Re: [PATCH 1/2] ppc/pnv: initialize 'taddr' in pnv_phb3_translate_tve()

[Matheus K. Ferst]

On 26/01/2022 10:41, Daniel Henrique Barboza wrote:
> The 'taddr' variable is left unintialized, being set only inside the
> "while ((lev--) >= 0)" loop where we get the TCE address. The 'lev' var
> is an int32_t that is being initiliazed by the GETFIELD() macro, which
> returns an uint64_t.
>
> For a human reader this means that 'lev' will always be positive or zero.
> But some compilers may beg to differ. 'lev' being an int32_t can in theory
> be set as negative, and the "while ((lev--) >= 0)" loop might never be
> reached, and 'taddr' will be left unitialized.

If we expect this code to execute at least once, wouldn't it be better 
to use a do-while? E.g.:

do {
    lev--;

    /* Grab the TCE address */
    taddr = base | (((addr >> sh) & ((1ul << tbl_shift) - 1)) << 3);
    if (dma_memory_read(&address_space_memory, taddr, &tce,
    /* ... */
    }
    sh -= tbl_shift;
    base = tce & ~0xfffull;
} while (lev >= 0);

Otherwise, I think we'll need to initialize tce too.

Thanks,
Matheus K. Ferst
Instituto de Pesquisas ELDORADO <http://www.eldorado.org.br/>
Analista de Software
Aviso Legal - Disclaimer <https://www.eldorado.org.br/disclaimer.html>