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Linux/arch/arc/kernel/process.c

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  1 /*
  2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
  3  *
  4  * This program is free software; you can redistribute it and/or modify
  5  * it under the terms of the GNU General Public License version 2 as
  6  * published by the Free Software Foundation.
  7  *
  8  * Amit Bhor, Kanika Nema: Codito Technologies 2004
  9  */
 10 
 11 #include <linux/errno.h>
 12 #include <linux/module.h>
 13 #include <linux/sched.h>
 14 #include <linux/sched/task.h>
 15 #include <linux/sched/task_stack.h>
 16 
 17 #include <linux/mm.h>
 18 #include <linux/fs.h>
 19 #include <linux/unistd.h>
 20 #include <linux/ptrace.h>
 21 #include <linux/slab.h>
 22 #include <linux/syscalls.h>
 23 #include <linux/elf.h>
 24 #include <linux/tick.h>
 25 
 26 SYSCALL_DEFINE1(arc_settls, void *, user_tls_data_ptr)
 27 {
 28         task_thread_info(current)->thr_ptr = (unsigned int)user_tls_data_ptr;
 29         return 0;
 30 }
 31 
 32 /*
 33  * We return the user space TLS data ptr as sys-call return code
 34  * Ideally it should be copy to user.
 35  * However we can cheat by the fact that some sys-calls do return
 36  * absurdly high values
 37  * Since the tls dat aptr is not going to be in range of 0xFFFF_xxxx
 38  * it won't be considered a sys-call error
 39  * and it will be loads better than copy-to-user, which is a definite
 40  * D-TLB Miss
 41  */
 42 SYSCALL_DEFINE0(arc_gettls)
 43 {
 44         return task_thread_info(current)->thr_ptr;
 45 }
 46 
 47 SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
 48 {
 49         struct pt_regs *regs = current_pt_regs();
 50         u32 uval;
 51         int ret;
 52 
 53         /*
 54          * This is only for old cores lacking LLOCK/SCOND, which by defintion
 55          * can't possibly be SMP. Thus doesn't need to be SMP safe.
 56          * And this also helps reduce the overhead for serializing in
 57          * the UP case
 58          */
 59         WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
 60 
 61         /* Z indicates to userspace if operation succeded */
 62         regs->status32 &= ~STATUS_Z_MASK;
 63 
 64         ret = access_ok(uaddr, sizeof(*uaddr));
 65         if (!ret)
 66                  goto fail;
 67 
 68 again:
 69         preempt_disable();
 70 
 71         ret = __get_user(uval, uaddr);
 72         if (ret)
 73                  goto fault;
 74 
 75         if (uval != expected)
 76                  goto out;
 77 
 78         ret = __put_user(new, uaddr);
 79         if (ret)
 80                  goto fault;
 81 
 82         regs->status32 |= STATUS_Z_MASK;
 83 
 84 out:
 85         preempt_enable();
 86         return uval;
 87 
 88 fault:
 89         preempt_enable();
 90 
 91         if (unlikely(ret != -EFAULT))
 92                  goto fail;
 93 
 94         down_read(&current->mm->mmap_sem);
 95         ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
 96                                FAULT_FLAG_WRITE, NULL);
 97         up_read(&current->mm->mmap_sem);
 98 
 99         if (likely(!ret))
100                  goto again;
101 
102 fail:
103         force_sig(SIGSEGV, current);
104         return ret;
105 }
106 
107 #ifdef CONFIG_ISA_ARCV2
108 
109 void arch_cpu_idle(void)
110 {
111         /* Re-enable interrupts <= default irq priority before commiting SLEEP */
112         const unsigned int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;
113 
114         __asm__ __volatile__(
115                 "sleep %0       \n"
116                 :
117                 :"I"(arg)); /* can't be "r" has to be embedded const */
118 }
119 
120 #elif defined(CONFIG_EZNPS_MTM_EXT)     /* ARC700 variant in NPS */
121 
122 void arch_cpu_idle(void)
123 {
124         /* only the calling HW thread needs to sleep */
125         __asm__ __volatile__(
126                 ".word %0       \n"
127                 :
128                 :"i"(CTOP_INST_HWSCHD_WFT_IE12));
129 }
130 
131 #else   /* ARC700 */
132 
133 void arch_cpu_idle(void)
134 {
135         /* sleep, but enable both set E1/E2 (levels of interrutps) before committing */
136         __asm__ __volatile__("sleep 0x3 \n");
137 }
138 
139 #endif
140 
141 asmlinkage void ret_from_fork(void);
142 
143 /*
144  * Copy architecture-specific thread state
145  *
146  * Layout of Child kernel mode stack as setup at the end of this function is
147  *
148  * |     ...        |
149  * |     ...        |
150  * |    unused      |
151  * |                |
152  * ------------------
153  * |     r25        |   <==== top of Stack (thread.ksp)
154  * ~                ~
155  * |    --to--      |   (CALLEE Regs of kernel mode)
156  * |     r13        |
157  * ------------------
158  * |     fp         |
159  * |    blink       |   @ret_from_fork
160  * ------------------
161  * |                |
162  * ~                ~
163  * ~                ~
164  * |                |
165  * ------------------
166  * |     r12        |
167  * ~                ~
168  * |    --to--      |   (scratch Regs of user mode)
169  * |     r0         |
170  * ------------------
171  * |      SP        |
172  * |    orig_r0     |
173  * |    event/ECR   |
174  * |    user_r25    |
175  * ------------------  <===== END of PAGE
176  */
177 int copy_thread(unsigned long clone_flags,
178                 unsigned long usp, unsigned long kthread_arg,
179                 struct task_struct *p)
180 {
181         struct pt_regs *c_regs;        /* child's pt_regs */
182         unsigned long *childksp;       /* to unwind out of __switch_to() */
183         struct callee_regs *c_callee;  /* child's callee regs */
184         struct callee_regs *parent_callee;  /* paren't callee */
185         struct pt_regs *regs = current_pt_regs();
186 
187         /* Mark the specific anchors to begin with (see pic above) */
188         c_regs = task_pt_regs(p);
189         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
190         c_callee = ((struct callee_regs *)childksp) - 1;
191 
192         /*
193          * __switch_to() uses thread.ksp to start unwinding stack
194          * For kernel threads we don't need to create callee regs, the
195          * stack layout nevertheless needs to remain the same.
