On Thu, Jul 6, 2023 at 3:20 PM Will Hawkins <hawkinsw@xxxxxx> wrote: > > The execution of every function proceeds as if it has access to its own > stack space. > > Signed-off-by: Will Hawkins <hawkinsw@xxxxxx> > --- > Documentation/bpf/instruction-set.rst | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst > index 751e657973f0..717259767a41 100644 > --- a/Documentation/bpf/instruction-set.rst > +++ b/Documentation/bpf/instruction-set.rst > @@ -30,6 +30,11 @@ The eBPF calling convention is defined as: > R0 - R5 are scratch registers and eBPF programs needs to spill/fill them if > necessary across calls. > > +Every function invocation proceeds as if it has exclusive access to an > +implementation-defined amount of stack space. R10 is a pointer to the byte of > +memory with the highest address in that stack space. The contents > +of a function invocation's stack space do not persist between invocations. Such description belongs in a future psABI doc. instruction-set.rst is not a place to describe how registers are used. For example x86-64 JIT maps BPF R10 to RBP. Yet there is -fomit-frame-pointer. So we might very well do something like that in the future.
