Signed-off-by: Timo Beckers <timo@isovalent.com>

Signed-off-by: Timo Beckers <timo@isovalent.com>

This patch implements the sigsetAdd function to add a signal to a signal set.
Care was taken to make this build and run correctly on different GOOS and
GOARCH combinations.

Signed-off-by: Timo Beckers <timo@isovalent.com>

sys.maskProfilerSignal() locks the calling goroutine to its underlying OS
thread and blocks the SIGPROF signal from interrupting the thread.

sys.unmaskProfilerSignal() reverses the operation and should be used in
tandem to properly restore OS thread state afterwards.

Add a wrapper around unix.PthreadSigmask added in a recent version of x/sys.

Signed-off-by: Timo Beckers <timo@isovalent.com>

If a thread receives a signal while blocked in BPF_PROG_LOAD, the verifier
can cooperatively interrupt itself by checking pending signals for the thread
and return -EAGAIN from the syscall to request userspace to retry.

When a Go program is built and run with pprof enabled, threads are routinely
sent a SIGPROF to make them dump profiling information, which can lead to a
runaway reaction if the program takes longer to verify than the interrupt
frequency. To prevent this, mask SIGPROF before calling BPF_PROG_LOAD and
remove it when done.

Signed-off-by: Timo Beckers <timo@isovalent.com>