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* [PATCH v3 0/3] extern inline native_save_fl for paravirt
@ 2018-06-07 18:32 Nick Desaulniers
  2018-06-07 18:32 ` [PATCH v3 1/3] compiler-gcc.h: add gnu_inline to all inline declarations Nick Desaulniers
                   ` (2 more replies)
  0 siblings, 3 replies; 8+ messages in thread
From: Nick Desaulniers @ 2018-06-07 18:32 UTC (permalink / raw)
  To: akpm, hpa, mingo, tglx
  Cc: linux-efi, linux-kernel, x86, virtualization, astrachan,
	manojgupta, ghackmann, sedat.dilek, tstellar, keescook,
	yamada.masahiro, michal.lkml, linux-kbuild, geert, will.deacon,
	mawilcox, arnd, rientjes, acme, pombredanne, aryabinin, kstewart,
	boris.ostrovsky, jan.kiszka, rostedt, kirill.shutemov,
	ard.biesheuvel, akataria, brijesh.singh, caoj.fnst, gregkh,
	jarkko.sakkinen, jgross, jpoimboe, mka, ndesaulniers,
	thomas.lendacky, tweek, mjg59, joe

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

-- 
2.17.1.1185.g55be947832-goog

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2018-06-07 20:16 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-06-07 18:32 [PATCH v3 0/3] extern inline native_save_fl for paravirt Nick Desaulniers
2018-06-07 18:32 ` [PATCH v3 1/3] compiler-gcc.h: add gnu_inline to all inline declarations Nick Desaulniers
2018-06-07 18:43   ` Joe Perches
2018-06-07 18:32 ` [PATCH v3 2/3] x86/asm: add _ASM_ARG* constants for argument registers to <asm/asm.h> Nick Desaulniers
2018-06-07 20:13   ` H. Peter Anvin
2018-06-07 20:15     ` Nick Desaulniers
2018-06-07 18:32 ` [PATCH v3 3/3] x86: paravirt: make native_save_fl extern inline Nick Desaulniers
2018-06-07 18:39   ` Nick Desaulniers

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