ifunc references to shared library functions are not resolved correctly

[monkuous]

When an ifunc in a shared library is referenced, mlibc's dynamic linker currently resolves it to the resolver function instead of the target function. This is because such references are linked with the R_<arch>_JUMP_SLOT and R_<arch>_GLOB_DAT relocations instead of the R_<arch>_IRELATIVE one. The dynamic linker is supposed to handle this by detecting that the resolved symbol is STT_GNU_IFUNC and dereferencing it, but mlibc doesn't do this.

Test case

test1.c:

static int foo_impl(void) {
    return 1;
}

static int (*foo_resolver(void))(void) {
    return foo_impl;
}

int foo(void) __attribute__((ifunc("foo_resolver")));

test2.c:

#include <stdio.h>

int foo(void);

int main(void) {
    printf("%d\n", foo());
}

$ gcc test1.c -o libtest.so -shared
$ gcc test2.c -o test -L. -ltest -Wl,-rpath=.
$ ./test
# expected output (glibc): 1
# actual output (mlibc): address of foo_impl, truncated to 32 bits and interpreted as signed