c - How does the user-mode kernel in UML interface with the underlying kernel on the host -


in user mode linux (uml) trace thread annuls system calls made user-space process , redirects them kernel running in user-space. @ point userspace kernel require assistance of host os. how user-mode kernel call underlying host kernel, normal system calls? or use kind of ioctl mechanism or else?

i found simple explanation of uml design here. may useful you.

uml constructs using ptrace system call tracing mechanism.

  1. when process in user space, system called intercepted ptrace.
  2. when in kernel, no interception. when process executes system call or receives signal, tracing thread forces process run in kernel.
  3. after transition, process state restored , continues.

system call virtualization

  1. by switching user , kernel , system calls interception
  2. note: system call must annulled in host kernel.
  3. the process state preserved.
  4. when system call complete, process obtains returned value in saved registers , returned user mode.

also, article explains system call virtualization using ptrace following picture.

http://www.csee.wvu.edu/~katta/uml/graphics/vsyscall.jpg. red line represents normal syscall procedure.


-

Comments

Post a Comment

Popular posts from this blog

c# - Binding a comma separated list to a List<int> in asp.net web api -

the default binder in web api expecst http://url.com/webapi/report/?pageids=3243&pageids=2365 to bind public ihttpactionresult report(list<int> pageids){ // exciting webapi code} i wish bind http://url.com/webapi/report/?pageids=3243,2365 as running out of space in url get . i have created class public class commaseparatedmodelbinder : system.web.http.modelbinding.imodelbinder { public bool bindmodel(httpactioncontext actioncontext, modelbindingcontext bindingcontext) { //binding in here } } and registered in webapiconfig.cs var provider = new simplemodelbinderprovider( typeof(list<int>), new commaseparatedmodelbinder()); config.services.insert(typeof(modelbinderprovider), 0, provider); i have altered method signature use model binder so public ihttpactionresult report( [modelbinder] list<int> pageids){ // exciting webapi code} however break point in binder not being
Read more

Delphi 7 and decode UTF-8 base64 -

in delphi 7, have widestring encoded base64(that received web service widestring result) : pd94bwwgdmvyc2lvbj0ims4wij8+dqo8c3ryaw5nptiq2lpyqjwvc3ryaw5npg== when decoded it, result not utf-8: <?xml version="1.0"?> <string>طھط³طھ</string> but when decoded base64decode.org, result true : <?xml version="1.0"?> <string>تست</string> i have use encddecd unit decodestring function. the problem have using decodestring . function, in delphi 7, treats decoded binary data being ansi encoded. , problem text utf-8 encoded. to continue encddecd unit have couple of options. can switch decodestream . instance, code produce utf-8 encoded text file data: {$apptype console} uses classes, encddecd; const data = 'pd94bwwgdmvyc2lvbj0ims4wij8+dqo8c3ryaw5nptiq2lpyqjwvc3ryaw5npg=='; var input: tstringstream; output: tfilestream; begin input := tstringstream.create(data); try output := tfilestream.
Read more

html - Is there any way to exclude a single element from the style? (Bootstrap) -

so, have img logo, overlaid on div styled background-image: url("...") , , both elements inside 2 div classes .to-color , .to-overlay respectively, black transparent overlay. is there way exclude logo style given these 2 classes? here's jsfiddle example: link html , css example: - html - <div class="to-color"> <div class="to-overlay"> <div class="respo"> <div class="row"> <div class="col-xs-4 col-xs-offset-4 text-center"> <img src="http://ansonalex.com/wp-content/uploads/2011/06/google-logo-768x260.png" alt="..." class="img-responsive"> </div> </div> </div> </div> </div> - css - .to-color { background-color: #000; } .to-overlay { opacity : 0.5; } .respo { background-image: url("https://source.unsplash.com/category/objects/1600x900"); background-position: center center;
Read more