[PATCH] elf: Initialize tunables_env_alias with loop to avoid memset

[H.J. Lu]

On Sat, Sep 7, 2024 at 10:05 AM Jesse Huang <jesse.huang@sifive.com> wrote:
>
> In static binaries, __tunables_init is called before the IREL relocation
> is performed. This causes a problem where IFUNC for memset is provided,
> because the initializer list here is translated to a call to memset,
> which gets redirected to the PLT.

Why doesn't dl-symbol-redir-ifunc.h work for you?

> At the moment, all of the GOT entries still points to the top of the PLT,
> thus the call first jump to the entry of memset in PLT, then jump to the
> first entry of PLT, that finally leads to a infinite loop.
>
> Fixed by using a for loop to initialize the array.
> ---
>  elf/dl-tunables.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index 147cc4cf23..33f88ccf55 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -301,7 +301,9 @@ __tunables_init (char **envp)
>      return;
>
>    enum { tunable_num_env_alias = array_length (tunable_env_alias_list) };
> -  struct tunable_toset_t tunables_env_alias[tunable_num_env_alias] = { 0 };
> +  struct tunable_toset_t tunables_env_alias[tunable_num_env_alias];
> +  for (int i = 0; i < tunable_num_env_alias; i++)
> +    tunables_env_alias[i] = (struct tunable_toset_t) { NULL, NULL, 0 };
>
>    while ((envp = get_next_env (envp, &envname, &envval, &prev_envp)) != NULL)
>      {
> --
> 2.46.0
>


-- 
H.J.