196          * Also, since __switch_to anyways unwinds callee regs, we use
197          * this to populate kernel thread entry-pt/args into callee regs,
198          * so that ret_from_kernel_thread() becomes simpler.
199          */
200         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
201 
202         /* __switch_to expects FP(0), BLINK(return addr) at top */
203         childksp[0] = 0;                        /* fp */
204         childksp[1] = (unsigned long)ret_from_fork; /* blink */
205 
206         if (unlikely(p->flags & PF_KTHREAD)) {
207                 memset(c_regs, 0, sizeof(struct pt_regs));
208 
209                 c_callee->r13 = kthread_arg;
210                 c_callee->r14 = usp;  /* function */
211 
212                 return 0;
213         }
214 
215         /*--------- User Task Only --------------*/
216 
217         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
218         childksp[0] = 0;                                /* for POP fp */
219         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
220 
221         /* Copy parents pt regs on child's kernel mode stack */
222         *c_regs = *regs;
223 
224         if (usp)
225                 c_regs->sp = usp;
226 
227         c_regs->r0 = 0;         /* fork returns 0 in child */
228 
229         parent_callee = ((struct callee_regs *)regs) - 1;
230         *c_callee = *parent_callee;
231 
232         if (unlikely(clone_flags & CLONE_SETTLS)) {
233                 /*
234                  * set task's userland tls data ptr from 4th arg
235                  * clone C-lib call is difft from clone sys-call
236                  */
237                 task_thread_info(p)->thr_ptr = regs->r3;
238         } else {
239                 /* Normal fork case: set parent's TLS ptr in child */
240                 task_thread_info(p)->thr_ptr =
241                 task_thread_info(current)->thr_ptr;
242         }
243 
244 
245         /*
246          * setup usermode thread pointer #1:
247          * when child is picked by scheduler, __switch_to() uses @c_callee to
248          * populate usermode callee regs: this works (despite being in a kernel
249          * function) since special return path for child @ret_from_fork()
250          * ensures those regs are not clobbered all the way to RTIE to usermode
251          */
252         c_callee->r25 = task_thread_info(p)->thr_ptr;
253 
254 #ifdef CONFIG_ARC_CURR_IN_REG
255         /*
256          * setup usermode thread pointer #2:
257          * however for this special use of r25 in kernel, __switch_to() sets
258          * r25 for kernel needs and only in the final return path is usermode
259          * r25 setup, from pt_regs->user_r25. So set that up as well
260          */
261         c_regs->user_r25 = c_callee->r25;
262 #endif
263 
264         return 0;
265 }
266 
267 /*
268  * Do necessary setup to start up a new user task
269  */
270 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
271 {
272         regs->sp = usp;
273         regs->ret = pc;
274 
275         /*
276          * [U]ser Mode bit set
277          * [L] ZOL loop inhibited to begin with - cleared by a LP insn
278          * Interrupts enabled
279          */
280         regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
281 
282 #ifdef CONFIG_EZNPS_MTM_EXT
283         regs->eflags = 0;
284 #endif
285 
286         /* bogus seed values for debugging */
287         regs->lp_start = 0x10;
288         regs->lp_end = 0x80;
289 }
290 
291 /*
292  * Some archs flush debug and FPU info here
293  */
294 void flush_thread(void)
295 {
296 }
297 
298 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
299 {
300         return 0;
301 }
302 
303 int elf_check_arch(const struct elf32_hdr *x)
304 {
305         unsigned int eflags;
306 
307         if (x->e_machine != EM_ARC_INUSE) {
308                 pr_err("ELF not built for %s ISA\n",
309                         is_isa_arcompact() ? "ARCompact":"ARCv2");
310                 return 0;
311         }
312 
313         eflags = x->e_flags;
314         if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
315                 pr_err("ABI mismatch - you need newer toolchain\n");
316                 force_sigsegv(SIGSEGV, current);
317                 return 0;
318         }
319 
320         return 1;
321 }
322 EXPORT_SYMBOL(elf_check_arch);
323 

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