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
 23SYSCALL_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 */
 39SYSCALL_DEFINE0(arc_gettls)
 40{
 41	return task_thread_info(current)->thr_ptr;
 42}
 43
 44SYSCALL_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
 65again:
 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
 81out:
 82	preempt_enable();
 83	return uval;
 84
 85fault:
 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
 99fail:
100	force_sig(SIGSEGV);
101	return ret;
102}
103
104#ifdef CONFIG_ISA_ARCV2
105
106void 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
119void 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
130void 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
138asmlinkage 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 */
174int 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 */
267void 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 */
291void flush_thread(void)
292{
293}
294
295int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
296{
297	return 0;
298}
299
300int 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}
319EXPORT_SYMBOL(elf_check_arch);