[Bug ld/20475] Linking PIC executables with a linker script that does not place _GLOBAL_OFFSET_TABLE_ results in incorrect relocation

[whitequark at whitequark dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=20475

whitequark at whitequark dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|FIXED                       |---

--- Comment #9 from whitequark at whitequark dot org ---
Reopening since further testing indicates that Alan's suggestion only worked
partially. My minimal testcase, as described in the first comment, works as
expected now, but the non-minimized one crashes, in a different way.
Specifically, it contains the rough equivalent of the following C code in Rust
(built as -fPIC as before):

    struct fmt {
      void (*fn)(void *arg);
      void *arg;
    }

    void f() {
      struct fmt x = {
        .fn  = h,
        .arg = ...,
      };
      g(&x);
    }

    void g(struct fmt *x) {
      x->fn(x->arg);
    }

    void h(void *arg);

The way it crashes is when calling x->fn(); it jumps into a garbage address.

It is not yet clear to me what is the root cause. However, I suspect that
R_OR1K_GOT16 is at fault, because pinning _GLOBAL_OFFSET_TABLE_ to the
beginning of .got as before makes the code work as expected.

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