tree d5ef283426b675e5e8d776e70f6e4655f3437e2c
parent 3b3b681097fae73b7f5dcdd42db6cfdf32943d4c
author Will Deacon <will.deacon@arm.com> 1510676159 +0000
committer Catalin Marinas <catalin.marinas@arm.com> 1515437011 +0000

arm64: use RET instruction for exiting the trampoline

Speculation attacks against the entry trampoline can potentially resteer
the speculative instruction stream through the indirect branch and into
arbitrary gadgets within the kernel.

This patch defends against these attacks by forcing a misprediction
through the return stack: a dummy BL instruction loads an entry into
the stack, so that the predicted program flow of the subsequent RET
instruction is to a branch-to-self instruction which is finally resolved
as a branch to the kernel vectors with speculation suppressed.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>