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From: Florian Weimer <fweimer@redhat.com>
To: Fangrui Song via Libc-alpha <libc-alpha@sourceware.org>
Subject: Re: [PATCH] elf: Remove fallback to the start of DT_STRTAB for dladdr
Date: Mon, 02 May 2022 08:56:21 +0200	[thread overview]
Message-ID: <87sfps8lt6.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <20220501215049.2143788-1-maskray@google.com> (Fangrui Song via Libc-alpha's message of "Sun, 1 May 2022 14:50:49 -0700")

* Fangrui Song via Libc-alpha:

> When neither DT_HASH nor DT_GNU_HASH is present, the code scans
> [DT_SYMTAB, DT_STRTAB). However, there is no guarantee that .dynstr
> immediately follows .dynsym (e.g. lld typically places .gnu.version
> after .dynsym).

The code is compatible with lld because it always generates a hash
table.  Maybe it was added to support old binaries without a hash table.
So we would have to check if such binaries exist from the early
libc.so.6 days (or check if binutils every generated ELF binaries
without a hash table).  The glibc comment isn't clear if this was added
because it was required at the time, or just because it seemed a good
idea.

I couldn't find any binaries with DT_SYMTAB, but without DT_HASH or
DT_GNU_HASH in my collection, but doesn't mean that they don't exist.

Thanks,
Florian


  reply	other threads:[~2022-05-02  6:56 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-01 21:50 Fangrui Song
2022-05-02  6:56 ` Florian Weimer [this message]
2022-05-02  7:04   ` Fangrui Song
2022-05-02  7:21     ` Florian Weimer
2022-05-02  7:30       ` Fangrui Song
2022-05-02  8:26         ` Florian Weimer
2022-05-02  8:34 ` Florian Weimer
2022-05-02 16:06   ` Fangrui Song

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