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Message-ID: <20201126121158.GB53384@kernel.org>
Date: Thu, 26 Nov 2020 09:11:58 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Leo Yan <leo.yan@...aro.org>
Cc: Andre Przywara <andre.przywara@....com>,
Dave Martin <Dave.Martin@....com>,
James Clark <james.clark@....com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Al Grant <Al.Grant@....com>, Wei Li <liwei391@...wei.com>,
John Garry <john.garry@...wei.com>,
Will Deacon <will@...nel.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v9 01/16] perf arm-spe: Refactor printing string to buffer
Em Thu, Nov 19, 2020 at 11:24:26PM +0800, Leo Yan escreveu:
> When outputs strings to the decoding buffer with function snprintf(),
> SPE decoder needs to detects if any error returns from snprintf() and if
> so needs to directly bail out. If snprintf() returns success, it needs
> to update buffer pointer and reduce the buffer length so can continue to
> output the next string into the consequent memory space.
>
> This complex logics are spreading in the function arm_spe_pkt_desc() so
> there has many duplicate codes for handling error detecting, increment
> buffer pointer and decrement buffer size.
>
> To avoid the duplicate code, this patch introduces a new helper function
> arm_spe_pkt_out_string() which is used to wrap up the complex logics,
> and it's used by the caller arm_spe_pkt_desc(). This patch moves the
> variable 'blen' as the function's local variable so allows to remove
> the unnecessary braces and improve the readability.
>
> This patch simplifies the return value for arm_spe_pkt_desc(): '0' means
> success and other values mean an error has occurred. To realize this,
> it relies on arm_spe_pkt_out_string()'s parameter 'err', the 'err' is a
> cumulative value, returns its final value if printing buffer is called
> for one time or multiple times. Finally, the error is handled in a
> central place, rather than directly bailing out in switch-cases, it
> returns error at the end of arm_spe_pkt_desc().
>
> This patch changes the caller arm_spe_dump() to respect the updated
> return value semantics of arm_spe_pkt_desc().
>
> Suggested-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> Reviewed-by: Andre Przywara <andre.przywara@....com>
> Reviewed-by: Dave Martin <Dave.Martin@....com>
> ---
> .../arm-spe-decoder/arm-spe-pkt-decoder.c | 302 +++++++++---------
> tools/perf/util/arm-spe.c | 2 +-
> 2 files changed, 151 insertions(+), 153 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 671a4763fb47..fbededc1bcd4 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
> @@ -9,6 +9,7 @@
> #include <endian.h>
> #include <byteswap.h>
> #include <linux/bitops.h>
> +#include <stdarg.h>
>
> #include "arm-spe-pkt-decoder.h"
>
> @@ -258,192 +259,189 @@ int arm_spe_get_packet(const unsigned char *buf, size_t len,
> return ret;
> }
>
> +static int arm_spe_pkt_out_string(int *err, char **buf_p, size_t *blen,
> + const char *fmt, ...)
> +{
> + va_list ap;
> + int ret;
Ok, from a quick look this continues confusing, but at least its not
named scnprintf() and then people won't expect the usual semantics.
Applying.
- Arnaldo
> + /* Bail out if any error occurred */
> + if (err && *err)
> + return *err;
> +
> + va_start(ap, fmt);
> + ret = vsnprintf(*buf_p, *blen, fmt, ap);
> + va_end(ap);
> +
> + if (ret < 0) {
> + if (err && !*err)
> + *err = ret;
> +
> + /*
> + * A return value of *blen or more means that the output was
> + * truncated and the buffer is overrun.
> + */
> + } else if ((size_t)ret >= *blen) {
> + (*buf_p)[*blen - 1] = '\0';
> +
> + /*
> + * Set *err to 'ret' to avoid overflow if tries to
> + * fill this buffer sequentially.
