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Mon, 05 Aug 2019 03:41:10 -0700 (PDT) To: Peter Wu , Alexei Starovoitov , Daniel Borkmann Cc: netdev@vger.kernel.org, Stanislav Fomichev , Jakub Kicinski References: <20190805001541.8096-1-peter@lekensteyn.nl> From: Quentin Monnet Openpgp: preference=signencrypt Autocrypt: addr=quentin.monnet@netronome.com; prefer-encrypt=mutual; keydata= mQINBFnqRlsBEADfkCdH/bkkfjbglpUeGssNbYr/TD4aopXiDZ0dL2EwafFImsGOWmCIIva2 MofTQHQ0tFbwY3Ir74exzU9X0aUqrtHirQHLkKeMwExgDxJYysYsZGfM5WfW7j8X4aVwYtfs AVRXxAOy6/bw1Mccq8ZMTYKhdCgS3BfC7qK+VYC4bhM2AOWxSQWlH5WKQaRbqGOVLyq8Jlxk 2FGLThUsPRlXKz4nl+GabKCX6x3rioSuNoHoWdoPDKsRgYGbP9LKRRQy3ZeJha4x+apy8rAM jcGHppIrciyfH38+LdV1FVi6sCx8sRKX++ypQc3fa6O7d7mKLr6uy16xS9U7zauLu1FYLy2U N/F1c4F+bOlPMndxEzNc/XqMOM9JZu1XLluqbi2C6JWGy0IYfoyirddKpwzEtKIwiDBI08JJ Cv4jtTWKeX8pjTmstay0yWbe0sTINPh+iDw+ybMwgXhr4A/jZ1wcKmPCFOpb7U3JYC+ysD6m 6+O/eOs21wVag/LnnMuOKHZa2oNsi6Zl0Cs6C7Vve87jtj+3xgeZ8NLvYyWrQhIHRu1tUeuf T8qdexDphTguMGJbA8iOrncHXjpxWhMWykIyN4TYrNwnyhqP9UgqRPLwJt5qB1FVfjfAlaPV sfsxuOEwvuIt19B/3pAP0nbevNymR3QpMPRl4m3zXCy+KPaSSQARAQABtC1RdWVudGluIE1v bm5ldCA8cXVlbnRpbi5tb25uZXRAbmV0cm9ub21lLmNvbT6JAj0EEwEIACcFAlnqRlsCGyMF CQlmAYAFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQNvcEyYwwfB7tChAAqFWG30+DG3Sx B7lfPaqs47oW98s5tTMprA+0QMqUX2lzHX7xWb5v8qCpuujdiII6RU0ZhwNKh/SMJ7rbYlxK qCOw54kMI+IU7UtWCej+Ps3LKyG54L5HkBpbdM8BLJJXZvnMqfNWx9tMISHkd/LwogvCMZrP TAFkPf286tZCIz0EtGY/v6YANpEXXrCzboWEiIccXRmbgBF4VK/frSveuS7OHKCu66VVbK7h kyTgBsbfyQi7R0Z6w6sgy+boe7E71DmCnBn57py5OocViHEXRgO/SR7uUK3lZZ5zy3+rWpX5 nCCo0C1qZFxp65TWU6s8Xt0Jq+Fs7Kg/drI7b5/Z+TqJiZVrTfwTflqPRmiuJ8lPd+dvuflY JH0ftAWmN3sT7cTYH54+HBIo1vm5UDvKWatTNBmkwPh6d3cZGALZvwL6lo0KQHXZhCVdljdQ rwWdE25aCQkhKyaCFFuxr3moFR0KKLQxNykrVTJIRuBS8sCyxvWcZYB8tA5gQ/DqNKBdDrT8 F9z2QvNE5LGhWDGddEU4nynm2bZXHYVs2uZfbdZpSY31cwVS/Arz13Dq+McMdeqC9J2wVcyL DJPLwAg18Dr5bwA8SXgILp0QcYWtdTVPl+0s82h+ckfYPOmkOLMgRmkbtqPhAD95vRD7wMnm ilTVmCi6+ND98YblbzL64YG5Ag0EWepGWwEQAM45/7CeXSDAnk5UMXPVqIxF8yCRzVe+UE0R QQsdNwBIVdpXvLxkVwmeu1I4aVvNt3Hp2eiZJjVndIzKtVEoyi5nMvgwMVs8ZKCgWuwYwBzU Vs9eKABnT0WilzH3gA5t9LuumekaZS7z8IfeBlZkGXEiaugnSAESkytBvHRRlQ8b1qnXha3g XtxyEqobKO2+dI0hq0CyUnGXT40Pe2woVPm50qD4HYZKzF5ltkl/PgRNHo4gfGq9D7dW2OlL 5I9qp+zNYj1G1e/ytPWuFzYJVT30MvaKwaNdurBiLc9VlWXbp53R95elThbrhEfUqWbAZH7b ALWfAotD07AN1msGFCES7Zes2AfAHESI8UhVPfJcwLPlz/Rz7/K6zj5U6WvH6aj4OddQFvN/ icvzlXna5HljDZ+kRkVtn+9zrTMEmgay8SDtWliyR8i7fvnHTLny5tRnE5lMNPRxO7wBwIWX TVCoBnnI62tnFdTDnZ6C3rOxVF6FxUJUAcn+cImb7Vs7M5uv8GufnXNUlsvsNS6kFTO8eOjh 4fe5IYLzvX9uHeYkkjCNVeUH5NUsk4NGOhAeCS6gkLRA/3u507UqCPFvVXJYLSjifnr92irt 0hXm89Ms5fyYeXppnO3l+UMKLkFUTu6T1BrDbZSiHXQoqrvU9b1mWF0CBM6aAYFGeDdIVe4x ABEBAAGJAiUEGAEIAA8FAlnqRlsCGwwFCQlmAYAACgkQNvcEyYwwfB4QwhAAqBTOgI9k8MoM gVA9SZj92vYet9gWOVa2Inj/HEjz37tztnywYVKRCRfCTG5VNRv1LOiCP1kIl/+crVHm8g78 iYc5GgBKj9O9RvDm43NTDrH2uzz3n66SRJhXOHgcvaNE5ViOMABU+/pzlg34L/m4LA8SfwUG ducP39DPbF4J0OqpDmmAWNYyHh/aWf/hRBFkyM2VuizN9cOS641jrhTO/HlfTlYjIb4Ccu9Y S24xLj3kkhbFVnOUZh8celJ31T9GwCK69DXNwlDZdri4Bh0N8DtRfrhkHj9JRBAun5mdwF4m