Add commentary about the new "asmlinkage_protect()" macro (d10d89ec) · Commits · 戴 / test

include/asm-x86/linkage.h

+11 −0

Original line number	Diff line number	Diff line
		@@ -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...) \

+13 −0

Original line number	Diff line number	Diff line
		@@ -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