Message-ID: <20210118190613.GB464579@xps15>
Date:   Mon, 18 Jan 2021 12:06:13 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Mike Leach <mike.leach@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
        leo.yan@...aro.org, linux-kernel@...r.kernel.org,
        suzuki.poulose@....com, peterz@...radead.org, mingo@...hat.com,
        acme@...nel.org, will@...nel.org, john.garry@...wei.com,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org
Subject: Re: [PATCH v2] perf: cs-etm: update ETM metadata format

Hey Mike,

On Fri, Jan 15, 2021 at 05:27:02PM +0000, Mike Leach wrote:
> The current fixed metadata version format (version 0), means that adding
> metadata parameter items renders files from a previous version of perf
> unreadable. Per CPU parameters appear in a fixed order, but there is no
> field to indicate the number of ETM parameters per CPU.
> 
> This patch updates the per CPU parameter blocks to include a NR_PARAMs
> value which indicates the number of parameters in the block.
> 
> The header version is incremented to 1. Fixed ordering is retained,
> new ETM parameters are added to the end of the list.
> 
> The reader code is updated to be able to read current version 0 files,
> For version 1, the reader will read the number of parameters in the
> per CPU block. This allows the reader to process older or newer files
> that may have different numbers of parameters than in use at the
> time perf was built.
> 
> Changes since v1 (from Review by Leo):
> 1. Split printing routine into sub functions per version
> 2. Renamed NR_PARAMs to NR_TRC_PARAMs to emphasise use as count of trace
> related parameters, not total block parameter.
> 3. Misc other fixes.
> 
> Signed-off-by: Mike Leach <mike.leach@...aro.org>
> ---
>  tools/perf/arch/arm/util/cs-etm.c |   7 +-
>  tools/perf/util/cs-etm.c          | 212 ++++++++++++++++++++++++------
>  tools/perf/util/cs-etm.h          |  30 ++++-
>  3 files changed, 200 insertions(+), 49 deletions(-)
> 
> diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
> index bd446aba64f7..b0470f2a955a 100644
> --- a/tools/perf/arch/arm/util/cs-etm.c
> +++ b/tools/perf/arch/arm/util/cs-etm.c
> @@ -572,7 +572,7 @@ static void cs_etm_get_metadata(int cpu, u32 *offset,
>  				struct auxtrace_record *itr,
>  				struct perf_record_auxtrace_info *info)
>  {
> -	u32 increment;
> +	u32 increment, nr_trc_params;
>  	u64 magic;
>  	struct cs_etm_recording *ptr =
>  			container_of(itr, struct cs_etm_recording, itr);
> @@ -607,6 +607,7 @@ static void cs_etm_get_metadata(int cpu, u32 *offset,
>  
>  		/* How much space was used */
>  		increment = CS_ETMV4_PRIV_MAX;
> +		nr_trc_params = CS_ETMV4_PRIV_MAX - CS_ETMV4_TRCCONFIGR;
>  	} else {
>  		magic = __perf_cs_etmv3_magic;
>  		/* Get configuration register */
> @@ -624,11 +625,13 @@ static void cs_etm_get_metadata(int cpu, u32 *offset,
>  
>  		/* How much space was used */
