linux-kernel - [tip:perf/core] perf config: Bail out when a handler returns failure for a key-value pair

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Date:   Mon, 17 Jun 2019 12:18:06 -0700
From:   tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     ast@...nel.org, linux-kernel@...r.kernel.org, hpa@...or.com,
        tglx@...utronix.de, daniel@...earbox.net, adrian.hunter@...el.com,
        songliubraving@...com, treeze.taeung@...il.com,
        mathieu.poirier@...aro.org, kafai@...com, acme@...hat.com,
        yhs@...com, namhyung@...nel.org, suzuki.poulose@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        mingo@...nel.org, mike.leach@...aro.org
Subject: [tip:perf/core] perf config: Bail out when a handler returns
 failure for a key-value pair

Commit-ID:  22d4621987faf651fee92c532a3eaba9a0e31ba0
Gitweb:     https://git.kernel.org/tip/22d4621987faf651fee92c532a3eaba9a0e31ba0
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Thu, 6 Jun 2019 10:56:55 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Mon, 10 Jun 2019 15:50:01 -0300

perf config: Bail out when a handler returns failure for a key-value pair

So perf_config() uses:

  int ret = 0;

  perf_config_set__for_each_entry(config_set, section, item) {
          ...
          ret = fn();
          if (ret < 0)
                  break;
  }

  return ret;

Expecting that that break will imediatelly go to function exit to return
that error value (ret).

The problem is that perf_config_set__for_each_entry() expands into two
nested for() loops, one traversing the sections in a config and the
second the items in each of those sections, so we have to change that
'break' to a goto label right before that final 'return ret'.

With that, for instance 'perf trace' now correctly bails out when a
event that is requested to be added via its 'trace.add_events'
~/.perfconfig entry gets rejected by the kernel BPF verifier:

  # perf trace ls
  event syntax error: '/home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o'
                       \___ Kernel verifier blocks program loading

  (add -v to see detail)
  Run 'perf list' for a list of valid events
  Error: wrong config key-value pair trace.add_events=/home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
  #

While before it would continue and explode later, when trying to find
maps that would have been in place had that augmented_raw_syscalls.o
precompiled BPF proggie been accepted by the, humm, bast... rigorous
kernel BPF verifier 8-)

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Martin KaFai Lau <kafai@...com>
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Mike Leach <mike.leach@...aro.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Song Liu <songliubraving@...com>
Cc: Suzuki Poulouse <suzuki.poulose@....com>
Cc: Taeung Song <treeze.taeung@...il.com>
Cc: Yonghong Song <yhs@...com>
Fixes: 8a0a9c7e9146 ("perf config: Introduce new init() and exit()")
Link: https://lkml.kernel.org/n/tip-qvqxfk9d0rn1l7lcntwiezrr@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/config.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 7e3c1b60120c..e7d2c08d263a 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -739,11 +739,15 @@ int perf_config(config_fn_t fn, void *data)
 			if (ret < 0) {
 				pr_err("Error: wrong config key-value pair %s=%s\n",
 				       key, value);
-				break;
+				/*
+				 * Can't be just a 'break', as perf_config_set__for_each_entry()
+				 * expands to two nested for() loops.
+				 */
+				goto out;
 			}
 		}
 	}
-
+out:
 	return ret;
 }