[PATCH v2 08/13] support: Add support_count_maps

[Adhemerval Zanella Netto]

LGTM, some suggestion below.

On 28/07/24 16:03, Florian Weimer wrote:
> ---
>  support/Makefile                 |  2 ++
>  support/support.h                |  5 +++
>  support/support_count_maps.c     | 51 +++++++++++++++++++++++++++++++
>  support/tst-support_count_maps.c | 52 ++++++++++++++++++++++++++++++++
>  4 files changed, 110 insertions(+)
>  create mode 100644 support/support_count_maps.c
>  create mode 100644 support/tst-support_count_maps.c
> 
> diff --git a/support/Makefile b/support/Makefile
> index aa57207bdc..bc35faa325 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -53,6 +53,7 @@ libsupport-routines = \
>    support_chroot \
>    support_copy_file \
>    support_copy_file_range \
> +  support_count_maps \
>    support_create_timer \
>    support_descriptor_supports_holes \
>    support_descriptors \
> @@ -319,6 +320,7 @@ tests = \
>    tst-support-process_state \
>    tst-support_blob_repeat \
>    tst-support_capture_subprocess \
> +  tst-support_count_maps \
>    tst-support_descriptors \
>    tst-support_format_dns_packet \
>    tst-support_quote_blob \
> diff --git a/support/support.h b/support/support.h
> index ba21ec9b5a..5769e8c5f3 100644
> --- a/support/support.h
> +++ b/support/support.h
> @@ -96,6 +96,11 @@ int support_descriptor_supports_holes (int fd);
>     WHY_MSG as part of the diagnostic.  */
>  void support_need_proc (const char *why_msg);
>  
> +/* Counts the number of mappings in the process address space.
> +   Currently implemented using /proc/self/maps on Linux, so it needs
> +   that to exist.  */
> +size_t support_count_maps (void);
> +
>  /* Error-checking wrapper functions which terminate the process on
>     error.  */
>  
> diff --git a/support/support_count_maps.c b/support/support_count_maps.c
> new file mode 100644
> index 0000000000..2a6dd9fee3
> --- /dev/null
> +++ b/support/support_count_maps.c
> @@ -0,0 +1,51 @@
> +/* Count the number of mappings.
> +   Copyright (C) 2024 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <support/support.h>
> +#include <support/check.h>
> +#include <support/xstdio.h>
> +#include <errno.h>
> +
> +size_t
> +support_count_maps (void)
> +{

Maybe add a support_need_proc().

> +  FILE *fp = fopen ("/proc/self/maps", "r");
> +  if (fp == NULL)
> +    {
> +      if (errno == ENOENT)
> +        FAIL_UNSUPPORTED ("support_count_maps: test needs /proc/self/maps");
> +      else
> +        FAIL_EXIT1 ("cannot open /proc/self/maps: %m");
> +    }

And then you can just use xfopen here.

> +  size_t count = 0;
> +  while (true)
> +    {
> +      switch (getc_unlocked (fp))
> +        {
> +        case EOF:
> +          /* Error will be reported by xfclose below.  */
> +          goto out;
> +        case '\n':
> +          ++count;
> +          break;
> +        }
> +    }
> + out:
> +  xfclose (fp);
> +  return count;
> +}
> diff --git a/support/tst-support_count_maps.c b/support/tst-support_count_maps.c
> new file mode 100644
> index 0000000000..e904a00cd4
> --- /dev/null
> +++ b/support/tst-support_count_maps.c
> @@ -0,0 +1,52 @@
> +/* Test counting the number of mappings.
> +   Copyright (C) 2024 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <stdio.h>
> +#include <support/support.h>
> +#include <support/check.h>
> +#include <support/xstdio.h>
> +#include <sys/mman.h>
> +#include <support/xunistd.h>
> +
> +static int
> +do_test (void)
> +{
> +  long int page_size = xsysconf (_SC_PAGESIZE);
> +
> +  size_t initial = support_count_maps ();
> +  printf ("info: initial number of maps: %zu\n", initial);
> +
> +  void *ptr = xmmap (NULL, 2 * page_size, PROT_READ | PROT_WRITE,
> +                     MAP_PRIVATE | MAP_ANONYMOUS, -1);
> +  size_t one_mapping = support_count_maps ();
> +  printf ("info: new number of maps: %zu\n", one_mapping);
> +  TEST_COMPARE (initial + 1, one_mapping);
> +
> +  /* The mapping gets split due to the protection flags change.  */
> +  xmprotect (ptr, page_size, PROT_READ);
> +  size_t two_mappings = support_count_maps ();
> +  TEST_COMPARE (initial + 2, two_mappings);
> +
> +  xmunmap (ptr, 2 * page_size);
> +  size_t final = support_count_maps ();
> +  TEST_COMPARE (initial, final);
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>