Latest News - Software Engineer (MSFT)

I will write about my new adventures and my new studies since joining MSFT.
First and foremost, I got into MSFT recently, and am studying device driver code.
There is an increasingly interest in kernel programming, as of late.
And as such, I will go over two main macros that are used for the Linux Kernel, as well as generic kernel programming knowledge.

As a side note, I am studying the Memory Manager in the Linux Kernel, and finishing the Linux Device Driver (3rd ed.) and becoming more knowledgeable into the xkrnl. I will post about basics of Device Driver (xkrnl) programming, as well as new things I learn as I study the xkrnl's VMM.

The two macros I will note is the offset_of and the container_of.
#define offset_of(struct_type, member) \
( (unsigned long) ( \
(&(struct_type *)0)->member \
) )
#define container_of(ptr, struct_type, member) \
( (struct_type *) ( \
(char *)ptr - offset_of(struct_type, member)\
) )

The offset_of macro, is used to find the member field offset in the struct 'struct type', and container_of is used to find the containing structure, given an address 'ptr', such that ptr is the member 'member' of struct 'struct_type'.

The interesting part is the offset_of() macro, which gives the exact offset position, by using the trick where if you deference and then take the address of a NULL pointer, it will just jump to the address, ignoring the dereference.