cmd/link,debug/elf: mips32, add .gnu.attributes and .MIPS.abiflags sections

MIPS32 uses .gnu.attributes and .MIPS.abiflags sections to mark FP ABI
the object is using, and the kernel will set the correct FP mode for it.

Currrently Go doesn't generate these 2 sections. If we link object
without these 2 sections togather FPXX objects, the result will be FPXX,
which is wrong:
   FP32 + FPXX -> FP32
   FPXX + FP64 -> FP64
   FP32 + FP64 -> reject

These 2 sections is also needed to support FPXX and FP64 in future.

More details about FP32/FPXX/FP64 are explained in:
    https://web.archive.org/web/20180828210612/https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking

Fixes #39677

Change-Id: Ia34e7461dee38a4f575dd8ace609988744512ac1
Reviewed-on: https://go-review.googlesource.com/c/go/+/239217
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Meng Zhuo <mzh@golangcn.org>
2 files changed
tree: c1d0875a1515b6d829816a055f602791b0506deb
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. AUTHORS
  11. codereview.cfg
  12. CONTRIBUTING.md
  13. CONTRIBUTORS
  14. favicon.ico
  15. LICENSE
  16. PATENTS
  17. README.md
  18. robots.txt
  19. SECURITY.md
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