R2js

When to use

Pick this skill when SQL alone can't answer the question:

• r2 commands not surfaced as tables (e.g. ESIL emulation, aae*, agC call-graph dump, p8 raw-byte read at an address, wx to patch bytes, …)
• multi-step r2 scripts where each step depends on r2 state, not just table data
• custom analyses written in r2js (#!js) — typed JS that runs inside r2 with full SDK access
• pivoting from SQL results back into r2 (e.g. drop temporary flags so the next SQL query sees them)

How r2xsql exposes raw r2 access

r2xsql holds a Backend (either LibrBackend or R2PipeBackend) and forwards arbitrary commands through Session::raw_cmd(std::string). From the CLI, raw r2 commands are reachable via:

Recommended pattern: do the analysis pass in r2js, persist its results as r2 flags / comments, then query those from SQL.

Recipe — emulate a function and capture register state

// my_emulate.r2.js
const target = 0x401000;
r2cmd(`s ${target}`);                  // seek
r2cmd("aei; aeim; aeip");              // init ESIL, mem, ip
for (let i = 0; i < 50; i++) r2cmd("aes");   // step 50 instructions
const regs = r2cmd("arj");             // dump registers as JSON
const rax  = JSON.parse(regs).rax;
r2cmd(`CC ESIL: rax=${rax.toString(16)} after 50 steps @ ${target}`);

Then SQL-side:

SELECT text FROM comments WHERE text LIKE 'ESIL:%';

Recipe — bridge query → r2js → query

1. SQL: find candidate addresses.

   SELECT addr FROM funcs WHERE cc > 25;
   

2. r2js: feed each address into a custom pass that doesn't fit SQL:

   const addrs = [0x401000, 0x402000];   // from step 1
   addrs.forEach(a => {
     r2cmd(`s ${a}`);
     const summary = r2cmd("agCd");      // some non-tabular output
     r2cmd(`f sym.complex_${a.toString(16)} 1 ${a}`);  // tag it
   });
   

3. SQL: re-query and the tags are visible:

   SELECT name, addr FROM flags WHERE name LIKE 'sym.complex_%';
   

Raw hex byte patching → use the patches table, not r2js

r2xsql has a SQL write surface for this: INSERT INTO patches(addr, patched_bytes) VALUES(...) stages a raw hex patch, UPDATE patches SET committed = 1 WHERE addr = ... commits it (see the data skill's patches section for the full column set and the commit/undo scoping caveats — commit is table-wide, undo is stack-top-only). Reach for r2js only when patches genuinely can't express what you need: an assembled-instruction patch (wa) or a string/zero-terminated write (wz) instead of raw hex, which patches doesn't support in its current version.

r2cmd("wa nop @ 0x401234");        // assembled patch -- not a `patches` INSERT
r2cmd("Ps");                       // persist via project

Caveats

• Session::raw_cmd bypasses the table layer entirely — there's no parsing, no schema, no pushdown. You're responsible for parsing whatever r2 prints.
• r2js scripts run inside r2 (not inside r2xsql) — they don't see the SQL database directly. Bridge via flags/comments as above.
• Raw passthrough is available on every transport: -q "."/REPL from the CLI, .r2cmd <command> over HTTP, and the host shell in the in-r2 plugin. The raw path bypasses the table layer (no schema, no pushdown).