xref: /openbmc/linux/arch/arc/kernel/process.c (revision b830f94f)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
4  *
5  * Amit Bhor, Kanika Nema: Codito Technologies 2004
6  */
7 
8 #include <linux/errno.h>
9 #include <linux/module.h>
10 #include <linux/sched.h>
11 #include <linux/sched/task.h>
12 #include <linux/sched/task_stack.h>
13 
14 #include <linux/mm.h>
15 #include <linux/fs.h>
16 #include <linux/unistd.h>
17 #include <linux/ptrace.h>
18 #include <linux/slab.h>
19 #include <linux/syscalls.h>
20 #include <linux/elf.h>
21 #include <linux/tick.h>
22 
23 SYSCALL_DEFINE1(arc_settls, void *, user_tls_data_ptr)
24 {
25 	task_thread_info(current)->thr_ptr = (unsigned int)user_tls_data_ptr;
26 	return 0;
27 }
28 
29 /*
30  * We return the user space TLS data ptr as sys-call return code
31  * Ideally it should be copy to user.
32  * However we can cheat by the fact that some sys-calls do return
33  * absurdly high values
34  * Since the tls dat aptr is not going to be in range of 0xFFFF_xxxx
35  * it won't be considered a sys-call error
36  * and it will be loads better than copy-to-user, which is a definite
37  * D-TLB Miss
38  */
39 SYSCALL_DEFINE0(arc_gettls)
40 {
41 	return task_thread_info(current)->thr_ptr;
42 }
43 
44 SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
45 {
46 	struct pt_regs *regs = current_pt_regs();
47 	u32 uval;
48 	int ret;
49 
50 	/*
51 	 * This is only for old cores lacking LLOCK/SCOND, which by defintion
52 	 * can't possibly be SMP. Thus doesn't need to be SMP safe.
53 	 * And this also helps reduce the overhead for serializing in
54 	 * the UP case
55 	 */
56 	WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
57 
58 	/* Z indicates to userspace if operation succeded */
59 	regs->status32 &= ~STATUS_Z_MASK;
60 
61 	ret = access_ok(uaddr, sizeof(*uaddr));
62 	if (!ret)
63 		 goto fail;
64 
65 again:
66 	preempt_disable();
67 
68 	ret = __get_user(uval, uaddr);
69 	if (ret)
70 		 goto fault;
71 
72 	if (uval != expected)
73 		 goto out;
74 
75 	ret = __put_user(new, uaddr);
76 	if (ret)
77 		 goto fault;
78 
79 	regs->status32 |= STATUS_Z_MASK;
80 
81 out:
82 	preempt_enable();
83 	return uval;
84 
85 fault:
86 	preempt_enable();
87 
88 	if (unlikely(ret != -EFAULT))
89 		 goto fail;
90 
91 	down_read(&current->mm->mmap_sem);
92 	ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
93 			       FAULT_FLAG_WRITE, NULL);
94 	up_read(&current->mm->mmap_sem);
95 
96 	if (likely(!ret))
97 		 goto again;
98 
99 fail:
100 	force_sig(SIGSEGV);
101 	return ret;
102 }
103 
104 #ifdef CONFIG_ISA_ARCV2
105 
106 void arch_cpu_idle(void)
107 {
108 	/* Re-enable interrupts <= default irq priority before commiting SLEEP */
109 	const unsigned int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;
110 
111 	__asm__ __volatile__(
112 		"sleep %0	\n"
113 		:
114 		:"I"(arg)); /* can't be "r" has to be embedded const */
115 }
116 
117 #elif defined(CONFIG_EZNPS_MTM_EXT)	/* ARC700 variant in NPS */
118 
119 void arch_cpu_idle(void)
120 {
121 	/* only the calling HW thread needs to sleep */
122 	__asm__ __volatile__(
123 		".word %0	\n"
124 		:
125 		:"i"(CTOP_INST_HWSCHD_WFT_IE12));
126 }
127 
128 #else	/* ARC700 */
129 
130 void arch_cpu_idle(void)
131 {
132 	/* sleep, but enable both set E1/E2 (levels of interrutps) before committing */
133 	__asm__ __volatile__("sleep 0x3	\n");
134 }
135 
136 #endif
137 
138 asmlinkage void ret_from_fork(void);
139 
140 /*
141  * Copy architecture-specific thread state
142  *
143  * Layout of Child kernel mode stack as setup at the end of this function is
144  *
145  * |     ...        |
146  * |     ...        |
147  * |    unused      |
148  * |                |
149  * ------------------
150  * |     r25        |   <==== top of Stack (thread.ksp)
151  * ~                ~
152  * |    --to--      |   (CALLEE Regs of kernel mode)
153  * |     r13        |
154  * ------------------
155  * |     fp         |
156  * |    blink       |   @ret_from_fork
157  * ------------------
158  * |                |
159  * ~                ~
160  * ~                ~
161  * |                |
162  * ------------------
163  * |     r12        |
164  * ~                ~
165  * |    --to--      |   (scratch Regs of user mode)
166  * |     r0         |
167  * ------------------
168  * |      SP        |
169  * |    orig_r0     |
170  * |    event/ECR   |
171  * |    user_r25    |
172  * ------------------  <===== END of PAGE
173  */
174 int copy_thread(unsigned long clone_flags,
175 		unsigned long usp, unsigned long kthread_arg,
176 		struct task_struct *p)
177 {
178 	struct pt_regs *c_regs;        /* child's pt_regs */
179 	unsigned long *childksp;       /* to unwind out of __switch_to() */
180 	struct callee_regs *c_callee;  /* child's callee regs */
181 	struct callee_regs *parent_callee;  /* paren't callee */
182 	struct pt_regs *regs = current_pt_regs();
183 
184 	/* Mark the specific anchors to begin with (see pic above) */
185 	c_regs = task_pt_regs(p);
186 	childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
187 	c_callee = ((struct callee_regs *)childksp) - 1;
188 
189 	/*
190 	 * __switch_to() uses thread.ksp to start unwinding stack
191 	 * For kernel threads we don't need to create callee regs, the
192 	 * stack layout nevertheless needs to remain the same.
