nostr:npub1upkp7fd7rc3lrjg23r8gy0wc723vze7mxlx5984ut6zurjzpf5xss4tcwy You have of course seen the classic https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html

nostr:npub1upkp7fd7rc3lrjg23r8gy0wc723vze7mxlx5984ut6zurjzpf5xss4tcwy maybe ltrace, for tracing library calls (vs strace system calls)?

nostr:npub1upkp7fd7rc3lrjg23r8gy0wc723vze7mxlx5984ut6zurjzpf5xss4tcwy As far as "Linux spy tools", `bpftrace` is a neat one.

The *really* arcane things happen lower in the stack here. Architecture specific system call ABI, how a trap/syscall instruction triggers a context switch into kernel mode, how the kernel schedules IO operations, sends commands to drivers, how they actually communicate with hardware with mmio/interrupts/DMA/etc.

But then you could have a full length book just on how printing hello world works.