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Date: Thu, 8 Oct 2020 14:46:06 +0100
From: André Przywara <andre.przywara@....com>
To: Leo Yan <leo.yan@...aro.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
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>,
Wei Li <liwei391@...wei.com>,
James Clark <james.clark@....com>,
Dave Martin <Dave.Martin@....com>,
linux-kernel@...r.kernel.org, Al Grant <Al.Grant@....com>
Subject: Re: [PATCH v2 05/14] perf arm-spe: Refactor printing string to buffer
On 29/09/2020 14:39, Leo Yan wrote:
Hi,
> 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_snprintf() which is used to wrap up the complex logics, and
> the caller arm_spe_pkt_desc() will call it and simply check the returns
> value.
>
> This patch also moves the variable 'blen' as the function's local
> variable, this allows to remove the unnecessary braces and improve the
> readability.
Ah, many thanks for tackling this, I wondered about those code
duplications and missing error handling already.
So I tried some sed pattern on the "old" part of the patch, to get to
the new format and spot any differences apart from mechanically changing
"snprintf(buf, buf_len," to "arm_spe_pkt_snprintf(&buf, &blen,".
See below.
>
> Suggested-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
Very nice cleanup! If you can address this one '"%s", name' comment
below, then:
Reviewed-by: Andre Przywara <andre.przywara@....com>
> ---
> .../arm-spe-decoder/arm-spe-pkt-decoder.c | 247 ++++++++++--------
> 1 file changed, 135 insertions(+), 112 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 4f0aeb62e97b..96b717a19163 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"
>
> @@ -256,192 +257,214 @@ int arm_spe_get_packet(const unsigned char *buf, size_t len,
> return ret;
> }
>
> +static int arm_spe_pkt_snprintf(char **buf_p, size_t *blen,
> + const char *fmt, ...)
> +{
> + va_list ap;
> + int ret;
> +
> + va_start(ap, fmt);
> + ret = vsnprintf(*buf_p, *blen, fmt, ap);
> + va_end(ap);
> +
> + if (ret < 0)
> + return ret;
> +
> + *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;
> unsigned long long payload = packet->payload;
> const char *name = arm_spe_pkt_name(packet->type);
> + size_t blen = buf_len;
>
> 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;
> + return arm_spe_pkt_snprintf(&buf, &blen, name);
Isn't it considered safer to use '..., "%s", name)', because that would
handle percent signs in "name" correctly?
Not really an issue in the current code, but good style, I believe.
> + case ARM_SPE_EVENTS:
> + ret = arm_spe_pkt_snprintf(&buf, &blen, "EV");
> + if (ret < 0)
> + return ret;
> +
> if (payload & 0x1) {
> - ret = snprintf(buf, buf_len, " EXCEPTION-GEN");
So this was actually a bug before, right? Because "buf" does no longer
have buf_len bytes available at this point, it should have been blen
here already. Which gets fixed with all your changes!
Thanks!
