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Add missing relocations and segment flags to the documentation. #222

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Mar 14, 2024
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Add missing relocations and segment flags to the documentation. #222

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b9b9a4a
Add missing relocations and segment flags to the documentation.
kateinoigakukun Mar 11, 2024
c32222a
Fix typo reject -> avoid
kateinoigakukun Mar 11, 2024
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5 changes: 5 additions & 0 deletions DynamicLinking.md
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Expand Up @@ -161,6 +161,11 @@ relocation types for accessing data and functions address relative to
(`-fPIC`) where absolute function addresses are not known at link time.
- `17 / R_WASM_MEMORY_ADDR_REL_SLEB64` - the 64-bit counterpart of
`R_WASM_MEMORY_ADDR_REL_SLEB`.
- `21 / R_WASM_MEMORY_ADDR_TLS_SLEB` (in LLVM 12.0) - an offset from the
`__tls_base` symbol encoded as a 5-byte [varint32]. Used for PIC case to reject
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absolute relocation.
- `25 / R_WASM_MEMORY_ADDR_TLS_SLEB64` (in LLVM 13.0) - the 64-bit counterpart
of `R_WASM_MEMORY_ADDR_TLS_SLEB`.

All code that gets linked into a WebAssembly dynamic library must be compiled
as position independant. The corresponding absolute reloction types
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18 changes: 15 additions & 3 deletions Linking.md
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Expand Up @@ -127,16 +127,27 @@ of `R_WASM_MEMORY_ADDR_SLEB`. A 64-bit linear memory index encoded as a 10-byte
- `16 / R_WASM_MEMORY_ADDR_I64` (since LLVM 11.0) - the 64-bit counterpart of
`R_WASM_MEMORY_ADDR`. A 64-bit linear memory index encoded as a [uint64], e.g.
taking the 64-bit address of a C++ global in a static data initializer.
- `18 / R_WASM_TABLE_INDEX_SLEB64` (in LLVM `master`) - the 64-bit counterpart
- `18 / R_WASM_TABLE_INDEX_SLEB64` (in LLVM 12.0) - the 64-bit counterpart
of `R_WASM_TABLE_INDEX_SLEB`. A function table index encoded as a 10-byte
[varint64]. Used to refer to the immediate argument of a `i64.const`
instruction, e.g. taking the address of a function in Wasm64.
- `19 / R_WASM_TABLE_INDEX_I64` (in LLVM `master`) - the 64-bit counterpart of
- `19 / R_WASM_TABLE_INDEX_I64` (in LLVM 12.0) - the 64-bit counterpart of
`R_WASM_TABLE_INDEX_I32`. A function table index encoded as a [uint64], e.g.
taking the address of a function in a static data initializer.
- `20 / R_WASM_TABLE_NUMBER_LEB` (in LLVM `master`) - a table number encoded as
- `20 / R_WASM_TABLE_NUMBER_LEB` (in LLVM 12.0) - a table number encoded as
a 5-byte [varuint32]. Used for the table immediate argument in the table.*
instructions.
- `22 / R_WASM_FUNCTION_OFFSET_I64` (in LLVM 12.0) - the 64-bit counterpart
of `R_WASM_FUNCTION_OFFSET_I32`. A byte offset within code section for the
specific function encoded as a [uint64].
- `23 / R_WASM_MEMORY_ADDR_LOCREL_I32` (in LLVM 13.0) - a byte offset between
the relocating address and a linear memory index encoded as a [uint32]. Used
for pointer-relative addressing.
- `24 / R_WASM_TABLE_INDEX_REL_SLEB64` (in LLVM 13.0) - the 64-bit counterpart
of `R_WASM_TABLE_INDEX_REL_SLEB`. A function table index encoded as a 10-byte
[varint64].
- `26 / R_WASM_FUNCTION_INDEX_I32` (in LLVM 17.0) - a function index encoded as
a [uint32]. Used in custom sections for function annotations (`__attribute__((annotate(<name>)))`).

**Note**: Please note that the 64bit relocations are not yet stable and
therefore, subject to change.
Expand Down Expand Up @@ -233,6 +244,7 @@ where a `segment` is encoded as:
The current set of valid flag for segments are:
- `1 / WASM_SEGMENT_FLAG_STRINGS` - Signals that the segment contains only null terminated strings allowing the linker to perform merging.
- `2 / WASM_SEGMENT_FLAG_TLS` - The segment contains thread-local data. This means that a unique copy of this segment will be created for each thread.
- `4 / WASM_SEG_FLAG_RETAIN` - If the object file is included in the final link, the segment should be retained in the final output regardless of whether it is used by the program.

For `WASM_INIT_FUNCS` the following fields are present in the
subsection:
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