Re: [PATCH v2 5/8] x86/gdbsx: convert "user" to "guest" accesses

["Roger Pau Monné" <roger.pau@citrix.com>]

On Wed, Feb 17, 2021 at 09:21:36AM +0100, Jan Beulich wrote:
> Using copy_{from,to}_user(), this code was assuming to be called only by
> PV guests. Use copy_{from,to}_guest() instead, transforming the incoming
> structure field into a guest handle (the field should really have been
> one in the first place). Also do not transform the debuggee address into
> a pointer.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

One minor comment below that can be taken care of when committing I
think.

> ---
> v2: Re-base (bug fix side effect was taken care of already).
> 
> --- a/xen/arch/x86/debug.c
> +++ b/xen/arch/x86/debug.c
> @@ -108,12 +108,11 @@ dbg_pv_va2mfn(dbgva_t vaddr, struct doma
>  }
>  
>  /* Returns: number of bytes remaining to be copied */
> -static unsigned int dbg_rw_guest_mem(struct domain *dp, void * __user gaddr,
> -                                     void * __user buf, unsigned int len,
> -                                     bool toaddr, uint64_t pgd3)
> +static unsigned int dbg_rw_guest_mem(struct domain *dp, unsigned long addr,
> +                                     XEN_GUEST_HANDLE_PARAM(void) buf,
> +                                     unsigned int len, bool toaddr,
> +                                     uint64_t pgd3)
>  {
> -    unsigned long addr = (unsigned long)gaddr;
> -
>      while ( len > 0 )
>      {
>          char *va;
> @@ -134,20 +133,18 @@ static unsigned int dbg_rw_guest_mem(str
>  
>          if ( toaddr )
>          {
> -            copy_from_user(va, buf, pagecnt);    /* va = buf */
> +            copy_from_guest(va, buf, pagecnt);
>              paging_mark_dirty(dp, mfn);
>          }
>          else
> -        {
> -            copy_to_user(buf, va, pagecnt);    /* buf = va */
> -        }
> +            copy_to_guest(buf, va, pagecnt);
>  
>          unmap_domain_page(va);
>          if ( !gfn_eq(gfn, INVALID_GFN) )
>              put_gfn(dp, gfn_x(gfn));
>  
>          addr += pagecnt;
> -        buf += pagecnt;
> +        guest_handle_add_offset(buf, pagecnt);
>          len -= pagecnt;
>      }
>  
> @@ -161,7 +158,7 @@ static unsigned int dbg_rw_guest_mem(str
>   * pgd3: value of init_mm.pgd[3] in guest. see above.
>   * Returns: number of bytes remaining to be copied.
>   */
> -unsigned int dbg_rw_mem(void * __user addr, void * __user buf,
> +unsigned int dbg_rw_mem(unsigned long gva, XEN_GUEST_HANDLE_PARAM(void) buf,
>                          unsigned int len, domid_t domid, bool toaddr,
>                          uint64_t pgd3)

You change the prototype below to make pgd3 unsigned long, so you
should change the type here also? (and likely in dbg_rw_guest_mem?)

Thanks, Roger.