tools/testing/selftests/bpf/prog_tests/fexit_sleep.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* Copyright (c) 2021 Facebook */
   3 #define _GNU_SOURCE
   4 #include <sched.h>
   5 #include <test_progs.h>
   6 #include <time.h>
   7 #include <sys/mman.h>
   8 #include <sys/syscall.h>
   9 #include "fexit_sleep.skel.h"
  10
  11 static int do_sleep(void *skel)
  12 {
  13         struct fexit_sleep *fexit_skel = skel;
  14         struct timespec ts1 = { .tv_nsec = 1 };
  15         struct timespec ts2 = { .tv_sec = 10 };
  16
  17         fexit_skel->bss->pid = getpid();
  18         (void)syscall(__NR_nanosleep, &ts1, NULL);
  19         (void)syscall(__NR_nanosleep, &ts2, NULL);
  20         return 0;
  21 }
  22
  23 #define STACK_SIZE (1024 * 1024)
  24 static char child_stack[STACK_SIZE];
  25
  26 void test_fexit_sleep(void)
  27 {
  28         struct fexit_sleep *fexit_skel = NULL;
  29         int wstatus, duration = 0;
  30         pid_t cpid;
  31         int err, fexit_cnt;
  32
  33         fexit_skel = fexit_sleep__open_and_load();
  34         if (CHECK(!fexit_skel, "fexit_skel_load", "fexit skeleton failed\n"))
  35                 goto cleanup;
  36
  37         err = fexit_sleep__attach(fexit_skel);
  38         if (CHECK(err, "fexit_attach", "fexit attach failed: %d\n", err))
  39                 goto cleanup;
  40
  41         cpid = clone(do_sleep, child_stack + STACK_SIZE, CLONE_FILES | SIGCHLD, fexit_skel);
  42         if (CHECK(cpid == -1, "clone", strerror(errno)))
  43                 goto cleanup;
  44
  45         /* wait until first sys_nanosleep ends and second sys_nanosleep starts */
  46         while (READ_ONCE(fexit_skel->bss->fentry_cnt) != 2);
  47         fexit_cnt = READ_ONCE(fexit_skel->bss->fexit_cnt);
  48         if (CHECK(fexit_cnt != 1, "fexit_cnt", "%d", fexit_cnt))
  49                 goto cleanup;
  50
  51         /* close progs and detach them. That will trigger two nop5->jmp5 rewrites
  52          * in the trampolines to skip nanosleep_fexit prog.
  53          * The nanosleep_fentry prog will get detached first.
  54          * The nanosleep_fexit prog will get detached second.
  55          * Detaching will trigger freeing of both progs JITed images.
  56          * There will be two dying bpf_tramp_image-s, but only the initial
  57          * bpf_tramp_image (with both _fentry and _fexit progs will be stuck
  58          * waiting for percpu_ref_kill to confirm). The other one
  59          * will be freed quickly.
  60          */
  61         close(bpf_program__fd(fexit_skel->progs.nanosleep_fentry));
  62         close(bpf_program__fd(fexit_skel->progs.nanosleep_fexit));
  63         fexit_sleep__detach(fexit_skel);
  64
  65         /* kill the thread to unwind sys_nanosleep stack through the trampoline */
  66         kill(cpid, 9);
  67
  68         if (CHECK(waitpid(cpid, &wstatus, 0) == -1, "waitpid", strerror(errno)))
  69                 goto cleanup;
  70         if (CHECK(WEXITSTATUS(wstatus) != 0, "exitstatus", "failed"))
  71                 goto cleanup;
  72
  73         /* The bypassed nanosleep_fexit prog shouldn't have executed.
  74          * Unlike progs the maps were not freed and directly accessible.
  75          */
  76         fexit_cnt = READ_ONCE(fexit_skel->bss->fexit_cnt);
  77         if (CHECK(fexit_cnt != 1, "fexit_cnt", "%d", fexit_cnt))
  78                 goto cleanup;
  79
  80 cleanup:
  81         fexit_sleep__destroy(fexit_skel);
  82 }