cmd/link/internal/loong64: use BREAK 0 as the code pad sequence
As the comment on CodePad goes, we "might want to pad with a trap
instruction to catch wayward programs". The current behavior of
zero-padding is equivalent to padding with an instruction of 0x00000000,
which is invalid according to the LoongArch manuals nevertheless, but
rumor has it that some early and/or engineering samples of Loongson
3A5000 recognized it (maybe behaving like NOP). It is better to avoid
undocumented behavior and ensure execution flow would not overflow the
pads.
Change-Id: I531b1eabeb355e9ad4a2d5340e61f2fe71349297
Reviewed-on: https://go-review.googlesource.com/c/go/+/475616 Reviewed-by: abner chenc <chenguoqi@loongson.cn> Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com>