Re: [XEN v5 02/10] xen/arm: Typecast the DT values into paddr_t

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

On 19/04/2023 14:54, Michal Orzel wrote:
> On 19/04/2023 15:19, Michal Orzel wrote:
> > Hi Ayan,
> >
> > On 13/04/2023 19:37, Ayan Kumar Halder wrote:
> > > The DT functions (dt_read_number(), device_tree_get_reg(), fdt_get_mem_rsv())
> > > currently accept or return 64-bit values.
> > >
> > > In future when we support 32-bit physical address, these DT functions are
> > > expected to accept/return 32-bit or 64-bit values (depending on the width of
> > > physical address). Also, we wish to detect if any truncation has occurred
> > > (i.e. while parsing 32-bit physical addresses from 64-bit values read from DT).
> > >
> > > device_tree_get_reg() should now be able to return paddr_t. This is invoked by
> > > various callers to get DT address and size.
> > >
> > > For fdt_get_mem_rsv(), we have introduced a wrapper named
> > > fdt_get_mem_rsv_paddr() which will invoke fdt_get_mem_rsv() and translate
> > > uint64_t to paddr_t. The reason being we cannot modify fdt_get_mem_rsv() as it
> > > has been imported from external source.
> > >
> > > For dt_read_number(), we have also introduced a wrapper named dt_read_paddr()
> > > dt_read_paddr() to read physical addresses. We chose not to modify the original
> > > function as it is used in places where it needs to specifically read 64-bit
> > > values from dt (For e.g. dt_property_read_u64()).
> > >
> > > Xen prints warning when it detects truncation in cases where it is not able to
> > > return error.
> > >
> > > Also, replaced u32/u64 with uint32_t/uint64_t in the functions touched
> > > by the code changes.
> > >
> > > Also, initialized variables to fix the warning "-Werror=maybe-uninitialized".
> > I can see that now you explicitly set to 0 variables passed to 
> > fdt_get_mem_rsv_paddr()
> > which haven't been initialized before being passed to fdt_get_mem_rsv(). Is 
> > this what
> > you are reffering to? I cannot reproduce it, hence my question.
> I can see why did you get this error.
> Before your change, we always checked for an error from fdt_get_mem_rsv() by 
> checking if < 0.
> In your wrapper fdt_get_mem_rsv_paddr(), you switched (not sure why) to 
> checking if not zero.
> Becasue of this, you got an error and tried to fix it by initializing the 
> variables to 0.
I actually wanted to return the error code obtained from 
fdt_get_mem_rsv() to the caller.
In this case, it returns a single error code. So does this look sane to 
you ?
diff --git a/xen/include/xen/libfdt/libfdt-xen.h 
b/xen/include/xen/libfdt/libfdt-xen.h
index 3296a368a6..1da87d6668 100644
--- a/xen/include/xen/libfdt/libfdt-xen.h
+++ b/xen/include/xen/libfdt/libfdt-xen.h
@@ -22,9 +22,8 @@ static inline int fdt_get_mem_rsv_paddr(const void 
*fdt, int n,
     uint64_t dt_size;
     int ret = 0;

-    ret = fdt_get_mem_rsv(fdt, n, &dt_addr, &dt_size);
-    if ( ret )
-        return ret;
+    if ( fdt_get_mem_rsv(fdt, n, &dt_addr, &dt_size) < 0 )
+        return -FDT_ERR_BADOFFSET;

     if ( dt_addr != (paddr_t)dt_addr )
     {

- Ayan

> ~Michal