Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 7 Sep 2017 10:51:21 -0700 | Subject | xt_hashlimig build error (was Re: [RFC 01/17] x86/asm/64: Remove the restore_c_regs_and_iret label) |
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On Thu, Sep 7, 2017 at 3:29 AM, Ingo Molnar <mingo@kernel.org> wrote: > > not the best of kernels, 32-bit allyesconfig doesn't even appear to build: > > net/netfilter/xt_hashlimit.o: In function `hashlimit_mt_common.isra.6': > xt_hashlimit.c:(.text+0x1146): undefined reference to `__udivdi3'
I think this is due to commit bea74641e378 ("netfilter: xt_hashlimit: add rate match mode").
It adds a 64-bit divide in user2rate_bytes() afaik, and to make things worse it seems to be a really stupid one too.
Although I guess "worse" is not bad when the stupidity of it should mean that it's easy to avoid the 64-bit issue.
Oddly, user2rate() that actually *does* need a 64-bit divide, seems to do it right and use "div64_u64()" to do so.
But user2rate_bytes() could easily avoid any 64-bit issues, since it divides the max 32-bit (unsigned) number with a 64-bit unsigned number.
It would be easy to just say
- "if high 32 bits are set, result is 0"
- else do a 32-bit divide
or just use "div64_u64()" in that code too.
But honestly, that math is odd in other ways too (is that "r-1" _supposed_ to underflow to -1 for large 'user' counts?), so somebody needs to look at that logic.
And there might be some other 64-bit divide I missed, so please, netfilter people, check the 32-bit build.
Linus
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