jolt generate

Generate target specifications and linker scripts for custom memory layouts

Overview

The jolt generate command provides utilities for advanced users who need to customize the RISC-V target specification or linker script for their guest programs. This is useful when working with custom memory layouts or non-standard build configurations.

Subcommands

jolt generate target

Generates a custom RISC-V target specification JSON file.

jolt generate target [OPTIONS]

--profile · string

Use a predefined target profile

--target · string

Specify a custom target triple

--output · string · default: "<target-triple>.json"

Output path for the generated target specification (short: -o)

Example:

# Generate target spec from a profile
jolt generate target --profile riscv64imac-unknown-none-elf -o my-target.json

# Generate target spec from a custom triple
jolt generate target --target riscv64imac-unknown-none-elf -o custom.json

The generated JSON file contains the complete target specification including:

• Architecture settings (data layout, pointer width)
• ABI configuration
• Supported features
• Linker configuration

You can then use this target specification with rustc --target=my-target.json for custom builds.

jolt generate linker

Generates a linker script with custom memory layout.

jolt generate linker [OPTIONS]

--output · string · default: "linker.ld"

Output path for the generated linker script (short: -o)

--ram-start · hex

Starting address for RAM

--ram-size · hex

Size of RAM region

--stack-size · hex

Size of the stack region

--heap-size · hex

Size of the heap region

Example:

# Generate linker script with custom memory layout
jolt generate linker -o custom-linker.ld

# The generated script will include memory regions and sections
# that match your specified layout

The generated linker script defines:

• Memory regions (RAM, ROM, etc.)
• Section placements (.text, .data, .bss, .heap, .stack)
• Entry point and initialization code locations

Use Cases

Custom Memory Layout

When you need a specific memory layout for your guest program:

# Generate custom linker script
jolt generate linker -o custom.ld

# Use it with build
RUSTFLAGS="-C link-arg=-Tcustom.ld" jolt build

Cross-Compilation

When targeting a custom RISC-V variant:

# Generate target specification
jolt generate target --target riscv64gc-unknown-linux-gnu -o riscv64gc.json

# Build with custom target
jolt build --target riscv64gc.json

Debugging Build Issues

Generate the default configuration to understand what Jolt uses:

# See the default target spec
jolt generate target --profile riscv64imac-unknown-none-elf

# See the default linker script
jolt generate linker

Notes

Most users do not need these commands. The default target specification and linker script work for typical zkVM programs.

Custom target specifications must be compatible with RV64IMAC instruction set. Jolt requires specific RISC-V features to function correctly.

Related Commands

• jolt build - Build guest programs (uses target specs internally)
• jolt new - Create new projects (includes default configuration)