Hi Peter, Thanks for looking into this (and for the fixes)! Some comments below.
2019-08-05 01:15 UTC+0100 ~ Peter Wu <pe...@lekensteyn.nl> > /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 <quentin.mon...@netronome.com> > Signed-off-by: Peter Wu <pe...@lekensteyn.nl> > --- > 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
