Re: [PATCH v2 6/6] perf arm_spe: Print remaining IMPDEF event numbers

[Jie Gan]

Hi James,

On 4/7/2026 10:05 PM, James Clark wrote:
> Any IMPDEF events not printed out from a known core's IMPDEF list or for
> a completely unknown core will still not be shown to the user. Fix this
> by printing the remaining bits as comma separated raw numbers, e.g.
> "IMPDEF:1,2,3,4".
>
> Suggested-by: Al Grant <al.grant@xxxxxxx>
> Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
> ---
>   tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)
>
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> index b74f887a48f2..c65b22a2179c 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> @@ -8,6 +8,7 @@
>   #include <string.h>
>   #include <endian.h>
>   #include <byteswap.h>
> +#include <linux/bitmap.h>
>   #include <linux/bitops.h>
>   #include <stdarg.h>
>   #include <linux/kernel.h>
> @@ -365,6 +366,23 @@ static int arm_spe_pkt_desc_event(const struct arm_spe_pkt *packet,
>   						   payload);
>   	}
>   
> +	/*
> +	 * Print remaining IMPDEF bits that weren't printed above as raw
> +	 * "IMPDEF:1,2,3,4" etc.
> +	 */
> +	if (payload) {
> +		int i;
> +
> +		arm_spe_pkt_out_string(&err, &buf, &buf_len, " IMPDEF:");
> +		for_each_set_bit(i, &payload, 64) {

for_each_set_bit(i, &payload, 64) passes &payload where payload is u64. 
The macro expands to find_next_bit(const unsigned long *addr, ...). On a 
32-bit host unsigned long is 32 bits wide, so only the low 32 bits of 
payload would be scanned; bits 32–63 would be silently ignored. While 
perf is almost always built on a 64-bit host today, the tools/ tree is 
explicitly portable and the compiler will emit a -Wpointer-arith / 
-Wincompatible-pointer-types warning on a 32-bit build.

Thanks,
Jie

> +			const char *sep = payload & (payload - 1) ? "," : "";
> +
> +			arm_spe_pkt_out_string(&err, &buf, &buf_len, "%d%s", i,
> +					       sep);
> +			payload &= ~BIT_ULL(i);
> +		}
> +	}
> +
>   	return err;
>   }
>