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From: Nick Desaulniers <ndesaulniers@google.com>
To: mingo@redhat.com, tglx@linutronix.de
Cc: akpm@linux-foundation.org, hpa@zytor.com,
	linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
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Subject: [PATCH v6 0/3] extern inline native_save_fl for paravirt
Date: Thu, 21 Jun 2018 09:23:21 -0700	[thread overview]
Message-ID: <20180621162324.36656-1-ndesaulniers@google.com> (raw)

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 v5:
  Reworded commits to include Juergen's ack and switch a Suggested-by
  for Reviewed-by tag. No code changes.

Changes since v4:
  Take Arnd's and hpa's suggestions properly feature detect gnu_inline
  attribute to support gcc 4.1.

Changes since v3:
  Take Joe's suggestion to hoist __inline__ and __inline out of
  conditional block.

Changes since v2:
  Take hpa's _ASM_ARG patch into the set in order to simplify cross
  32b/64b x86 assembly and rebase my final patch to use it.  Apply
  Sedat's typo fix to commit message and sign off on it. Take Joe's
  suggestion 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.


*** BLURB HERE ***

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    | 29 ++++++++++++----
 5 files changed, 109 insertions(+), 8 deletions(-)
 create mode 100644 arch/x86/kernel/irqflags.S

-- 
2.18.0.rc2.346.g013aa6912e-goog


             reply	other threads:[~2018-06-21 16:23 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-21 16:23 Nick Desaulniers [this message]
2018-06-21 16:23 ` [PATCH v6 1/3] compiler-gcc.h: add gnu_inline to all inline declarations Nick Desaulniers
2018-07-03 15:59   ` [tip:x86/urgent] compiler-gcc.h: Add __attribute__((gnu_inline)) " tip-bot for Nick Desaulniers
2018-06-21 16:23 ` [PATCH v6 2/3] x86/asm: add _ASM_ARG* constants for argument registers to <asm/asm.h> Nick Desaulniers
2018-07-03 15:59   ` [tip:x86/urgent] x86/asm: Add " tip-bot for H. Peter Anvin
2018-06-21 16:23 ` [PATCH v6 3/3] x86: paravirt: make native_save_fl extern inline Nick Desaulniers
2018-06-22  2:24   ` Ingo Molnar
2018-06-22 17:10     ` Nick Desaulniers
2018-06-26  7:13       ` Ingo Molnar
2018-06-26 16:22         ` Nick Desaulniers
2018-07-03  7:21           ` Juergen Gross
2018-07-03 16:00   ` [tip:x86/urgent] x86/paravirt: Make native_save_fl() " tip-bot for Nick Desaulniers
     [not found]   ` <1e19dbef068b45a4a4e9eb4072e097be@AcuMS.aculab.com>
2018-07-16 17:27     ` [PATCH v6 3/3] x86: paravirt: make native_save_fl " Nick Desaulniers

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