>  		increment = CS_ETM_PRIV_MAX;
> +		nr_trc_params = CS_ETM_PRIV_MAX - CS_ETM_ETMCR;
>  	}
>  
>  	/* Build generic header portion */
>  	info->priv[*offset + CS_ETM_MAGIC] = magic;
>  	info->priv[*offset + CS_ETM_CPU] = cpu;
> +	info->priv[*offset + CS_ETM_NR_TRC_PARAMS] = nr_trc_params;
>  	/* Where the next CPU entry should start from */
>  	*offset += increment;
>  }
> @@ -674,7 +677,7 @@ static int cs_etm_info_fill(struct auxtrace_record *itr,
>  
>  	/* First fill out the session header */
>  	info->type = PERF_AUXTRACE_CS_ETM;
> -	info->priv[CS_HEADER_VERSION_0] = 0;
> +	info->priv[CS_HEADER_VERSION] = CS_HEADER_CURRENT_VERSION;
>  	info->priv[CS_PMU_TYPE_CPUS] = type << 32;
>  	info->priv[CS_PMU_TYPE_CPUS] |= nr_cpu;
>  	info->priv[CS_ETM_SNAPSHOT] = ptr->snapshot_mode;
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index a2a369e2fbb6..23115f9633dc 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -2435,7 +2435,7 @@ static bool cs_etm__is_timeless_decoding(struct cs_etm_auxtrace *etm)
>  }
>  
>  static const char * const cs_etm_global_header_fmts[] = {
> -	[CS_HEADER_VERSION_0]	= "	Header version		       %llx\n",
> +	[CS_HEADER_VERSION]	= "	Header version		       %llx\n",
>  	[CS_PMU_TYPE_CPUS]	= "	PMU type/num cpus	       %llx\n",
>  	[CS_ETM_SNAPSHOT]	= "	Snapshot		       %llx\n",
>  };
> @@ -2443,6 +2443,7 @@ static const char * const cs_etm_global_header_fmts[] = {
>  static const char * const cs_etm_priv_fmts[] = {
>  	[CS_ETM_MAGIC]		= "	Magic number		       %llx\n",
>  	[CS_ETM_CPU]		= "	CPU			       %lld\n",
> +	[CS_ETM_NR_TRC_PARAMS]	= "	NR_TRC_PARAMS		       %llx\n",
>  	[CS_ETM_ETMCR]		= "	ETMCR			       %llx\n",
>  	[CS_ETM_ETMTRACEIDR]	= "	ETMTRACEIDR		       %llx\n",
>  	[CS_ETM_ETMCCER]	= "	ETMCCER			       %llx\n",
> @@ -2452,6 +2453,7 @@ static const char * const cs_etm_priv_fmts[] = {
>  static const char * const cs_etmv4_priv_fmts[] = {
>  	[CS_ETM_MAGIC]		= "	Magic number		       %llx\n",
>  	[CS_ETM_CPU]		= "	CPU			       %lld\n",
> +	[CS_ETM_NR_TRC_PARAMS]	= "	NR_TRC_PARAMS		       %llx\n",
>  	[CS_ETMV4_TRCCONFIGR]	= "	TRCCONFIGR		       %llx\n",
>  	[CS_ETMV4_TRCTRACEIDR]	= "	TRCTRACEIDR		       %llx\n",
>  	[CS_ETMV4_TRCIDR0]	= "	TRCIDR0			       %llx\n",
> @@ -2461,24 +2463,152 @@ static const char * const cs_etmv4_priv_fmts[] = {
>  	[CS_ETMV4_TRCAUTHSTATUS] = "	TRCAUTHSTATUS		       %llx\n",
>  };
>  
> -static void cs_etm__print_auxtrace_info(__u64 *val, int num)
> +static const char * const param_unk_fmt =
> +	"	Unknown parameter [%d]	       %llx\n";
> +static const char * const magic_unk_fmt =
> +	"	Magic number Unknown	       %llx\n";
> +
> +static void cs_etm__print_cpu_metadata_v0(__u64 *val, int *offset)
> +{
> +	int i = *offset, j, nr_params = 0;
> +	__u64 magic;
> +
> +	/* common header block */
> +	magic = val[i];
> +	fprintf(stdout, cs_etm_priv_fmts[0], val[i++]);
> +	fprintf(stdout, cs_etm_priv_fmts[1], val[i++]);

