[src/trunk]: src Introduce enhancements to the kcov(4) code

[kamil <kamil%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/ce9693b7beaa
branches:  trunk
changeset: 997522:ce9693b7beaa
user:      kamil <kamil%NetBSD.org@localhost>
date:      Sun Mar 10 22:34:14 2019 +0000

description:
Introduce enhancements to the kcov(4) code

Add new tests verifying dup2(2) scenarios:
 - kcov_dup2
 - kcov_basic_dup2_pc
 - kcov_basic_dup2_cmp

The dup2(2) trick is used by syzkaller and assert that it works.
All new tests pass.

While there add minor non-functional cleanup changes.

diffstat:

 sys/kern/subr_kcov.c   |   4 +-
 tests/modules/t_kcov.c |  80 +++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 71 insertions(+), 13 deletions(-)

diffs (174 lines):

diff -r ec80034b9113 -r ce9693b7beaa sys/kern/subr_kcov.c
--- a/sys/kern/subr_kcov.c      Sun Mar 10 22:28:56 2019 +0000
+++ b/sys/kern/subr_kcov.c      Sun Mar 10 22:34:14 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_kcov.c,v 1.5 2019/03/10 17:51:00 kamil Exp $      */
+/*     $NetBSD: subr_kcov.c,v 1.6 2019/03/10 22:34:14 kamil Exp $      */
 
 /*
  * Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -417,7 +417,7 @@
        }
 
        if (kd->mode != KCOV_MODE_TRACE_CMP) {
-               /* PC tracing mode not enabled */
+               /* CMP tracing mode not enabled */
                return;
        }
 
diff -r ec80034b9113 -r ce9693b7beaa tests/modules/t_kcov.c
--- a/tests/modules/t_kcov.c    Sun Mar 10 22:28:56 2019 +0000
+++ b/tests/modules/t_kcov.c    Sun Mar 10 22:34:14 2019 +0000
@@ -57,6 +57,34 @@
        return fd;
 }
 
+static int
+pick_unassigned_fd(int greater_than_fd)
+{
+       int fd2;
+
+       fd2 = greater_than_fd;
+       do {
+               ++fd2;
+       } while (fcntl(fd2, F_GETFL) != -1 || errno != EBADF);
+
+       return fd2;
+}
+
+ATF_TC_WITHOUT_HEAD(kcov_dup2);
+ATF_TC_BODY(kcov_dup2, tc)
+{
+       int fd1, fd2;
+       fd1 = open_kcov();
+
+       fd2 = pick_unassigned_fd(fd1);
+
+       /* Test the dup2(2) trick used by syzkaller */
+       ATF_REQUIRE_EQ(dup2(fd1, fd2), fd2);
+
+       close(fd1);
+       close(fd2);
+}
+
 ATF_TC_WITHOUT_HEAD(kcov_multiopen);
 ATF_TC_BODY(kcov_multiopen, tc)
 {
@@ -216,11 +244,7 @@
        ATF_CHECK(ioctl(fd, KCOV_IOC_DISABLE) == 0);
        ATF_CHECK(ioctl(fd, KCOV_IOC_DISABLE) == -1);
 
-       /* Re-enabling should also work */
-       ATF_CHECK(ioctl(fd, KCOV_IOC_ENABLE, &mode) == 0);
-       ATF_CHECK(ioctl(fd, KCOV_IOC_DISABLE) == 0);
-
-       /* Re-enablibling and changing mode should also work */
+       /* Re-enabling and changing mode should also work */
        mode = KCOV_MODE_NONE;
        ATF_CHECK(ioctl(fd, KCOV_IOC_ENABLE, &mode) == 0);
        ATF_CHECK(ioctl(fd, KCOV_IOC_DISABLE) == 0);
@@ -262,14 +286,22 @@
 }
 
 static void *
-common_head(int *fdp)
+common_head_raw(bool fd_dup, int *fdp)
 {
        void *data;
-       int fd;
+       int fd, fd2;
        uint64_t size = PAGE_SIZE / KCOV_ENTRY_SIZE;
 
        fd = open_kcov();
 
+       /* Test the dup2(2) trick used by syzkaller */
+       if (fd_dup) {
+               fd2 = pick_unassigned_fd(fd);
+               ATF_REQUIRE_EQ(dup2(fd, fd2), fd2);
+               close(fd);
+               fd = fd2;
+       }
+
        ATF_REQUIRE_MSG(ioctl(fd, KCOV_IOC_SETBUFSIZE, &size) == 0,
            "Unable to set the kcov buffer size");
 
@@ -280,6 +312,13 @@
        return data;
 }
 
+static void *
+common_head(int *fdp)
+{
+
+       return common_head_raw(false, fdp);
+}
+
 static void
 common_tail(int fd, kcov_int_t *data)
 {
@@ -291,12 +330,12 @@
 }
 
 static void
-kcov_basic(int mode)
+kcov_basic(bool fd_dup, int mode)
 {
        kcov_int_t *buf;
        int fd;
 
-       buf = common_head(&fd);
+       buf = common_head_raw(fd_dup, &fd);
        ATF_REQUIRE_MSG(ioctl(fd, KCOV_IOC_ENABLE, &mode) == 0,
            "Unable to enable kcov ");
 
@@ -315,7 +354,7 @@
 ATF_TC_BODY(kcov_basic_pc, tc)
 {
 
-       kcov_basic(KCOV_MODE_TRACE_PC);
+       kcov_basic(false, KCOV_MODE_TRACE_PC);
 }
 
 ATF_TC_WITHOUT_HEAD(kcov_basic_cmp);
@@ -324,7 +363,23 @@
 
        atf_tc_skip("XXX: GCC8 needed");
 
-       kcov_basic(KCOV_MODE_TRACE_CMP);
+       kcov_basic(false, KCOV_MODE_TRACE_CMP);
+}
+
+ATF_TC_WITHOUT_HEAD(kcov_basic_dup2_pc);
+ATF_TC_BODY(kcov_basic_dup2_pc, tc)
+{
+
+       kcov_basic(true, KCOV_MODE_TRACE_PC);
+}
+
+ATF_TC_WITHOUT_HEAD(kcov_basic_dup2_cmp);
+ATF_TC_BODY(kcov_basic_dup2_cmp, tc)
+{
+
+       atf_tc_skip("XXX: GCC8 needed");
+
+       kcov_basic(true, KCOV_MODE_TRACE_CMP);
 }
 
 ATF_TC_WITHOUT_HEAD(kcov_multienable_on_the_same_thread);
@@ -486,6 +541,7 @@
 ATF_TP_ADD_TCS(tp)
 {
 
+       ATF_TP_ADD_TC(tp, kcov_dup2);
        ATF_TP_ADD_TC(tp, kcov_multiopen);
        ATF_TP_ADD_TC(tp, kcov_open_close_open);
        ATF_TP_ADD_TC(tp, kcov_bufsize);
@@ -498,6 +554,8 @@
        ATF_TP_ADD_TC(tp, kcov_mmap_enable_thread_close);
        ATF_TP_ADD_TC(tp, kcov_basic_pc);
        ATF_TP_ADD_TC(tp, kcov_basic_cmp);
+       ATF_TP_ADD_TC(tp, kcov_basic_dup2_pc);
+       ATF_TP_ADD_TC(tp, kcov_basic_dup2_cmp);
        ATF_TP_ADD_TC(tp, kcov_multienable_on_the_same_thread);
        ATF_TP_ADD_TC(tp, kcov_buffer_access_from_custom_thread);
        ATF_TP_ADD_TC(tp, kcov_thread);