1 files changed, 81 insertions, 0 deletions
diff --git a/arch/loongarch/kernel/syscall.c b/arch/loongarch/kernel/syscall.c
new file mode 100644
index 000000000000..168bd97540f8
--- /dev/null
+++ b/arch/loongarch/kernel/syscall.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Author: Hanlu Li <lihanlu@loongson.cn>
+ *         Huacai Chen <chenhuacai@loongson.cn>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#include <linux/capability.h>
+#include <linux/entry-common.h>
+#include <linux/errno.h>
+#include <linux/linkage.h>
+#include <linux/objtool.h>
+#include <linux/randomize_kstack.h>
+#include <linux/syscalls.h>
+#include <linux/unistd.h>
+
+#include <asm/asm.h>
+#include <asm/exception.h>
+#include <asm/loongarch.h>
+#include <asm/signal.h>
+#include <asm/switch_to.h>
+#include <asm-generic/syscalls.h>
+
+#undef __SYSCALL
+#define __SYSCALL(nr, call)	[nr] = (call),
+#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
+
+SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, unsigned long,
+		prot, unsigned long, flags, unsigned long, fd, unsigned long, offset)
+{
+	if (offset & ~PAGE_MASK)
+		return -EINVAL;
+
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
+}
+
+void *sys_call_table[__NR_syscalls] = {
+	[0 ... __NR_syscalls - 1] = sys_ni_syscall,
+#include <asm/syscall_table_64.h>
+};
+
+typedef long (*sys_call_fn)(unsigned long, unsigned long,
+	unsigned long, unsigned long, unsigned long, unsigned long);
+
+void noinstr __no_stack_protector do_syscall(struct pt_regs *regs)
+{
+	unsigned long nr;
+	sys_call_fn syscall_fn;
+
+	nr = regs->regs[11];
+	/* Set for syscall restarting */
+	if (nr < NR_syscalls)
+		regs->regs[0] = nr + 1;
+
+	regs->csr_era += 4;
+	regs->orig_a0 = regs->regs[4];
+	regs->regs[4] = -ENOSYS;
+
+	nr = syscall_enter_from_user_mode(regs, nr);
+
+	add_random_kstack_offset();
+
+	if (nr < NR_syscalls) {
+		syscall_fn = sys_call_table[nr];
+		regs->regs[4] = syscall_fn(regs->orig_a0, regs->regs[5], regs->regs[6],
+					   regs->regs[7], regs->regs[8], regs->regs[9]);
+	}
+
+	/*
+	 * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
+	 * bits. The actual entropy will be further reduced by the compiler
+	 * when applying stack alignment constraints: 16-bytes (i.e. 4-bits)
+	 * aligned, which will remove the 4 low bits from any entropy chosen
+	 * here.
+	 *
+	 * The resulting 6 bits of entropy is seen in SP[9:4].
+	 */
+	choose_random_kstack_offset(drdtime());
+
+	syscall_exit_to_user_mode(regs);
+}