Re: [PATCHv3 bpf-next 2/8] bpf: Add user memory kfuncs

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Nov 05, 2026 at 04:34:40PM -0800, Andrii Nakryiko wrote:

SNIP

> > +/**
> > + * bpf_copy_to_user() - Copy data to the current task's address space
> > + * @unsafe_ptr__ign: Destination address in the current task's address space
> > + * @src:     Source address, in kernel space
> > + * @src__sz: Number of bytes to copy
> > + * @flags:   Reserved for future use; must be zero
> > + *
> > + * Faults in the destination and writes the way ptrace(PTRACE_POKETEXT) does:
> > + * a private mapping doesn't have to be writable. A partial copy is not undone,
> > + * the bytes before the fault stay written.
> > + *
> > + * The caller must coordinate with other threads so they do not execute the
> > + * destination range while it is being modified, and ensure execution begins
> > + * only after the copy completes.
> > + *
> > + * Return: 0 on success, -EINVAL if @flags is non-zero, or -EFAULT if the copy
> > + * fails or is partial.
> > + */
> > +__bpf_kfunc int bpf_copy_to_user(void __user *unsafe_ptr__ign, const void *src,
> > +                                u32 src__sz, u64 flags)
> 
> you'll eventually want bpf_copy_to_user_dynptr (we already have
> bpf_copy_from_user_dynptr), so might as well add it from the get go?

ok, might be useful will check.. will send as follow up

thanks,
jirka


> 
> > +{
> > +       int ret;
> > +
> > +       if (unlikely(flags))
> > +               return -EINVAL;
> > +       if (unlikely(src__sz > S32_MAX))
> > +               return -EINVAL;
> > +       if (unlikely(!src__sz))
> > +               return 0;
> > +       ret = access_process_vm(current, (unsigned long)unsafe_ptr__ign, (void *)src,
> > +                               src__sz, FOLL_FORCE | FOLL_WRITE);
> > +       return ret == src__sz ? 0 : -EFAULT;
> > +}
> > +
> 
> [...]