Update ISA documentation

* Add section numbers
* Add glossary formatting for fields
* Use consistent field names
* Add appendix with opcode table
* Add ISA version information
* Add text about underflow, overflow, and division by zero
* Add other text based on info in other documents

Signed-off-by: Dave Thaler <[email protected]>

Author: dthaler

README.md

@@ -0,0 +1,27 @@
+# eBPF Standard Documentation
+
+This repository is a working draft of standard eBPF documentation
+to be published by the eBPF Foundation in PDF format.
+
+The authoritative source from which it is built is expected to be
+in the Linux kernel.org repository, but not be Linux specific.
+
+A GitHub mirror should be used, as is presently done for libbpf and
+bpftool, so that other platforms and tools can easily use it.
+As such, the documentation uses the subset of RST that GitHub
+renders correctly.
+
+The documentation can be IETF RFC style MUST/SHOULD/MAY language
+if desired.  It does not currently do so.
+
+## Questions
+
+1. Any objections to the github mirror approach?
+
+2. Should we include or exclude Linux implementation notes
+   and Clang implementation notes?
+
+3. How do we handle the legacy packet instructions?
+
+4. How do we handle the wide instructions that reference
+   map fd, map indices, BTF ids, and BPF callbacks?

isa/README.md

@@ -8,6 +8,8 @@ Some documentation links include:
 * https://www.kernel.org/doc/Documentation/networking/filter.txt
 * https://pchaigno.github.io/bpf/2021/10/20/ebpf-instruction-sets.html
 * https://www.kernel.org/doc/html/latest/bpf/bpf_design_QA.html#instruction-level-questions
+* https://lore.kernel.org/bpf/[email protected]/
+* https://github.com/iovisor/bpf-docs/pull/26/files
 
 Some implementation links include: