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SubjectRe: [PATCHv4 06/10] arm64: add basic pointer authentication support
On 5/3/2018 9:20 AM, Mark Rutland wrote:
> This patch adds basic support for pointer authentication, allowing
> userspace to make use of APIAKey. The kernel maintains an APIAKey value
> for each process (shared by all threads within), which is initialised to
> a random value at exec() time.
> To describe that address authentication instructions are available, the
> ID_AA64ISAR0.{APA,API} fields are exposed to userspace. A new hwcap,
> APIA, is added to describe that the kernel manages APIAKey.
> Instructions using other keys (APIBKey, APDAKey, APDBKey) are disabled,
> and will behave as NOPs. These may be made use of in future patches.
> No support is added for the generic key (APGAKey), though this cannot be
> trapped or made to behave as a NOP. Its presence is not advertised with
> a hwcap.
> Signed-off-by: Mark Rutland <>
> Cc: Catalin Marinas <>
> Cc: Ramana Radhakrishnan <>
> Cc: Suzuki K Poulose <>
> Cc: Will Deacon <>
> ---

Mark, I was able to verify that a buffer overflow exploit results in a segfault
with these PAC patches. When I compile the same binary without
"-msign-return-address=none", I am able to successfully overflow the stack and
execute malicious code.


Tested-by: Adam Wallis <>

Adam Wallis
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

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