[PATCH 0/3] Relocation-related fixes

[Anup Patel]

On Sun, Sep 17, 2023 at 11:22 PM Vivian Wang <dramforever at live.com> wrote:
>
> I was looking into various implementations of "DIY" runtime relocations.
> One thing led to another, and here are three patches.
>
> This area does seem fairly obscure, so advice on proper/better ways to
> do things are definitely needed. Thanks in advance for any help.
>
> Patch 1 fixes a crash on RV32 that happens to 50% of built binaries
> essentially randomly.
>
> Patch 2 removes handling of R_RISCV_{32,64}. Why they have been added in
> the first place is a complete mystery to me, since these are for dynamic
> linking only, which is simply not a thing here. I've also never seen a
> toolchain generate these for *static*-pie. And yes the generated binary
> boots fine.
>
> From what I can tell, Linux, musl, glibc all only handle
> R_RISCV_RELATIVE for static-pie. (Okay, also IRELATIVE, but just don't
> use ifuncs.) The only other place I can find that does anything with
> .dynsym is U-Boot's RISC-V relocation code [1], and the code is there
> without explanation either.
>
> Maybe some ancient toolchains generated R_RISCV_{32,64} for static
> linking? I have no idea.
>
> Since we don't need .dynsym, I went ahead and did patch 3. I tried
> fiddling around with -fvisibility= but it seems that, given that OpenSBI
> is built as a static library, --exclude-libs ALL looked liked the
> simplest solution. Or should we just /DISCARD/ .dynsym etc. instead?
>
> Cc'd Vincent Chen - Since you're the author of 0f20e8adcf42 "firmware:
> Support position independent execution" I'm hope you can give some
> insight. Thanks in advance.
>
> [1]: https://github.com/u-boot/u-boot/commit/e8e39597a33cc53aacbaf4ef5cae60ed86d6a20a
>
> Vivian Wang (3):
>   firmware: Remove ALIGN in .rela.dyn in linker script
>   firmware: Remove handling of R_RISCV_{32,64}
>   Makefile: Add --exclude-libs ALL to avoid .dynsym

I quickly tried this series with both GCC 12.2.0 and CLANG 14.0.0
on the RV64 virt machine and RV32 virt machine. It worked fine
at my end.

Applied this series to the riscv/opensbi repo.

Thanks,
Anup

>
>  Makefile                |  1 +
>  firmware/fw_base.S      | 22 ----------------------
>  firmware/fw_base.ldS    |  7 -------
>  include/sbi/riscv_elf.h |  8 --------
>  4 files changed, 1 insertion(+), 37 deletions(-)
>
> --
> 2.41.0
>
>
> --
> opensbi mailing list
> opensbi at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/opensbi