Andre
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " EXCEPTION-GEN");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x2) {
> - ret = snprintf(buf, buf_len, " RETIRED");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " RETIRED");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x4) {
> - ret = snprintf(buf, buf_len, " L1D-ACCESS");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " L1D-ACCESS");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x8) {
> - ret = snprintf(buf, buf_len, " L1D-REFILL");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " L1D-REFILL");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x10) {
> - ret = snprintf(buf, buf_len, " TLB-ACCESS");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " TLB-ACCESS");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x20) {
> - ret = snprintf(buf, buf_len, " TLB-REFILL");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " TLB-REFILL");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x40) {
> - ret = snprintf(buf, buf_len, " NOT-TAKEN");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " NOT-TAKEN");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x80) {
> - ret = snprintf(buf, buf_len, " MISPRED");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " MISPRED");
> + if (ret < 0)
> + return ret;
> }
> if (idx > 1) {
> if (payload & 0x100) {
> - ret = snprintf(buf, buf_len, " LLC-ACCESS");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " LLC-ACCESS");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x200) {
> - ret = snprintf(buf, buf_len, " LLC-REFILL");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " LLC-REFILL");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x400) {
> - ret = snprintf(buf, buf_len, " REMOTE-ACCESS");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " REMOTE-ACCESS");
> + if (ret < 0)
> + return ret;
> }
> }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> return buf_len - blen;
> - }
> +
> 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;
> -
> - if (payload & 0x1)
> - ret = snprintf(buf, buf_len, "ST");
> - else
> - ret = snprintf(buf, buf_len, "LD");
> - buf += ret;
> - blen -= ret;
> + case 0:
> + return arm_spe_pkt_snprintf(&buf, &blen,
> + payload & 0x1 ? "COND-SELECT" : "INSN-OTHER");
> + case 1:
> + ret = arm_spe_pkt_snprintf(&buf, &blen,
> + payload & 0x1 ? "ST" : "LD");
> + if (ret < 0)
> + return ret;
> +
> if (payload & 0x2) {
> if (payload & 0x4) {
> - ret = snprintf(buf, buf_len, " AT");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " AT");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x8) {
> - ret = snprintf(buf, buf_len, " EXCL");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " EXCL");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x10) {
> - ret = snprintf(buf, buf_len, " AR");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " AR");
> + if (ret < 0)
> + return ret;
> }
> } else if (payload & 0x4) {
> - ret = snprintf(buf, buf_len, " SIMD-FP");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " SIMD-FP");
> + if (ret < 0)
> + return ret;
> }
> +
> + return buf_len - blen;
> +
> + case 2:
> + ret = arm_spe_pkt_snprintf(&buf, &blen, "B");
> 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;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " COND");
> + if (ret < 0)
> + return ret;
> }
> if (payload & 0x2) {
> - ret = snprintf(buf, buf_len, " IND");
> - buf += ret;
> - blen -= ret;
> + ret = arm_spe_pkt_snprintf(&buf, &blen, " IND");
> + if (ret < 0)
> + return ret;
> }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> +
> return buf_len - blen;
> - }
> - default: return 0;
> +
> + default:
> + return 0;
> }
> case ARM_SPE_DATA_SOURCE:
> case ARM_SPE_TIMESTAMP:
> - return snprintf(buf, buf_len, "%s %lld", name, payload);
> + return arm_spe_pkt_snprintf(&buf, &blen, "%s %lld", name, payload);
> case ARM_SPE_ADDRESS:
> switch (idx) {
> case 0:
> 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",
> + return arm_spe_pkt_snprintf(&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 2:
> + return arm_spe_pkt_snprintf(&buf, &blen,
> + "VA 0x%llx", payload);
> 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;
> + return arm_spe_pkt_snprintf(&buf, &blen,
> + "PA 0x%llx ns=%d", payload, ns);
> + default:
> + return 0;
> }
> 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;
> - 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;
> - }
> + return arm_spe_pkt_snprintf(&buf, &blen, "%s 0x%lx el%d",
> + name, (unsigned long)payload, idx + 1);
> + case ARM_SPE_COUNTER:
> + ret = arm_spe_pkt_snprintf(&buf, &blen, "%s %d ", name,
> + (unsigned short)payload);
> if (ret < 0)
> return ret;
> - blen -= ret;
> +
> + switch (idx) {
> + case 0:
> + ret = arm_spe_pkt_snprintf(&buf, &blen, "TOT");
> + if (ret < 0)
> + return ret;
> + break;
> + case 1:
> + ret = arm_spe_pkt_snprintf(&buf, &blen, "ISSUE");
> + if (ret < 0)
> + return ret;
> + break;
> + case 2:
> + ret = arm_spe_pkt_snprintf(&buf, &blen, "XLAT");
> + if (ret < 0)
> + return ret;
> + break;
> + default:
> + break;
> + }
> +
> return buf_len - blen;
> - }
> +
> default:
> break;
> }
>
> - return snprintf(buf, buf_len, "%s 0x%llx (%d)",
> - name, payload, packet->index);
> + return arm_spe_pkt_snprintf(&buf, &blen, "%s 0x%llx (%d)",
> + name, payload, packet->index);
> }
>
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