Messages in this thread | | | Subject | Re: [PATCH -next] powerpc/mm: check base flags in ioremap_prot | From | Christophe Leroy <> | Date | Fri, 3 Sep 2021 11:16:56 +0200 |
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Le 03/09/2021 à 11:03, Nanyong Sun a écrit : > Some drivers who call ioremap_prot without setting base flags like > ioremap_prot(addr, len, 0) may work well before > commit 56f3c1413f5c ("powerpc/mm: properly set PAGE_KERNEL flags in > ioremap()"), but now they will get a virtual address "successfully" > from ioremap_prot and badly fault on memory access later because that > patch also dropped the hack adding of base flags for ioremap_prot. > > So return NULL and throw a warning if the caller of ioremap_prot did > not set base flags properly. Why not just hack adding PAGE_KERNEL flags > in the ioremap_prot, because most scenarios can be covered by high level > functions like ioremap(), ioremap_coherent(), ioremap_cache()... > so it is better to keep max flexibility for this low level api.
As far as I can see, there is no user of this fonction that sets flags to 0 in the kernel tree.
Did you find any ? If you did, I think it is better to fix the caller.
Christophe
> > Signed-off-by: Nanyong Sun <sunnanyong@huawei.com> > --- > arch/powerpc/mm/ioremap.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/powerpc/mm/ioremap.c b/arch/powerpc/mm/ioremap.c > index 57342154d2b0..b7eda0f0d04d 100644 > --- a/arch/powerpc/mm/ioremap.c > +++ b/arch/powerpc/mm/ioremap.c > @@ -46,6 +46,10 @@ void __iomem *ioremap_prot(phys_addr_t addr, unsigned long size, unsigned long f > pte_t pte = __pte(flags); > void *caller = __builtin_return_address(0); > > + /* The caller should set base page flags properly */ > + if (WARN_ON((flags & _PAGE_PRESENT) == 0))
This probably doesn't work for some plateforms like book3s/64. You should use helpers like pte_present().
See the comment at https://elixir.bootlin.com/linux/v5.14/source/arch/powerpc/include/asm/book3s/64/pgtable.h#L591
> + return NULL; > + > /* writeable implies dirty for kernel addresses */ > if (pte_write(pte)) > pte = pte_mkdirty(pte); >
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