yLTMSs4Jwa7MaIwwb1h3d75Ws7oAmv7y0+RgZXbAk2XN32VM7emkKoPgOx6Q5o8giPRX8mpc PiYojrO4B4vaeKAmsmVer/Sb5y9EoD7+D7WygJu2bDrqOm7U7vOQybzZPBLqXYxl/F5vOobC 5rQZgudR5bI8uQM0DpYb+Pwk3bMEUZQ4t497aq2vyMLRi483eqT0eG1QBE4O8dFNYdK5XUIz oHhplrRgXwPBSOkMMlLKu+FJsmYVFeLAJ81sfmFuTTliRb3Fl2Q27cEr7kNKlsz/t6vLSEN2 j8x+tWD8x53SEOSn94g2AyJA9Txh2xBhWGuZ9CpBuXjtPrnRSd8xdrw36AL53goTt/NiLHUd RHhSHGnKaQ6MfrTge5Q0h5A= Subject: Re: [PATCH] tools: bpftool: fix reading from /proc/config.gz Message-ID: <503ed83d-d485-775a-5cde-63e705862fa2@netronome.com> Date: Mon, 5 Aug 2019 11:41:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190805001541.8096-1-peter@lekensteyn.nl> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Peter, Thanks for looking into this (and for the fixes)! Some comments below. 2019-08-05 01:15 UTC+0100 ~ Peter Wu > /proc/config has never existed as far as I can see, but /proc/config.gz As far as I understood (from examining Cilium [0]), /proc/config _is_ used by some distributions, such as CoreOS. This is why we look at that location in bpftool. [0] https://github.com/cilium/cilium/blob/master/bpf/run_probes.sh#L42 > is present on Arch Linux. Execute an external gunzip program to avoid > linking to zlib and rework the option scanning code since a pipe is not > seekable. This also fixes a file handle leak on some error paths. > > Fixes: 4567b983f78c ("tools: bpftool: add probes for kernel configuration options") > Cc: Quentin Monnet > Signed-off-by: Peter Wu > --- > tools/bpf/bpftool/feature.c | 92 +++++++++++++++++++++---------------- > 1 file changed, 52 insertions(+), 40 deletions(-) > > diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c > index d672d9086fff..e9e10f582047 100644 > --- a/tools/bpf/bpftool/feature.c > +++ b/tools/bpf/bpftool/feature.c > @@ -284,34 +284,34 @@ static void probe_jit_limit(void) > } > } > > -static char *get_kernel_config_option(FILE *fd, const char *option) > +static bool get_kernel_config_option(FILE *fd, char **buf_p, size_t *n_p, > + char **value) Maybe we could rename this function, and have "next" appear in it somewhere? After your changes, it does not return the value for a specific option anymore. > { > - size_t line_n = 0, optlen = strlen(option); > - char *res, *strval, *line = NULL; > - ssize_t n; > + char *sep; > + ssize_t linelen; Please order the declarations in reverse-Christmas tree style. > > - rewind(fd); > - while ((n = getline(&line, &line_n, fd)) > 0) { > - if (strncmp(line, option, optlen)) > + while ((linelen = getline(buf_p, n_p, fd)) > 0) { > + char *line = *buf_p; Please leave a blank line after declarations. > + if (strncmp(line, "CONFIG_", 7)) > continue; > - /* Check we have at least '=', value, and '\n' */ > - if (strlen(line) < optlen + 3) > - continue; > - if (*(line + optlen) != '=') > + > + sep = memchr(line, '=', linelen); > + if (!sep) > continue; > > /* Trim ending '\n' */ > - line[strlen(line) - 1] = '\0'; > + line[linelen - 1] = '\0'; > + > + /* Split on '=' and ensure that a value is present. */ > + *sep = '\0'; > + if (!sep[1]) > + continue; > > - /* Copy