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0766f278d8
Most kernel memory that is allocated after boot does not need to be executable. There are a few exceptions. For example, kernel modules do need executable memory, but they don't use UMA or malloc(9). The BPF JIT compiler also needs executable memory and did use malloc(9) until r317072. (Note that a side effect of r316767 was that the "small allocation" path in UMA on amd64 already returned non-executable memory. This meant that some calls to malloc(9) or the UMA zone(9) allocator could return executable memory, while others could return non-executable memory. This change makes the behavior consistent.) This change makes malloc(9) return non-executable memory unless the new M_EXEC flag is specified. After this change, the UMA zone(9) allocator will always return non-executable memory, and a KASSERT will catch attempts to use the M_EXEC flag to allocate executable memory using uma_zalloc() or its variants. Allocations that do need executable memory have various choices. They may use the M_EXEC flag to malloc(9), or they may use a different VM interfact to obtain executable pages. Now that malloc(9) again allows executable allocations, this change also reverts most of r317072. PR: 228927 Reviewed by: alc, kib, markj, jhb (previous version) Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D15691 |
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