From 9e1725b410594911cc5981b6c7b4cea4ec054ca8 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Wed, 3 Oct 2018 14:30:54 -0700 Subject: x86/refcount: Work around GCC inlining bug As described in: 77b0bf55bc67: ("kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs") GCC's inlining heuristics are broken with common asm() patterns used in kernel code, resulting in the effective disabling of inlining. The workaround is to set an assembly macro and call it from the inline assembly block. As a result GCC considers the inline assembly block as a single instruction. (Which it isn't, but that's the best we can get.) This patch allows GCC to inline simple functions such as __get_seccomp_filter(). To no-one's surprise the result is that GCC performs more aggressive (read: correct) inlining decisions in these senarios, which reduces the kernel size and presumably also speeds it up: text data bss dec hex filename 18140970 10225412 2957312 31323694 1ddf62e ./vmlinux before 18140140 10225284 2957312 31322736 1ddf270 ./vmlinux after (-958) 16 fewer static text symbols: Before: 40302 After: 40286 (-16) these got inlined instead. Functions such as kref_get(), free_user(), fuse_file_get() now get inlined. Hurray! [ mingo: Rewrote the changelog. ] Tested-by: Kees Cook Signed-off-by: Nadav Amit Acked-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jan Beulich Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20181003213100.189959-5-namit@vmware.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/macros.S | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/kernel/macros.S') diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S index cee28c3246dc..f1fe1d570365 100644 --- a/arch/x86/kernel/macros.S +++ b/arch/x86/kernel/macros.S @@ -7,3 +7,4 @@ */ #include +#include -- cgit v1.2.3