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