 if (!in_sched_functions(pc)) 141 return pc; 142 fp = *(unsigned long *) fp; 143 } while (count++ < 16); 144 145 return 0; 146 } 147 148 /* 149 * Called on the exit path of event entry; see vm_entry.S 150 * 151 * Interrupts will already be disabled. 152 * 153 * Returns 0 if there's no need to re-check for more work. 154 */ 155 156 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags) 157 { 158 if (!(thread_info_flags & _TIF_WORK_MASK)) { 159 return 0; 160 } /* shortcut -- no work to be done */ 161 162 local_irq_enable(); 163 164 if (thread_info_flags & _TIF_NEED_RESCHED) { 165 schedule(); 166 return 1; 167 } 168 169 if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) { 170 do_signal(regs); 171 return 1; 172 } 173 174 if (thread_info_flags & _TIF_NOTIFY_RESUME) { 175 resume_user_mode_work(regs); 176 return 1; 177 } 178 179 /* Should not even reach here */ 180 panic("%s: bad thread_info flags 0x%08x\n", __func__, 181 thread_info_flags); 182 } 183