There was some work done on XOM (eXecute-only-memory) for arm64, but on at least x86 there isn't a separate page table bit for just read permissions, so there's no way[0][1] to express R^X, PROT_EXEC without PROT_READ is not possible.
Amusingly the 80286 supported execute-only segments, but this was dropped from 32-bit x86.
[0] It is possible on Intel in VM guests using EPT (Extended Page Tables), mlarkin@ experimented with protecting the host kernel in a special VM, called "Underjack". AMD SVM supports nothing like this.
[1] The custom AMD APU SoC in Sony's PS5 console supports "xotext" via NDA'd extensions, but there's no public documentation. (If _anyone_ knows details, pls share)
... btw, PROT_WRITE-only mappings are also impossible on x86 as well, so PROT_WRITE implicitly means PROT_READ. Not that I'm aware of any valid reason anyone might want this.
Amusingly the 80286 supported execute-only segments, but this was dropped from 32-bit x86.
[0] It is possible on Intel in VM guests using EPT (Extended Page Tables), mlarkin@ experimented with protecting the host kernel in a special VM, called "Underjack". AMD SVM supports nothing like this.
[1] The custom AMD APU SoC in Sony's PS5 console supports "xotext" via NDA'd extensions, but there's no public documentation. (If _anyone_ knows details, pls share)
... btw, PROT_WRITE-only mappings are also impossible on x86 as well, so PROT_WRITE implicitly means PROT_READ. Not that I'm aware of any valid reason anyone might want this.