What is .arm in assembly code ? -

-

the following code taken https://github.com/xilinx/linux-xlnx/blob/master/arch/arm/kernel/head.s

i have never done arm assembly programming can me understand going on in these lines? .ar.? etc: 

.arm                __head entry(stext)   thumb( adr     r9, bsym(1f)    )   @ kernel entered in arm.  thumb( bx  r9              )   @ if thumb-2 kernel,  thumb( .thumb                  )   @ switch thumb now.  thumb(1:                       )

also kindly point me tutorials getting starting with.

plenty of arm microcontrollers have 2 different instruction sets:

  1. the default 32 bit arm instruction set
  2. the lightweight 16 bit thumb instruction set

during program execution, arm chip can switch between 2 modes in order run instructions of these sets.

the purpose of these lines seems selection of right mode (i.e., .arm or .thumb) in order execute subsequent code.

edit: sorry, made mistake. real purpose specify set of instruction used in generated code. example, if write add r0, r1, #3, binary instruction produced belong either arm or thumb instruction set, depending on directive chose between .arm , .thumb.

from https://sourceware.org/binutils/docs/as/arm-directives.html :

.arm

this performs same action .code 32.

-

.thumb

this performs same action .code 16.

-

.code [16|32]

this directive selects instruction set being generated. value 16 selects thumb, value 32 selecting arm.


Comments

Post a Comment

Popular posts from this blog

sql server - MSSQL Text and Varchar(MAX) fields shown (MEMO) in DBGrid -

-
Image
i have encountered problem in mssql & delphi xe3. text , varchar(max) fields seemed (memo) or (widememo) in tdbgrid & tdbadvgrid (tms dbgrid). in first screenshot can see table fiels, in second screentshot can see sample data in database: in screenshot, see how in dbgrid or in query results. i figured out changing field type char , varchar not max solves issue don't know why having problem. can please let me know?
Read more

qml - Is it possible to implement SystemTrayIcon functionality in Qt Quick application -

-
i writing qtquick desktop application. use both c++ (for functionality) , qml (for ui) in it. use qquickview show interface written in qml. i want application reside in system tray when minimised. i mean functionality similar example. http://qt-project.org/doc/qt-4.8/desktop-systray.html . trying implement feature not find way in qt quick application. here main.cpp code: #include <qguiapplication> #include <qqmlengine> #include <qqmlcontext> #include <qqmlfileselector> #include <qquickview> #include "myapp.h" int main(int argc, char* argv[]) { qguiapplication app(argc,argv); app.setapplicationname(qfileinfo(app.applicationfilepath()).basename()); qdir::setcurrent(qapp->applicationdirpath()); myapp myappobject; qquickview view; view.connect(view.engine(), signal(quit()), &app, slot(quit())); view.rootcontext()->setcontextproperty("myappobject", &myappobject); new qqmlfilese...
Read more

mysql - Flyway migration, Unable to obtain Jdbc connection from DataSource -

-
i trying use flyway create , manage mysql database. here code have got far. flywaymigration.java : class applys migration public class flywaymigration { public flywaymigration(databaseconfiguration configuration, flyway flyway) { flyway.setdatasource(configuration.getdatasource()); flyway.migrate(); } public static void main(string[] args) { new flywaymigration(new databaseconfiguration("database.properties"), new flyway()); } } databaseconfiguration.java : configuration class, class configure datasource applyed flyway.setdatasource method public class databaseconfiguration { private final logger logger = loggerfactory.getlogger(this.getclass()); private propertiesutil prop = null; public databaseconfiguration(string file) { prop = new propertiesutil(file); } public string getdatasourceclass() { return prop.getproperty("mysql.data.source.class"); } pu...
Read more