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SubjectRe: kernel compiled with frame pointer
Sushil wrote:
>
> I agree. Sitting in the front of desktop I can see if the source files are
> getting compiled with or without -fomit-frame-pointer. But, while writing
> a function in a kernel source file, I want to know whether the caller of
> this function was compiled with or without -fomit-frame-pointer because
> this will affect the location of return address to it on the stack.
>
> So, I assume that if CONFIG_FRAME_POINTER is defined then the kernel (and
> hopefully the caller function also) is being compiled without
> -fomit-frame-pointer and then look for the return address appropriately.

Ah -- I see, you are looking at some sort of kernel debugger. Well,
then one way would be to look at entry and exit points. i386 Frame
pointers are set up with `pushl %ebp / movl %esp, %ebp / subl $local, %esp`
or sometimes [not by gcc AFAIK with `enter`]. Exit points are similarly
`movl %ebp, %esp / popl %ebp / ret`. Some versions of gcc do generate
`leave / ret`.

You could look for these byte signatures. Should be quite reliable with
a good System.map.

-- Robert
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