I want to create a chroot environment that has access to hand-picked programs but is completely isolated from the rest of the system.

I created three folders in this chroot folder: bin, lib, lib64. I then copied an executable, in this case /bin/bash into bin. ldd /bin/bash shows this output:

linux-vdso.so.1 =>  (0x00007ffff01f6000)
libtinfo.so.5 => /lib/x86_64-linux-gnu/libtinfo.so.5 (0x00007f35ed501000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f35ed2fd000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f35ecf33000)
/lib64/ld-linux-x86-64.so.2 (0x00007f35ed72a000)

I can copy all of these libraries, except linux-vdso.so.1. If I sudo find / -name "linux-vdso.so.1" I get no output.

What should I do now?


The VDSO is special, it is directly provided by the kernel.

You see that it has addresses, even if it doesn't have a file name, so it got mapped fine. You don't need to do anything to get the VDSO in the chroot.

The kernel VDSO is a collection of kernel functions that don't always require a mode switch, e.g. reading exact timers is handled by the rdtsc assembler instruction on processors that support it, and by a kernel syscalls on processors that don't. If this were a normal system call, modern processors would have to deal with the syscall overhead for a single non-privileged assembler instruction, and if rdtsc was always inlined, programs would no longer run on older machines.


You should try running your programs ;-)

linux-vdso.so.1 is a virtual library that is automatically mapped in the address space of a process by the kernel, see vdso(7). It does not exist in the filesystem.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.