Comments (3)
Looks like the issue is more general and may not be limited to implib's use from a shared library. I've updated the title and description
from implib.so.
Yup, we ran into this during gh-15 and unfortunately I do not have a good solution for it.
One way to deal with that is to dlopen() the wrapped library with RTLD_DEEPBIND. This would tell dynamic linker to bind the symbols to the library itself and avoid the unfortunate recursion. It would bypass the implib's wrapper, but I think it's the right thing to do when we build implib with visible symbols.
Right, this is one solution. It has a disadvantage of changing the symbol resolution logic which may not be suitable for some users so I decided to not enable it by default. For now users may load library with RTLD_DEEPBIND by using --dlopen-callback
.
It would be great if glibc provided us with APIs for separate library loading and ctor execution...
For completeness, the other potential solution would be to detect the is_lib_loading
case and run dlopen
with RTLD_NOLOAD
(or locate library by hand, by searching for library via dl_iterate_phdr
). The located library could then be used to call dlsym
. Unfortunately it's unclear how to naturally extend this solution to --no-dlopen
or --dlopen-callback
cases.
from implib.so.
For completeness, the other potential solution would be to detect the is_lib_loading case and run dlopen with RTLD_NOLOAD (or locate library by hand, by searching for library via dl_iterate_phdr). The located library could then be used to call dlsym. Unfortunately it's unclear how to naturally extend this solution to --no-dlopen or --dlopen-callback cases.
Actually it's possible to just call dlopen
with default arguments (i.e. without RTLD_NOLOAD
) inside the constructor and it will return the loaded library. So we can expect that in most cases just calling the load callback second time when is_lib_loading
is true will return the handle.
In --no-dlopen
case we could search for library via dl_iterate_phdr
and then dlopen
it.
This is still fragile though. In particular
- load callback needs to be reentrant
- the approach will not work if library is loaded by custom loader
from implib.so.
Related Issues (20)
- Option to hide global symbols HOT 3
- Android support? HOT 5
- --no-dlopen option defines NO_DLOPEN in *.so.init.c not correctly HOT 1
- Suggestion for an alternative implementation for --no-dlopen option HOT 15
- function called during library load HOT 7
- question regarding multi-threading limitation HOT 1
- question about cfi_adjust_cfa_offset after just entering into fuction HOT 9
- [Feature Request] mipsel support HOT 17
- Creating a shared library from init.c and tramp.S HOT 5
- Invalid asm for arm when there are more than 256/4096 functions HOT 4
- Aarch64 trampoline asm can't handle large $number HOT 3
- Library soname should be used as load name HOT 4
- Calling exit after library loading failure is not really safe HOT 2
- Shebang should use python3 from path HOT 1
- Support for exported variables HOT 2
- Question about LLVM HOT 4
- Hide the generated symbols HOT 3
- missing .note.GNU-stack section implies executable stack HOT 2
- Generating vtables and typeinfos HOT 7
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from implib.so.