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SubjectRe: [PATCH v9 44/44] kselftest/arm64: Check GCR_EL1 after context switch
On Tue, Nov 10, 2020 at 11:12 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>
> This test is specific to MTE and verifies that the GCR_EL1 register
> is context switched correctly.
>
> It spawn 1024 processes and each process spawns 5 threads. Each thread

Nit: "spawns"


> + srand(time(NULL) ^ (pid << 16) ^ (tid << 16));
> +
> + prctl_tag_mask = rand() % 0xffff;

Nit: if you want values between 0 and 0xffff you probably want to use
bitwise AND.


> +
> +int execute_test(pid_t pid)
> +{
> + pthread_t thread_id[MAX_THREADS];
> + int thread_data[MAX_THREADS];
> +
> + for (int i = 0; i < MAX_THREADS; i++)
> + pthread_create(&thread_id[i], NULL,
> + execute_thread, (void *)&pid);

It might be simpler to call getpid() in execute_thread() instead.

> +int mte_gcr_fork_test()
> +{
> + pid_t pid[NUM_ITERATIONS];
> + int results[NUM_ITERATIONS];
> + pid_t cpid;
> + int res;
> +
> + for (int i = 0; i < NUM_ITERATIONS; i++) {
> + pid[i] = fork();
> +
> + if (pid[i] == 0) {

pid[i] isn't used anywhere else. Did you want to keep the pids to
ensure that all children finished the work?
If not, we can probably go with a scalar here.


> + for (int i = 0; i < NUM_ITERATIONS; i++) {
> + wait(&res);
> +
> + if(WIFEXITED(res))
> + results[i] = WEXITSTATUS(res);
> + else
> + --i;

Won't we get stuck in this loop if fork() returns -1 for one of the processes?

> + }
> +
> + for (int i = 0; i < NUM_ITERATIONS; i++)
> + if (results[i] == KSFT_FAIL)
> + return KSFT_FAIL;
> +
> + return KSFT_PASS;
> +}
> +


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Alexander Potapenko
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