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8cd969d28f
This patch implements support for saving and restoring the SVE registers around signals. A fixed-size header struct sve_context is always included in the signal frame encoding the thread's vector length at the time of signal delivery, optionally followed by a variable-layout structure encoding the SVE registers. Because of the need to preserve backwards compatibility, the FPSIMD view of the SVE registers is always dumped as a struct fpsimd_context in the usual way, in addition to any sve_context. The SVE vector registers are dumped in full, including bits 127:0 of each register which alias the corresponding FPSIMD vector registers in the hardware. To avoid any ambiguity about which alias to restore during sigreturn, the kernel always restores bits 127:0 of each SVE vector register from the fpsimd_context in the signal frame (which must be present): userspace needs to take this into account if it wants to modify the SVE vector register contents on return from a signal. FPSR and FPCR, which are used by both FPSIMD and SVE, are not included in sve_context because they are always present in fpsimd_context anyway. For signal delivery, a new helper fpsimd_signal_preserve_current_state() is added to update _both_ the FPSIMD and SVE views in the task struct, to make it easier to populate this information into the signal frame. Because of the redundancy between the two views of the state, only one is updated otherwise. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Dave Martin <Dave.Martin@arm.com> Cc: Alex Bennée <alex.bennee@linaro.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> |
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