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Use EI_CLASS for base ABI encoding. #47

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Use EI_CLASS for base ABI encoding. #47

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4da1932
Use EI_CLASS for base ABI encoding.
scylaac Apr 19, 2022
7720b73
Refer to e_flags[2:0] as the "base ABI modifier".
scylaac Jul 25, 2022
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79 changes: 39 additions & 40 deletions docs/LoongArch-ELF-ABI-CN.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -129,8 +129,10 @@ v1.00

====

[[c-lang-data-model]]
== C 语言数据类型规格

[[dm-lp64]]
.LP64 数据模型 （对应基础 ABI 类型：`lp64d` `lp64f` `lp64s`）
[%header,cols="3,^1,^1"]
|===
Expand Down Expand Up @@ -179,6 +181,7 @@ v1.00
|16
|===

[[dm-ilp32]]
.ILP32 数据模型 （对应基础 ABI 类型：`ilp32d` `ilp32f` `ilp32s`）
[%header,cols="3,^1,^1"]
|===
Expand Down Expand Up @@ -235,7 +238,7 @@ v1.00
本节内容中关于 ELF 目标文件的通用格式定义
均参考 http://sco.com/developers/gabi/latest/contents.html[最新版本的 SysV gABI]。

=== `EI_CLASS`: ELF 文件格式
=== EI_CLASS: ELF 文件格式

[%header,cols="2m,^1m,^3"]
|===
Expand All @@ -245,80 +248,76 @@ v1.00

|ELFCLASS32
|1
|32 位 ELF 格式
|32 位 ELF 格式 (ELF32)

|ELFCLASS64
|2
|64 位 ELF 格式
|64 位 ELF 格式 (ELF64)
|===

=== `e_machine`: 体系结构 ID
=== e_machine: 体系结构 ID

`LoongArch (258)`

=== `e_flags`: ABI 类型和版本标记
=== e_flags: ABI 类型和版本标记

[%header,cols="1,1,1,1"]
|===
|`[31:8]` 位 | `[7:6]` 位 | `[5:3]` 位 | `[2:0]` 位

|（保留） | ABI 版本 | ABI 扩展特性 | 基础 ABI 类型
|（保留） | ABI 版本 | ABI 扩展特性 | 基础 ABI 修饰符
|===

`e_flags[7:0]` 完整标记了 ELF 目标文件使用的 ABI 类型。
`EI_CLASS` 和 `e_flags[7:0]` 完整确定了 ELF 目标文件使用的 ABI 类型。

其中，**基础 ABI 类型**由 `EI_CLASS` 和 `e_flags[2:0]` 共同标记，
前者唯一确定了 C 语言整数和指针类型的表示（<<c-lang-data-model, 数据模型>>）和传参方式，
后者则在此基础上表示其他基础 ABI 性质，如浮点类型传参方式，称为 **基础 ABI 修饰符**。

因此，龙芯架构的 ELF64 / ELF32 目标文件分别仅用于编码 `lp64*` / `ilp32*` ABI 的程序。

`0x0` `0x4` `0x5` `0x6` `0x7` 为 `e_flags[2:0]` 的保留值。

[[base-abi-type-marks]]
.基础 ABI 类型标记
[%header,cols="2m,^1,^3"]
[%header,cols="2m,^1m,^1m,^3"]
|===
|基础 ABI 名称
|枚举值 (`e_flags[2:0]`)
|EI_CLASS | 基础 ABI 修饰符 (`e_flags[2:0]`)
|含义

|
|`0x0`
|保留值

|lp64s
|`0x1`
|lp64s | ELFCLASS64 | 0x1
|使用 64 位通用寄存器和栈传参，
数据模型为 LP64（`long` 和指针类型宽度为64位，`int` 为32位）

|lp64f
|`0x2`
|使用 64 位通用寄存器，32位浮点寄存器和栈传参，
数据模型为 LP64（`long` 和指针类型宽度为64位，`int` 为32位）
数据模型为 <<dm-lp64, `LP64`>>（`long` 和指针类型宽度为 64 位，`int` 为 32 位）

