Re: [PATCH 3/8] linux_dep: Move close_range() conditional handling to linux_dep.h

[Stefano Brivio <sbrivio@redhat.com>]

On Wed,  6 Nov 2024 17:54:16 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> util.h has some #ifdefs and weak definitions to handle compatibility with
> various kernel versions.  Move this to linux_dep.h which handles several
> other similar cases.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  linux_dep.h | 20 ++++++++++++++++++++
>  util.h      | 19 -------------------
>  2 files changed, 20 insertions(+), 19 deletions(-)
> 
> diff --git a/linux_dep.h b/linux_dep.h
> index eae9c3c..3a41e42 100644
> --- a/linux_dep.h
> +++ b/linux_dep.h
> @@ -125,4 +125,24 @@ struct tcp_info_linux {
>  #define FALLOC_FL_COLLAPSE_RANGE	0x08
>  #endif
>  
> +#include <linux/close_range.h>
> +
> +#ifdef CLOSE_RANGE_UNSHARE	/* Linux kernel >= 5.9 */
> +/* glibc < 2.34 and musl as of 1.2.5 need these */
> +#ifndef SYS_close_range
> +#define SYS_close_range		436
> +#endif
> +__attribute__ ((weak))
> +/* cppcheck-suppress funcArgNamesDifferent */
> +int close_range(unsigned int first, unsigned int last, int flags) {
> +	return syscall(SYS_close_range, first, last, flags);
> +}
> +#else
> +/* No reasonable fallback option */
> +/* cppcheck-suppress funcArgNamesDifferent */
> +int close_range(unsigned int first, unsigned int last, int flags) {
> +	return 0;
> +}
> +#endif
> +
>  #endif /* LINUX_DEP_H */
> diff --git a/util.h b/util.h
> index 2858b10..fdc3af8 100644
> --- a/util.h
> +++ b/util.h
> @@ -17,7 +17,6 @@
>  #include <arpa/inet.h>
>  #include <unistd.h>
>  #include <sys/syscall.h>
> -#include <linux/close_range.h>
>  
>  #include "log.h"
>  
> @@ -158,24 +157,6 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
>  
>  struct ctx;
>  
> -#ifdef CLOSE_RANGE_UNSHARE	/* Linux kernel >= 5.9 */
> -/* glibc < 2.34 and musl as of 1.2.5 need these */
> -#ifndef SYS_close_range
> -#define SYS_close_range		436
> -#endif
> -__attribute__ ((weak))
> -/* cppcheck-suppress funcArgNamesDifferent */
> -int close_range(unsigned int first, unsigned int last, int flags) {
> -	return syscall(SYS_close_range, first, last, flags);
> -}
> -#else
> -/* No reasonable fallback option */
> -/* cppcheck-suppress funcArgNamesDifferent */
> -int close_range(unsigned int first, unsigned int last, int flags) {
> -	return 0;
> -}
> -#endif
> -

This breaks the build on Alpine as well:

util.c: In function 'close_open_files':
util.c:729:22: error: implicit declaration of function 'close_range'; did you mean 'SYS_close_range'? [-Wimplicit-function-declaration]
  729 |                 rc = close_range(STDERR_FILENO + 1, ~0U, CLOSE_RANGE_UNSHARE);
      |                      ^~~~~~~~~~~
      |                      SYS_close_range
util.c:729:58: error: 'CLOSE_RANGE_UNSHARE' undeclared (first use in this function)
  729 |                 rc = close_range(STDERR_FILENO + 1, ~0U, CLOSE_RANGE_UNSHARE);
      |                                                          ^~~~~~~~~~~~~~~~~~~

and is fixed by including "linux_dep.h" from util.c.

-- 
Stefano