summaryrefslogtreecommitdiff
path: root/arch/arc/kernel/process.c
blob: 315528f04bc128ed184f22af58a093a3ad68f053 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * Amit Bhor, Kanika Nema: Codito Technologies 2004
 */

#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>

#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/elf.h>
#include <linux/tick.h>

#include <asm/fpu.h>

SYSCALL_DEFINE1(arc_settls, void *, user_tls_data_ptr)
{
	task_thread_info(current)->thr_ptr = (unsigned int)user_tls_data_ptr;
	return 0;
}

/*
 * We return the user space TLS data ptr as sys-call return code
 * Ideally it should be copy to user.
 * However we can cheat by the fact that some sys-calls do return
 * absurdly high values
 * Since the tls dat aptr is not going to be in range of 0xFFFF_xxxx
 * it won't be considered a sys-call error
 * and it will be loads better than copy-to-user, which is a definite
 * D-TLB Miss
 */
SYSCALL_DEFINE0(arc_gettls)
{
	return task_thread_info(current)->thr_ptr;
}

SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
{
	struct pt_regs *regs = current_pt_regs();
	u32 uval;
	int ret;

	/*
	 * This is only for old cores lacking LLOCK/SCOND, which by defintion
	 * can't possibly be SMP. Thus doesn't need to be SMP safe.
	 * And this also helps reduce the overhead for serializing in
	 * the UP case
	 */
	WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));

	/* Z indicates to userspace if operation succeded */
	regs->status32 &= ~STATUS_Z_MASK;

	ret = access_ok(uaddr, sizeof(*uaddr));
	if (!ret)
		 goto fail;

again:
	preempt_disable();

	ret = __get_user(uval, uaddr);
	if (ret)
		 goto fault;

	if (uval != expected)
		 goto out;

	ret = __put_user(new, uaddr);
	if (ret)
		 goto fault;

	regs->status32 |= STATUS_Z_MASK;

out:
	preempt_enable();
	return uval;

fault:
	preempt_enable();

	if (unlikely(ret != -EFAULT))
		 goto fail;

	down_read(&current->mm->mmap_sem);
	ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
			       FAULT_FLAG_WRITE, NULL);
	up_read(&current->mm->mmap_sem);

	if (likely(!ret))
		 goto again;

fail:
	force_sig(SIGSEGV);
	return ret;
}

#ifdef CONFIG_ISA_ARCV2

void arch_cpu_idle(void)
{
	/* Re-enable interrupts <= default irq priority before commiting SLEEP */
	const unsigned int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;

	__asm__ __volatile__(
		"sleep %0	\n"
		:
		:"I"(arg)); /* can't be "r" has to be embedded const */
}

#elif defined(CONFIG_EZNPS_MTM_EXT)	/* ARC700 variant in NPS */

void arch_cpu_idle(void)
{
	/* only the calling HW thread needs to sleep */
	__asm__ __volatile__(
		".word %0	\n"
		:
		:"i"(CTOP_INST_HWSCHD_WFT_IE12));
}

#else	/* ARC700 */

void arch_cpu_idle(void)
{
	/* sleep, but enable both set E1/E2 (levels of interrutps) before committing */
	__asm__ __volatile__("sleep 0x3	\n");
}

#endif

asmlinkage void ret_from_fork(void);

/*
 * Copy architecture-specific thread state
 *
 * Layout of Child kernel mode stack as setup at the end of this function is
 *
 * |     ...        |
 * |     ...        |
 * |    unused      |
 * |                |
 * ------------------
 * |     r25        |   <==== top of Stack (thread.ksp)
 * ~                ~
 * |    --to--      |   (CALLEE Regs of kernel mode)
 * |     r13        |
 * ------------------
 * |     fp         |
 * |    blink       |   @ret_from_fork
 * ------------------
 * |                |
 * ~                ~
 * ~                ~
 * |                |
 * ------------------
 * |     r12        |
 * ~                ~
 * |    --to--      |   (scratch Regs of user mode)
 * |     r0         |
 * ------------------
 * |      SP        |
 * |    orig_r0     |
 * |    event/ECR   |
 * |    user_r25    |
 * ------------------  <===== END of PAGE
 */
int copy_thread_tls(unsigned long clone_flags, unsigned long usp,
	unsigned long kthread_arg, struct task_struct *p, unsigned long tls)
{
	struct pt_regs *c_regs;        /* child's pt_regs */
	unsigned long *childksp;       /* to unwind out of __switch_to() */
	struct callee_regs *c_callee;  /* child's callee regs */
	struct callee_regs *parent_callee;  /* paren't callee */
	struct pt_regs *regs = current_pt_regs();

