X86 machine code enter and FreeBSD kernel

[Erich Dollansky]

Hi,

Reko Turja wrote:
> I received no reply on this question at questions mailing list, so I try 
> asking this here. Hope I'm not asking this in completely wrong list.
> 
> In recent discussion in OpenWatcom lists it was noticed that at least
> certain addressing modes of assembler ENTER instruction causes a crash
> when used in Linux. GCC circumnavigates this by not emitting ENTER
> instructions in machine code. Linus's comment on the above issue can be
> found on:
> 
> http://groups.google.co.nz/groups?selm=7i86ni%24b7n%241%40palladium.transmeta.com 
> 
> 
> What's the status of the above "feature" in FreeBSD, does the kernel 
> support the
> whole x86 instruction set without similar cut corners?
> 
This here is out of my memory from the days when 'enter' was a new 
instruction. So, do not kill me if I am wrong.

'enter' allows to specify a nesting level. Languages like Pascal can use 
this for functions which are local to other functions to enable the 
inner function to access the stack of the outer function.

C does not support this at all. So, if you use this instruction, it must 
be used with a nesting level of zero. This will not cause any problems 
but will be a plain waste of CPU time.

Erich