[dpdk-users] Secondary process cannot call functions on hugepages

[Fengkai Sun <qcloud1014@gmail.com>]

Hi list,

Recently I read about the multi-process support of dpdk and found the
feature of keeping the hugepage mappings between primary and secondary
processes very interesting.
Therefore, I made the following experiments:

1. I modify the glibc to make dlopen() map shared libraries on hugepages.
This is done by changing the underlying mapping strategy from mmap to pread.
2. I allocate a continuous address by rte_malloc(), and instruct dlopen()
to map a shared library there, let's call it lib1.so.
3. After dlopen() succeeds, I use dlsym() in the primary process to locate
the global variables and functions in lib1.so, and it turns out they are
correctly mapped and functions can be called without a problem.
4. Because hugepage seems to get away with the effect of ASLR, I record the
address of those global variables and functions in lib1.so, and verify them
in the secondary process.
    The secondary can access the global variables at the same address, but
when it tries to call the function, a segfault occurs.
5. I try to use dlopen() with the same arguments as the primary process in
the secondary process, but it just gives a segfault.

Unfortunately, gdb also gives a segfault when the program starts up, so I
cannot give some useful debug info.

My question is, does dpdk permit functions to be loaded on hugepages and be
called by multiple functions? Though the two processes see the exact same
content on the hugepage, the secondary just cannot call the function on it.

Any intuitive advice is appreciated.

--
Best,
Fengkai