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Diffstat (limited to 'Documentation/arch/riscv/uabi.rst')
| -rw-r--r-- | Documentation/arch/riscv/uabi.rst | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/arch/riscv/uabi.rst b/Documentation/arch/riscv/uabi.rst index 2b420bab0527..ddb8359a46ed 100644 --- a/Documentation/arch/riscv/uabi.rst +++ b/Documentation/arch/riscv/uabi.rst @@ -68,3 +68,15 @@ Misaligned accesses Misaligned scalar accesses are supported in userspace, but they may perform poorly. Misaligned vector accesses are only supported if the Zicclsm extension is supported. + +Pointer masking +--------------- + +Support for pointer masking in userspace (the Supm extension) is provided via +the ``PR_SET_TAGGED_ADDR_CTRL`` and ``PR_GET_TAGGED_ADDR_CTRL`` ``prctl()`` +operations. Pointer masking is disabled by default. To enable it, userspace +must call ``PR_SET_TAGGED_ADDR_CTRL`` with the ``PR_PMLEN`` field set to the +number of mask/tag bits needed by the application. ``PR_PMLEN`` is interpreted +as a lower bound; if the kernel is unable to satisfy the request, the +``PR_SET_TAGGED_ADDR_CTRL`` operation will fail. The actual number of tag bits +is returned in ``PR_PMLEN`` by the ``PR_GET_TAGGED_ADDR_CTRL`` operation. |