New subject: [PATCH 2/7] arm64: Implement copy_thread_tls

7 Jan 2020


      [Cc Kees in case he knows something about where arch specific tests live
 or whether we have a framework for this]
On Mon, Jan 06, 2020 at 07:03:32PM +0100, Amanieu d'Antras wrote:
...
On Mon, Jan 6, 2020 at 6:39 PM Will Deacon will@kernel.org wrote:
...
I also ran the native and compat selftests but, unfortunately, they all
pass even without this patch. Do you reckon it would be possible to update
them to check the tls pointer?
Here's the program I used for testing on arm64. I considered adding it
to the selftests but there is no portable way of reading the TLS
register on all architectures.
I'm not saying you need to do this right now.
It feels like we must've run into the "this is architecture
specific"-and-we-want-to-test-this issue before... Do we have a place
where architecture specific selftests live?
...
#include <sys/syscall.h>
#include <unistd.h>
#include <stdio.h>
#include <stdint.h>
#define __NR_clone3 435
struct clone_args {
    uint64_t flags;
    uint64_t pidfd;
    uint64_t child_tid;
    uint64_t parent_tid;
    uint64_t exit_signal;
    uint64_t stack;
    uint64_t stack_size;
    uint64_t tls;
};
#define USE_CLONE3
int main() {
    printf("Before fork: tp = %p\n", __builtin_thread_pointer());
#ifdef USE_CLONE3
    struct clone_args args = {
        .flags = CLONE_SETTLS,
        .tls = (uint64_t)__builtin_thread_pointer(),
    };
    int ret = syscall(__NR_clone3, &args, sizeof(args));
#else
    int ret = syscall(__NR_clone, CLONE_SETTLS, 0, 0,
__builtin_thread_pointer(), 0);
#endif
    printf("Fork returned %d, tp = %p\n", ret, __builtin_thread_pointer());
}

Re: [PATCH 2/7] arm64: Implement copy_thread_tls