Please use CS_ETM_MAGIC and CS_ETM_CPU as indexes into cs_etm_priv_fmts[].

> +
> +	if (magic == __perf_cs_etmv3_magic) {

                start = CS_ETM_ETMCR;

> +		nr_params = CS_ETM_NR_TRC_PARAMS_V0;
> +		/* after common block, offset format index past NR_PARAMS */
> +		for (j = 3; j < nr_params + 3; j++, i++)

                for (j = start; j < nr_params + start; j++; i++)

That way we don't have to guess what '3' means.  It is clear to us because we
are familiar with the code but I imagine it would be confusing for someone who is
trying to figure out what we did.


> +			fprintf(stdout, cs_etm_priv_fmts[j], val[i]);
> +	} else if (magic == __perf_cs_etmv4_magic) {
> +		nr_params = CS_ETMV4_NR_TRC_PARAMS_V0;
> +		/* after common block, offset format index past NR_PARAMS */
> +		for (j = 3; j < nr_params + 3; j++, i++)
> +			fprintf(stdout, cs_etmv4_priv_fmts[j], val[i]);
> +	} else {
> +		/* failure - note bad magic value */
> +		fprintf(stdout, magic_unk_fmt, magic);
> +	}
> +	*offset = i;

I don't like introcuding coupling between functions but I haven't found an
alternative that looks better.

> +}
> +
> +static void cs_etm__print_cpu_metadata_v1(__u64 *val, int *offset)
>  {
> -	int i, j, cpu = 0;
> +	int i = *offset, j, total_params = 0;
> +	__u64 magic;
>  
> -	for (i = 0; i < CS_HEADER_VERSION_0_MAX; i++)
> -		fprintf(stdout, cs_etm_global_header_fmts[i], val[i]);
> +	magic = val[i + CS_ETM_MAGIC];
> +	/* total params to print is NR_PARAMS + common block size for v1 */
> +	total_params = val[i + CS_ETM_NR_TRC_PARAMS] + CS_ETM_COMMON_BLK_MAX_V1;
>  
> -	for (i = CS_HEADER_VERSION_0_MAX; cpu < num; cpu++) {
> -		if (val[i] == __perf_cs_etmv3_magic)
> -			for (j = 0; j < CS_ETM_PRIV_MAX; j++, i++)
> +	if (magic == __perf_cs_etmv3_magic) {
> +		for (j = 0; j < total_params; j++, i++) {
> +			/* if newer record - could be excess params */
> +			if (j >= CS_ETM_PRIV_MAX)
> +				fprintf(stdout, param_unk_fmt, j, val[i]);
> +			else
>  				fprintf(stdout, cs_etm_priv_fmts[j], val[i]);
> -		else if (val[i] == __perf_cs_etmv4_magic)
> -			for (j = 0; j < CS_ETMV4_PRIV_MAX; j++, i++)
> +		}
> +	} else if (magic == __perf_cs_etmv4_magic) {
> +		/* after common block */

The main header has already been printed in cs_etm__print_auxtrace_info() and
as such the only thing this function is concerned with are the CPU specific
block.  But all the CPU specific block will be printed, which makes the above
comment quite confusing.  I suggest removing it or make it clearer.  

> +		for (j = 0; j < total_params; j++, i++) {
> +			/* if newer record - could be excess params */
> +			if (j >= CS_ETMV4_PRIV_MAX)
> +				fprintf(stdout, param_unk_fmt, j, val[i]);
> +			else
>  				fprintf(stdout, cs_etmv4_priv_fmts[j], val[i]);
> -		else
> -			/* failure.. return */
> -			return;
> +		}
> +	} else {
> +		/* failure - note bad magic value */
> +		fprintf(stdout, magic_unk_fmt, magic);
>  	}
> +	*offset = i;

I spent some time trying to break cs_etm__print_cpu_metadata_v0() and
cs_etm__print_cpu_metadata_v1 but couldn't find a successful case.  I think what
you have will work. 

