x86: kprobes remove fix_riprel #ifdef

Move #ifdef around function definiton into the function and unconditionally return on X86_32. Saves an ifdef from the one callsite.

Signed-off-by Harvey Harrison <[email protected]>

---
Ingo, Masami, final leftovers from some unsent kprobes unification work.

Net reduction of one #ifdef section.

 arch/x86/kernel/kprobes.c |   11 +++++++----
 1 files changed, 7 insertions(+), 4 deletions(-)

arch/x86/kernel/kprobes.c +7 -4

index b1804e4..1ac532e 100644
@@ -263,15 +263,16 @@ static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
 	return 0;
 }
 
-#ifdef CONFIG_X86_64
 /*
  * Adjust the displacement if the instruction uses the %rip-relative
  * addressing mode.
  * If it does, Return the address of the 32-bit displacement word.
  * If not, return null.
+ * Only applicable to X86_64
  */
 static void __kprobes fix_riprel(struct kprobe *p)
 {
+#ifdef CONFIG_X86_64
 	u8 *insn = p->ainsn.insn;
 	s64 disp;
 	int need_modrm;

@@ -335,15 +336,17 @@ static void __kprobes fix_riprel(struct kprobe *p)
 			*(s32 *)insn = (s32) disp;
 		}
 	}
-}
+#else
+	return;
 #endif
+}
 
 static void __kprobes arch_copy_kprobe(struct kprobe *p)
 {
 	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
-#ifdef CONFIG_X86_64
+
 	fix_riprel(p);
-#endif
+
 	if (can_boost(p->addr))
 		p->ainsn.boostable = 0;
 	else

Hello Harvey,

A similar idea was already nack-ed by Ananth.
http://sources.redhat.com/ml/systemtap/2007-q4/msg00468.html
And I agree his thought.

Especially, "riprel" does not exist on x86_32, so fix_riprel() is meaningless on it.
Thus, I think it would better be ifdef'd in call-site.

Quoted 6 lines · Masami Hiramatsu

Hello Harvey,

A similar idea was already nack-ed by Ananth.
http://sources.redhat.com/ml/systemtap/2007-q4/msg00468.html
And I agree his thought.

Quoted 3 lines

Especially, "riprel" does not exist on x86_32, so fix_riprel() is meaningless on it.
Thus, I think it would better be ifdef'd in call-site.

but we regularly do this in generic code: we add calls that are NOPs on some architectures. For example flush_cache_page() makes no sense on the x86 architecture.

So i'm inclined to apply Harvey's cleanup - less
#ifdef complexity in higher-level code is very much favored, even if "riprel" is a NOP concept on 32-bit.

Ingo

Indeed.
By the way, flush_cache_page() is defined as a do-while(0) on x86. Would it better to define fix_riprel() as a do-while(0) on x86-32? I think this obviously indicates that function has no effect.

Quoted 4 lines · Masami Hiramatsu

Indeed.
By the way, flush_cache_page() is defined as a do-while(0) on x86. Would it better to define fix_riprel() as a do-while(0) on x86-32? I think this obviously indicates that function has no effect.

NOPs should always be an inline. flush_cache_page()'s macro use is historic - feel free to send cleanup patches against cacheflush.h.

or even better, since most architectures dont need explicit cache-flushes, provide an asm-generic/cache_flush-nop.h file that is #include-ed by asm-x86/cacheflush.h. (and by other architectures)

Ingo