Messages in this thread Patch in this message | | | From | Michael Ellerman <> | Subject | Re: [PATCH] powerpc/64s: Fix possible corruption on big endian due to pgd/pud_present() | Date | Wed, 20 Feb 2019 22:18:38 +1100 |
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Segher Boessenkool <segher@kernel.crashing.org> writes: > On Mon, Feb 18, 2019 at 11:49:18AM +1100, Michael Ellerman wrote: >> Balbir Singh <bsingharora@gmail.com> writes: >> > Fair enough, my point was that the compiler can help out. I'll see what >> > -Wconversion finds on my local build :) >> >> I get about 43MB of warnings here :) > > Yes, -Wconversion complains about a lot of things that are idiomatic C. > There is a reason -Wconversion is not in -Wall or -Wextra.
Actually a lot of those go away when I add -Wno-sign-conversion.
And what's left seems mostly reasonable, they all indicate the possibility of a bug I think.
In fact this works and would have caught the bug:
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index d8c8d7c9df15..3114e3f368e2 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -904,7 +904,12 @@ static inline int pud_none(pud_t pud) static inline int pud_present(pud_t pud) { + __diag_push(); + __diag_warn(GCC, 8, "-Wconversion", "ulong -> int"); + return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PRESENT)); + + __diag_pop(); } extern struct page *pud_page(pud_t pud);
Obviously we're not going to instrument every function like that. But we could start instrumenting particular files.
cheers
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