x86/jump-labels: Macrofy inline assembly code to work around GCC inlining bugs
authorNadav Amit <namit@vmware.com>
Fri, 5 Oct 2018 20:27:18 +0000 (13:27 -0700)
committerIngo Molnar <mingo@kernel.org>
Sat, 6 Oct 2018 13:52:17 +0000 (15:52 +0200)
commit5bdcd510c2ac9efaf55c4cbd8d46421d8e2320cd
treedb62e809d2470e86fa7f87425b24fc61d151b8cc
parentd5a581d84ae6b8a4a740464b80d8d9cf1e7947b2
x86/jump-labels: Macrofy inline assembly code to work around GCC inlining bugs

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 - which is also a minor cleanup for the jump-label code.

As a result the code size is slightly increased, but inlining decisions
are better:

      text     data     bss      dec     hex  filename
  18163528 10226300 2957312 31347140 1de51c4  ./vmlinux before
  18163608 10227348 2957312 31348268 1de562c  ./vmlinux after (+1128)

And functions such as intel_pstate_adjust_policy_max(),
kvm_cpu_accept_dm_intr(), kvm_register_readl() are inlined.

Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20181005202718.229565-4-namit@vmware.com
Link: https://lore.kernel.org/lkml/20181003213100.189959-11-namit@vmware.com/T/#u
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/entry/calling.h
arch/x86/include/asm/jump_label.h
arch/x86/kernel/macros.S