ec6e822d1a
When pointer authentication is in use, data/instruction pointers have a number of PAC bits inserted into them. The number and position of these bits depends on the configured TCR_ELx.TxSZ and whether tagging is enabled. ARMv8.3 allows tagging to differ for instruction and data pointers. For userspace debuggers to unwind the stack and/or to follow pointer chains, they need to be able to remove the PAC bits before attempting to use a pointer. This patch adds a new structure with masks describing the location of the PAC bits in userspace instruction and data pointers (i.e. those addressable via TTBR0), which userspace can query via PTRACE_GETREGSET. By clearing these bits from pointers (and replacing them with the value of bit 55), userspace can acquire the PAC-less versions. This new regset is exposed when the kernel is built with (user) pointer authentication support, and the address authentication feature is enabled. Otherwise, the regset is hidden. Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com> Cc: Will Deacon <will.deacon@arm.com> [will: Fix to use vabits_user instead of VA_BITS and rename macro] Signed-off-by: Will Deacon <will.deacon@arm.com> |
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