* pkg/proc: convert freebsd ptrace code to cgo
There is little point in having cgo call a custom C function, when the same
can be done directly from cgo (with less code and effort). Split the amd64
specific code into ptrace_freebsd_amd64.go. Also avoid mixing C.ptrace()
with syscall.SYS_PTRACE.
This will make further changes easier - no functional change intended.
* pkg/proc: check return values of ptrace calls on freebsd
The return values of the PT_GETNUMLWPS and PT_GETLWPLIST ptrace calls were
previously unchecked. While these should not fail, panic instead of using
-1 with slice allocation/handling.
* pkg/proc: return *amd64util.AMD64Xstate from freebsd ptraceGetRegset
Return a pointer to a struct, rather than a struct - this simplifies the
code in both the caller and the ptraceGetRegset function, while also avoiding
struct copying.
* pkg/proc: fix floating point register setting on freebsd
The original code could never work - PT_SETREGS on freebsd does not
take an iovec, nor does it set FP registers. Furthermore, the xsave
bytes were not stored in the amd64util.AMD64Xstate struct.
Updates #3001
* pkg/proc: re-enable function call injection on freebsd
Floating point registers can now be set and restored correctly.
This is a partial revert of 51090f003bace1f8cc37b8480ffdb6f6cc91fa5a.
Fixes#3001
* pkg/proc: deduplicate register setting code on freebsd
9c5777e762