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Date: Sat, 26 May 2018 10:24:43 +0200
From: Phillip Berndt <phillip.berndt@...glemail.com>
To: musl@...ts.openwall.com
Subject: Re: TLS issue on aarch64

2018-05-26 2:54 GMT+02:00 Szabolcs Nagy <nsz@...t70.net>:
> indeed you need another alignment there, i came up with the
> following fix:
>
> (on mips/ppc i expect it not to change anything: tp is
> at a page aligned offset from the end of struct pthread,
> so one alignment is enough there, but on aarch64/arm/sh4
> this makes a difference, and seems to pass my simple tests)
>
> diff --git a/src/env/__init_tls.c b/src/env/__init_tls.c
> index 1c5d98a0..8e70024d 100644
> --- a/src/env/__init_tls.c
> +++ b/src/env/__init_tls.c
> @@ -41,9 +41,12 @@ void *__copy_tls(unsigned char *mem)
>  #ifdef TLS_ABOVE_TP
>         dtv = (void **)(mem + libc.tls_size) - (libc.tls_cnt + 1);
>
> -       mem += -((uintptr_t)mem + sizeof(struct pthread)) & (libc.tls_align-1);
> +       /* Ensure TP is aligned.  */
> +       mem += -(uintptr_t)TP_ADJ(mem) & (libc.tls_align-1);
>         td = (pthread_t)mem;
>         mem += sizeof(struct pthread);
> +       /* Ensure TLS is aligned after struct pthread.  */
> +       mem += -(uintptr_t)mem & (libc.tls_align-1);
>
>         for (i=1, p=libc.tls_head; p; i++, p=p->next) {
>                 dtv[i] = mem + p->offset;

I took the demo from my first mail and tested your patch with all alignments
up to the page size: They all seem to work fine. Awesome :)

- Phillip

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