> +}
> +
> +static void cs_etm__print_auxtrace_info(__u64 *val, int num)
> +{
> +	int i, cpu = 0, version;
> +
> +	for (i = 0; i < CS_HEADER_VERSION_MAX; i++)
> +		fprintf(stdout, cs_etm_global_header_fmts[i], val[i]);
> +	version = val[0];
> +	if (version > CS_HEADER_CURRENT_VERSION) {
> +		/* failure.. return */
> +		fprintf(stdout, "	Unknown Header Version = %x, ", version);
> +		fprintf(stdout, "Version supported <= %x\n", CS_HEADER_CURRENT_VERSION);
> +		return;
> +	}
> +
> +	for (i = CS_HEADER_VERSION_MAX; cpu < num; cpu++) {
> +		if (version == 0)
> +			cs_etm__print_cpu_metadata_v0(val, &i);
> +		else if (version == 1)
> +			cs_etm__print_cpu_metadata_v1(val, &i);
> +	}
> +}
> +
> +/*
> + * Read a single cpu parameter block from the auxtrace_info priv block.
> + *
> + * For version 1 there is a per cpu nr_params entry. If we are handling
> + * version 1 file, then there may be less, the same, or more params
> + * indicated by this value than the compile time number we understand.
> + *
> + * For a version 0 info block, there are a fixed number, and we need to
> + * fill out the nr_param value in the metadata we create.
> + */
> +static u64 *cs_etm__create_meta_blk(u64 *buff_in, int *buff_in_offset,
> +				    int out_blk_size, int nr_params_v0)
> +{
> +	u64 *metadata = NULL;
> +	int hdr_version;
> +	int nr_in_params, nr_out_params, nr_cmn_params;
> +	int i, k;
> +
> +	metadata = zalloc(sizeof(*metadata) * out_blk_size);
> +	if (!metadata)
> +		return NULL;
> +
> +	/* read block current index & version */
> +	i = *buff_in_offset;
> +	hdr_version = buff_in[CS_HEADER_VERSION];
> +
> +	if (!hdr_version) {
> +	/* read version 0 info block into a version 1 metadata block  */
> +		nr_in_params = nr_params_v0;
> +		metadata[CS_ETM_MAGIC] = buff_in[i + CS_ETM_MAGIC];
> +		metadata[CS_ETM_CPU] = buff_in[i + CS_ETM_CPU];
> +		metadata[CS_ETM_NR_TRC_PARAMS] = nr_in_params;
> +		/* remaining block params at offset +1 from source */
> +		for (k = 2; k < nr_in_params; k++)

                for (k = CS_ETM_ETMCR; ...)

> +			metadata[k+1] = buff_in[i + k];

                        metadata[k + 1] = buff_in[i + k];

> +		/* version 0 has 2 common params */
> +		nr_cmn_params = 2;
> +	} else {
> +	/* read version 1 info block - input and output nr_params may differ */
> +		/* version 1 has 3 common params */
> +		nr_cmn_params = 3;
> +		nr_in_params = buff_in[i + CS_ETM_NR_TRC_PARAMS];
> +
> +		/* if input has more params than output - skip excess */
> +		nr_out_params = nr_in_params + nr_cmn_params;
> +		if (nr_out_params > out_blk_size)
> +			nr_out_params = out_blk_size;

I don't think we should try to fix what is broken.  I would return an error to
give us a chance to look at outlying conditions.

> +
> +		for (k = 0; k < nr_out_params; k++)

                for (k = CS_ETMV4_TRCCONFIGR; ...)

Other than the above I think this patch works.

