1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file handles the architecture dependent parts of process handling. 4 * 5 * Copyright IBM Corp. 1999, 2009 6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>, 7 * Hartmut Penner <hp@de.ibm.com>, 8 * Denis Joseph Barrow, 9 */ 10 11 #include <linux/elf-randomize.h> 12 #include <linux/compiler.h> 13 #include <linux/cpu.h> 14 #include <linux/sched.h> 15 #include <linux/sched/debug.h> 16 #include <linux/sched/task.h> 17 #include <linux/sched/task_stack.h> 18 #include <linux/kernel.h> 19 #include <linux/mm.h> 20 #include <linux/elfcore.h> 21 #include <linux/smp.h> 22 #include <linux/slab.h> 23 #include <linux/interrupt.h> 24 #include <linux/tick.h> 25 #include <linux/personality.h> 26 #include <linux/syscalls.h> 27 #include <linux/kprobes.h> 28 #include <linux/random.h> 29 #include <linux/init_task.h> 30 #include <linux/entry-common.h> 31 #include <linux/io.h> 32 #include <asm/guarded_storage.h> 33 #include <asm/access-regs.h> 34 #include <asm/switch_to.h> 35 #include <asm/cpu_mf.h> 36 #include <asm/processor.h> 37 #include <asm/ptrace.h> 38 #include <asm/exec.h> 39 #include <asm/fpu.h> 40 #include <asm/irq.h> 41 #include <asm/nmi.h> 42 #include <asm/smp.h> 43 #include <asm/stacktrace.h> 44 #include <asm/runtime_instr.h> 45 #include <asm/unwind.h> 46 #include "entry.h" 47 48 void ret_from_fork(void) asm("ret_from_fork"); 49 50 void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs) 51 { 52 int (*func)(void *arg); 53 54 schedule_tail(prev); 55 56 if (!user_mode(regs)) { 57 /* Kernel thread */ 58 func = (void *)regs->gprs[9]; 59 func((void *)regs->gprs[10]); 60 } 61 clear_pt_regs_flag(regs, PIF_SYSCALL); 62 syscall_exit_to_user_mode(regs); 63 } 64 65 void flush_thread(void) 66 { 67 } 68 69 void arch_setup_new_exec(void) 70 { 71 if (get_lowcore()->current_pid != current->pid) { 72 get_lowcore()->current_pid = current->pid; 73 if (test_facility(40)) 74 lpp(&get_lowcore()->lpp); 75 } 76 } 77 78 void arch_release_task_struct(struct task_struct *tsk) 79 { 80 runtime_instr_release(tsk); 81 guarded_storage_release(tsk); 82 } 83 84 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) 85 { 86 save_user_fpu_regs(); 87 88 *dst = *src; 89 dst->thread.kfpu_flags = 0; 90 91 /* 92 * Don't transfer over the runtime instrumentation or the guarded 93 * storage control block pointers. These fields are cleared here instead 94 * of in copy_thread() to avoid premature freeing of associated memory 95 * on fork() failure. Wait to clear the RI flag because ->stack still 96 * refers to the source thread. 97 */ 98 dst->thread.ri_cb = NULL; 99 dst->thread.gs_cb = NULL; 100 dst->thread.gs_bc_cb = NULL; 101 102 return 0; 103 } 104 105 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) 106 { 107 u64 clone_flags = args->flags; 108 unsigned long new_stackp = args->stack; 109 unsigned long tls = args->tls; 110 struct fake_frame 111 { 112 struct stack_frame sf; 113 struct pt_regs childregs; 114 } *frame; 115 116 frame = container_of(task_pt_regs(p), struct fake_frame, childregs); 117 p->thread.ksp = (unsigned long) frame; 118 /* Save access registers to new thread structure. */ 119 save_access_regs(&p->thread.acrs[0]); 120 /* start new process with ar4 pointing to the correct address space */ 121 /* Don't copy debug registers */ 122 memset(&p->thread.per_user, 0, sizeof(p->thread.per_user)); 123 memset(&p->thread.per_event, 0, sizeof(p->thread.per_event)); 124 clear_tsk_thread_flag(p, TIF_SINGLE_STEP); 125 p->thread.per_flags = 0; 126 /* Initialize per thread user and system timer values */ 127 p->thread.user_timer = 0; 128 p->thread.guest_timer = 0; 129 p->thread.system_timer = 0; 130 p->thread.hardirq_timer = 0; 131 p->thread.softirq_timer = 0; 132 p->thread.last_break = 1; 133 /* 134 * s390 stores the svc return address in arch_data when calling 135 * sigreturn()/restart_syscall() via vdso. 1 means no valid address 136 * stored. 