x86_64: re-add a newline to RESTORE_CONTEXT

RESTORE_CONTEXT lost a newline in
commit 658fdbef66e5e9be79b457edc2cbbb3add840aa9:
http://www.mail-archive.com/[email protected]/msg00559.html

Reported by Steven M. Christey.

@@ -21,7 +21,7 @@
 
 /* frame pointer must be last for get_wchan */
 #define SAVE_CONTEXT    "pushf ; pushq %%rbp ; movq %%rsi,%%rbp\n\t"
-#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\t"
+#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\n\t"
 
 #define __EXTRA_CLOBBER  \
 	,"rcx","rbx","rdx","r8","r9","r10","r11","r12","r13","r14","r15"

I don't think we should add such changes for external patchkits.

In general kgdb shouldn't add any patches at all. If the existing hooks are not enough they should submit their changes needed so that it can just work.

-Andi

But the patch is a bugfix. Without it, you cannot do

	RESTORE_CONTEXT	\
	.globl ...	\

Was the addition of this restriction to RESTORE_CONTEXT deliberate, or mistaken?

RESTORE_CONTEXT is a private macro and I don't see why we should support out of tree usages for that. As long as it works as it is in the tree it is fine.

-Andi

In other words we'll leave it in its present buggy form so that it will explode next time someone tries to use it for something new, rather than a) fixing that potential problem and b) fixing a real problem with a popular external GPLed product.

Unfathomable.

It shouldn't be used for anything new. It's really a private macro in the context switch code, nothing that any other code is supposed to use.

kgdb shouldn't need any patches to core kernel I had it some time ago running fine just by hooking it into the die hooks (and minor changes to the serial layer, with netpoll these shouldn't be even needed anymore)

If the kgdb people need more changes they should submit them.

But I suspect if they change RESTORE_CONTEXT they're doing something wrong anyways and they just need to fix their code properly.

-Andi

Their use was broken in the first place - they shouldn't have made assumptions about the contents of the macro, by writing this like

	RESTORE_CONTEXT "\n\t"	\
	".globl ..."	\

if they really need to make use of the macro. This is similar to requirements of other (assembly) macros that normally also don't have a line terminator and hence require the users to add appropriate line termination after the macro name (and eventual arguments).

I would even go as far as asking for removing the \n\t on SAVE_CONTEXT and the left \t on RESTORE_CONTEXT.

Jan