|lp64d
|`0x3`
|使用 64 位通用寄存器，64位浮点寄存器和栈传参，
数据模型为 LP64（`long` 和指针类型宽度为64位，`int` 为32位）
|lp64f | ELFCLASS64 | 0x2
|使用 64 位通用寄存器，32 位浮点寄存器和栈传参，
数据模型为 <<dm-lp64, `LP64`>>（`long` 和指针类型宽度为 64 位，`int` 为 32 位）

|
|`0x4`
|保留值
|lp64d | ELFCLASS64 | 0x3
|使用 64 位通用寄存器，64 位浮点寄存器和栈传参，
数据模型为 <<dm-lp64, `LP64`>>（`long` 和指针类型宽度为 64 位，`int` 为 32 位）

|ilp32s
|`0x5`
|ilp32s | ELFCLASS32 | 0x1
|使用 32 位通用寄存器和栈传参，
数据模型为 ILP32（`int`，`long` 和指针类型宽度为32位）
数据模型为 <<dm-ilp32, `ILP32`>>（`int`，`long` 和指针类型宽度为 32 位）

|ilp32f
|`0x6`
|使用 32 位通用寄存器，32位浮点寄存器和栈传参，
数据模型为 ILP32（`int`，`long` 和指针类型宽度为32位）
|ilp32f | ELFCLASS32 | 0x2
|使用 32 位通用寄存器，32 位浮点寄存器和栈传参，
数据模型为 <<dm-ilp32, `ILP32`>>（`int`，`long` 和指针类型宽度为 32 位）

|ilp32d
|`0x7`
|使用 32 位通用寄存器，64位浮点寄存器和栈传参，
数据模型为 ILP32（`int`，`long` 和指针类型宽度为32位）
|ilp32d | ELFCLASS32 | 0x3
|使用 32 位通用寄存器，64 位浮点寄存器和栈传参，
数据模型为 <<dm-ilp32, `ILP32`>>（`int`，`long` 和指针类型宽度为 32 位）
|===

`e_flags[5:3]` 标记了 ABI 扩展特性。

.ABI 扩展特性标记
[%header,cols="2m,^1,^3"]
|===
|ABI 扩展特性名称
|枚举值 (`e_flags[5:3]`)
|e_flags[5:3]
|含义

|base
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74 changes: 39 additions & 35 deletions docs/LoongArch-ELF-ABI-EN.adoc
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Expand Up @@ -129,8 +129,10 @@ For the components not yet upstream, and not interacting with other components t

====

[[c-lang-data-model]]
== Type Size and Alignment

[[dm-lp64]]
.LP64 Data Model (base ABI types: `lp64d` `lp64f` `lp64s`)
[%header,cols="3,^1,^1"]
|===
Expand Down Expand Up @@ -179,6 +181,7 @@ For the components not yet upstream, and not interacting with other components t
|16
|===

[[dm-ilp32]]
.ILP32 Data Model (base ABI types: `ilp32d` `ilp32f` `ilp32s`)
[%header,cols="3,^1,^1"]
|===
Expand Down Expand Up @@ -227,15 +230,16 @@ For the components not yet upstream, and not interacting with other components t
|16
|===

For all base ABI types of LoongArch, the `char` datatype is signed by default.
For all <<base-abi-type-marks, base ABI types>> of LoongArch,
the `char` datatype is signed by default.


== ELF Object Files

All common ELF definitions referenced in this section
can be found in http://sco.com/developers/gabi/latest/contents.html[the latest SysV gABI specification].

