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ctypes.CDLL fails on FreeBSD: ld-elf.so.1: Can't find module with TLS index 1 #92828

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yurivict opened this issue May 16, 2022 · 5 comments
Open

ctypes.CDLL fails on FreeBSD: ld-elf.so.1: Can't find module with TLS index 1 #92828

yurivict opened this issue May 16, 2022 · 5 comments
Labels
OS-freebsd topic-ctypes type-bug An unexpected behavior, bug, or error

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@yurivict
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This code fails on FreeBSD 13 with Python-3.8:

import os
import sys
import ctypes
from ctypes.util import find_library

_RTLD_NOLOAD = os.RTLD_NOLOAD
_SYSTEM_UINT = ctypes.c_uint64 if sys.maxsize > 2 ** 32 else ctypes.c_uint32
_SYSTEM_UINT_HALF = ctypes.c_uint32 if sys.maxsize > 2 ** 32 else ctypes.c_uint16

class _dl_phdr_info(ctypes.Structure):
    _fields_ = [
        ("dlpi_addr", _SYSTEM_UINT),  # Base address of object
        ("dlpi_name", ctypes.c_char_p),  # path to the library
        ("dlpi_phdr", ctypes.c_void_p),  # pointer on dlpi_headers
        ("dlpi_phnum", _SYSTEM_UINT_HALF),  # number of elements in dlpi_phdr
    ]

def match_library_callback(info, size, data):
    print("match_library_callback")
    # Get the path of the current library
    filepath = info.contents.dlpi_name
    if filepath:
        filepath = filepath.decode("utf-8")

        # Store the library controller if it is supported and selected
        self._make_controller_from_path(filepath)
        return 0

libc_name = find_library("c")
print("libc_name="+libc_name)
libc = ctypes.CDLL(libc_name, mode=_RTLD_NOLOAD)

c_func_signature = ctypes.CFUNCTYPE(
            ctypes.c_int,  # Return type
            ctypes.POINTER(_dl_phdr_info),
            ctypes.c_size_t,
            ctypes.c_char_p,
)
c_match_library_callback = c_func_signature(match_library_callback)
data = ctypes.c_char_p(b"")

libc.dl_iterate_phdr(c_match_library_callback, data) # failing line

It fails with the message:

ld-elf.so.1: Can't find module with TLS index 1

This code is from the Python library threadpoolctl that fails with the same error message.
@yurivict yurivict added the type-bug An unexpected behavior, bug, or error label May 16, 2022
@jeremiedbb jeremiedbb mentioned this issue May 16, 2022
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@vukitoso
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Did you manage to solve this problem? If so, how?

@ptrajdos
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ptrajdos commented Aug 6, 2023 •
edited
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Hi,
I've managed to replicate the issue in C (Freebsd 13.2, and GCC: 12.2.0, Clang 14.0.5).
It seems that loading libc via dlopen and then calling dl_iterate_phdr causes the problem.
I hope it will help someone.

Best Regards,
Pawel

#include <link.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>

/**
 * mwe.c
 * Compile via: 
 * gcc -rdynamic mwe.c -o mwe -g -D_GNU_SOURCE
 * or
 * clang -rdynamic mwe.c -o mwe -g -D_GNU_SOURCE 
*/
static int callback(struct dl_phdr_info *info, size_t size, void *data) {
	//A simple callback function
 	printf("Name: \"%s\" (%d segments)\n", info->dlpi_name, info->dlpi_phnum);
 	return 0;
}

typedef int (*lib_func)(int (*callback)(struct dl_phdr_info *, size_t, void *), void* data);

int call_from_libc(){
	/**
	 * Calls dl_iterate_phdr indirectly by loading libc via dlopen
	 * */
	void     *handle  = NULL;
	lib_func  func    = NULL;
	handle = dlopen("/lib/libc.so.7",RTLD_NOW|RTLD_NOLOAD);// Put the name of your libc shared object
	if (handle == NULL){
		fprintf(stderr, "Unable to open lib: %s\n", dlerror());
		return -1;
	 }
	func = dlsym(handle, "dl_iterate_phdr");

	if (func == NULL) {
		fprintf(stderr, "Unable to get symbol\n");
		return -1;
	}

	func(callback, NULL);
	return 0;
}

int main(int argc, char *argv[]) {
	printf("Direct call:\n");
 	dl_iterate_phdr(callback, NULL);//It works

	printf("Indirect call:\n");
 	call_from_libc();//It causes 'ld-elf.so.1: Can't find module with TLS index 1'

 	exit(EXIT_SUCCESS);
}

@yurivict
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yurivict commented Aug 7, 2023

@ptrajdos Thank you very much for this testcase.
I created the FreeBSD bug report with this code.

@yurivict
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yurivict commented Aug 7, 2023 •
edited
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The answer is:

 Konstantin Belousov freebsd_committer 2023-08-07 00:30:20 PDT

This is expected outcome, since libc only provides stubs to satisfy the static
linker.

In the test program, change the "/lib/libc.so.7" path into RTLD_DEFAULT. It
should work then.

@yurivict
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yurivict commented Aug 9, 2023

libc in FreeBSD was modified such that the dl_iterate_phdr will be properly resolved.
This problem should be now fixed in FreeBSD 14 (CURRENT), and will be fixed in FreeBSD 13 after a week once this patch will be merged there.

@ptrajdos ptrajdos mentioned this issue Aug 9, 2023
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@yurivict @serhiy-storchaka @ptrajdos @vukitoso @kumaraditya303
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