On Mon, Aug 24, 2020 at 7:05 PM Yonatan Gizachew <emeg...@gmail.com> wrote: > > We were trying to run a go c-shared library on a emulator (Written in C/C++). > We use gccgo compiler to create .so file from test.go file, so that the > runtime could be liked dynamically. Currently we are facing a problem while > packages were imported in main.init. > Here is a disassembly of the main.init function which was called from > runtime.main > https://github.com/Emegua/golang_nuts/blob/master/main_init.S > We tried to debug the issue, and until now, it seems the problem is related > to TLS. > We made breakpoint using b ../../../src/libgo/go/runtime/malloc.go:660. > When the c:= gomcache() is executed, a __tls_get_addr function retrieves some > address from TLS. > Refer to the following bt. > https://github.com/Emegua/golang_nuts/blob/master/gdb_bt_1 > > From runtime.gomcache function here: > https://github.com/Emegua/golang_nuts/blob/663517937f34580288c2d07249ade515a7bf4c44/runtime1.go#L490 > > From the retrieved address (i.e, getg()), now it tries to retrieve its member > variable (called mcache) by accessing to specific index using pointer > dereferencing. > Please see here the disassembled > https://github.com/Emegua/golang_nuts/blob/master/disas_1.S > > After a few steps, it retrieves the correct values c. > > https://github.com/Emegua/golang_nuts/blob/6a246ae7715823688a74581649c77da4369f8717/malloc.go#L661 > But while importing some packages, say runtime package, the same process > (i.e., dereferencing the pointer obtained by __tls_get_addr) retrieves 0x0 > which is nullptr. > > From the following line, we inspected the all dereferenced value of pointer, > step by step. > > The results are as follows. Left column is before the import of runtime, > right column is while importing runtime. As it shows, retrieved pointer is > same for both situation (i.e., 0x7f7ae76d7b18), but it contains different > value so the resulting dereferenced pointer(i.e., c) is also different. > Please refer to the following image. > > gccgo --version > gccgo (Ubuntu 8.4.0-1ubuntu1~18.04) 8.4.0 > > What would be any possible explanation for the segfault?
I don't know what is happening. It appears that somehow you are on a thread that wasn't properly initialized. Could you take a step back and show the steps you took to get to this point? How exactly did you create the .so file? How exactly are you running it? Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcVx7Bffqo5goWBV1HcAQd0HQsN0qSi5VgUOwP4mYSoxjQ%40mail.gmail.com.
