implicit declaration of function get_free_pages
 

getting warnings:implicit declaration of function get_free_pages

while allocating memory by using get_free_pages

...and since you provide NOTHING that even gives us a HINT of your situation, what do you think we'll be able to tell you?? You posted a vague warning message...that's all. Unless you provide DETAILS (version/distro of Linux, what language the program was written in, what program it IS, where you got it, what you're trying to do, etc.), there's nothing anyone, anywhere will be able to tell you

im writing a code in linux kernel by using c to allocate dynamic memory up to 1MB for buff by using get_free_pages()function in kernel module

Ok...and you STILL don't tell us anything that would let us help you. AGAIN

• Version/distro of Linux?
• Kernel you're using?
• The code?
• What you've done/tried?

Since this is your code, unless we see it, how do you think we'll be able to help you, or tell you anything more than "You've got a bug in your code...fix it".

And did you check which header file declares this function and did you '#include" it in your code?