3rd-party/linux-kernel-module-cheat
1
0
Fork 0
mirror of https://github.com/cirosantilli/linux-kernel-module-cheat.git synced 2026-01-23 02:05:57 +01:00
Code Issues Releases Wiki Activity

x86 asm: move most of registers from x86-assembly-cheat

Browse Source
This commit is contained in:
Ciro Santilli 六四事件 法轮功
2019-06-22 00:00:03 +00:00
parent fd5b62edfe
commit 8efd4f8a43
2 changed files with 104 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
README.adoc
View File

@@ -11847,6 +11847,7 @@ Other infrastructure sanity checks that you might want to look into include:
After seeing an <<userland-assembly,ADD hello world>>, you need to learn the general registers:
* x86: <<x86-registers>>
* arm
** link:userland/arch/arm/registers.S[]
* aarch64
@@ -12354,6 +12355,45 @@ Applications: http://stackoverflow.com/questions/234906/whats-the-purpose-of-the
Arch agnostic infrastructure getting started at: <<userland-assembly>>.
=== x86 registers
link:userland/arch/x86_64/registers.S
....
|-----------------------------------------------|
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|-----------------------------------------------|
| | | AH | AL |
|-----------------------------------------------|
| | | AX |
|-----------------------------------------------|
| | EAX |
|-----------------------------------------------|
| RAX |
|-----------------------------------------------|
....
For the newer x86_64 registers, the naming convention is somewhat saner:
....
|-----------------------------------------------|
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|-----------------------------------------------|
| | |R12H |R12L |
|-----------------------------------------------|
| | | R12W |
|-----------------------------------------------|
| | R12D |
|-----------------------------------------------|
| R12 |
|-----------------------------------------------|
....
Most of the 8 older x86 general purpose registers are not "really" general purpose in the sense that a few instructions magically use them without an explicit encoding. This is reflected in their names:
* RAX: Accumulator. The general place where you add, subtract and otherwise manipulate results in-place. Magic for example for <<MUL,x86 binary arithmetic instructions>>
* RCX, RSI, RDI: Counter, Source and Destination. Used in <<x86-string-instructions>>
=== x86 addressing modes
Example: link:userland/arch/x86_64/address_modes.S[]
@@ -12631,7 +12671,7 @@ These instructions do some operation on an array item, and automatically update
** link:userland/arch/x86_64/movs.S[]: MOVS: MOV String: move from one memory to another with addresses given by RSI and RDI. Could be used to implement `memmov`.
** link:userland/arch/x86_64/scas.S[]: SCAS: SCan String: compare memory to the value in a register. Could be used to implement `strchr`.
The RSI and RDI registers are actually named after these intructions! S is the source of string instructions, D is the destination of string instructions.
The RSI and RDI registers are actually named after these intructions! S is the source of string instructions, D is the destination of string instructions: https://stackoverflow.com/questions/1856320/purpose-of-esi-edi-registers
The direction of the index increment depends on the direction flag of the FLAGS register: 0 means forward and 1 means backward: https://stackoverflow.com/questions/9636691/what-are-cld-and-std-for-in-x86-assembly-language-what-does-df-do
@@ -15402,11 +15442,17 @@ which also downloads build dependencies.
Then the following times just to the faster:
....
./build-docs
./build-doc
....
Source: link:build-doc[]
Then just open the HTML output at:
....
xdg-open out/README.html
....
[[documentation-verification]]
==== Documentation verification