> + */
> + if (err && !*err)
> + *err = ret;
> + } else {
> + *buf_p += ret;
> + *blen -= ret;
> + }
> +
> + return ret;
> +}
> +
> int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf,
> size_t buf_len)
> {
> - int ret, ns, el, idx = packet->index;
> + int ns, el, idx = packet->index;
> unsigned long long payload = packet->payload;
> const char *name = arm_spe_pkt_name(packet->type);
> + char *buf_orig = buf;
> + size_t blen = buf_len;
> + int err = 0;
>
> switch (packet->type) {
> case ARM_SPE_BAD:
> case ARM_SPE_PAD:
> case ARM_SPE_END:
> - return snprintf(buf, buf_len, "%s", name);
> - case ARM_SPE_EVENTS: {
> - size_t blen = buf_len;
> -
> - ret = 0;
> - ret = snprintf(buf, buf_len, "EV");
> - buf += ret;
> - blen -= ret;
> - if (payload & 0x1) {
> - ret = snprintf(buf, buf_len, " EXCEPTION-GEN");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x2) {
> - ret = snprintf(buf, buf_len, " RETIRED");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x4) {
> - ret = snprintf(buf, buf_len, " L1D-ACCESS");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x8) {
> - ret = snprintf(buf, buf_len, " L1D-REFILL");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x10) {
> - ret = snprintf(buf, buf_len, " TLB-ACCESS");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x20) {
> - ret = snprintf(buf, buf_len, " TLB-REFILL");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x40) {
> - ret = snprintf(buf, buf_len, " NOT-TAKEN");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x80) {
> - ret = snprintf(buf, buf_len, " MISPRED");
> - buf += ret;
> - blen -= ret;
> - }
> + arm_spe_pkt_out_string(&err, &buf, &blen, "%s", name);
> + break;
> + case ARM_SPE_EVENTS:
> + arm_spe_pkt_out_string(&err, &buf, &blen, "EV");
> +
> + if (payload & 0x1)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " EXCEPTION-GEN");
> + if (payload & 0x2)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " RETIRED");
> + if (payload & 0x4)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " L1D-ACCESS");
> + if (payload & 0x8)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " L1D-REFILL");
> + if (payload & 0x10)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " TLB-ACCESS");
> + if (payload & 0x20)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " TLB-REFILL");
> + if (payload & 0x40)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " NOT-TAKEN");
> + if (payload & 0x80)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " MISPRED");
> if (idx > 1) {
> - if (payload & 0x100) {
> - ret = snprintf(buf, buf_len, " LLC-ACCESS");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x200) {
> - ret = snprintf(buf, buf_len, " LLC-REFILL");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x400) {
> - ret = snprintf(buf, buf_len, " REMOTE-ACCESS");
> - buf += ret;
> - blen -= ret;
> - }
> + if (payload & 0x100)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " LLC-ACCESS");
> + if (payload & 0x200)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " LLC-REFILL");
> + if (payload & 0x400)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " REMOTE-ACCESS");
> }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> - return buf_len - blen;
> - }
> + break;
> case ARM_SPE_OP_TYPE:
> switch (idx) {
> - case 0: return snprintf(buf, buf_len, "%s", payload & 0x1 ?
> - "COND-SELECT" : "INSN-OTHER");
> - case 1: {
> - size_t blen = buf_len;
> + case 0:
> + arm_spe_pkt_out_string(&err, &buf, &blen,
> + payload & 0x1 ? "COND-SELECT" : "INSN-OTHER");
> + break;
> + case 1:
> + arm_spe_pkt_out_string(&err, &buf, &blen,
> + payload & 0x1 ? "ST" : "LD");
>
> - if (payload & 0x1)
> - ret = snprintf(buf, buf_len, "ST");
> - else
> - ret = snprintf(buf, buf_len, "LD");
> - buf += ret;
> - blen -= ret;
> if (payload & 0x2) {
> - if (payload & 0x4) {
> - ret = snprintf(buf, buf_len, " AT");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x8) {
> - ret = snprintf(buf, buf_len, " EXCL");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x10) {
> - ret = snprintf(buf, buf_len, " AR");
> - buf += ret;
> - blen -= ret;
> - }
> + if (payload & 0x4)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " AT");
> + if (payload & 0x8)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " EXCL");
