linux-kernel - Re: [PATCH v1] perf arm-spe: Unaligned pointer work around

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Date: Wed, 15 May 2024 17:38:28 +0200
From: James Clark <james.clark@....com>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
 Kan Liang <kan.liang@...ux.intel.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] perf arm-spe: Unaligned pointer work around



On 14/05/2024 07:24, Ian Rogers wrote:
> Use get_unaligned_leXX instead of leXX_to_cpu to handle unaligned
> pointers. Such pointers occur with libFuzzer testing.
> 
> A similar change for intel-pt was done in:
> https://lore.kernel.org/r/20231005190451.175568-6-adrian.hunter@intel.com
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---

Reviewed-by: James Clark <james.clark@....com>

>  .../arm-spe-decoder/arm-spe-pkt-decoder.c     | 23 ++++---------------
>  1 file changed, 5 insertions(+), 18 deletions(-)
> 
> 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 a454c6737563..7bf607d0f6d8 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
> @@ -10,24 +10,11 @@
>  #include <byteswap.h>
>  #include <linux/bitops.h>
>  #include <stdarg.h>
> +#include <linux/kernel.h>
> +#include <asm-generic/unaligned.h>
>  
>  #include "arm-spe-pkt-decoder.h"
>  
> -#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> -#define le16_to_cpu bswap_16
> -#define le32_to_cpu bswap_32
> -#define le64_to_cpu bswap_64
> -#define memcpy_le64(d, s, n) do { \
> -	memcpy((d), (s), (n));    \
> -	*(d) = le64_to_cpu(*(d)); \
> -} while (0)
> -#else
> -#define le16_to_cpu
> -#define le32_to_cpu
> -#define le64_to_cpu
> -#define memcpy_le64 memcpy
> -#endif
> -
>  static const char * const arm_spe_packet_name[] = {
>  	[ARM_SPE_PAD]		= "PAD",
>  	[ARM_SPE_END]		= "END",
> @@ -70,9 +57,9 @@ static int arm_spe_get_payload(const unsigned char *buf, size_t len,
>  
>  	switch (payload_len) {
>  	case 1: packet->payload = *(uint8_t *)buf; break;
> -	case 2: packet->payload = le16_to_cpu(*(uint16_t *)buf); break;
> -	case 4: packet->payload = le32_to_cpu(*(uint32_t *)buf); break;
> -	case 8: packet->payload = le64_to_cpu(*(uint64_t *)buf); break;
> +	case 2: packet->payload = get_unaligned_le16(buf); break;
> +	case 4: packet->payload = get_unaligned_le32(buf); break;
> +	case 8: packet->payload = get_unaligned_le64(buf); break;
>  	default: return ARM_SPE_BAD_PACKET;
>  	}
>