1// SPDX-License-Identifier: GPL-2.0+
 2/*
 3 * Author: Hanlu Li <lihanlu@loongson.cn>
 4 *         Huacai Chen <chenhuacai@loongson.cn>
 5 *
 6 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
 7 */
 8#include <linux/capability.h>
 9#include <linux/entry-common.h>
10#include <linux/errno.h>
11#include <linux/linkage.h>
12#include <linux/objtool.h>
13#include <linux/randomize_kstack.h>
14#include <linux/syscalls.h>
15#include <linux/unistd.h>
16
17#include <asm/asm.h>
18#include <asm/exception.h>
19#include <asm/loongarch.h>
20#include <asm/signal.h>
21#include <asm/switch_to.h>
22#include <asm-generic/syscalls.h>
23
24#undef __SYSCALL
25#define __SYSCALL(nr, call)	[nr] = (call),
26#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
27
28SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, unsigned long,
29		prot, unsigned long, flags, unsigned long, fd, unsigned long, offset)
30{
31	if (offset & ~PAGE_MASK)
32		return -EINVAL;
33
34	return ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
35}
36
37void *sys_call_table[__NR_syscalls] = {
38	[0 ... __NR_syscalls - 1] = sys_ni_syscall,
39#include <asm/syscall_table_64.h>
40};
41
42typedef long (*sys_call_fn)(unsigned long, unsigned long,
43	unsigned long, unsigned long, unsigned long, unsigned long);
44
45void noinstr __no_stack_protector do_syscall(struct pt_regs *regs)
46{
47	unsigned long nr;
48	sys_call_fn syscall_fn;
49
50	nr = regs->regs[11];
51	/* Set for syscall restarting */
52	if (nr < NR_syscalls)
53		regs->regs[0] = nr + 1;
54
55	regs->csr_era += 4;
56	regs->orig_a0 = regs->regs[4];
57	regs->regs[4] = -ENOSYS;
58
59	nr = syscall_enter_from_user_mode(regs, nr);
60
61	add_random_kstack_offset();
62
63	if (nr < NR_syscalls) {
64		syscall_fn = sys_call_table[nr];
65		regs->regs[4] = syscall_fn(regs->orig_a0, regs->regs[5], regs->regs[6],
66					   regs->regs[7], regs->regs[8], regs->regs[9]);
67	}
68
69	/*
70	 * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
71	 * bits. The actual entropy will be further reduced by the compiler
72	 * when applying stack alignment constraints: 16-bytes (i.e. 4-bits)
73	 * aligned, which will remove the 4 low bits from any entropy chosen
74	 * here.
75	 *
76	 * The resulting 6 bits of entropy is seen in SP[9:4].
77	 */
78	choose_random_kstack_offset(drdtime());
79
80	syscall_exit_to_user_mode(regs);
81}