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Rework Nonstandard Relocations #458

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33 changes: 18 additions & 15 deletions riscv-elf.adoc
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Expand Up @@ -556,15 +556,6 @@ Description:: Additional information about the relocation
<|
|===

Nonstandard extensions are free to use relocation numbers 192-255 for any
purpose. These vendor-specific relocations must be preceded by a
`R_RISCV_VENDOR` relocation against a vendor ID symbol.

Where possible, tools should present relocation as their vendor-specific
relocation types, otherwise a generic name of `R_RISCV_CUSTOM<enum value>` must
be shown. Data contained in paired `RISCV_VENDOR` can be used to select the
appropriate vendor when performing relocations.

This section and later ones contain fragments written in assembler. The precise
assembler syntax, including that of the relocations, is described in the
_RISC-V Assembly Programmer's Manual_ <<rv-asm>>.
Expand All @@ -576,15 +567,27 @@ and fill the space with a single ULEB128-encoded value.
This is achieved by prepending the redundant `0x80` byte as necessary.
The linker must not alter the length of the ULEB128-encoded value.

==== Vendor identifiers
==== Nonstandard Relocations (a.k.a. Vendor-Specific Relocations)

Vendor identifiers are dummy symbols used in the corresponding `R_RISCV_VENDOR`
relocation (irrespective of ELF class/XLEN) and must be unique amongst all
vendors providing custom relocations. Vendor identifiers may be suffixed with a
tag to provide extra relocations for a given vendor.
Nonstandard extensions are free to use relocation numbers 192-255 for any
purpose. These vendor-specific relocations must be preceded by a
`R_RISCV_VENDOR` relocation against a vendor identifier symbol. The preceding
`R_RISCV_VENDOR` relocation is used by the linker to choose the correct
implementation for the associated nonstandard relocation.

The vendor identifier symbol should be a defined symbol and should set the type
to `STT_NOTYPE`, binding to `STB_LOCAL`, and the size of symbol to zero.

Vendor identifiers must be unique amongst all vendors providing custom
relocations. Vendor identifiers may be suffixed with a tag to provide extra
relocations for a given vendor.

NOTE: Please refer to the _RISC-V Toolchain Conventions_
<<rv-toolchain-conventions>> for the full list.
<<rv-toolchain-conventions>> for the full list of vendor identifiers.

Where possible, tools should present relocation as their vendor-specific
relocation types, otherwise a generic name of `R_RISCV_CUSTOM<enum value>` must
be shown.

==== Calculation Symbols

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