=== `EI_CLASS`: File class
=== EI_CLASS: File class

[%header,cols="2m,^1m,^3"]
|===
Expand All @@ -252,71 +256,71 @@ can be found in http://sco.com/developers/gabi/latest/contents.html[the latest S
|ELF64 object file
|===

=== `e_machine`: Identifies the machine
=== e_machine: Identifies the machine

`LoongArch (258)`

=== `e_flags`: Identifies ABI type and version
=== e_flags: Identifies ABI type and version

[%header,cols="1,1,1,1"]
|====
| Bit 31 - 8 | Bit 7 - 6 | Bit 5 - 3 | Bit 2 - 0
| (reserved) | ABI version | ABI extension | Base ABI
| (reserved) | ABI version | ABI extension | Base ABI Modifier
|====

The ABI type of an ELF object is uniquely identified by `e_flags[7:0]` in its header.
The ABI type of an ELF object is uniquely identified by `EI_CLASS` and `e_flags[7:0]` in its header.

Within this combination, `EI_CLASS` and `e_flags[2:0]` correspond to the **base ABI** type,
where the expression of C integral and pointer types (<<c-lang-data-model, data model>>)
is uniquely determined by `EI_CLASS` value, and `e_flags[2:0]` represents additional properties
of the base ABI type, including the FP calling convention. We refer to `e_flags[2:0]` as
the **base ABI modifier*.

As a result, programs in `lp64*` / `ilp32*` ABI should only be encoded with ELF64 / ELF32
object files, respectively.

`0x0` `0x4` `0x5` `0x6` `0x7` are reserved values for `e_flags[2:0]`.

[[base-abi-type-marks]]
.Base ABI Types
[%header,cols="2m,^1,^3"]
[%header,cols="2m,^1m,^1m,^3"]
|===
|Name
|Value of `e_flags[2:0]`
|EI_CLASS | Base ABI Modifier (`e_flags[2:0]`)
|Description

|
|`0x0`
|(reserved)

|lp64s
|`0x1`
|lp64s | ELFCLASS64 | 0x1
|Uses 64-bit GPRs and the stack for parameter passing.
Data model is LP64, where `long` and pointers are 64-bit while `int` is 32-bit.
Data model is <<dm-lp64, LP64>>, where `long` and pointers are 64-bit while `int` is 32-bit.

|lp64f
|`0x2`
|lp64f | ELFCLASS64 | 0x2
|Uses 64-bit GPRs, 32-bit FPRs and the stack for parameter passing.
Data model is LP64, where `long` and pointers are 64-bit while `int` is 32-bit.
Data model is <<dm-lp64, LP64>>, where `long` and pointers are 64-bit while `int` is 32-bit.

|lp64d
|`0x3`
|lp64d | ELFCLASS64 | 0x3
|Uses 64-bit GPRs, 64-bit FPRs and the stack for parameter passing.
Data model is LP64, where `long` and pointers are 64-bit while `int` is 32-bit.

|
|`0x4`
|(reserved)
Data model is <<dm-lp64, LP64>>, where `long` and pointers are 64-bit while `int` is 32-bit.

|ilp32s
|`0x5`
|ilp32s | ELFCLASS32 | 0x1
|Uses 32-bit GPRs and the stack for parameter passing.
Data model is ILP32, where `int`, `long` and pointers are 32-bit.
Data model is <<dm-ilp32, ILP32>>, where `int`, `long` and pointers are 32-bit.

|ilp32f
|`0x6`
|ilp32f | ELFCLASS32 | 0x2
|Uses 32-bit GPRs, 32-bit FPRs and the stack for parameter passing.
Data model is ILP32, where `int`, `long` and pointers are 32-bit.
Data model is <<dm-ilp32, ILP32>>, where `int`, `long` and pointers are 32-bit.

|ilp32d
|`0x7`
|ilp32d | ELFCLASS32 | 0x3
|Uses 32-bit GPRs, 64-bit FPRs and the stack for parameter passing.
Data model is ILP32, where `int`, `long` and pointers are 32-bit.
Data model is <<dm-ilp32, ILP32>>, where `int`, `long` and pointers are 32-bit.
|===

`e_flags[5:3]` correspond to the ABI extension type.

.ABI Extension types
[%header,cols="2m,^1,^3"]
|===
|Name
|Value of `e_flags[5:3]`
|e_flags[5:3]
|Description

|base
Expand Down