and return config option value */ > - strval = line + optlen + 1; > - res = strdup(strval); > - free(line); > - return res; > + *value = sep + 1; > + return true; > } > - free(line); > > - return NULL; > + return false; > } > > static void probe_kernel_image_config(void) > @@ -386,31 +386,34 @@ static void probe_kernel_image_config(void) > /* test_bpf module for BPF tests */ > "CONFIG_TEST_BPF", > }; > + char *values[ARRAY_SIZE(options)] = { }; > char *value, *buf = NULL; > struct utsname utsn; > char path[PATH_MAX]; > size_t i, n; > ssize_t ret; > - FILE *fd; > + FILE *fd = NULL; > + bool is_pipe = false; Reverse-Christmas-tree style please. > > if (uname(&utsn)) > - goto no_config; > + goto end_parse; Just thinking, maybe if uname() fails we can skip /boot/config-$(uname -r) but still attempt to parse /proc/config{,.gz} instead of printing only NULL options? > > snprintf(path, sizeof(path), "/boot/config-%s", utsn.release); > > fd = fopen(path, "r"); > if (!fd && errno == ENOENT) { > - /* Some distributions put the config file at /proc/config, give > - * it a try. > - * Sometimes it is also at /proc/config.gz but we do not try > - * this one for now, it would require linking against libz. > + /* Some distributions build with CONFIG_IKCONFIG=y and put the > + * config file at /proc/config.gz. We try to invoke an external > + * gzip program to avoid linking to libz. > + * Hide stderr to avoid interference with the JSON output. Because some distributions do use /proc/config, we should keep this. You can probably add /proc/config.gz as another attempt below (or even above) the current case? > */ > - fd = fopen("/proc/config", "r"); > + fd = popen("gunzip -c /proc/config.gz 2>/dev/null", "r"); > + is_pipe = true; > } > if (!fd) { > p_info("skipping kernel config, can't open file: %s", > strerror(errno)); > - goto no_config; > + goto end_parse; > } > /* Sanity checks */ > ret = getline(&buf, &n, fd); > @@ -418,27 +421,36 @@ static void probe_kernel_image_config(void) > if (!buf || !ret) { > p_info("skipping kernel config, can't read from file: %s", > strerror(errno)); > - free(buf); > - goto no_config; > + goto end_parse; > } > if (strcmp(buf, "# Automatically generated file; DO NOT EDIT.\n")) { > p_info("skipping kernel config, can't find correct file"); > - free(buf); > - goto no_config; > + goto end_parse; > + } > + > + while (get_kernel_config_option(fd, &buf, &n, &value))> + for (i = 0; i < ARRAY_SIZE(options); i++) { > + if (values[i] || strcmp(buf, options[i])) Can we have an option set multiple times in the config file? If so, maybe have a p_info() if values are different to warn users that conflicting values were found? (Reading the file just once is a nice improvement over my version, by the way, thanks!) > + continue; > + > + values[i] = strdup(value); > + } > + } > + > +end_parse: > + if (fd) { > + if (is_pipe) { > + if (pclose(fd)) > + p_info("failed to read /proc/config.gz"); > + } else > + fclose(fd); Please use braces on all branches of the conditional statement (else). Thanks, Quentin