Tweak malloc_stack on OpenBSD to match other implementations; explain lack of guard page #54564
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I started a build with it to check it is fine (but from reading the diff
it LGTM).
Regarding the missing `mprotect`, it is intented: on OpenBSD, any
mmap-ed region has guard page managed by the kernel, so there is no need
for it. Additionally, a memory region used as stack (memeory allocated
with MAP_STACK option) has strict permission, and you can't "create" a
guard page on such memory by using `mprotect` on it.
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Thanks for the clarification, much appreciated! I think it is important to document such details (and we should do so in many more places). So I took the liberty and turned your nice explanation into a source comment. Please let me know if this is OK for you. |
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The other malloc_stack implementations were switched to using jl_atomic_fetch_add_relaxed on 2024-02-23. I suspect that this simply overlapped in time with the creation of the OpenBSD patches, which were submitted in March, but presumably work started before that :-).
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LGTM thanks. |
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… lack of guard page (JuliaLang#54564) The other malloc_stack implementations were switched to using jl_atomic_fetch_add_relaxed on 2024-02-23. I suspect that this simply overlapped in time with the creation of the OpenBSD patches, which were submitted in March, but presumably work started before that :-). CC @semarie please check that I am not messing up something for you. Also, while at it, I noticed that the OpenBSD `malloc_stack` is missing the `mprotect` for setting up a guard page, which concerns me a bit. Is there a deeper reason for this omission?
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The other malloc_stack implementations were switched to using jl_atomic_fetch_add_relaxed on 2024-02-23. I suspect that this simply overlapped in time with the creation of the OpenBSD patches, which were submitted in March, but presumably work started before that :-).
CC @semarie please check that I am not messing up something for you.
Also, while at it, I noticed that the OpenBSD
malloc_stackis missing themprotectfor setting up a guard page, which concerns me a bit. Is there a deeper reason for this omission?