From f0b0cf3b884f0ad5f62329ecd7248b20afc90a62 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 10 Apr 2008 17:35:23 -0700
Subject: [PATCH] --- yaml --- r: 88238 b: refs/heads/master c:
 d10d89ec78114f925f63c5126a2b2490f501a462 h: refs/heads/master v: v3

---
 [refs]                          |  2 +-
 trunk/include/asm-x86/linkage.h | 11 +++++++++++
 trunk/include/linux/linkage.h   | 13 +++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 8bb667f05cda..3db9fed710a2 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 598af051a79d05b751fe793f1fe09fcf74763e02
+refs/heads/master: d10d89ec78114f925f63c5126a2b2490f501a462
diff --git a/trunk/include/asm-x86/linkage.h b/trunk/include/asm-x86/linkage.h
index d605eeba0f70..c048353f4b85 100644
--- a/trunk/include/asm-x86/linkage.h
+++ b/trunk/include/asm-x86/linkage.h
@@ -14,6 +14,17 @@
  */
 #define asmregparm __attribute__((regparm(3)))
 
+/*
+ * Make sure the compiler doesn't do anything stupid with the
+ * arguments on the stack - they are owned by the *caller*, not
+ * the callee. This just fools gcc into not spilling into them,
+ * and keeps it from doing tailcall recursion and/or using the
+ * stack slots for temporaries, since they are live and "used"
+ * all the way to the end of the function.
+ *
+ * NOTE! On x86-64, all the arguments are in registers, so this
+ * only matters on a 32-bit kernel.
+ */
 #define asmlinkage_protect(n, ret, args...) \
 	__asmlinkage_protect##n(ret, ##args)
 #define __asmlinkage_protect_n(ret, args...) \
diff --git a/trunk/include/linux/linkage.h b/trunk/include/linux/linkage.h
index fe2a39c489b6..b163c5c40dbc 100644
--- a/trunk/include/linux/linkage.h
+++ b/trunk/include/linux/linkage.h
@@ -17,6 +17,19 @@
 # define asmregparm
 #endif
 
+/*
+ * This is used by architectures to keep arguments on the stack
+ * untouched by the compiler by keeping them live until the end.
+ * The argument stack may be owned by the assembly-language
+ * caller, not the callee, and gcc doesn't always understand
+ * that.
+ *
+ * We have the return value, and a maximum of six arguments.
+ *
+ * This should always be followed by a "return ret" for the
+ * protection to work (ie no more work that the compiler might
+ * end up needing stack temporaries for).
+ */
 #ifndef asmlinkage_protect
 # define asmlinkage_protect(n, ret, args...)	do { } while (0)
 #endif