Re: [PATCH v2 04/14] perf arm-spe: Fix packet length handling

[André Przywara]

On 29/09/2020 14:39, Leo Yan wrote:
> When process address packet and counter packet, if the packet contains

       processing

> extended header, it misses to account the extra one byte for header
> length calculation, thus returns the wrong packet length.
> 
> To correct the packet length calculation, one possible fixing is simply
> to plus extra 1 for extended header, but will spread some duplicate code
> in the flows for processing address packet and counter packet.
> Alternatively, we can refine the function arm_spe_get_payload() to not
> only support short header and allow it to support extended header, and
> rely on it for the packet length calculation.
> 
> So this patch refactors function arm_spe_get_payload() with a new
> argument 'ext_hdr' for support extended header; the packet processing
> flows can invoke this function to unify the packet length calculation.
> 
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>

That looks alright to me.

Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>

Cheers,
Andre

> ---
>  .../arm-spe-decoder/arm-spe-pkt-decoder.c     | 34 +++++++------------
>  1 file changed, 12 insertions(+), 22 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 5a8696031e16..4f0aeb62e97b 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
> @@ -80,14 +80,15 @@ const char *arm_spe_pkt_name(enum arm_spe_pkt_type type)
>  	(1 << (((val) & SPE_HEADER_SZ_MASK) >> SPE_HEADER_SZ_SHIFT))
>  
>  static int arm_spe_get_payload(const unsigned char *buf, size_t len,
> +			       unsigned char ext_hdr,
>  			       struct arm_spe_pkt *packet)
>  {
> -	size_t payload_len = PAYLOAD_LEN(buf[0]);
> +	size_t payload_len = PAYLOAD_LEN(buf[ext_hdr]);
>  
> -	if (len < 1 + payload_len)
> +	if (len < 1 + ext_hdr + payload_len)
>  		return ARM_SPE_NEED_MORE_BYTES;
>  
> -	buf++;
> +	buf += 1 + ext_hdr;
>  
>  	switch (payload_len) {
>  	case 1: packet->payload = *(uint8_t *)buf; break;
> @@ -97,7 +98,7 @@ static int arm_spe_get_payload(const unsigned char *buf, size_t len,
>  	default: return ARM_SPE_BAD_PACKET;
>  	}
>  
> -	return 1 + payload_len;
> +	return 1 + ext_hdr + payload_len;
>  }
>  
>  static int arm_spe_get_pad(struct arm_spe_pkt *packet)
> @@ -128,7 +129,7 @@ static int arm_spe_get_timestamp(const unsigned char *buf, size_t len,
>  				 struct arm_spe_pkt *packet)
>  {
>  	packet->type = ARM_SPE_TIMESTAMP;
> -	return arm_spe_get_payload(buf, len, packet);
> +	return arm_spe_get_payload(buf, len, 0, packet);
>  }
>  
>  static int arm_spe_get_events(const unsigned char *buf, size_t len,
> @@ -143,14 +144,14 @@ static int arm_spe_get_events(const unsigned char *buf, size_t len,
>  	 */
>  	packet->index = PAYLOAD_LEN(buf[0]);
>  
> -	return arm_spe_get_payload(buf, len, packet);
> +	return arm_spe_get_payload(buf, len, 0, packet);
>  }
>  
>  static int arm_spe_get_data_source(const unsigned char *buf, size_t len,
>  				   struct arm_spe_pkt *packet)
>  {
>  	packet->type = ARM_SPE_DATA_SOURCE;
> -	return arm_spe_get_payload(buf, len, packet);
> +	return arm_spe_get_payload(buf, len, 0, packet);
>  }
>  
>  static int arm_spe_get_context(const unsigned char *buf, size_t len,
> @@ -158,8 +159,7 @@ static int arm_spe_get_context(const unsigned char *buf, size_t len,
>  {
>  	packet->type = ARM_SPE_CONTEXT;
>  	packet->index = buf[0] & 0x3;
> -
> -	return arm_spe_get_payload(buf, len, packet);
> +	return arm_spe_get_payload(buf, len, 0, packet);
>  }
>  
>  static int arm_spe_get_op_type(const unsigned char *buf, size_t len,
> @@ -167,41 +167,31 @@ static int arm_spe_get_op_type(const unsigned char *buf, size_t len,
>  {
>  	packet->type = ARM_SPE_OP_TYPE;
>  	packet->index = buf[0] & 0x3;
> -	return arm_spe_get_payload(buf, len, packet);
> +	return arm_spe_get_payload(buf, len, 0, packet);
>  }
>  
>  static int arm_spe_get_counter(const unsigned char *buf, size_t len,
>  			       const unsigned char ext_hdr, struct arm_spe_pkt *packet)
>  {
> -	if (len < 2)
> -		return ARM_SPE_NEED_MORE_BYTES;
> -
>  	packet->type = ARM_SPE_COUNTER;
>  	if (ext_hdr)
>  		packet->index = ((buf[0] & 0x3) << 3) | (buf[1] & 0x7);
>  	else
>  		packet->index = buf[0] & 0x7;
>  
> -	packet->payload = le16_to_cpu(*(uint16_t *)(buf + 1));
> -
> -	return 1 + ext_hdr + 2;
> +	return arm_spe_get_payload(buf, len, ext_hdr, packet);
>  }
>  
>  static int arm_spe_get_addr(const unsigned char *buf, size_t len,
>  			    const unsigned char ext_hdr, struct arm_spe_pkt *packet)
>  {
> -	if (len < 8)
> -		return ARM_SPE_NEED_MORE_BYTES;
> -
>  	packet->type = ARM_SPE_ADDRESS;
>  	if (ext_hdr)
>  		packet->index = ((buf[0] & 0x3) << 3) | (buf[1] & 0x7);
>  	else
>  		packet->index = buf[0] & 0x7;
>  
> -	memcpy_le64(&packet->payload, buf + 1, 8);
> -
> -	return 1 + ext_hdr + 8;
> +	return arm_spe_get_payload(buf, len, ext_hdr, packet);
>  }
>  
>  static int arm_spe_do_get_packet(const unsigned char *buf, size_t len,
>