Thanks,
Mathieu

> +			metadata[k] = buff_in[i + k];
> +
> +		/* record the actual nr params we copied */
> +		metadata[CS_ETM_NR_TRC_PARAMS] = nr_out_params - nr_cmn_params;
> +	}
> +
> +	/* adjust in offset by number of in params used */
> +	i += nr_in_params + nr_cmn_params;
> +	*buff_in_offset = i;
> +	return metadata;
>  }
>  
>  int cs_etm__process_auxtrace_info(union perf_event *event,
> @@ -2492,11 +2622,12 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
>  	int info_header_size;
>  	int total_size = auxtrace_info->header.size;
>  	int priv_size = 0;
> -	int num_cpu;
> -	int err = 0, idx = -1;
> -	int i, j, k;
> +	int num_cpu, trcidr_idx;
> +	int err = 0;
> +	int i, j;
>  	u64 *ptr, *hdr = NULL;
>  	u64 **metadata = NULL;
> +	u64 hdr_version;
>  
>  	/*
>  	 * sizeof(auxtrace_info_event::type) +
> @@ -2512,16 +2643,17 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
>  	/* First the global part */
>  	ptr = (u64 *) auxtrace_info->priv;
>  
> -	/* Look for version '0' of the header */
> -	if (ptr[0] != 0)
> +	/* Look for version of the header */
> +	hdr_version = ptr[0];
> +	if (hdr_version > CS_HEADER_CURRENT_VERSION)
>  		return -EINVAL;
>  
> -	hdr = zalloc(sizeof(*hdr) * CS_HEADER_VERSION_0_MAX);
> +	hdr = zalloc(sizeof(*hdr) * CS_HEADER_VERSION_MAX);
>  	if (!hdr)
>  		return -ENOMEM;
>  
>  	/* Extract header information - see cs-etm.h for format */
> -	for (i = 0; i < CS_HEADER_VERSION_0_MAX; i++)
> +	for (i = 0; i < CS_HEADER_VERSION_MAX; i++)
>  		hdr[i] = ptr[i];
>  	num_cpu = hdr[CS_PMU_TYPE_CPUS] & 0xffffffff;
>  	pmu_type = (unsigned int) ((hdr[CS_PMU_TYPE_CPUS] >> 32) &
> @@ -2552,35 +2684,31 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
>  	 */
>  	for (j = 0; j < num_cpu; j++) {
>  		if (ptr[i] == __perf_cs_etmv3_magic) {
> -			metadata[j] = zalloc(sizeof(*metadata[j]) *
> -					     CS_ETM_PRIV_MAX);
> -			if (!metadata[j]) {
> -				err = -ENOMEM;
> -				goto err_free_metadata;
> -			}
> -			for (k = 0; k < CS_ETM_PRIV_MAX; k++)
> -				metadata[j][k] = ptr[i + k];
> +			metadata[j] =
> +				cs_etm__create_meta_blk(ptr, &i,
> +							CS_ETM_PRIV_MAX,
> +							CS_ETM_NR_TRC_PARAMS_V0);
>  
>  			/* The traceID is our handle */
> -			idx = metadata[j][CS_ETM_ETMTRACEIDR];
> -			i += CS_ETM_PRIV_MAX;
> +			trcidr_idx = CS_ETM_ETMTRACEIDR;
> +
>  		} else if (ptr[i] == __perf_cs_etmv4_magic) {
> -			metadata[j] = zalloc(sizeof(*metadata[j]) *
> -					     CS_ETMV4_PRIV_MAX);
> -			if (!metadata[j]) {
> -				err = -ENOMEM;
> -				goto err_free_metadata;
> -			}
> -			for (k = 0; k < CS_ETMV4_PRIV_MAX; k++)
> -				metadata[j][k] = ptr[i + k];
> +			metadata[j] =
> +				cs_etm__create_meta_blk(ptr, &i,
> +							CS_ETMV4_PRIV_MAX,
> +							CS_ETMV4_NR_TRC_PARAMS_V0);
>  
>  			/* The traceID is our handle */
> -			idx = metadata[j][CS_ETMV4_TRCTRACEIDR];
> -			i += CS_ETMV4_PRIV_MAX;
> +			trcidr_idx = CS_ETMV4_TRCTRACEIDR;
> +		}
> +
> +		if (!metadata[j]) {
> +			err = -ENOMEM;
> +			goto err_free_metadata;
>  		}
>  
>  		/* Get an RB node for this CPU */
> -		inode = intlist__findnew(traceid_list, idx);
> +		inode = intlist__findnew(traceid_list, metadata[j][trcidr_idx]);