137 */ 138 p->restart_block.arch_data = 1; 139 140 frame->sf.back_chain = 0; 141 frame->sf.gprs[11 - 6] = (unsigned long)&frame->childregs; 142 frame->sf.gprs[12 - 6] = (unsigned long)p; 143 /* new return point is ret_from_fork */ 144 frame->sf.gprs[14 - 6] = (unsigned long)ret_from_fork; 145 /* fake return stack for resume(), don't go back to schedule */ 146 frame->sf.gprs[15 - 6] = (unsigned long)frame; 147 148 /* Store access registers to kernel stack of new process. */ 149 if (unlikely(args->fn)) { 150 /* kernel thread */ 151 memset(&frame->childregs, 0, sizeof(struct pt_regs)); 152 frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_IO | 153 PSW_MASK_EXT | PSW_MASK_MCHECK; 154 frame->childregs.gprs[9] = (unsigned long)args->fn; 155 frame->childregs.gprs[10] = (unsigned long)args->fn_arg; 156 frame->childregs.orig_gpr2 = -1; 157 frame->childregs.last_break = 1; 158 return 0; 159 } 160 frame->childregs = *current_pt_regs(); 161 frame->childregs.gprs[2] = 0; /* child returns 0 on fork. */ 162 frame->childregs.flags = 0; 163 if (new_stackp) 164 frame->childregs.gprs[15] = new_stackp; 165 /* 166 * Clear the runtime instrumentation flag after the above childregs 167 * copy. The CB pointer was already cleared in arch_dup_task_struct(). 168 */ 169 frame->childregs.psw.mask &= ~PSW_MASK_RI; 170 171 /* Set a new TLS ? */ 172 if (clone_flags & CLONE_SETTLS) { 173 p->thread.acrs[0] = (unsigned int)(tls >> 32); 174 p->thread.acrs[1] = (unsigned int)tls; 175 } 176 return 0; 177 } 178 179 void execve_tail(void) 180 { 181 current->thread.ufpu.fpc = 0; 182 fpu_sfpc(0); 183 } 184 185 struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next) 186 { 187 save_user_fpu_regs(); 188 save_kernel_fpu_regs(&prev->thread); 189 save_access_regs(&prev->thread.acrs[0]); 190 save_ri_cb(prev->thread.ri_cb); 191 save_gs_cb(prev->thread.gs_cb); 192 update_cr_regs(next); 193 restore_kernel_fpu_regs(&next->thread); 194 restore_access_regs(&next->thread.acrs[0]); 195 restore_ri_cb(next->thread.ri_cb, prev->thread.ri_cb); 196 restore_gs_cb(next->thread.gs_cb); 197 return __switch_to_asm(prev, next); 198 } 199 200 unsigned long __get_wchan(struct task_struct *p) 201 { 202 struct unwind_state state; 203 unsigned long ip = 0; 204 205 if (!try_get_task_stack(p)) 206 return 0; 207 208 unwind_for_each_frame(&state, p, NULL, 0) { 209 if (state.stack_info.type != STACK_TYPE_TASK) { 210 ip = 0; 211 break; 212 } 213 214 ip = unwind_get_return_address(&state); 215 if (!ip) 216 break; 217 218 if (!in_sched_functions(ip)) 219 break; 220 } 221 222 put_task_stack(p); 223 return ip; 224 } 225 226 unsigned long arch_align_stack(unsigned long sp) 227 { 228 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) 229 sp -= get_random_u32_below(PAGE_SIZE); 230 return sp & ~0xf; 231 } 232 233 static inline unsigned long brk_rnd(void) 234 { 235 return (get_random_u16() & BRK_RND_MASK) << PAGE_SHIFT; 236 } 237 238 unsigned long arch_randomize_brk(struct mm_struct *mm) 239 { 240 unsigned long ret; 241 242 ret = PAGE_ALIGN(mm->brk + brk_rnd()); 243 return (ret > mm->brk) ? ret : mm->brk; 244 } 245