zx_vmar_protect

Summary

Set protection of virtual memory pages.

Declaration

#include <zircon/syscalls.h>

zx_status_t zx_vmar_protect(zx_handle_t handle,
                            zx_vm_option_t options,
                            zx_vaddr_t addr,
                            size_t len);

Description

zx_vmar_protect() alters the access protections for the memory mappings in the range of len bytes starting from addr. The options argument should be a bitwise-or of one or more of the following:

  • ZX_VM_PERM_READ Map as readable. It is an error if handle does not have ZX_VM_CAN_MAP_READ permissions or handle does not have the ZX_RIGHT_READ right. It is also an error if the VMO handle used to create the mapping did not have the ZX_RIGHT_READ right.
  • ZX_VM_PERM_WRITE Map as writable. It is an error if handle does not have ZX_VM_CAN_MAP_WRITE permissions or handle does not have the ZX_RIGHT_WRITE right. It is also an error if the VMO handle used to create the mapping did not have the ZX_RIGHT_WRITE right.
  • ZX_VM_PERM_EXECUTE Map as executable. It is an error if handle does not have ZX_VM_CAN_MAP_EXECUTE permissions or handle does not have the ZX_RIGHT_EXECUTE right. It is also an error if the VMO handle used to create the mapping did not have the ZX_RIGHT_EXECUTE right.
  • ZX_VM_PERM_READ_IF_XOM_UNSUPPORTED Map as readable if the system does not support mapping execute-only pages. If the system can map execute-only this flag is ignored.

For any mappings in sub-regions in the requested range, their access permissions must either be reduced, or left unchanged, by the requested change.

len must be page-aligned.

Rights

If options & ZX_VM_PERM_READ, handle must be of type ZX_OBJ_TYPE_VMAR and have ZX_RIGHT_READ.

If options & ZX_VM_PERM_WRITE, handle must be of type ZX_OBJ_TYPE_VMAR and have ZX_RIGHT_WRITE.

If options & ZX_VM_PERM_EXECUTE, handle must be of type ZX_OBJ_TYPE_VMAR and have ZX_RIGHT_EXECUTE.

Return value

zx_vmar_protect() returns ZX_OK on success.

Errors

ZX_ERR_BAD_HANDLE handle is not a valid handle.

ZX_ERR_WRONG_TYPE handle is not a VMAR handle.

ZX_ERR_INVALID_ARGS prot_flags is an unsupported combination of flags (e.g., ZX_VM_PERM_WRITE but not ZX_VM_PERM_READ), addr is not page-aligned, len is 0, or some subrange of the requested range is occupied by a subregion and handle did not have ZX_RIGHT_OP_CHILDREN.

ZX_ERR_NOT_FOUND Some subrange of the requested range is not mapped.

ZX_ERR_ACCESS_DENIED handle does not have the proper rights for the requested change, the original VMO handle used to create the mapping did not have the rights for the requested change, or the VMAR itself does not allow the requested change, or there is a mapping in a sub-region that would have its mapping permissions increased.

ZX_ERR_NO_MEMORY Failure due to lack of memory. There is no good way for userspace to handle this (unlikely) error. In a future build this error will no longer occur.

Notes

For failures other than ZX_ERR_NO_MEMORY, all access permissions in the range will have been left unchanged.

See also