Re: [PATCH v5 06/21] perf arm-spe: Refactor printing string to buffer

From: André Przywara
Date: Thu Oct 29 2020 - 06:24:46 EST

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In reply to: Leo Yan: "[PATCH v5 06/21] perf arm-spe: Refactor printing string to buffer"
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On 29/10/2020 07:19, 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
> it's used by the caller arm_spe_pkt_desc(); if printing buffer is called
> for multiple times in a flow, the error is a cumulative value and simply
> returns its final 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.
>
> Suggested-by: Dave Martin <Dave.Martin@xxxxxxx>
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
> .../arm-spe-decoder/arm-spe-pkt-decoder.c | 263 ++++++++----------
> 1 file changed, 113 insertions(+), 150 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 04fd7fd7c15f..9147b88ae00c 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 +259,154 @@ int arm_spe_get_packet(const unsigned char *buf, size_t len,
> return ret;
> }
>
> +static int arm_spe_pkt_snprintf(int *err, 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) {
> + if (err && !*err)
> + *err = ret;
> + } else {
> + *buf_p += ret;
> + *blen -= ret;
> + }
> +
> + return ret;
> +}

So this now implements the old behaviour of ignoring previous errors, in
all cases, since we don't check for errors and bail out in the callers.

If you simply check for validity of err and for it being 0 before
proceeding with the va_start() above, this should be fixed.

Cheers,
Andre

> +
> 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);
> + 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;
> - }
> + return arm_spe_pkt_snprintf(&err, &buf, &blen, "%s", name);
> + case ARM_SPE_EVENTS:
> + arm_spe_pkt_snprintf(&err, &buf, &blen, "EV");
> +
> + if (payload & 0x1)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " EXCEPTION-GEN");
> + if (payload & 0x2)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " RETIRED");
> + if (payload & 0x4)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " L1D-ACCESS");
> + if (payload & 0x8)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " L1D-REFILL");
> + if (payload & 0x10)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " TLB-ACCESS");
> + if (payload & 0x20)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " TLB-REFILL");
> + if (payload & 0x40)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " NOT-TAKEN");
> + if (payload & 0x80)
> + arm_spe_pkt_snprintf(&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_snprintf(&err, &buf, &blen, " LLC-ACCESS");
> + if (payload & 0x200)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " LLC-REFILL");
> + if (payload & 0x400)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " REMOTE-ACCESS");
> }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> - return buf_len - blen;
> - }
> + return err ?: (int)(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;
> + case 0:
> + return arm_spe_pkt_snprintf(&err, &buf, &blen,
> + payload & 0x1 ? "COND-SELECT" : "INSN-OTHER");
> + case 1:
> + arm_spe_pkt_snprintf(&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_snprintf(&err, &buf, &blen, " AT");
> + if (payload & 0x8)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " EXCL");
> + if (payload & 0x10)
> + arm_spe_pkt_snprintf(&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;
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " SIMD-FP");
> }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> - return buf_len - blen;
> - }
> - default: return 0;
> +
> + return err ?: (int)(buf_len - blen);
> +
> + case 2:
> + arm_spe_pkt_snprintf(&err, &buf, &blen, "B");
> +
> + if (payload & 0x1)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " COND");
> + if (payload & 0x2)
> + arm_spe_pkt_snprintf(&err, &buf, &blen, " IND");
> +
> + return err ?: (int)(buf_len - blen);
> +
> + 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(&err, &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(&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 2:
> + return arm_spe_pkt_snprintf(&err, &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(&err, &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;
> + return arm_spe_pkt_snprintf(&err, &buf, &blen, "%s 0x%lx el%d",
> + name, (unsigned long)payload, idx + 1);
> + case ARM_SPE_COUNTER:
> + arm_spe_pkt_snprintf(&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_snprintf(&err, &buf, &blen, "TOT");
> + break;
> + case 1:
> + arm_spe_pkt_snprintf(&err, &buf, &blen, "ISSUE");
> + break;
> + case 2:
> + arm_spe_pkt_snprintf(&err, &buf, &blen, "XLAT");
> + break;
> + default:
> + break;
> }
> - if (ret < 0)
> - return ret;
> - blen -= ret;
> - return buf_len - blen;
> - }
> +
> + return err ?: (int)(buf_len - blen);
> +
> default:
> break;
> }
>
> - return snprintf(buf, buf_len, "%s 0x%llx (%d)",
> - name, payload, packet->index);
> + return arm_spe_pkt_snprintf(&err, &buf, &blen, "%s 0x%llx (%d)",
> + name, payload, packet->index);
> }
>

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In reply to: Leo Yan: "[PATCH v5 06/21] perf arm-spe: Refactor printing string to buffer"
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