perf tools: Prevent out-of-bounds access to registers

The size of the cache of register values is arch-dependant
(PERF_REGS_MAX). This has the potential of causing an out-of-bounds
access in the function "perf_reg_value" if the local architecture
contains less registers than the one the perf.data file was recorded on.

Since the maximum number of registers is bound by the bitmask "u64
cache_mask", and the size of the cache when running under x86 systems is
64 already, fix the size to 64 and add a range-check to the function
"perf_reg_value" to prevent out-of-bounds access.

Reported-by: Alexandre Truong <[email protected]>
Reviewed-by: Kajol Jain <[email protected]>
Signed-off-by: German Gomez <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: John Garry <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Poirier <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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