Dear all, I'm having a rather odd problem, and I think it all boils down to what compiler/linker flags I am using. As an overview, I am trying to implement subcontexts in virtual memory. Basically, I am writing two programs: a server program and a client program. The server program creates a file, foo, and dumps all of its memory into this file (by parsing /proc/self/maps) including, hopefully, any functions that happen to be implemented within it. The client program processes foo and maps all of the memory within it into its own virtual memory. Ideally, once this happens, the client program can make function calls into the server programs memory, even through the server program has already terminated. Here's where things get sticky. Say that I have functions "bar" and "baz" in the server program that contains a very simple print statement within it. The problem presents itself when a client program tries to call this function. If "bar" has been called directly in the execution of the server program (i.e., when it is dumping its memory to the file), everything works just fine. If instead bar is NOT called in the server program in this manner, a segmentation fault occurs. What's even weirder is that if "bar" is called but "baz" isn't, a call to "baz" does NOT cause a segmentation fault. When I analyze the segmentation fault in gdb, it seems like the stack has been corrupted somewhere. A "where" command eventually elicits an address of 0x0. I've been compiling using -fPIE for the compiler and -pie for the linker, as the code needs to be position independent so that the memory locations that the client server is trying to map don't overlap with its own maps. Other than that, I've tried every combination of flags known to man. I've tried various combinations of: -fno-plt -Wl,-z,now -Wl,-z,relro I tried these because I thought the issue might be the difference between the PLT/GOT in the server program vs. in the client program. I also thought that the problem might lay in the generation of the PLT/GOT in the server program. Both of these debugging paths seem to have been misguided, as neither of them were fruitful. -static-pie -fPIC -pic My understanding of these is that under my circumstances, -fPIE and -pie do the same thing as -fPIC and -pic. Any and all help, feedback, or guidance would be greatly appreciated. Many thanks, Fay
