releases/4.19.29/bpf-selftests-fix-handling-of-sparse-cpu-allocations.patch

   1 From 8fb8de9f1fd5b7356b445c3aeb01061b999b9127 Mon Sep 17 00:00:00 2001
   2 From: Martynas Pumputis <m@lambda.lt>
   3 Date: Thu, 31 Jan 2019 10:19:33 +0100
   4 Subject: bpf, selftests: fix handling of sparse CPU allocations
   5
   6 [ Upstream commit 1bb54c4071f585ebef56ce8fdfe6026fa2cbcddd ]
   7
   8 Previously, bpf_num_possible_cpus() had a bug when calculating a
   9 number of possible CPUs in the case of sparse CPU allocations, as
  10 it was considering only the first range or element of
  11 /sys/devices/system/cpu/possible.
  12
  13 E.g. in the case of "0,2-3" (CPU 1 is not available), the function
  14 returned 1 instead of 3.
  15
  16 This patch fixes the function by making it parse all CPU ranges and
  17 elements.
  18
  19 Signed-off-by: Martynas Pumputis <m@lambda.lt>
  20 Acked-by: Yonghong Song <yhs@fb.com>
  21 Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
  22 Signed-off-by: Sasha Levin <sashal@kernel.org>
  23 ---
  24  tools/testing/selftests/bpf/bpf_util.h | 30 +++++++++++++++++---------
  25  1 file changed, 20 insertions(+), 10 deletions(-)
  26
  27 diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
  28 index 315a44fa32af..84fd6f1bf33e 100644
  29 --- a/tools/testing/selftests/bpf/bpf_util.h
  30 +++ b/tools/testing/selftests/bpf/bpf_util.h
  31 @@ -13,7 +13,7 @@ static inline unsigned int bpf_num_possible_cpus(void)
  32         unsigned int start, end, possible_cpus = 0;
  33         char buff[128];
  34         FILE *fp;
  35 -       int n;
  36 +       int len, n, i, j = 0;
  37
  38         fp = fopen(fcpu, "r");
  39         if (!fp) {
  40 @@ -21,17 +21,27 @@ static inline unsigned int bpf_num_possible_cpus(void)
  41                 exit(1);
  42         }
  43
  44 -       while (fgets(buff, sizeof(buff), fp)) {
  45 -               n = sscanf(buff, "%u-%u", &start, &end);
  46 -               if (n == 0) {
  47 -                       printf("Failed to retrieve # possible CPUs!\n");
  48 -                       exit(1);
  49 -               } else if (n == 1) {
  50 -                       end = start;
  51 +       if (!fgets(buff, sizeof(buff), fp)) {
  52 +               printf("Failed to read %s!\n", fcpu);
  53 +               exit(1);
  54 +       }
  55 +
  56 +       len = strlen(buff);
  57 +       for (i = 0; i <= len; i++) {
  58 +               if (buff[i] == ',' || buff[i] == '\0') {
  59 +                       buff[i] = '\0';
  60 +                       n = sscanf(&buff[j], "%u-%u", &start, &end);
  61 +                       if (n <= 0) {
  62 +                               printf("Failed to retrieve # possible CPUs!\n");
  63 +                               exit(1);
  64 +                       } else if (n == 1) {
  65 +                               end = start;
  66 +                       }
  67 +                       possible_cpus += end - start + 1;
  68 +                       j = i + 1;
  69                 }
  70 -               possible_cpus = start == 0 ? end + 1 : 0;
  71 -               break;
  72         }
  73 +
  74         fclose(fp);
  75
  76         return possible_cpus;
  77 --
  78 2.19.1
  79