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Other than the too-long lines in the arm64 vm_map_prot2perms implementation I think this is good.
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Sorry, one more comment. I wonder if vm_map_prot2perms should be vm_prot2perms now that it's no longer in vm_map.c.
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Yeah I have a similar feeling that the name / placement may not be entirely right. I considered also moving it to vm_machdep, but given that it is a cheri-specific thing perhaps it fits well in cheri_machdep. |
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Remove the definition indirection via CHERI_PERMS_PROT2PERM_*; instead, make vm_map_prot2perms fully machine-dependent. Since vm_map_prot2perms is no longer in vm_map.c, rename it to vm_prot2perms. Add a base_perms argument to vm_prot2perms. This removes the direct use of CHERI_PROT2PERM_MASK and makes it clearer that the permission mask is inherited from a base permission bitmask that is altered according to VM_PROT_*. Add a CHERI_PERMS_RWX_MASK macro that serves a similar function as CHERI_PROT2PERMS_MASK, but this is more general. This is useful to clearly separate the permission bits that the system implicitly ties to RWX memory access from the permission bits that are part of other mechanisms, such as c18n, sealing, etc. Note that this serves a different purpose from the existing USER/KERNEL permission bit macros.
This prevents issuing PERM_SYSCALL for data capabilities.
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This should simplify the handling of prot2perm in a few ways:
#definelayers otherwise.base_permsargument tovm_map_prot2permso that it is clearer that the permissions are being "inherited" from a base bitmask and modified according to VM_PROT.Currently this places vm_map_prot2perms in cheri_machdep.c, it is unclear to me whether this is the right place. It may also make sense to rename it to something else.