Re: [Minios-devel] [UNIKRAFT RFC PATCH] plat/common:Add helper to simplify accessing fdt for arm

["Jianyong Wu (Arm Technology China)" <Jianyong.Wu@xxxxxxx>]

Hi,

> -----Original Message-----
> From: Julien Grall <julien.grall@xxxxxxx>
> Sent: Thursday, November 15, 2018 5:52 PM
> To: Jianyong Wu (Arm Technology China) <Jianyong.Wu@xxxxxxx>; minios-
> devel@xxxxxxxxxxxxxxxxxxxx; simon.kuenzer@xxxxxxxxx
> Cc: Kaly Xin (Arm Technology China) <Kaly.Xin@xxxxxxx>; nd
> <nd@xxxxxxx>; Wei Chen (Arm Technology China) <Wei.Chen@xxxxxxx>
> Subject: Re: [Minios-devel] [UNIKRAFT RFC PATCH] plat/common:Add helper
> to simplify accessing fdt for arm
> 
> 
> 
> On 11/15/18 6:09 AM, Jianyong Wu (Arm Technology China) wrote:
> > Hi,
> 
> Hi,
> 
> 
> >>>> +
> >>>> +        UK_ASSERT(device != -1);
> >>>> +        naddr = fdt_address_cells(dtb, device);
> >>>> +        UK_ASSERT(naddr < FDT_MAX_NCELLS);
> >>>> +
> >>>> +        *nsize = fdt_size_cells(dtb, device);
> >>>> +        UK_ASSERT(*nsize < FDT_MAX_NCELLS);
> >>>> +
> >>>> +        *regs = fdt_getprop(dtb, device, "reg", &prop_len);
> >>>> +        prop_min_len = (int)sizeof(fdt32_t) * (naddr + *nsize);
> >>>> +        UK_ASSERT(*regs != NULL && prop_len >= prop_min_len);
> >>>
> >>> This assert is not very useful for "regs" property describing more
> >>> than
> >>> 1 regions. I think it would make sense to move the check in the
> >>> uk_dtb_read_term to check if the region requested by the caller is
> correct.
> >>
> >> Ok, I will check reg in uk_dtb_read_term.
> >
> > But, how to check reg in uk_dtb_read_term? I have an idea that check
> > *(reg + index*(naddr+nsize) *4) Does that make sence?
> 
> You want to make sure you are not going to read past the size of the
> property. So ((index + 1) * (naddr + nsize) * 4) < size should be fine.

The "size" in this function is not the size of all reg, it is just the length 
of one term like distributor in gic.
We not get the all regs cell size in this function.

> 
> Cheers,
> 
> --
> Julien Grall
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