perf: arm64: Add SVE vector granule register to user regs
authorJames Clark <james.clark@arm.com>
Thu, 1 Sep 2022 13:26:57 +0000 (14:26 +0100)
committerWill Deacon <will@kernel.org>
Thu, 22 Sep 2022 14:06:02 +0000 (15:06 +0100)
commitcbb0c02caf4bd98b9e0cd6d7420734b8e9a35703
tree77998269afeffb99865493242d49ac78038eb8b0
parentd813a19e7d2ec0c57477ee114f9b5e9a43cacb76
perf: arm64: Add SVE vector granule register to user regs

Dwarf based unwinding in a function that pushes SVE registers onto
the stack requires the unwinder to know the length of the SVE register
to calculate the stack offsets correctly. This was added to the Arm
specific Dwarf spec as the VG pseudo register[1].

Add the vector length at position 46 if it's requested by userspace and
SVE is supported. If it's not supported then fail to open the event.

The vector length must be on each sample because it can be changed
at runtime via a prctl or ptrace call. Also by adding it as a register
rather than a separate attribute, minimal changes will be required in an
unwinder that already indexes into the register list.

[1]: https://github.com/ARM-software/abi-aa/blob/main/aadwarf64/aadwarf64.rst

Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: James Clark <james.clark@arm.com>
Link: https://lore.kernel.org/r/20220901132658.1024635-2-james.clark@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
arch/arm64/include/uapi/asm/perf_regs.h
arch/arm64/kernel/perf_regs.c
drivers/perf/arm_pmu.c