* Andy Lutomirski <[email protected]> wrote:
> > > ENTRY(entry_INT80_32)
> >
> > entry_INT80_32() is only used on pure 32-bit kernels, 64-bit kernels use
> > entry_INT80_compat(). So the above text should not talk about 64-bit
> > programs, as
> > they can never trigger this specific entry point, right?
> >
>
> 64-bit programs can and sometimes do trigger this entry point. [...]
How can 64-bit programs trigger entry_INT80_32? It's only ever set on 32-bit
kernels:
#ifdef CONFIG_X86_32
set_system_trap_gate(IA32_SYSCALL_VECTOR, entry_INT80_32);
set_bit(IA32_SYSCALL_VECTOR, used_vectors);
#endif
> [...] It does a 32-bit syscall regardless of the caller's bitness, but it
> returns back to the caller's original context, whatever it was.
That's true of INT $0x80, but I'm talking about the entry point: AFAICS
entry_INT80_32 can only ever execute on 32-bit kernels.
We don't even build the entry_32.S::entry_INT80_32 entry point on 64-bit
kernels:
obj-y := entry_$(BITS).o [...]
>
> > So I'd change the explanation to something like:
> >
> > > + * This entry point is active on 32-bit kernels and can thus be used by
> > > 32-bit
> > > + * programs to perform 32-bit system calls. (Programs running on 64-bit
> > > + * kernels executing INT $0x80 will land on another entry point:
> > > + * entry_INT80_compat. The ABI is identical.)
>
> I like the part in parentheses.
So the part in parentheses conflict with your above statement :)
What I wanted to say with this:
> > > + * This entry point is active on 32-bit kernels and can thus be used by
> > > 32-bit
> > > + * programs to perform 32-bit system calls. (Programs running on 64-bit
> > > + * kernels executing INT $0x80 will land on another entry point:
> > > + * entry_INT80_compat. The ABI is identical.)
... is what it says: that entry_INT80_32 is only active on 32-bit kernels,
running
32-bit programs, performing 32-bit system calls.
Programs running on 64-bit kernels can use INT $0x80 as well, but will land on
another, different, 64-bit kernel specific entry point.
What am I missing?
Thanks,
Ingo