193 	 * Also, since __switch_to anyways unwinds callee regs, we use
194 	 * this to populate kernel thread entry-pt/args into callee regs,
195 	 * so that ret_from_kernel_thread() becomes simpler.
196 	 */
197 	p->thread.ksp = (unsigned long)c_callee;	/* THREAD_KSP */
198 
199 	/* __switch_to expects FP(0), BLINK(return addr) at top */
200 	childksp[0] = 0;			/* fp */
201 	childksp[1] = (unsigned long)ret_from_fork; /* blink */
202 
203 	if (unlikely(p->flags & PF_KTHREAD)) {
204 		memset(c_regs, 0, sizeof(struct pt_regs));
205 
206 		c_callee->r13 = kthread_arg;
207 		c_callee->r14 = usp;  /* function */
208 
209 		return 0;
210 	}
211 
212 	/*--------- User Task Only --------------*/
213 
214 	/* __switch_to expects FP(0), BLINK(return addr) at top of stack */
215 	childksp[0] = 0;				/* for POP fp */
216 	childksp[1] = (unsigned long)ret_from_fork;	/* for POP blink */
217 
218 	/* Copy parents pt regs on child's kernel mode stack */
219 	*c_regs = *regs;
220 
221 	if (usp)
222 		c_regs->sp = usp;
223 
224 	c_regs->r0 = 0;		/* fork returns 0 in child */
225 
226 	parent_callee = ((struct callee_regs *)regs) - 1;
227 	*c_callee = *parent_callee;
228 
229 	if (unlikely(clone_flags & CLONE_SETTLS)) {
230 		/*
231 		 * set task's userland tls data ptr from 4th arg
232 		 * clone C-lib call is difft from clone sys-call
233 		 */
234 		task_thread_info(p)->thr_ptr = regs->r3;
235 	} else {
236 		/* Normal fork case: set parent's TLS ptr in child */
237 		task_thread_info(p)->thr_ptr =
238 		task_thread_info(current)->thr_ptr;
239 	}
240 
241 
242 	/*
243 	 * setup usermode thread pointer #1:
244 	 * when child is picked by scheduler, __switch_to() uses @c_callee to
245 	 * populate usermode callee regs: this works (despite being in a kernel
246 	 * function) since special return path for child @ret_from_fork()
247 	 * ensures those regs are not clobbered all the way to RTIE to usermode
248 	 */
249 	c_callee->r25 = task_thread_info(p)->thr_ptr;
250 
251 #ifdef CONFIG_ARC_CURR_IN_REG
252 	/*
253 	 * setup usermode thread pointer #2:
254 	 * however for this special use of r25 in kernel, __switch_to() sets
255 	 * r25 for kernel needs and only in the final return path is usermode
256 	 * r25 setup, from pt_regs->user_r25. So set that up as well
257 	 */
258 	c_regs->user_r25 = c_callee->r25;
259 #endif
260 
261 	return 0;
262 }
263 
264 /*
265  * Do necessary setup to start up a new user task
266  */
267 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
268 {
269 	regs->sp = usp;
270 	regs->ret = pc;
271 
272 	/*
273 	 * [U]ser Mode bit set
274 	 * [L] ZOL loop inhibited to begin with - cleared by a LP insn
275 	 * Interrupts enabled
276 	 */
277 	regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
278 
279 #ifdef CONFIG_EZNPS_MTM_EXT
280 	regs->eflags = 0;
281 #endif
282 
283 	/* bogus seed values for debugging */
284 	regs->lp_start = 0x10;
285 	regs->lp_end = 0x80;
286 }
287 
288 /*
289  * Some archs flush debug and FPU info here
290  */
291 void flush_thread(void)
292 {
293 }
294 
295 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
296 {
297 	return 0;
298 }
299 
300 int elf_check_arch(const struct elf32_hdr *x)
301 {
302 	unsigned int eflags;
303 
304 	if (x->e_machine != EM_ARC_INUSE) {
305 		pr_err("ELF not built for %s ISA\n",
306 			is_isa_arcompact() ? "ARCompact":"ARCv2");
307 		return 0;
308 	}
309 
310 	eflags = x->e_flags;
311 	if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
312 		pr_err("ABI mismatch - you need newer toolchain\n");
313 		force_sigsegv(SIGSEGV);
314 		return 0;
315 	}
316 
317 	return 1;
318 }
319 EXPORT_SYMBOL(elf_check_arch);
320