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SubjectRe: [PATCH v5 0/3] extern inline native_save_fl for paravirt
On Wed, Jun 13, 2018 at 11:05 PM, Nick Desaulniers
<ndesaulniers@google.com> wrote:
> 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 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.
>
> 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.rc1.244.gcf134e6275-goog
>

Hi Nick,

thanks for v5 of your patchset.

I was able to boot into bare metal.

root@iniza:~# cat /proc/version
Linux version 4.14.49-1-iniza-llvmlinux (sedat.dilek@gmail.com@iniza)
(clang version 7.0.0- (trunk)) #1 SMP 2018-06-14

root@iniza:~# dpkg -l | grep clang-7
ii clang-7
1:7~svn334344-1~exp1+0~20180609091248.1814~1.gbp8ccab3 amd64 C,
C++ and Objective-C compiler

Feel free to add my Tested-By.

Regards,
- Sedat -

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