> + if (payload & 0x10)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " AR");
> } else if (payload & 0x4) {
> - ret = snprintf(buf, buf_len, " SIMD-FP");
> - buf += ret;
> - blen -= ret;
> - }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> - return buf_len - blen;
> - }
> - case 2: {
> - size_t blen = buf_len;
> -
> - ret = snprintf(buf, buf_len, "B");
> - buf += ret;
> - blen -= ret;
> - if (payload & 0x1) {
> - ret = snprintf(buf, buf_len, " COND");
> - buf += ret;
> - blen -= ret;
> - }
> - if (payload & 0x2) {
> - ret = snprintf(buf, buf_len, " IND");
> - buf += ret;
> - blen -= ret;
> - }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> - return buf_len - blen;
> + arm_spe_pkt_out_string(&err, &buf, &blen, " SIMD-FP");
> }
> - default: return 0;
> + break;
> + case 2:
> + arm_spe_pkt_out_string(&err, &buf, &blen, "B");
> +
> + if (payload & 0x1)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " COND");
> + if (payload & 0x2)
> + arm_spe_pkt_out_string(&err, &buf, &blen, " IND");
> +
> + break;
> + default:
> + /* Unknown index */
> + err = -1;
> + break;
> }
> + break;
> case ARM_SPE_DATA_SOURCE:
> case ARM_SPE_TIMESTAMP:
> - return snprintf(buf, buf_len, "%s %lld", name, payload);
> + arm_spe_pkt_out_string(&err, &buf, &blen, "%s %lld", name, payload);
> + break;
> case ARM_SPE_ADDRESS:
> switch (idx) {
> case 0:
> - case 1: ns = !!(packet->payload & NS_FLAG);
> + case 1:
> + ns = !!(packet->payload & NS_FLAG);
> el = (packet->payload & EL_FLAG) >> 61;
> payload &= ~(0xffULL << 56);
> - return snprintf(buf, buf_len, "%s 0x%llx el%d ns=%d",
> + arm_spe_pkt_out_string(&err, &buf, &blen,
> + "%s 0x%llx el%d ns=%d",
> (idx == 1) ? "TGT" : "PC", payload, el, ns);
> - case 2: return snprintf(buf, buf_len, "VA 0x%llx", payload);
> - case 3: ns = !!(packet->payload & NS_FLAG);
> + break;
> + case 2:
> + arm_spe_pkt_out_string(&err, &buf, &blen,
> + "VA 0x%llx", payload);
> + break;
> + case 3:
> + ns = !!(packet->payload & NS_FLAG);
> payload &= ~(0xffULL << 56);
> - return snprintf(buf, buf_len, "PA 0x%llx ns=%d",
> - payload, ns);
> - default: return 0;
> + arm_spe_pkt_out_string(&err, &buf, &blen,
> + "PA 0x%llx ns=%d", payload, ns);
> + break;
> + default:
> + /* Unknown index */
> + err = -1;
> + break;
> }
> + break;
> case ARM_SPE_CONTEXT:
> - return snprintf(buf, buf_len, "%s 0x%lx el%d", name,
> - (unsigned long)payload, idx + 1);
> - case ARM_SPE_COUNTER: {
> - size_t blen = buf_len;
> -
> - ret = snprintf(buf, buf_len, "%s %d ", name,
> - (unsigned short)payload);
> - buf += ret;
> - blen -= ret;
> + arm_spe_pkt_out_string(&err, &buf, &blen, "%s 0x%lx el%d",
> + name, (unsigned long)payload, idx + 1);
> + break;
> + case ARM_SPE_COUNTER:
> + arm_spe_pkt_out_string(&err, &buf, &blen, "%s %d ", name,
> + (unsigned short)payload);
> switch (idx) {
> - case 0: ret = snprintf(buf, buf_len, "TOT"); break;
> - case 1: ret = snprintf(buf, buf_len, "ISSUE"); break;
> - case 2: ret = snprintf(buf, buf_len, "XLAT"); break;
> - default: ret = 0;
> + case 0:
> + arm_spe_pkt_out_string(&err, &buf, &blen, "TOT");
> + break;
> + case 1:
> + arm_spe_pkt_out_string(&err, &buf, &blen, "ISSUE");
> + break;
> + case 2:
> + arm_spe_pkt_out_string(&err, &buf, &blen, "XLAT");
> + break;
> + default:
> + break;
> }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> - return buf_len - blen;
> - }
> + break;
> default:
> + /* Unknown packet type */
> + err = -1;
> break;
> }
>
> - return snprintf(buf, buf_len, "%s 0x%llx (%d)",
> - name, payload, packet->index);
> + /* Output raw data if detect any error */
> + if (err) {
> + err = 0;
> + arm_spe_pkt_out_string(&err, &buf_orig, &buf_len, "%s 0x%llx (%d)",
> + name, payload, packet->index);
> + }
> +
> + return err;
> }
> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> index 3882a5360ada..8901a1656a41 100644
> --- a/tools/perf/util/arm-spe.c
> +++ b/tools/perf/util/arm-spe.c
> @@ -113,7 +113,7 @@ static void arm_spe_dump(struct arm_spe *spe __maybe_unused,
> if (ret > 0) {
> ret = arm_spe_pkt_desc(&packet, desc,
> ARM_SPE_PKT_DESC_MAX);
> - if (ret > 0)
> + if (!ret)
> color_fprintf(stdout, color, " %s\n", desc);
> } else {
> color_fprintf(stdout, color, " Bad packet!\n");
> --
> 2.17.1
>
--
- Arnaldo
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