[PATCH v3 0/3] extern inline native_save_fl for paravirt
From: Nick Desaulniers
Date: Thu Jun 07 2018 - 14:32:34 EST
paravirt depends on a custom calling convention (callee saved), but
expects this from a static inline function that it then forces to be
outlined. This is problematic because different compilers or flags can
then add a stack guard that violates the calling conventions.
Uses extern inline with the out-of-line definition in assembly to
prevent compilers from adding stack guards to the outlined version.
Other parts of the codebase overwrite KBUILD_CFLAGS, which is *extremely
problematic* for extern inline, as the sematics are completely the
opposite depending on what C standard is used.
http://blahg.josefsipek.net/?p=529
Changes since v2:
Take hpa's _ASM_ARG patch into the set in order to simplify cross
32b/64b x86 assembly. Apply Sedat's typo fix to commit message and
sign off on it. Take Joe's sugguestion to simplify __inline__ and
__inline. Add Arnd to list of folks who made helpful suggestions.
Changes since v1:
Prefer gnu_inline function attribute instead of explicitly setting C
standard compiler flag in problematic Makefiles. We should instead
carefully evaluate if those Makefiles should be overwriting
KBUILD_CFLAGS at all. Dropped the previous first two patches and added
a new first patch.
H. Peter Anvin (1):
x86/asm: add _ASM_ARG* constants for argument registers to <asm/asm.h>
Nick Desaulniers (2):
compiler-gcc.h: add gnu_inline to all inline declarations
x86: paravirt: make native_save_fl extern inline
arch/x86/include/asm/asm.h | 59 +++++++++++++++++++++++++++++++++
arch/x86/include/asm/irqflags.h | 2 +-
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/irqflags.S | 26 +++++++++++++++
include/linux/compiler-gcc.h | 17 ++++++----
5 files changed, 98 insertions(+), 7 deletions(-)
create mode 100644 arch/x86/kernel/irqflags.S
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2.17.1.1185.g55be947832-goog