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Date: Thu, 26 Jun 2014 10:50:08 +0300
From: Timo Teras <timo.teras@....fi>
To: Isaac Dunham <ibid.ag@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: ELF loader rejects older glibc binary
On Wed, 25 Jun 2014 20:59:24 -0700
Isaac Dunham <ibid.ag@...il.com> wrote:
> Long version:
> I'm trying to use a Brother DCP7065DN network printer with Alpine
> Linux; the drivers
> are closed-source though modified binaries are redistributable.
> The format used is a binary format having some relationship to PCL;
> I can't reverse-engineer it, so I'm stuck using the binary drivers
> for now.
> The drivers in question may be found here:
> http://support.brother.com/g/b/downloadlist.aspx?c=us&lang=en&prod=dcp7065dn_all&os=128
>
> I grabbed the "LPR printer driver".
> After extracting it (ar x dcp7065*deb; tar xvzf data.tar.gz),
> I found the binaries in
> usr/local/Brother/Printer/DCP7065DN/{inf,lpd}/;
> the one I'd suggest poking at first is
> "usr/local/Brother/Printer/DCP7065DN/lpd/rawtobr3" (I previously
> determined that rawtobr3 does all the conversions).
> After locating the binaries and verifying with file that they were
> dynamically linked ELF binaries, I ran ldd.
> When this failed with the message:
> ldd: rawtobr3: Not a valid dynamic program
> I then ran "strace ldd rawtobr3"; the output indicates that musl
> mmap'd it and failed without trying to run it:
>
> ---start strace output---
> execve("/usr/bin/ldd", ["ldd", "rawtobr3"], [/* 19 vars */]) = 0
> open("rawtobr3", O_RDONLY|O_LARGEFILE) = 3
> read(3,
> "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\2\0\3\0\1\0\0\0\324\207\4\0104\0\0\0"...,
> 936) = 936 mmap2(0x8048000, 49152, PROT_READ|PROT_EXEC, MAP_PRIVATE,
> 3, 0) = 0x566f1000 munmap(0x566f1000, 49152) = 0
> writev(2, [{"ldd: rawtobr3: Not a valid dynam"..., 43}, {NULL, 0}],
> 2ldd: rawtobr3: Not a valid dynamic program ) = 43
> exit_group(1) = ? +++ exited with 1 +++
> ---end strace output---
>
> strings suggests that it expects glibc 2.1 ABI, and that almost all
> the symbol requirements are met (_IO_stdin_used being the possible
> exception).
Do note that Alpine Linux runs grsec which includes PaX features. One
is that text relocations are disabled by default.
Try first:
paxctl -c -pem /path/to/rawtobr3
if it makes any difference.
If it was missing symbol, you should get an error message with the
symbol name(s) that are missing.
/Timo
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