	/* Mark the specific anchors to begin with (see pic above) */
	c_regs = task_pt_regs(p);
	childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
	c_callee = ((struct callee_regs *)childksp) - 1;

	/*
	 * __switch_to() uses thread.ksp to start unwinding stack
	 * For kernel threads we don't need to create callee regs, the
	 * stack layout nevertheless needs to remain the same.
	 * Also, since __switch_to anyways unwinds callee regs, we use
	 * this to populate kernel thread entry-pt/args into callee regs,
	 * so that ret_from_kernel_thread() becomes simpler.
	 */
	p->thread.ksp = (unsigned long)c_callee;	/* THREAD_KSP */

	/* __switch_to expects FP(0), BLINK(return addr) at top */
	childksp[0] = 0;			/* fp */
	childksp[1] = (unsigned long)ret_from_fork; /* blink */

	if (unlikely(p->flags & PF_KTHREAD)) {
		memset(c_regs, 0, sizeof(struct pt_regs));

		c_callee->r13 = kthread_arg;
		c_callee->r14 = usp;  /* function */

		return 0;
	}

	/*--------- User Task Only --------------*/

	/* __switch_to expects FP(0), BLINK(return addr) at top of stack */
	childksp[0] = 0;				/* for POP fp */
	childksp[1] = (unsigned long)ret_from_fork;	/* for POP blink */

	/* Copy parents pt regs on child's kernel mode stack */
	*c_regs = *regs;

	if (usp)
		c_regs->sp = usp;

	c_regs->r0 = 0;		/* fork returns 0 in child */

	parent_callee = ((struct callee_regs *)regs) - 1;
	*c_callee = *parent_callee;

	if (unlikely(clone_flags & CLONE_SETTLS)) {
		/*
		 * set task's userland tls data ptr from 4th arg
		 * clone C-lib call is difft from clone sys-call
		 */
		task_thread_info(p)->thr_ptr = tls;
	} else {
		/* Normal fork case: set parent's TLS ptr in child */
		task_thread_info(p)->thr_ptr =
		task_thread_info(current)->thr_ptr;
	}


	/*
	 * setup usermode thread pointer #1:
	 * when child is picked by scheduler, __switch_to() uses @c_callee to
	 * populate usermode callee regs: this works (despite being in a kernel
	 * function) since special return path for child @ret_from_fork()
	 * ensures those regs are not clobbered all the way to RTIE to usermode
	 */
	c_callee->r25 = task_thread_info(p)->thr_ptr;

#ifdef CONFIG_ARC_CURR_IN_REG
	/*
	 * setup usermode thread pointer #2:
	 * however for this special use of r25 in kernel, __switch_to() sets
	 * r25 for kernel needs and only in the final return path is usermode
	 * r25 setup, from pt_regs->user_r25. So set that up as well
	 */
	c_regs->user_r25 = c_callee->r25;
#endif

	return 0;
}

/*
 * Do necessary setup to start up a new user task
 */
void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long usp)
{
	regs->sp = usp;
	regs->ret = pc;

	/*
	 * [U]ser Mode bit set
	 * [L] ZOL loop inhibited to begin with - cleared by a LP insn
	 * Interrupts enabled
	 */
	regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;

#ifdef CONFIG_EZNPS_MTM_EXT
	regs->eflags = 0;
#endif

	fpu_init_task(regs);

	/* bogus seed values for debugging */
	regs->lp_start = 0x10;
	regs->lp_end = 0x80;
}

/*
 * Some archs flush debug and FPU info here
 */
void flush_thread(void)
{
}

int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
{
	return 0;
}

int elf_check_arch(const struct elf32_hdr *x)
{
	unsigned int eflags;

	if (x->e_machine != EM_ARC_INUSE) {
		pr_err("ELF not built for %s ISA\n",
			is_isa_arcompact() ? "ARCompact":"ARCv2");
		return 0;
	}

	eflags = x->e_flags;
	if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
		pr_err("ABI mismatch - you need newer toolchain\n");
		force_sigsegv(SIGSEGV);
		return 0;
	}

	return 1;
}
EXPORT_SYMBOL(elf_check_arch);