>  
>  		/* Something went wrong, no need to continue */
>  		if (!inode) {
> @@ -2601,7 +2729,7 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
>  	}
>  
>  	/*
> -	 * Each of CS_HEADER_VERSION_0_MAX, CS_ETM_PRIV_MAX and
> +	 * Each of CS_HEADER_VERSION_MAX, CS_ETM_PRIV_MAX and
>  	 * CS_ETMV4_PRIV_MAX mark how many double words are in the
>  	 * global metadata, and each cpu's metadata respectively.
>  	 * The following tests if the correct number of double words was
> diff --git a/tools/perf/util/cs-etm.h b/tools/perf/util/cs-etm.h
> index 4ad925d6d799..e153d02df0de 100644
> --- a/tools/perf/util/cs-etm.h
> +++ b/tools/perf/util/cs-etm.h
> @@ -17,23 +17,37 @@ struct perf_session;
>   */
>  enum {
>  	/* Starting with 0x0 */
> -	CS_HEADER_VERSION_0,
> +	CS_HEADER_VERSION,
>  	/* PMU->type (32 bit), total # of CPUs (32 bit) */
>  	CS_PMU_TYPE_CPUS,
>  	CS_ETM_SNAPSHOT,
> -	CS_HEADER_VERSION_0_MAX,
> +	CS_HEADER_VERSION_MAX,
>  };
>  
> +/*
> + * Update the version for new format.
> + *
> + * New version 1 format adds a param count to the per cpu metadata.
> + * This allows easy adding of new metadata parameters.
> + * Requires that new params always added after current ones.
> + * Also allows client reader to handle file versions that are different by
> + * checking the number of params in the file vs the number expected.
> + */
> +#define CS_HEADER_CURRENT_VERSION 1
> +
>  /* Beginning of header common to both ETMv3 and V4 */
>  enum {
>  	CS_ETM_MAGIC,
>  	CS_ETM_CPU,
> +	/* Number of trace config params in following ETM specific block */
> +	CS_ETM_NR_TRC_PARAMS,
> +	CS_ETM_COMMON_BLK_MAX_V1,
>  };
>  
>  /* ETMv3/PTM metadata */
>  enum {
>  	/* Dynamic, configurable parameters */
> -	CS_ETM_ETMCR = CS_ETM_CPU + 1,
> +	CS_ETM_ETMCR = CS_ETM_COMMON_BLK_MAX_V1,
>  	CS_ETM_ETMTRACEIDR,
>  	/* RO, taken from sysFS */
>  	CS_ETM_ETMCCER,
> @@ -41,10 +55,13 @@ enum {
>  	CS_ETM_PRIV_MAX,
>  };
>  
> +/* define fixed version 0 length - allow new format reader to read old files. */
> +#define CS_ETM_NR_TRC_PARAMS_V0 (CS_ETM_ETMIDR - CS_ETM_ETMCR + 1)
> +
>  /* ETMv4 metadata */
>  enum {
>  	/* Dynamic, configurable parameters */
> -	CS_ETMV4_TRCCONFIGR = CS_ETM_CPU + 1,
> +	CS_ETMV4_TRCCONFIGR = CS_ETM_COMMON_BLK_MAX_V1,
>  	CS_ETMV4_TRCTRACEIDR,
>  	/* RO, taken from sysFS */
>  	CS_ETMV4_TRCIDR0,
> @@ -55,6 +72,9 @@ enum {
>  	CS_ETMV4_PRIV_MAX,
>  };
>  
> +/* define fixed version 0 length - allow new format reader to read old files. */
> +#define CS_ETMV4_NR_TRC_PARAMS_V0 (CS_ETMV4_TRCAUTHSTATUS - CS_ETMV4_TRCCONFIGR + 1)
> +
>  /*
>   * ETMv3 exception encoding number:
>   * See Embedded Trace Macrocell spcification (ARM IHI 0014Q)
> @@ -162,7 +182,7 @@ struct cs_etm_packet_queue {
>  
>  #define BMVAL(val, lsb, msb)	((val & GENMASK(msb, lsb)) >> lsb)
>  
> -#define CS_ETM_HEADER_SIZE (CS_HEADER_VERSION_0_MAX * sizeof(u64))
> +#define CS_ETM_HEADER_SIZE (CS_HEADER_VERSION_MAX * sizeof(u64))
>  
>  #define __perf_cs_etmv3_magic 0x3030303030303030ULL
>  #define __perf_cs_etmv4_magic 0x4040404040404040ULL
> -- 
> 2.17.1
> 

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