Messages in this thread | | | Date | Sun, 6 Jul 2014 12:24:42 -0700 | Subject | Re: [GIT PULL] bug fix for devicetree memory parsing | From | Linus Torvalds <> |
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On Sun, Jul 6, 2014 at 2:37 AM, Grant Likely <grant.likely@linaro.org> wrote: > > Can you pull this bug fix into your tree please?
I took it, but I think both your explanation and the patch itself is actually crap. It may fix the issue, but it's seriously confused.
Your explanation says that it's a 32-bit platform issue. No it's not. Most 32-bit configurations still have a 64-bit phys_addr_t (ie PAE/LPAE etc).
And the code is crap, because it uses ULONG_MAX etc in ways that simply make no f*cking sense. And why does it care about sizeof?
Why does the code not just do something like
#define MAX_PHYS_ADDR ((phys_addr_t) ~0)
and then do
if (base > MAX_PHYS_ADDR || base + size > MAX_PHYS_ADDR) ...
and be done with it? All those sizeof tests are completely pointless. If it turns out that phys_addr_t is the same size as u64, then the tests will never be true, and the compiler will happily optimize them away.
So I think this fixes a problem, but it's all ugly as hell. I ended up pulling it because I'm lazy and don't have a machine to test a proper fix on anyway, but I hope this can get cleaned up. And more importantly, I hope maintainers will spend a bit more time thinking about things like this. It's not just that the code is unnecessarily complex, it's WRONG. Comparing things to "ULONG_MAX" makes absolutely zero sense, since "ULONG_MAX" has nothing to do with anything. It's just stupid and misleading, and it just so happens to work by random luck because it so *happens* that phys_addr_t is smaller than "u64" only when ULONG_MAX happens to be the same size. But even that is not guaranteed (ie some stupid broken architecture might have a 32-bit physical address space despite having a 64-bit "long")
Linus
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