[release-branch.go1.18] runtime: make static/dynamic startup detection work with musl on ppc64le
The glibc loader explicitly sets the first doubleword on the stack (R1)
to $0 to indicate it was dynamically loaded.
An ELFv2 ABI compliant loader will set R3/R4 to argc/argv when starting
the process, and R13 to TLS. musl is not compliant. Instead it passes
argc/argv like the kernel, but R3/R4 are in an undefined state and R13
is valid.
With the knowledge above, the startup code can be modified to
dynamically handle all three cases when linked internally.
Fixes #51874
Change-Id: I5de33862c161900d9161817388bbc13a65fdc69c
Reviewed-on: https://go-review.googlesource.com/c/go/+/394654 Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Paul Murphy <murp@ibm.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Trust: Paul Murphy <murp@ibm.com>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/394794
Trust: Emmanuel Odeke <emmanuel@orijtech.com>