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    Subjectgcov: NULL pointer dereference with gcc 9.3.1
    Hi!

    Maybe this is a known (gcc?) issue, but I'm seeing a NULL pointer splat if
    I instrument my kernel (or a module, more specifically) using gcc 9.3.1.

    It looks like, during initialization in __gcov_init(), gcov_info struct is
    invalid: the filename seems to be correct but ->function is NULL and
    ->n_functions contains garbage. This will result in the NULL pointer if,
    for example, I run:

    # echo 1 > /sys/kernel/debug/gcov/reset

    Other installed gcc versions (7.5.0 and 10.3.0) work fine.

    Is this a know issue with this specific gcc versions? Anyway, it may
    be worth having something like (not tested!):

    diff --git a/kernel/gcov/gcc_base.c b/kernel/gcov/gcc_base.c
    index 3cf736b9f880..de3ea47f4f62 100644
    --- a/kernel/gcov/gcc_base.c
    +++ b/kernel/gcov/gcc_base.c
    @@ -13,6 +13,11 @@ void __gcov_init(struct gcov_info *info)
    {
    static unsigned int gcov_version;

    + if (!info || !info->functions) {
    + pr_err_once("Invalid gcov_info structure\n");
    + return;
    + }
    +
    mutex_lock(&gcov_lock);
    if (gcov_version == 0) {
    gcov_version = gcov_info_version(info);
    And also something similar in the clang code, I guess.

    I can send a real (tested) patch if you wish, but I just wanted to know if
    I'm missing something first.

    Cheers,
    --
    Luis

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