[LTP] [PATCH v3] syscalls/mlock05: add mlock test for locking and pre-faulting of memory

[Filippo Storniolo]

Hi!
I accidentally sent the v3 without small changes committed, please just
review v4.
I'm sorry for the inconvenience.

Kind regards,
F. Storniolo

On Thu, May 9, 2024 at 3:24 PM Filippo Storniolo <fstornio@redhat.com>
wrote:

> check Rss and Locked variables from /proc/$pid/smaps of the
> the new memory mapping.
> Rss and Locked size should be equal to the size
> of the memory allocation.
>
> Co-developed-by: Dennis Brendel <dbrendel@redhat.com>
> Signed-off-by: Filippo Storniolo <fstornio@redhat.com>
> ---
>  runtest/syscalls                           |   1 +
>  testcases/kernel/syscalls/mlock/.gitignore |   1 +
>  testcases/kernel/syscalls/mlock/mlock05.c  | 107 +++++++++++++++++++++
>  3 files changed, 109 insertions(+)
>  create mode 100644 testcases/kernel/syscalls/mlock/mlock05.c
>
> diff --git a/runtest/syscalls b/runtest/syscalls
> index 252123d8b..05a52fc8f 100644
> --- a/runtest/syscalls
> +++ b/runtest/syscalls
> @@ -781,6 +781,7 @@ mlock01 mlock01
>  mlock02 mlock02
>  mlock03 mlock03 -i 20
>  mlock04 mlock04
> +mlock05 mlock05
>
>  mlock201 mlock201
>  mlock202 mlock202
> diff --git a/testcases/kernel/syscalls/mlock/.gitignore
> b/testcases/kernel/syscalls/mlock/.gitignore
> index 306574bbc..1872229b8 100644
> --- a/testcases/kernel/syscalls/mlock/.gitignore
> +++ b/testcases/kernel/syscalls/mlock/.gitignore
> @@ -2,3 +2,4 @@
>  /mlock02
>  /mlock03
>  /mlock04
> +/mlock05
> diff --git a/testcases/kernel/syscalls/mlock/mlock05.c
> b/testcases/kernel/syscalls/mlock/mlock05.c
> new file mode 100644
> index 000000000..e7714453f
> --- /dev/null
> +++ b/testcases/kernel/syscalls/mlock/mlock05.c
> @@ -0,0 +1,107 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright Red Hat
> + * Author: Filippo Storniolo <fstornio@redhat.com>
> + */
> +
> +/*\
> + * [Description]
> + *
> + * Verify mlock() causes pre-faulting of PTEs and prevent memory to be
> swapped out.
> + *
> + * Find the new mapping in /proc/$pid/smaps and check Rss and Locked
> fields after
> + * mlock syscall:
> + * - Rss and Locked size should be equal to the size of the memory
> allocation
> + */
> +
> +#include "tst_test.h"
> +
> +#define MMAPLEN                        (1UL<<20)
> +#define LINELEN                        256
> +
> +static unsigned long get_proc_smaps_field(unsigned long
> desired_mapping_address, char *desired_field)
> +{
> +       bool mapping_found = false;
> +       char buffer[LINELEN] = "";
> +       FILE *file = NULL;
> +       int ret = 0;
> +
> +       file = fopen("/proc/self/smaps", "r");
> +       if (file == NULL) {
> +               tst_brk(TBROK | TERRNO, "cannot open file
> proc/self/smaps");
> +               return 0;
> +       }
> +
> +       // find desired field
> +       while (fgets(buffer, LINELEN, file) != NULL) {
> +               unsigned long mapping_address;
> +
> +               // check the starting address
> +               ret = sscanf(buffer, "%lx[^-]", &mapping_address);
> +
> +               // most lines will not match the pattern for the mapping
> address
> +               // so it is not treated as an error
> +               if (ret == -1)
> +                       continue;
> +
> +               if (mapping_address == desired_mapping_address) {
> +                       mapping_found = true;
> +                       break;
> +               }
> +       }
> +
> +       if (!mapping_found) {
> +               tst_brk(TBROK, "cannot find mapping %lx in
> proc/self/smaps", desired_mapping_address);
> +               return 0;
> +       }
> +
> +       // find desired field
> +       while (fgets(buffer, LINELEN, file) != NULL) {
> +               if (strstr(buffer, desired_field) != NULL) {
> +                       unsigned long desired_value;
> +
> +                       // extract the value for the requested field
> +                       ret = sscanf(buffer, "%*[^0-9]%lu%*[^0-9]",
> &desired_value);
> +                       fclose(file);
> +                       if (ret != 1) {
> +                               tst_brk(TBROK, "failure occured while
> reading field %s", desired_field);
> +                               return 0;
> +                       }
> +                       return desired_value;
> +               }
> +       }
> +
> +       fclose(file);
> +       tst_brk(TBROK, "cannot find %s field", desired_field);
> +
> +       return 0;
> +}
> +
> +static void verify_mlock(void)
> +{
> +       unsigned long Rss;
> +       unsigned long Locked;
> +       char *buf;
> +
> +       buf = SAFE_MMAP(NULL, MMAPLEN, PROT_WRITE, MAP_PRIVATE |
> MAP_ANONYMOUS, -1, 0);
> +       SAFE_MLOCK(buf, MMAPLEN);
> +
> +       printf("buf is %p\n", buf);
> +
> +       Rss = get_proc_smaps_field((unsigned long)buf, "Rss");
> +       Locked = get_proc_smaps_field((unsigned long)buf, "Locked");
> +
> +       // Convertion from KiB to B
> +       Rss *= 1024;
> +       Locked *= 1024;
> +
> +       TST_EXP_EQ_LU(Rss, MMAPLEN);
> +       TST_EXP_EQ_LU(Locked, MMAPLEN);
> +
> +       SAFE_MUNLOCK(buf, MMAPLEN);
> +       SAFE_MUNMAP(buf, MMAPLEN);
> +}
> +
> +static struct tst_test test = {
> +       .test_all = verify_mlock,
> +};
> --
> 2.44.0
>
>