If someone with decent C experience is interested in working on github.com/HardenedBSD/ha (HardenedBSD: Support multiple userland heap implementations), let me know. I can help you once you are at the point that you're building HardenedBSD and can make modifications to the libc.
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Can message me on IRC (strcat on freenode and oftc) and I'd be glad to help with it. Dropping it in as a replacement for jemalloc should be very easy. This is the entirety of the work for Android in Bionic: github.com/GrapheneOS/pla other than integrating the extra API extensions.
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It needs internal porting to support FreeBSD/ too. It will be integrated upstream into github.com/GrapheneOS/har once someone is building it and identifying / resolving portability issues like needing to disable mremap usage. It already supports Bionic / musl / glibc.
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It would also be nice to set up the build system integration to have it as the internal malloc implementation in , rather than the current support for interposition via dynamic linking. Can be built as a static lib and linked into musl just like the approach for Bionic.
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I can also provide some guidance on other libc hardening work including implementing production-oriented cross-DSO CFI (unlike compiler-rt), cross-DSO SafeStack, various smaller things like read-only-after-init data / setjmp mangling / internal function pointer protection, etc.
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