Add BTI landing pads to the AArch64 SHA2 assembly #15339
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The Arm Branch Target Identification (BTI) extension guards against branching to an unintended instruction. To support BTI add the landing pad instructions to the SHA2 functions. These are from the hint space so are a nop on hardware that lacks BTI support or if BTI isn't enabled. Signed-off-by: Andrew Turner <[email protected]>
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Thanks for the fix Andy |
allanjude
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Oct 3, 2023
behlendorf
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Oct 3, 2023
behlendorf
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Oct 4, 2023
The Arm Branch Target Identification (BTI) extension guards against branching to an unintended instruction. To support BTI add the landing pad instructions to the SHA2 functions. These are from the hint space so are a nop on hardware that lacks BTI support or if BTI isn't enabled. Reviewed-by: Allan Jude <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Tino Reichardt <[email protected]> Signed-off-by: Andrew Turner <[email protected]> Closes openzfs#14862 Closes openzfs#15339
behlendorf
pushed a commit
that referenced
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Oct 4, 2023
The Arm Branch Target Identification (BTI) extension guards against branching to an unintended instruction. To support BTI add the landing pad instructions to the SHA2 functions. These are from the hint space so are a nop on hardware that lacks BTI support or if BTI isn't enabled. Reviewed-by: Allan Jude <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Tino Reichardt <[email protected]> Signed-off-by: Andrew Turner <[email protected]> Closes #14862 Closes #15339
lundman
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Dec 12, 2023
The Arm Branch Target Identification (BTI) extension guards against branching to an unintended instruction. To support BTI add the landing pad instructions to the SHA2 functions. These are from the hint space so are a nop on hardware that lacks BTI support or if BTI isn't enabled. Reviewed-by: Allan Jude <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: Tino Reichardt <[email protected]> Signed-off-by: Andrew Turner <[email protected]> Closes openzfs#14862 Closes openzfs#15339
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Motivation and Context
When booting on AArch64 hardware with the Branch Target Identification (BTI) extension the kernel can panic as the SHA256 and SHA512 assembly functions don't have the needed landing pad instructions.
Description
This adds the needed
BTI Cinstruction, encoded using the hint variant so old assemblers will understand it. On hardware that doesn't understand BTI, or where BTI is not enabled this is a nop so is safe.How Has This Been Tested?
I booted on an Arm simulator with a kernel that enabled BTI for the ZFS module and ran the FreeBSD testsuite. Without this change the kernel will panic due to the lack of BTI instructions, with this change the test suite completes.
Types of changes
Checklist:
Signed-off-by.