Re: RFC: Treat RTLD_GLOBAL as unique to namespace when used with dlmopen

["Carlos O'Donell" <carlos at redhat dot com>]

On 07/24/2015 02:37 PM, Carlos O'Donell wrote:
> With a few more patches I get *almost* all the way there:

[carlos@athas dlmopen_expt]$ ./main
main(): lmid from dlopen(NULL) is 0 (handle = 0x0x7feda4b49168)
main(): dlmopen LM_ID_NEWLM ./libabc.so   RTLD_GLOBAL
main(): lmid from dlopen("libabc.so") is 1 (handle = 0x0x1cc7440)
main(): invoking abc_start()
    Called abc_start()
    abc_start(): lmid from dlopen(NULL) is 1 (handle = 0x0x1cc7440)
    abc_start(): dlmopen LM_ID_BASE  ./libdef.so   RTLD_GLOBAL
    abc_start(): dlopen              ./libjkl.so   RTLD_GLOBAL
    abc_start(): dlopen              ./libmno.so   RTLD_LOCAL
    abc_start(): dlopen              ./libqrs.so   RTLD_LOCAL
    abc_start(): invoking qrs_start()
        Called qrs_start()
        qrs_start(): lmid from dlopen(NULL) is 1 (handle = 0x0x1cc7440)
        qrs_start(): lookup of "abc" succeeded
        qrs_start(): lookup of "def" failed
        qrs_start(): lookup of "jkl" succeeded
        qrs_start(): lookup of "mno" failed
        qrs_start(): lookup of "main" failed
main(): lookup of "abc" failed
main(): lookup of "def" succeeded
main(): lookup of "jkl" failed
main(): lookup of "mno" failed
[carlos@athas dlmopen_expt]$ echo $?
0

I'm now passing your test.

I wonder if there is anything more complicated we can throw at it?

The design is solidly based on first principles about dynamic
loading, so I don't see anything we can't solve by reworking
the implementation slightly.

I guess the next step is to get all of this into master and start
telling people to use it to solve isolation problems like plugins.
Perhaps write a small blog post about plugin isolation.

Cheers,
Carlos.