arm64: 32-bit (compat) applications support

This patch adds support for 32-bit applications. The vectors page is a
binary blob mapped into the application user space at 0xffff0000 (the
AArch64 toolchain does not support compilation of AArch32 code). Full
compatibility with ARMv7 user space is supported. The use of deprecated
ARMv7 functionality (SWP, CP15 barriers) has been disabled by default on
AArch64 kernels and unaligned LDM/STM is not supported.

Please note that only the ARM 32-bit EABI is supported, so no OABI
compatibility.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

1 files changed, 164 insertions, 0 deletions

diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c
new file mode 100644
index 00000000000..967e92fdff0
--- /dev/null
+++ b/arch/arm64/kernel/sys_compat.c
@@ -0,0 +1,164 @@
+/*
+ * Based on arch/arm/kernel/sys_arm.c
+ *
+ * Copyright (C) People who wrote linux/arch/i386/kernel/sys_i386.c
+ * Copyright (C) 1995, 1996 Russell King.
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define __SYSCALL_COMPAT
+
+#include <linux/compat.h>
+#include <linux/personality.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+
+#include <asm/cacheflush.h>
+#include <asm/unistd.h>
+
+asmlinkage int compat_sys_fork(struct pt_regs *regs)
+{
+	return do_fork(SIGCHLD, regs->compat_sp, regs, 0, NULL, NULL);
+}
+
+asmlinkage int compat_sys_clone(unsigned long clone_flags, unsigned long newsp,
+			  int __user *parent_tidptr, int tls_val,
+			  int __user *child_tidptr, struct pt_regs *regs)
+{
+	if (!newsp)
+		newsp = regs->compat_sp;
+
+	return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
+}
+
+asmlinkage int compat_sys_vfork(struct pt_regs *regs)
+{
+	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->compat_sp,
+		       regs, 0, NULL, NULL);
+}
+
+asmlinkage int compat_sys_execve(const char __user *filenamei,
+				 compat_uptr_t argv, compat_uptr_t envp,
+				 struct pt_regs *regs)
+{
+	int error;
+	char * filename;
+
+	filename = getname(filenamei);
+	error = PTR_ERR(filename);
+	if (IS_ERR(filename))
+		goto out;
+	error = compat_do_execve(filename, compat_ptr(argv), compat_ptr(envp),
+				 regs);
+	putname(filename);
+out:
+	return error;
+}
+
+asmlinkage int compat_sys_sched_rr_get_interval(compat_pid_t pid,
+						struct compat_timespec __user *interval)
+{
+	struct timespec t;
+	int ret;
+	mm_segment_t old_fs = get_fs();
+
+	set_fs(KERNEL_DS);
+	ret = sys_sched_rr_get_interval(pid, (struct timespec __user *)&t);
+	set_fs(old_fs);
+	if (put_compat_timespec(&t, interval))
+		return -EFAULT;
+	return ret;
+}
+
+asmlinkage int compat_sys_sendfile(int out_fd, int in_fd,
+				   compat_off_t __user *offset, s32 count)
+{
+	mm_segment_t old_fs = get_fs();
+	int ret;
+	off_t of;
+
+	if (offset && get_user(of, offset))
+		return -EFAULT;
+
+	set_fs(KERNEL_DS);
+	ret = sys_sendfile(out_fd, in_fd, offset ? (off_t __user *)&of : NULL,
+			   count);
+	set_fs(old_fs);
+
+	if (offset && put_user(of, offset))
+		return -EFAULT;
+	return ret;
+}
+
+static inline void
+do_compat_cache_op(unsigned long start, unsigned long end, int flags)
+{
+	struct mm_struct *mm = current->active_mm;
+	struct vm_area_struct *vma;
+
+	if (end < start || flags)
+		return;
+
+	down_read(&mm->mmap_sem);
+	vma = find_vma(mm, start);
+	if (vma && vma->vm_start < end) {
+		if (start < vma->vm_start)
+			start = vma->vm_start;
+		if (end > vma->vm_end)
+			end = vma->vm_end;
+		up_read(&mm->mmap_sem);
+		__flush_cache_user_range(start & PAGE_MASK, PAGE_ALIGN(end));
+		return;
+	}
+	up_read(&mm->mmap_sem);
+}
+
+/*
+ * Handle all unrecognised system calls.
+ */
+long compat_arm_syscall(struct pt_regs *regs)
+{
+	unsigned int no = regs->regs[7];
+
+	switch (no) {
+	/*
+	 * Flush a region from virtual address 'r0' to virtual address 'r1'
+	 * _exclusive_.  There is no alignment requirement on either address;
+	 * user space does not need to know the hardware cache layout.
+	 *
+	 * r2 contains flags.  It should ALWAYS be passed as ZERO until it
+	 * is defined to be something else.  For now we ignore it, but may
+	 * the fires of hell burn in your belly if you break this rule. ;)
+	 *
+	 * (at a later date, we may want to allow this call to not flush
+	 * various aspects of the cache.  Passing '0' will guarantee that
+	 * everything necessary gets flushed to maintain consistency in
+	 * the specified region).
+	 */
+	case __ARM_NR_compat_cacheflush:
+		do_compat_cache_op(regs->regs[0], regs->regs[1], regs->regs[2]);
+		return 0;
+
+	case __ARM_NR_compat_set_tls:
+		current->thread.tp_value = regs->regs[0];
+		asm ("msr tpidrro_el0, %0" : : "r" (regs->regs[0]));
+		return 0;
+
+	default:
+		return -ENOSYS;
+	}
+}