Pkru

If supported by hardware, each mapped user linear address has an associated 4-bit protection key. Pkru new per-thread PKRU hardware register determines, for each protection key, whether user-mode addresses with that protection key may be read or written, pkru, pkru. Only one key may apply to a given range at a time.

Want to link to this manual page? Skip site navigation 1 Skip section navigation 2 Header And Logo. Peripheral Links. Donate to FreeBSD. The mechanism gives safety measures which can be used to avoid incidental read or modification of sensitive memory, or as a debugging feature.

Pkru

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Pkru new per-thread PKRU hardware register determines, for each protection key, pkru, whether user-mode addresses with that protection key may be read or written.

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Memory protection consists in managing access rights of memory pages, either to avoid bugs or preventing malicious behavior. This is usually done through system calls, for instance with mprotect on Linux, because modification of the page table entries requires privileged access. MPK also referred as PKU for Protection Keys for Userspace is a userspace hardware mechanism to control page table permissions, it works by tagging memory pages with protection keys using 4 previously unused bits, in other words we can use up to 16 distinct keys to tag our pages. Once a page is tagged we can change its protection rights at will, from userspace. But, because updating page table entries PTE requires privileged access, a system call is still necessary to tag the pages with a given key in the first place.

Pkru

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If access is not zero, read access is permitted. The default protec- tion key index is zero, it is used even if no key was explicitly as- signed to the address, or if the key was removed. Starting address is truncated to the page start, and the end is rounded up to the end of the page. The key indexes written into the page table entries are managed by the sysarch syscall. Privacy policy. The mechanism gives safety measures which can be used to avoid incidental read or modification of sensitive memory, or as a debugging feature. Starting address is truncated to the page start, and the end is rounded up to the end of the page. If the value pointed to by access is zero after the call, no read or write permissions is granted for map- pings which are assigned the key keyidx. Protection keys require that the system uses 4-level paging also called long mode , which means that it is only available on amd64 system. Peripheral Links. The non-zero value of the variable pointed to by the modify argument indicates that write access is permitted. The non-zero value of the variable pointed to by the modify argument indicates that write access is permitted.

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FreeBSD Only one key may apply to a given range at a time. After a successfull call, the range has the specified key assigned, even if the key is zero and it did not change the page table entries. Peripheral Links. If access is not zero, read access is permitted. Donate to FreeBSD. Want to link to this manual page? Protection keys require that the system uses 4-level paging also called long mode , which means that it is only available on amd64 sys- tem. Skip site navigation 1 Skip section navigation 2 Header And Logo. If access is not zero, read access is permitted. The system provides convenient library helpers for both the syscall and the instructions, described below. If the value pointed to by access is zero after the call, no read or write permissions is granted for mappings which are assigned the key keyidx. The mechanism gives safety measures which can be used to avoid incidental read or modification of sensitive memory, or as a debugging feature. All rights reserved.