From f9985441a763270a2af871655d971e982bcaf723 Mon Sep 17 00:00:00 2001 From: Evgenii Stepanov Date: Wed, 9 Mar 2022 13:04:42 -0800 Subject: [PATCH] Revert "FROMLIST: arm64/mte: Document ABI for asymmetric mode" This FROMLIST change has been updated. Reverting to be replaced with the final version FROMGIT. This reverts commit 926ce981052df354958d91fdf503b35648a19366. Bug: 217221156 Change-Id: I4e5c19675fc88987da9804a39a050ef050e2453a Signed-off-by: Evgenii Stepanov --- Documentation/arm64/memory-tagging-extension.rst | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/Documentation/arm64/memory-tagging-extension.rst b/Documentation/arm64/memory-tagging-extension.rst index 5218b838d062..7b99c8f428eb 100644 --- a/Documentation/arm64/memory-tagging-extension.rst +++ b/Documentation/arm64/memory-tagging-extension.rst @@ -76,9 +76,6 @@ configurable behaviours: with ``.si_code = SEGV_MTEAERR`` and ``.si_addr = 0`` (the faulting address is unknown). -- *Asymmetric* - Reads are handled as for synchronous mode while writes - are handled as for asynchronous mode. - The user can select the above modes, per thread, using the ``prctl(PR_SET_TAGGED_ADDR_CTRL, flags, 0, 0, 0)`` system call where ``flags`` contains any number of the following values in the ``PR_MTE_TCF_MASK`` @@ -88,7 +85,6 @@ bit-field: (ignored if combined with other options) - ``PR_MTE_TCF_SYNC`` - *Synchronous* tag check fault mode - ``PR_MTE_TCF_ASYNC`` - *Asynchronous* tag check fault mode -- ``PR_MTE_TCF_ASYMM`` - *Asymmetric* tag check fault mode If no modes are specified, tag check faults are ignored. If a single mode is specified, the program will run in that mode. If multiple @@ -143,14 +139,16 @@ tag checking mode as the CPU's preferred tag checking mode. The preferred tag checking mode for each CPU is controlled by ``/sys/devices/system/cpu/cpu/mte_tcf_preferred``, to which a -privileged user may write the value ``async``, ``sync`` or ``asymm``. The -default preferred mode for each CPU is ``async``. +privileged user may write the value ``async`` or ``sync``. The default +preferred mode for each CPU is ``async``. To allow a program to potentially run in the CPU's preferred tag checking mode, the user program may set multiple tag check fault mode bits in the ``flags`` argument to the ``prctl(PR_SET_TAGGED_ADDR_CTRL, flags, 0, 0, 0)`` system call. If the CPU's preferred tag checking -mode is in the task's set of provided tag checking modes, that +mode is in the task's set of provided tag checking modes (this will +always be the case at present because the kernel only supports two +tag checking modes, but future kernels may support more modes), that mode will be selected. Otherwise, one of the modes in the task's mode set will be selected in a currently unspecified manner.