On 2015-07-10 13:25, Russell King - ARM Linux wrote: > On Sat, Jun 06, 2015 at 01:48:00PM +0100, Russell King - ARM Linux wrote: >> On Sat, Jun 06, 2015 at 02:31:28PM +0200, Stefan Agner wrote: >> > @@ -1231,7 +1272,7 @@ static void __init devicemaps_init(const struct >> > machine_desc *mdesc) >> > >> > early_trap_init(vectors); >> > >> > - for (addr = VMALLOC_START; addr; addr += PMD_SIZE) >> > + for (addr = VMALLOC_START; addr < FIXADDR_START; addr += PMD_SIZE) >> > pmd_clear(pmd_off_k(addr)); >> >> You introduce a bug here - we no logner clear the very top entry of the >> page tables, which means it could contain anything - and means that the >> subsequent creation of the L2 table in early_pte_alloc() can fail. > > You trimmed my reply hard, and seemingly ignored this; the v4 patch > contains exactly the same code here, and therefore continues to leave > the top of the page table uninitialised.
Maybe I get something wrong here, but the very top PMD is left out on purpose, since early_fixmap_shutdown takes care of that. However v3 also did not clear the second to top PMD. I thought I did take care of that by using this slightly different for loop in v4: for (addr = VMALLOC_START; addr < (FIXADDR_TOP & PMD_MASK); addr += PMD_SIZE) However, looking now at the code I'm not sure if this is right either. I think what is needed is addr < (FIXADDR_TOP & ~PMD_MASK). This will make sure that only the top PMD is not cleared, which is taken care of by early fixmap... -- Stefan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
