perf: arm64: Add SVE vector granule register to user regs

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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>

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This commit is contained in:

James Clark 2022-09-01 14:26:57 +01:00 • committed by Will Deacon

parent d813a19e7d

commit cbb0c02caf

3 changed files with 36 additions and 3 deletions

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7

arch/arm64/include/uapi/asm/perf_regs.h

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30

arch/arm64/kernel/perf_regs.c

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2

drivers/perf/arm_pmu.c

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