ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 36 insertions, 0 deletions

diff --git a/security/keys/compat_dh.c b/security/keys/compat_dh.c
new file mode 100644
index 000000000..19384e7e9
--- /dev/null
+++ b/security/keys/compat_dh.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* 32-bit compatibility syscall for 64-bit systems for DH operations
+ *
+ * Copyright (C) 2016 Stephan Mueller <smueller@chronox.de>
+ */
+
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+/*
+ * Perform the DH computation or DH based key derivation.
+ *
+ * If successful, 0 will be returned.
+ */
+long compat_keyctl_dh_compute(struct keyctl_dh_params __user *params,
+			      char __user *buffer, size_t buflen,
+			      struct compat_keyctl_kdf_params __user *kdf)
+{
+	struct keyctl_kdf_params kdfcopy;
+	struct compat_keyctl_kdf_params compat_kdfcopy;
+
+	if (!kdf)
+		return __keyctl_dh_compute(params, buffer, buflen, NULL);
+
+	if (copy_from_user(&compat_kdfcopy, kdf, sizeof(compat_kdfcopy)) != 0)
+		return -EFAULT;
+
+	kdfcopy.hashname = compat_ptr(compat_kdfcopy.hashname);
+	kdfcopy.otherinfo = compat_ptr(compat_kdfcopy.otherinfo);
+	kdfcopy.otherinfolen = compat_kdfcopy.otherinfolen;
+	memcpy(kdfcopy.__spare, compat_kdfcopy.__spare,
+	       sizeof(kdfcopy.__spare));
+
+	return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
+}