Arm assembly foundation of SOC

On the whole , For this kind of soc The chip project is still unable to be completed quickly , But I study computer myself , There are other things about yourself OS And stm32 Project development experience , Whether you run the operating system or not , I have actually completed many projects , It should be thinking and capable .
Own operating system , Know everything about architecture , And I'm still from hardware , I am also familiar with SCM , Starting from these is enough , Why from what ubuntu Starting with , Ladies' , There are many problems , In a fog , Start with what you are familiar with , No matter what others do ！
Compilation seems to be learning linux Embedded development cannot be bypassed , Why? ？ Because after the chip starts , It doesn't run directly c Code , It needs to be configured first c Running environment , In the process of configuration , It can only be realized by assembly .

Basic knowledge

I was going to make up with this knowledge at last , But I found the bare metal development behind , Still use this , This content is not much , Let's make it up ！

GUN Assembly syntax

Because in linux The next thing to use is gcc Cross compilation of , So the compilation also follows GUN Standards for .
The basic syntax format is ：
label:instruction @comment//@ Followed by notes ; The instruction part cannot be mixed with uppercase and lowercase , Only use uppercase or lowercase .

Definition of program segment

use .section Pseudo operation to define . Such as .section [email protected] Define a testsection paragraph . Commonly used predefined segment names ：

.text Represents a code snippet .

.data Initialized data segment .
.bss Uninitialized data segment .
.rodata Read only data segment .

Function definition

The format is ：

Function name ：

The body of the function

[ Return statement ]@ It's not necessary

Common assembly instructions

Data transfer instructions

Instructions	Purpose	Source	describe
MOV	R0	R1	take R1 The data in it is copied to R0 in .
MRS	R0	CPSR	The special register CPSR The data in it is copied to R0 in .
MSR	CPSR	R1	take R1 The data inside is copied to a special register CPSR Li Zhong

Memory access instructions

ARM Memory cannot be accessed directly , such as RAM Data in . There should be registers between them .

Instructions	describe
LDR Rd, [Rn , #offset]	From memory Rn+offset The read data is stored in Rd In the register
STR Rd, [Rn, #offset]	take Rd Data written to memory Rn+offset Location

#: Or is it an immediate number

LDR:load, load , Is to read data from memory .

STR:store, send out , Write data to memory .

Stack pressing instruction

It will be used when writing the interrupt scene .

Instructions	describe
PUSH	Store the register list on the stack .
POP	Recover the register list from the stack

Another way of writing is ：STMFD and LDMFD, You can operate on vectors . This is with STR And LDM The difference between .

Jump instruction

Instructions	describe
B	Jump to label, If the jump range exceeds +/-2KB, You can specify B.W Use 32 Bit version of jump instruction , In this way, a wide range of Jump
BL	Jump to label address , And save the return address in LR in .

LR: Link register .

Arithmetic operations

Instructions	Calculation formula	remarks
ADD Rd, Rn, Rm	Rd = Rn + Rm	Addition operation , Instructions for ADD
SUB Rd, Rn, Rm	Rd = Rn – Rm	Subtraction
ADC Rd, Rn, Rm	Rd = Rn + Rm + carry	Addition with carry
SBC Rd, Rn ,Rm	Rd = Rn – Rm – Borrow position	subtraction with carry

Logical operation instructions

AND Bitwise AND

ORR Press bit or

BIC Clear by position Such as ：BIC Rd, Rn @Rd = Rd & (~Rn)

ORN Bitwise or not Such as ：ORN Rd, Rn, Rm @Rd = Rn | (Rm)

EOR Bitwise XOR

summary

frequently-used ARM Assembly command , That's all , When you encounter it later, please add it slowly .

Expanding knowledge

Several useful tools

qemu

It's actually a virtual machine , You can simulate a computer or arm function , transfer bootload use . stay linux Used more on . Compared with hardware, the simulation mode is jlink.

basybox

do linux Of the root file system .

scaratchbox

Cross compiling platform

uboot

The famous open source bootload

UEFI and Tranocore

Unified extensible component interface .
Standards for operating system and hardware adaptation , In this way, this standard is simulated by software , So you can go around , It can be installed to the corresponding win or linux On .

Tool chain

The self-contained tool chain has been installed in front , This is just from ARM The official website requires , Go through the process again , Nothing else . In words , Use the tool chain installed before .

Two tool chains ：GNU contain gcc and ARM(armcc),GNU It's open source. .
For tool chains , You can see arm Tool chain recommended by official documents , No need to press soc Made by the manufacturer .

ubuntu Install the standard tool chain

sudo apt-get install gcc g++ gcc-doc

ubuntu Install the cross tool chain

sudo apt-get install gcc-arm-linux-gnueabi
e:Embedded The embedded
a:app application
b:bina Binary system
i:interface Interface

Theoretical knowledge , You can take your time to add , These are all references , It's okay not to look first , I believe I still have a foundation , So skip directly to hardware programming . Later, I have time to add slowly .
— 2022 year 7 month 4 Japan

Supplement completed —2022 year 7 month 22 Japan