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 __user *, 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 definition
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 succeeded */
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 committing 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	raw_local_irq_disable();
119}
120
121#else	/* ARC700 */
122
123void arch_cpu_idle(void)
124{
125	/* sleep, but enable both set E1/E2 (levels of interrupts) before committing */
126	__asm__ __volatile__("sleep 0x3	\n");
127	raw_local_irq_disable();
128}
129
130#endif
131
132asmlinkage void ret_from_fork(void);
133
134/*
135 * Copy architecture-specific thread state
136 *
137 * Layout of Child kernel mode stack as setup at the end of this function is
138 *
139 * |     ...        |
140 * |     ...        |
141 * |    unused      |
142 * |                |
143 * ------------------
144 * |     r25        |   <==== top of Stack (thread_info.ksp)
145 * ~                ~
146 * |    --to--      |   (CALLEE Regs of kernel mode)
147 * |     r13        |
148 * ------------------
149 * |     fp         |
150 * |    blink       |   @ret_from_fork
151 * ------------------
152 * |                |
153 * ~                ~
154 * ~                ~
155 * |                |
156 * ------------------
157 * |     r12        |
158 * ~                ~
159 * |    --to--      |   (scratch Regs of user mode)
160 * |     r0         |
161 * ------------------
162 * |      SP        |
163 * |    orig_r0     |
164 * |    event/ECR   |
165 * ------------------  <===== END of PAGE
166 */
167int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
168{
169	unsigned long clone_flags = args->flags;
170	unsigned long usp = args->stack;
171	unsigned long tls = args->tls;
172	struct pt_regs *c_regs;        /* child's pt_regs */
173	unsigned long *childksp;       /* to unwind out of __switch_to() */
174	struct callee_regs *c_callee;  /* child's callee regs */
175	struct callee_regs *parent_callee;  /* paren't callee */
176	struct pt_regs *regs = current_pt_regs();
177
178	/* Mark the specific anchors to begin with (see pic above) */
179	c_regs = task_pt_regs(p);
180	childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
181	c_callee = ((struct callee_regs *)childksp) - 1;
182
183	/*
184	 * __switch_to() uses thread_info.ksp to start unwinding stack
185	 * For kernel threads we don't need to create callee regs, the
186	 * stack layout nevertheless needs to remain the same.
187	 * Also, since __switch_to anyways unwinds callee regs, we use
188	 * this to populate kernel thread entry-pt/args into callee regs,
189	 * so that ret_from_kernel_thread() becomes simpler.
190	 */
191	task_thread_info(p)->ksp = (unsigned long)c_callee;	/* THREAD_INFO_KSP */
192
193	/* __switch_to expects FP(0), BLINK(return addr) at top */
194	childksp[0] = 0;			/* fp */
195	childksp[1] = (unsigned long)ret_from_fork; /* blink */
196
197	if (unlikely(args->fn)) {
198		memset(c_regs, 0, sizeof(struct pt_regs));
199
200		c_callee->r13 = (unsigned long)args->fn_arg;
201		c_callee->r14 = (unsigned long)args->fn;
202
203		return 0;
204	}
205
206	/*--------- User Task Only --------------*/
207
208	/* __switch_to expects FP(0), BLINK(return addr) at top of stack */
209	childksp[0] = 0;				/* for POP fp */
210	childksp[1] = (unsigned long)ret_from_fork;	/* for POP blink */
211
212	/* Copy parents pt regs on child's kernel mode stack */
213	*c_regs = *regs;
214
215	if (usp)
216		c_regs->sp = usp;
217
218	c_regs->r0 = 0;		/* fork returns 0 in child */
219
220	parent_callee = ((struct callee_regs *)regs) - 1;
221	*c_callee = *parent_callee;
222
223	if (unlikely(clone_flags & CLONE_SETTLS)) {
224		/*
225		 * set task's userland tls data ptr from 4th arg
226		 * clone C-lib call is difft from clone sys-call
227		 */
228		task_thread_info(p)->thr_ptr = tls;
229	} else {
230		/* Normal fork case: set parent's TLS ptr in child */
231		task_thread_info(p)->thr_ptr =
232		task_thread_info(current)->thr_ptr;
233	}
234
235
236	/*
237	 * setup usermode thread pointer #1:
238	 * when child is picked by scheduler, __switch_to() uses @c_callee to
239	 * populate usermode callee regs: this works (despite being in a kernel
240	 * function) since special return path for child @ret_from_fork()
241	 * ensures those regs are not clobbered all the way to RTIE to usermode
242	 */
243	c_callee->r25 = task_thread_info(p)->thr_ptr;
244
245	return 0;
246}
247
248/*
249 * Do necessary setup to start up a new user task
250 */
251void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long usp)
252{
253	regs->sp = usp;
254	regs->ret = pc;
255
256	/*
257	 * [U]ser Mode bit set
258	 * [L] ZOL loop inhibited to begin with - cleared by a LP insn
259	 * Interrupts enabled
260	 */
261	regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
262
263	fpu_init_task(regs);
264
265	/* bogus seed values for debugging */
266	regs->lp_start = 0x10;
267	regs->lp_end = 0x80;
268}
269
270/*
271 * Some archs flush debug and FPU info here
272 */
273void flush_thread(void)
274{
275}
276
277int elf_check_arch(const struct elf32_hdr *x)
278{
279	unsigned int eflags;
280
281	if (x->e_machine != EM_ARC_INUSE) {
282		pr_err("ELF not built for %s ISA\n",
283			is_isa_arcompact() ? "ARCompact":"ARCv2");
284		return 0;
285	}
286
287	eflags = x->e_flags;
288	if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
289		pr_err("ABI mismatch - you need newer toolchain\n");
290		force_fatal_sig(SIGSEGV);
291		return 0;
292	}
293
294	return 1;
295}
296EXPORT_SYMBOL(elf_check_arch);
297