path: root/Documentation/arm64/tagged-address-abi.rst
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authorOlof Johansson <olof@lixom.net>2020-03-03 16:40:54 -0800
committerOlof Johansson <olof@lixom.net>2020-03-03 16:40:56 -0800
commit820d15632ec10bc0cf79595c5a635b795d149520 (patch)
tree9deb7defafc350a3c74365ebe370634f0406d821 /Documentation/arm64/tagged-address-abi.rst
parentMerge tag 'arm-soc/for-5.6/defconfig-fixes' of https://github.com/Broadcom/stblinux into arm/fixes (diff)
parentarm64: dts: socfpga: agilex: Fix gmac compatible (diff)
Merge tag 'socfpga_dts_fix_for_v5.6_v2' of git://git.kernel.org/pub/scm/linux/kernel/git/dinguyen/linux into arm/fixes
arm64: dts: agilex: fix gmac compatible - The compatible for Agilex GMAC should be "altr,socfpga-stmmac-a10-s10" * tag 'socfpga_dts_fix_for_v5.6_v2' of git://git.kernel.org/pub/scm/linux/kernel/git/dinguyen/linux: (578 commits) arm64: dts: socfpga: agilex: Fix gmac compatible Linux 5.6-rc4 KVM: VMX: check descriptor table exits on instruction emulation ext4: potential crash on allocation error in ext4_alloc_flex_bg_array() macintosh: therm_windtunnel: fix regression when instantiating devices jbd2: fix data races at struct journal_head kvm: x86: Limit the number of "kvm: disabled by bios" messages KVM: x86: avoid useless copy of cpufreq policy KVM: allow disabling -Werror KVM: x86: allow compiling as non-module with W=1 KVM: Pre-allocate 1 cpumask variable per cpu for both pv tlb and pv ipis KVM: Introduce pv check helpers KVM: let declaration of kvm_get_running_vcpus match implementation KVM: SVM: allocate AVIC data structures based on kvm_amd module parameter MAINTAINERS: Correct Cadence PCI driver path io_uring: fix 32-bit compatability with sendmsg/recvmsg net: dsa: mv88e6xxx: Fix masking of egress port mlxsw: pci: Wait longer before accessing the device after reset sfc: fix timestamp reconstruction at 16-bit rollover points vsock: fix potential deadlock in transport->release() ... Link: https://lore.kernel.org/r/20200303153509.28248-1-dinguyen@kernel.org Signed-off-by: Olof Johansson <olof@lixom.net>
Diffstat (limited to 'Documentation/arm64/tagged-address-abi.rst')
1 files changed, 9 insertions, 2 deletions
diff --git a/Documentation/arm64/tagged-address-abi.rst b/Documentation/arm64/tagged-address-abi.rst
index d4a85d535bf9..4a9d9c794ee5 100644
--- a/Documentation/arm64/tagged-address-abi.rst
+++ b/Documentation/arm64/tagged-address-abi.rst
@@ -44,8 +44,15 @@ The AArch64 Tagged Address ABI has two stages of relaxation depending
how the user addresses are used by the kernel:
1. User addresses not accessed by the kernel but used for address space
- management (e.g. ``mmap()``, ``mprotect()``, ``madvise()``). The use
- of valid tagged pointers in this context is always allowed.
+ management (e.g. ``mprotect()``, ``madvise()``). The use of valid
+ tagged pointers in this context is allowed with the exception of
+ ``brk()``, ``mmap()`` and the ``new_address`` argument to
+ ``mremap()`` as these have the potential to alias with existing
+ user addresses.
+ NOTE: This behaviour changed in v5.6 and so some earlier kernels may
+ incorrectly accept valid tagged pointers for the ``brk()``,
+ ``mmap()`` and ``mremap()`` system calls.
2. User addresses accessed by the kernel (e.g. ``write()``). This ABI
relaxation is disabled by default and the application thread needs to