Code Models

Code models define placement and locality assumptions that assemblers, linkers, and compilers may use when selecting address materialization, displacement, GOT, PLT, and relocation forms. Bedrock 32-bit displacement and direct control-transfer forms are signed, so direct 32-bit relative references cover a -2 GiB to +2 GiB - 1 window.

Bedrock Code Models

Model	Placement contract	Default access strategy
low	static addresses in 0x00000000..0x7fffffff	signed 32-bit absolute data and direct transfers
small	referenced code, data, GOT, and PLT fit one signed 32-bit relative window	PC-relative access; GOT/PLT for interposable symbols
medium	code, GOT, and PLT fit one signed 32-bit window; data placement is unrestricted	direct code; GOT-resolved 64-bit data addresses
high	static high image with internal references in a signed 32-bit displacement window	image-base or PC-relative access with full-width fallback
large	unrestricted 64-bit address space	full-width materialization and indirect transfer

low Model Details

The low model is a static image model whose named code and data lie between 0x00000000 and 0x7fffffff. Code uses direct signed 32-bit branch or call payloads; data uses absolute or base-relative signed 32-bit payloads. The model permits omission of both GOT and PLT.

Its default relocation set is R_BEDROCK_ABS32S, R_BEDROCK_IMM32S, R_BEDROCK_DISP32S, R_BEDROCK_BRDISP32S, and R_BEDROCK_CALL32S. The linker may shrink a direct transfer or address materialization after final placement proves that the result fits a shorter encoding.

small Model Details

The small model is position-independent and assumes that local code, nearby data, the GOT, and the PLT fit the signed 32-bit relative window of the use site or selected base. Code uses direct signed 32-bit transfers; data uses PC-relative or GOTPCREL signed 32-bit materialization.

Its default relocations are R_BEDROCK_BRDISP32S, R_BEDROCK_CALL32S, R_BEDROCK_GOTPCREL32S, R_BEDROCK_PLT32S, and R_BEDROCK_TLSDESC_GOTPCREL32S. The linker may shrink a relative form or replace GOT/TLSDESC access with a direct form when the resolved symbol is local and in range.

medium Model Details

The medium model keeps code, GOT, and PLT within a signed 32-bit relative window but permits data objects anywhere in the 64-bit address space. Code uses direct signed 32-bit transfers. Data normally uses a GOT-resolved 64-bit address reached through a signed 32-bit GOT reference.

Its default relocations are R_BEDROCK_BRDISP32S, R_BEDROCK_CALL32S, R_BEDROCK_GOTPCREL32S, R_BEDROCK_GOT64, R_BEDROCK_PLT32S, and R_BEDROCK_TLSDESC_GOTPCREL32S. A linker may replace a GOT data reference with a direct relative reference when final placement puts the object in range.

high Model Details

The high model is a static high-address image. Internal code may use direct signed 32-bit transfers or image-base-relative addressing. Data uses a PC-relative GOT or an image-base-relative form when in range; the GOT and PLT are image-local or base-relative.

Its default relocations are R_BEDROCK_BRDISP32S, R_BEDROCK_CALL32S, R_BEDROCK_GOTPCREL32S, R_BEDROCK_ABS64, and R_BEDROCK_DISP64. Compact internal references are permitted when final placement proves the signed 32-bit range; full-width and base-relative sequences remain valid.

large Model Details

The large model permits arbitrary placement. Code uses full-width address materialization followed by an indirect transfer when necessary; data, GOT, and PLT addresses are full width.

Its default relocations are R_BEDROCK_ABS64, R_BEDROCK_PCREL64, R_BEDROCK_GOTPCREL64, R_BEDROCK_PLT64, and R_BEDROCK_TLSDESC_GOTPCREL64. Final placement may justify relaxing any full-width form to a shorter encoding.