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+<h1>Patches contributed by University of Massachusetts at Lowell</h1><hr><pre>commit 581141cb4b10ebd865dcb7b80f5e712e2def5408
+Author: Albert D. Cahalan <acahalan@cs.uml.edu>
+Date:   Tue Feb 14 13:53:20 2006 -0800
+
+    [PATCH] x86: document sysenter path
+
+    This path isn't obvious.  It looks as if the kernel will be taking three
+    args from the user stack, but it only takes one from there.
+
+    Signed-off-by: Albert Cahalan <acahalan@gmail.com>
+    Signed-off-by: Andrew Morton <akpm@osdl.org>
+    Signed-off-by: Linus Torvalds <torvalds@osdl.org>
+
+diff --git a/arch/i386/kernel/vsyscall-sysenter.S b/arch/i386/kernel/vsyscall-sysenter.S
+index 4daefb2ec1b2..76b728159403 100644
+--- a/arch/i386/kernel/vsyscall-sysenter.S
++++ b/arch/i386/kernel/vsyscall-sysenter.S
+@@ -7,6 +7,21 @@
+  *    for details.
+  */
+
++/*
++ * The caller puts arg2 in %ecx, which gets pushed. The kernel will use
++ * %ecx itself for arg2. The pushing is because the sysexit instruction
++ * (found in entry.S) requires that we clobber %ecx with the desired %esp.
++ * User code might expect that %ecx is unclobbered though, as it would be
++ * for returning via the iret instruction, so we must push and pop.
++ *
++ * The caller puts arg3 in %edx, which the sysexit instruction requires
++ * for %eip. Thus, exactly as for arg2, we must push and pop.
++ *
++ * Arg6 is different. The caller puts arg6 in %ebp. Since the sysenter
++ * instruction clobbers %esp, the user's %esp won't even survive entry
++ * into the kernel. We store %esp in %ebp. Code in entry.S must fetch
++ * arg6 from the stack.
++ */
+ 	.text
+ 	.globl __kernel_vsyscall
+ 	.type __kernel_vsyscall,@function</pre><hr>