clj-ebpf.asm — org.clojars.pgdad/clj-ebpf 0.3.3

BPF assembly utilities including label resolution.

Provides symbolic label support for BPF programs, eliminating the need for manual jump offset calculations.

Example: (require '[clj-ebpf.asm :as asm] '[clj-ebpf.dsl :as dsl])

(asm/assemble-with-labels [(dsl/mov :r0 0) (asm/jmp-imm :jeq :r1 0 :success) (dsl/mov :r0 -1) (asm/jmp :done) (asm/label :success) (dsl/mov :r0 1) (asm/label :done) (dsl/exit-insn)])

assemble-with-labels clj

(assemble-with-labels instructions)

Assemble instructions with automatic label resolution.

This is the main entry point for programs using symbolic labels. Handles mixed sequences of:

• Label pseudo-instructions (created with label)
• Symbolic jump instructions (created with jmp-imm, jmp-reg, jmp)
• Regular DSL instructions (byte arrays)

Parameters:

• instructions: Sequence of instructions

Returns: Assembled bytecode (byte array)

Example: (assemble-with-labels [(dsl/mov :r0 0) (jmp-imm :jeq :r1 0 :success) (dsl/mov :r0 -1) (jmp :done) (label :success) (dsl/mov :r0 1) (label :done) (dsl/exit-insn)])

check-bounds clj

(check-bounds data-reg data-end-reg offset fail-label scratch-reg)

Generate bounds check with symbolic label for failure.

Like net/check-bounds but accepts keyword labels.

Parameters:

• data-reg: Register containing data pointer
• data-end-reg: Register containing data_end pointer
• offset: Number of bytes needed
• fail-label: Label (keyword) or offset (number) to jump on failure
• scratch-reg: Scratch register for calculation

Example: (check-bounds :r7 :r8 14 :pass :r9)

check-bounds-dynamic clj

(check-bounds-dynamic data-reg data-end-reg offset-reg fail-label scratch-reg)

Generate bounds check with dynamic offset.

Parameters:

• data-reg: Register containing data pointer
• data-end-reg: Register containing data_end pointer
• offset-reg: Register containing offset value
• fail-label: Label (keyword) or offset (number) to jump on failure
• scratch-reg: Scratch register for calculation

instruction-size clj

(instruction-size insn)

Return the size of an instruction in 8-byte units. Most instructions are 1, but lddw (64-bit immediate load) is 2.

ja clj

jmp clj

(jmp target)

Unconditional jump to symbolic target.

Parameters:

• target: Jump target - keyword label or numeric offset

Example: (jmp :done) ; symbolic (jmp 5) ; numeric

jmp-imm clj

(jmp-imm op dst imm target)

Conditional jump with immediate operand and symbolic target.

Parameters:

• op: Jump operation (:jeq, :jne, :jgt, :jge, :jlt, :jle, :jset, :jsgt, :jsge, :jslt, :jsle)
• dst: Destination register
• imm: Immediate value to compare
• target: Jump target - keyword label or numeric offset

If target is a keyword, it will be resolved during assembly. If target is a number, works like dsl/jmp-imm.

Example: (jmp-imm :jeq :r0 0 :is-zero) ; symbolic (jmp-imm :jeq :r0 0 5) ; numeric (backwards compat)

jmp-reg clj

(jmp-reg op dst src target)

Conditional jump with register operand and symbolic target.

Parameters:

• op: Jump operation
• dst: First register to compare
• src: Second register to compare
• target: Jump target - keyword label or numeric offset

Example: (jmp-reg :jgt :r0 :r1 :greater) ; symbolic (jmp-reg :jgt :r0 :r1 3) ; numeric

label clj

(label name)

Create a label pseudo-instruction. Labels mark positions in the instruction stream for jump targets. They don't generate bytecode - they're resolved during assembly.

Parameters:

• name: Keyword naming the label (e.g., :loop, :error, :done)

Example: (label :my-target)

label? clj

(label? insn)

Check if instruction is a label pseudo-instruction.

real-instruction? clj

(real-instruction? insn)

Check if this counts as a real instruction (not a label). Used for position counting.

resolve-labels clj

(resolve-labels instructions)

Resolve symbolic labels to numeric offsets.

Two-pass algorithm:

1. Collect all label positions
2. Resolve jump targets and filter out labels

Parameters:

• instructions: Sequence of instructions (may include labels and symbolic jumps)

Returns: Sequence of resolved instructions (byte arrays only, no labels)

symbolic-jump? clj

(symbolic-jump? insn)

Check if instruction is a symbolic jump (with keyword target).