回复： Failed in using LD_PRELOAD to hook mmap system call in qemu(through libvirt)

On Thu, Jan 06, 2022 at 07:44:25PM +0800, Xiong。 wrote: &gt; Dear sir: &gt; &nbsp; &nbsp; I want to hook mmap system call in qemu, and I use &gt; libvirt to passthrough the environment argument like this: &gt;&nbsp; <qemu:commandline&gt; &gt;&nbsp; &nbsp; <qemu:env name='LD_PRELOAD' value='/glibcHookMMAP.so'/&gt; &gt;&nbsp; </qemu:commandline&gt; &gt; But it failed. I can hardly find out what is the matter! &gt; The log in libvirt like this:ERROR: ld.so: object &gt; '/glibcHookMMAP.so' from LD_PRELOAD cannot be preloaded &gt; (cannot open shared object file): ignored.&nbsp; &nbsp; Firstly, &gt; I think it's the problem of authority. But the file &gt; glibcHookMMAP.so has been done with command `chmod 777`. &gt; My environment is as follows: Ubuntu 18.04.2 Linux &gt; 5.4.0-92 libvirt 4.0.0 qemu 2.11.1 On Thu, Jan 06, 2022 at 09:47:25PM +0800, Daniel P. Berrangé。 wrote: &gt; Aside from normal file permissions, the other likely problem on Ubuntu &gt; will be AppArmor policy. It likely won't allow QEMU to load files from &gt; the / directory - if you put your .so in /usr/local/lib it might &gt; work. On Thu, Jan 07, 2022 at 09:27:25AM +0800, Xiong。 wrote: &gt; I have a try, but it does not work and makes the same warning: &gt; ld.so: object '/usr/local/lib/glibcHookMMAP.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored. &gt; However, I use qemu command directly and it works. Command is like this: &gt; sudo LD_PRELOAD=/usr/local/lib/glibcHookMMAP.so qemu-system-x86_64 -enable-kvm ...(other args). &gt; After that, I get print information with my hook program. And I think the problem is in passing the environment args in libvirt. Sorry, I find out what's the matter. The AppArmor policy limits the libvirt, and modifing configuration works. Thank you for your advise!