[GLIB] Fix linking error for systems not providing <sys/memfd.h>

• Component: New Bugs
• Status: RESOLVED FIXED

[Sergio Villar Senin]

[GLIB] Fix linking error for systems not providing <sys/memfd.h>

[Sergio Villar Senin]

Created attachment 410931 [details]
Patch

[Sergio Villar Senin]

Created attachment 410934 [details]
Patch

[Sergio Villar Senin]

Thanks for the review Carlos!.

Adrian suggested to do a compile check, so I'm attaching an alternative patch with some extra cmake changes.

[Adrian Perez]

Comment on attachment 410931 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=410931&action=review

I think there is a better approach, as outlined below.

> Source/WebKit/UIProcess/Launcher/glib/BubblewrapLauncher.cpp:45
>  #include <sys/memfd.h>

It seems that there was a mistake in the manual pages for memfd_create,
and it was never intended for it to suggest using <sys/memfd.h>. There is
some discussion about that here.

  https://stackoverflow.com/questions/56615488/getting-gcc-error-sys-memfd-h-no-such-file-or-directory

> Source/WebKit/UIProcess/Launcher/glib/BubblewrapLauncher.cpp:49
> +#include <sys/mman.h>

The <sys/mman.h> header always exists, we do not need to check whether it's available.
What we can do is:

  1. Always include <sys/mman.h>. This also works for other systems, for example
     FreeBSD also has a memfd_create() function defined in this header:
     https://github.com/freebsd/freebsd/commit/575e351fdd996f72921b87e71c2c26466e887ed2

  2. If the MFD_* macros are not defined, include <linux/memfd.h> and use syscall2()
     Note: Use this fall only for linux, e.g. with a __has_include(<linux/memfd.h>) guard.

[Adrian Perez]

On a second thought, I think we do not need the CMake compile check
when using the approach of always using <sys/mman.h> and the fallback
with <linux/memfd.h>+syscall2() only on Linux. That will also cover
the BSDs which implement a compatible memfd_create() function, without
adding complexity in CMake.

BTW, thanks Sergio for the patch, and sorry for the back and forth
about the CMake check O:-)

[Konstantin Tokarev]

Does bubblewrap work on BSD at all? BubblewrapLauncher makes unconditional use of seccomp which is Linux-only.

[Konstantin Tokarev]

OTOH, we have other usage of memfd in Platform/unix/SharedMemoryUnix.cpp, where it indeed could be checked in more cross-platform way.

[Patrick Griffis]

(In reply to Konstantin Tokarev from comment #6)
> Does bubblewrap work on BSD at all?

No it is Linux specific.

[Carlos Garcia Campos]

Comment on attachment 410934 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=410934&action=review

> Source/cmake/OptionsCommon.cmake:-126
> -WEBKIT_CHECK_HAVE_INCLUDE(HAVE_LINUX_MEMFD_H linux/memfd.h)

We use this in SharedMemoryUnix.cpp

[Sergio Villar Senin]

Created attachment 411203 [details]
Patch

[Konstantin Tokarev]

I think it would be more correct to add compilation tests for memfd_create and use its results in all places where memfd is used

[EWS]

Committed r268472: <https://trac.webkit.org/changeset/268472>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 411203 [details].

[Radar WebKit Bug Importer]

<rdar://problem/70299014>