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From: Florian Weimer <fweimer@redhat.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org,  "H . J . Lu" <hjl.tools@gmail.com>
Subject: Re: [RFC] elf: Add elf checks for main executable
References: <20211118195547.3362263-1-adhemerval.zanella@linaro.org>
Date: Thu, 18 Nov 2021 21:00:03 +0100
In-Reply-To: <20211118195547.3362263-1-adhemerval.zanella@linaro.org>
 (Adhemerval Zanella's message of "Thu, 18 Nov 2021 16:55:47 -0300")
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* Adhemerval Zanella:

> +static inline void
> +_dl_check_ehdr (struct link_map *main_map)
> +{
> +  ElfW(Ehdr) *ehdr = (void *) main_map->l_map_start;
> +  int err = _dl_elfhdr_check (ehdr);
> +  if (err != DL_ELFHDR_OK)
> +    _dl_fatal_printf ("program loading error: %s\n", _dl_elfhdr_errstr (err));
> +}

I think you need to iterate through the load segments and see if there
is one with p_offset == 0 and p_memsz > 0 (the ELF header is smaller
than a page).  That's the one to use for this check.  If there is no
such segment, we have to skip the check.

Thanks,
Florian