Re: [PATCH 04/13] fixup! KVM: selftests: Add memory size parameter to the demand paging test

[Ben Gardon <bgardon@google.com>]

On Fri, Feb 14, 2020 at 6:59 AM Andrew Jones <drjones@redhat.com> wrote:
>
> [Rewrote parse_size() to simplify and provide user more flexibility as
>  to how sizes are input. Also fixed size overflow assert.]
> Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Ben Gardon <bgardon@google.com>

Great cleanup and fix, thank you.
> ---
>  tools/testing/selftests/kvm/lib/test_util.c | 76 +++++++++------------
>  1 file changed, 33 insertions(+), 43 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index 706e0f963a44..cbd7f51b07a1 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -4,58 +4,48 @@
>   *
>   * Copyright (C) 2020, Google LLC.
>   */
> -
> -#include "test_util.h"
> -
> +#include <stdlib.h>
>  #include <ctype.h>
> +#include <limits.h>
> +#include "test_util.h"
>
>  /*
>   * Parses "[0-9]+[kmgt]?".
>   */
>  size_t parse_size(const char *size)
>  {
> -       size_t len = strlen(size);
> -       size_t i;
> -       size_t scale_shift = 0;
>         size_t base;
> -
> -       TEST_ASSERT(len > 0, "Need at least 1 digit in '%s'", size);
> -
> -       /* Find the first letter in the string, indicating scale. */
> -       for (i = 0; i < len; i++) {
> -               if (!isdigit(size[i])) {
> -                       TEST_ASSERT(i > 0, "Need at least 1 digit in '%s'",
> -                                   size);
> -                       TEST_ASSERT(i == len - 1,
> -                                   "Expected letter at the end in '%s'.",
> -                                   size);
> -                       switch (tolower(size[i])) {
> -                       case 't':
> -                               scale_shift = 40;
> -                               break;
> -                       case 'g':
> -                               scale_shift = 30;
> -                               break;
> -                       case 'm':
> -                               scale_shift = 20;
> -                               break;
> -                       case 'k':
> -                               scale_shift = 10;
> -                               break;
> -                       default:
> -                               TEST_ASSERT(false, "Unknown size letter %c",
> -                                           size[i]);
> -                       }
> -               }
> +       char *scale;
> +       int shift = 0;
> +
> +       TEST_ASSERT(size && isdigit(size[0]), "Need at least one digit in '%s'", size);
> +
> +       base = strtoull(size, &scale, 0);
> +
> +       TEST_ASSERT(base != ULLONG_MAX, "Overflow parsing size!");
> +
> +       switch (tolower(*scale)) {
> +       case 't':
> +               shift = 40;
> +               break;
> +       case 'g':
> +               shift = 30;
> +               break;
> +       case 'm':
> +               shift = 20;
> +               break;
> +       case 'k':
> +               shift = 10;
> +               break;
> +       case 'b':
> +       case '\0':
> +               shift = 0;
> +               break;
> +       default:
> +               TEST_ASSERT(false, "Unknown size letter %c", *scale);
>         }
>
> -       TEST_ASSERT(scale_shift < 8 * sizeof(size_t),
> -                   "Overflow parsing scale!");
> -
> -       base = atoi(size);
> -
> -       TEST_ASSERT(!(base & ~((1 << (sizeof(size_t) - scale_shift)) - 1)),
> -              "Overflow parsing size!");
> +       TEST_ASSERT((base << shift) >> shift == base, "Overflow scaling size!");
>
> -       return base << scale_shift;
> +       return base << shift;
>  }
> --
> 2.21.1
>