Re: [Buildroot] [PATCH 1/1] package/procps-ng: fix build without __NR_pidfd_open

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

On Thu,  3 Nov 2022 18:48:18 +0100
Fabrice Fontaine <fontaine.fabrice@gmail.com> wrote:

> Fix the following build failure without __NR_pidfd_open raised since
> bump to version 3.3.17 in commit
> cc28c7aa6df7798ce5ca79d6d1c7c2eb115ba220 and
> https://gitlab.com/procps-ng/procps/-/commit/c8384e682c1cfb3b2dc797e0f8a3cbaaccf7a3da:
> 
> pgrep.c: In function 'pidfd_open':
> pgrep.c:748:17: error: '__NR_pidfd_open' undeclared (first use in this function); did you mean 'pidfd_open'?
>   748 |  return syscall(__NR_pidfd_open, pid, flags);
>       |                 ^~~~~~~~~~~~~~~
>       |                 pidfd_open
> 
> Fixes:
>  - http://autobuild.buildroot.org/results/f23a5156e641b2ebdd673973dec0f9c87760c688
> 
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> ---
>  .../procps-ng/0003-fix-pifd_open-check.patch  | 59 +++++++++++++++++++
>  1 file changed, 59 insertions(+)
>  create mode 100644 package/procps-ng/0003-fix-pifd_open-check.patch
> 
> diff --git a/package/procps-ng/0003-fix-pifd_open-check.patch b/package/procps-ng/0003-fix-pifd_open-check.patch
> new file mode 100644
> index 0000000000..7152901e70
> --- /dev/null
> +++ b/package/procps-ng/0003-fix-pifd_open-check.patch
> @@ -0,0 +1,59 @@
> +From 0cce3e981540c28d2f703b9ab16c04d0df8fa03d Mon Sep 17 00:00:00 2001
> +From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> +Date: Thu, 3 Nov 2022 18:24:53 +0100
> +Subject: [PATCH] fix pifd_open check
> +
> +Replace AC_CHECK_FUNC by AC_CHECK_FUNCS otherwise HAVE_PIDFD_OPEN will
> +never be defined resulting in the following build failure if pidfd_open
> +is available but __NR_pidfd_open is not available:
> +
> +pgrep.c: In function 'pidfd_open':
> +pgrep.c:748:17: error: '__NR_pidfd_open' undeclared (first use in this function); did you mean 'pidfd_open'?
> +  748 |  return syscall(__NR_pidfd_open, pid, flags);
> +      |                 ^~~~~~~~~~~~~~~
> +      |                 pidfd_open
> +
> +This build failure is raised since the addition of pwait in version
> +3.3.17 and
> +https://gitlab.com/procps-ng/procps/-/commit/c8384e682c1cfb3b2dc797e0f8a3cbaaccf7a3da
> +
> +Fixes:
> + - http://autobuild.buildroot.org/results/f23a5156e641b2ebdd673973dec0f9c87760c688
> +
> +Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> +[Upstream status:
> +https://gitlab.com/procps-ng/procps/-/merge_requests/166]
> +---
> + configure.ac | 2 +-
> + src/pgrep.c  | 2 +-
> + 2 files changed, 2 insertions(+), 2 deletions(-)
> +
> +diff --git a/configure.ac b/configure.ac
> +index 629881a6..1a3ccdb8 100644
> +--- a/configure.ac
> ++++ b/configure.ac
> +@@ -160,7 +160,7 @@ AC_TRY_COMPILE([#include <errno.h>],
> + 		AC_MSG_RESULT(yes),
> + 		AC_MSG_RESULT(no))
> + 
> +-AC_CHECK_FUNC([pidfd_open], [enable_pwait=yes], [
> ++AC_CHECK_FUNCS([pidfd_open], [enable_pwait=yes], [
> +   AC_MSG_CHECKING([for __NR_pidfd_open])
> +   AC_COMPILE_IFELSE([AC_LANG_SOURCE([
> + #include <sys/syscall.h>
> +diff --git a/pgrep.c b/pgrep.c
> +index c4ad5da3..29cfedf7 100644
> +--- a/pgrep.c
> ++++ b/pgrep.c
> +@@ -38,7 +38,7 @@
> + #include <stdbool.h>
> + #include <time.h>
> + 
> +-#if defined(ENABLE_PWAIT) && !defined(HAVE_PIDFD_OPEN)
> ++#if defined(ENABLE_PWAIT)
> + #include <sys/epoll.h>
> + #include <sys/syscall.h>
> + #endif

I think here the change should have been:

#if defined(ENABLE_PWAIT)
#include <sys/epoll.h>
#if !defined(HAVE_PIDFD_OPEN)
#include <sys/syscall.h>
#endif /* !HAVE_PIDFD_OPEN */
#endif

Indeed, the <sys/epoll.h> is needed for the pwait functionality.
However, the <sys/syscall.h> is only needed when the replacement
pidfd_open() function is provided, i.e when !HAVE_PIDFD_OPEN.

Anyway, I've applied as-is to Buildroot, but maybe for upstream this
change would be more correct.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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