-fwrapv concerns signed arithmetic. This calculation is with unsigned arithmetic, and the possibility of wrapping around to 0 is part of the language.
Doug Moore On 6/10/19 1:35 AM, Andriy Gapon wrote: > On 10/06/2019 06:07, Doug Moore wrote: >> Author: dougm >> Date: Mon Jun 10 03:07:10 2019 >> New Revision: 348843 >> URL: https://svnweb.freebsd.org/changeset/base/348843 >> >> Log: >> There are times when a len==0 parameter to mmap is okay. But on a >> 32-bit machine, a len parameter just a few bytes short of 4G, rounded >> up to a page boundary and hitting zero then, is not okay. Return >> failure in that case. >> >> Reported by: pho >> Reviewed by: alc, kib (mentor) >> Tested by: pho >> Differential Revision: https://reviews.freebsd.org/D20580 >> >> Modified: >> head/sys/vm/vm_mmap.c >> >> Modified: head/sys/vm/vm_mmap.c >> ============================================================================== >> --- head/sys/vm/vm_mmap.c Sun Jun 9 22:55:21 2019 (r348842) >> +++ head/sys/vm/vm_mmap.c Mon Jun 10 03:07:10 2019 (r348843) >> @@ -257,7 +257,10 @@ kern_mmap(struct thread *td, uintptr_t addr0, size_t s >> >> /* Adjust size for rounding (on both ends). */ >> size += pageoff; /* low end... */ >> - size = (vm_size_t) round_page(size); /* hi end */ >> + /* Check for rounding up to zero. */ >> + if (round_page(size) < size) > Is this guaranteed to work with all compilers? > I think that some smart compilers may think that this condition is impossible. > Are we finally using -fwrapv or something like it for kernel builds? > >> + return (EINVAL); >> + size = round_page(size); /* hi end */ >> >> /* Ensure alignment is at least a page and fits in a pointer. */ >> align = flags & MAP_ALIGNMENT_MASK; >> > _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
