x86: introduce ENTRY(KPROBE_ENTRY)_X86 assembly helpers to catch unbalanced declaration v3

Impact: improvements

It's usefull to catch unbalanced or messed or mixed declarations of ENTRY and KPROBES. These macros would help a bit.

For example the following code would compile without problems

        ENTRY_X86(mcount)
                retq
        END_X86(mcount)

But if you forget and mess the following form

        ENTRY_X86(mcount)
                retq
        END(mcount)

        ENTRY_X86(ftrace_caller)

The assembler will issue the following message:
Error: ENTRY_X86/KPROBE_X86 unbalanced,missed,mixed

Actually the checking is performed at every _X86 macro so maybe it's good idea to put ENTRY_KPROBE_FINAL_X86 at the end of .S file to be sure you didn't miss anything.

---
 arch/x86/include/asm/linkage.h |   60 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

Index: linux-2.6.git/arch/x86/include/asm/linkage.h
===================================================================
@@ -57,5 +57,65 @@
 #define __ALIGN_STR ".align 16,0x90"
 #endif
 
+/*
+ * to check ENTRY_X86/END_X86 and
+ * KPROBE_ENTRY_X86/KPROBE_END_X86
+ * unbalanced-missed-mixed appearance
+ */
+#define __set_entry_x86		.set ENTRY_X86_IN, 0
+#define __unset_entry_x86	.set ENTRY_X86_IN, 1
+#define __set_kprobe_x86	.set KPROBE_X86_IN, 0
+#define __unset_kprobe_x86	.set KPROBE_X86_IN, 1
+
+#define __macro_err_x86 .error "ENTRY_X86/KPROBE_X86 unbalanced,missed,mixed"
+
+#define __check_entry_x86	\
+	.ifdef ENTRY_X86_IN;	\
+	.ifeq ENTRY_X86_IN;	\
+	__macro_err_x86;	\
+	.abort;			\
+	.endif;			\
+	.endif
+
+#define __check_kprobe_x86	\
+	.ifdef KPROBE_X86_IN;	\
+	.ifeq KPROBE_X86_IN;	\
+	__macro_err_x86;	\
+	.abort;			\
+	.endif;			\
+	.endif
+
+#define __check_entry_kprobe_x86	\
+	__check_entry_x86;		\
+	__check_kprobe_x86
+
+#define ENTRY_KPROBE_FINAL_X86 __check_entry_kprobe_x86
+
+#define ENTRY_X86(name)			\
+	__check_entry_kprobe_x86;	\
+	__set_entry_x86;		\
+	.globl name;			\
+	__ALIGN;			\
+	name:
+
+#define END_X86(name)			\
+	__unset_entry_x86;		\
+	__check_entry_kprobe_x86;	\
+	.size name, .-name
+
+#define KPROBE_ENTRY_X86(name)		\
+	__check_entry_kprobe_x86;	\
+	__set_kprobe_x86;		\
+	.pushsection .kprobes.text, "ax"; \
+	.globl name;			\
+	__ALIGN;			\
+	name:
+
+#define KPROBE_END_X86(name)		\
+	__unset_kprobe_x86;		\
+	__check_entry_kprobe_x86;	\
+	.size name, .-name;		\
+	.popsection
+
 #endif /* _ASM_X86_LINKAGE_H */
 

[Cyrill Gorcunov - Sun, Nov 23, 2008 at 08:21:39PM +0300]

| Impact: improvements
| 
| It's usefull to catch unbalanced or messed or mixed declarations of ENTRY and
| KPROBES. These macros would help a bit.
|

...

Forgot to CC LKML, so I bounce the message to LKML and add this reply with LKML CC'ed. Sorry.

- Cyrill -

applied to tip/x86/irq, thanks Cyrill.

Now lets try a patch that makes use of it in the entry*.S files, and see the fallout?

Ingo

[Ingo Molnar - Sun, Nov 23, 2008 at 07:57:26PM +0100]

| 
| * Cyrill Gorcunov <[email protected]> wrote:
| 
| > | Impact: improvements
| > | 
| > | It's usefull to catch unbalanced or messed or mixed declarations of ENTRY and
| > | KPROBES. These macros would help a bit.
| 
| applied to tip/x86/irq, thanks Cyrill.
| 
| Now lets try a patch that makes use of it in the entry*.S files, and 
| see the fallout?
| 
| 	Ingo
| 

OK, let me fetch your branch first :)

- Cyrill -