[PATCH] elf: Support at least 32-byte alignment in static dlopen

[Alistair Francis]

On Fri, Jul 10, 2020 at 1:29 PM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> Otherwise loading a dynamically linked libc with rseq support fails,
> as result of the __rseq_abi TLS variable, which has an alignment
> of 32 bytes.

Fixes the RV32 regressions:

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Tested-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

>
> ---
>  csu/libc-tls.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/csu/libc-tls.c b/csu/libc-tls.c
> index 06e76bd395..3f1655f264 100644
> --- a/csu/libc-tls.c
> +++ b/csu/libc-tls.c
> @@ -112,6 +112,12 @@ __libc_setup_tls (void)
>    size_t tcb_offset;
>    const ElfW(Phdr) *phdr;
>
> +  /* libc.so with rseq has TLS with 32-byte alignment.  Static dlopen
> +     requires at least 32-byte alignment as well, otherwise loading
> +     libc.so will always fail.  */
> +  if (max_align < 32)
> +    max_align = 32;
> +
>    struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
>
>    /* Look through the TLS segment if there is any.  */
>