1/*
  2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
  3 *
  4 * This program is free software; you can redistribute it and/or modify
  5 * it under the terms of the GNU General Public License version 2 as
  6 * published by the Free Software Foundation.
  7 *
  8 * Amit Bhor, Kanika Nema: Codito Technologies 2004
  9 */
 10
 11#include <linux/errno.h>
 12#include <linux/module.h>
 13#include <linux/sched.h>
 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
 44void arch_cpu_idle(void)
 45{
 46	/* sleep, but enable all interrupts before committing */
 47	__asm__("sleep 0x3");
 48}
 49
 50asmlinkage void ret_from_fork(void);
 51
 52/* Layout of Child kernel mode stack as setup at the end of this function is
 53 *
 54 * |     ...        |
 55 * |     ...        |
 56 * |    unused      |
 57 * |                |
 58 * ------------------
 59 * |     r25        |   <==== top of Stack (thread.ksp)
 60 * ~                ~
 61 * |    --to--      |   (CALLEE Regs of user mode)
 62 * |     r13        |
 63 * ------------------
 64 * |     fp         |
 65 * |    blink       |   @ret_from_fork
 66 * ------------------
 67 * |                |
 68 * ~                ~
 69 * ~                ~
 70 * |                |
 71 * ------------------
 72 * |     r12        |
 73 * ~                ~
 74 * |    --to--      |   (scratch Regs of user mode)
 75 * |     r0         |
 76 * ------------------
 77 * |      SP        |
 78 * |    orig_r0     |
 79 * |    event/ECR   |
 80 * |    user_r25    |
 81 * ------------------  <===== END of PAGE
 82 */
 83int copy_thread(unsigned long clone_flags,
 84		unsigned long usp, unsigned long arg,
 85		struct task_struct *p)
 86{
 87	struct pt_regs *c_regs;        /* child's pt_regs */
 88	unsigned long *childksp;       /* to unwind out of __switch_to() */
 89	struct callee_regs *c_callee;  /* child's callee regs */
 90	struct callee_regs *parent_callee;  /* paren't callee */
 91	struct pt_regs *regs = current_pt_regs();
 92
 93	/* Mark the specific anchors to begin with (see pic above) */
 94	c_regs = task_pt_regs(p);
 95	childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
 96	c_callee = ((struct callee_regs *)childksp) - 1;
 97
 98	/*
 99	 * __switch_to() uses thread.ksp to start unwinding stack
100	 * For kernel threads we don't need to create callee regs, the
101	 * stack layout nevertheless needs to remain the same.
102	 * Also, since __switch_to anyways unwinds callee regs, we use
103	 * this to populate kernel thread entry-pt/args into callee regs,
104	 * so that ret_from_kernel_thread() becomes simpler.
105	 */
106	p->thread.ksp = (unsigned long)c_callee;	/* THREAD_KSP */
107
108	/* __switch_to expects FP(0), BLINK(return addr) at top */
109	childksp[0] = 0;			/* fp */
110	childksp[1] = (unsigned long)ret_from_fork; /* blink */
111
112	if (unlikely(p->flags & PF_KTHREAD)) {
113		memset(c_regs, 0, sizeof(struct pt_regs));
114
115		c_callee->r13 = arg; /* argument to kernel thread */
116		c_callee->r14 = usp;  /* function */
117
118		return 0;
119	}
120
121	/*--------- User Task Only --------------*/
122
123	/* __switch_to expects FP(0), BLINK(return addr) at top of stack */
124	childksp[0] = 0;				/* for POP fp */
125	childksp[1] = (unsigned long)ret_from_fork;	/* for POP blink */
126
127	/* Copy parents pt regs on child's kernel mode stack */
128	*c_regs = *regs;
129
130	if (usp)
131		c_regs->sp = usp;
132
133	c_regs->r0 = 0;		/* fork returns 0 in child */
134
135	parent_callee = ((struct callee_regs *)regs) - 1;
136	*c_callee = *parent_callee;
137
138	if (unlikely(clone_flags & CLONE_SETTLS)) {
139		/*
140		 * set task's userland tls data ptr from 4th arg
141		 * clone C-lib call is difft from clone sys-call
142		 */
143		task_thread_info(p)->thr_ptr = regs->r3;
144	} else {
145		/* Normal fork case: set parent's TLS ptr in child */
146		task_thread_info(p)->thr_ptr =
147		task_thread_info(current)->thr_ptr;
148	}
149
150	return 0;
151}
152
153/*
154 * Some archs flush debug and FPU info here
155 */
156void flush_thread(void)
157{
158}
159
160/*
161 * Free any architecture-specific thread data structures, etc.
162 */
163void exit_thread(void)
164{
165}
166
167int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
168{
169	return 0;
170}
171
172/*
173 * API: expected by schedular Code: If thread is sleeping where is that.
174 * What is this good for? it will be always the scheduler or ret_from_fork.
175 * So we hard code that anyways.
176 */
177unsigned long thread_saved_pc(struct task_struct *t)
178{
179	struct pt_regs *regs = task_pt_regs(t);
180	unsigned long blink = 0;
181
182	/*
183	 * If the thread being queried for in not itself calling this, then it
184	 * implies it is not executing, which in turn implies it is sleeping,
185	 * which in turn implies it got switched OUT by the schedular.
186	 * In that case, it's kernel mode blink can reliably retrieved as per
187	 * the picture above (right above pt_regs).
188	 */
189	if (t != current && t->state != TASK_RUNNING)
190		blink = *((unsigned int *)regs - 1);
191
192	return blink;
193}
194
195int elf_check_arch(const struct elf32_hdr *x)
196{
197	unsigned int eflags;
198
199	if (x->e_machine != EM_ARCOMPACT)
200		return 0;
201
202	eflags = x->e_flags;
203	if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_CURRENT) {
204		pr_err("ABI mismatch - you need newer toolchain\n");
205		force_sigsegv(SIGSEGV, current);
206		return 0;
207	}
208
209	return 1;
210}
211EXPORT_SYMBOL(elf_check_arch);