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Message-Id: <20190809003911.7852-1-peter@lekensteyn.nl>
Date: Fri, 9 Aug 2019 01:39:11 +0100
From: Peter Wu <peter@...ensteyn.nl>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>
Cc: netdev@...r.kernel.org, Stanislav Fomichev <sdf@...gle.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Quentin Monnet <quentin.monnet@...ronome.com>
Subject: [PATCH v3] tools: bpftool: fix reading from /proc/config.gz
/proc/config has never existed as far as I can see, but /proc/config.gz
is present on Arch Linux. Add support for decompressing config.gz using
zlib which is a mandatory dependency of libelf. Replace existing stdio
functions with gzFile operations since the latter transparently handles
uncompressed and gzip-compressed files.
Cc: Quentin Monnet <quentin.monnet@...ronome.com>
Signed-off-by: Peter Wu <peter@...ensteyn.nl>
---
v3: replace popen(gunzip) by linking directly to zlib. Reword commit
message, remove "Fixes" line. (this patch)
v2: fix style (reorder vars as reverse xmas tree, rename function,
braces), fallback to /proc/config.gz if uname() fails.
https://lkml.kernel.org/r/20190806010702.3303-1-peter@lekensteyn.nl
v1: https://lkml.kernel.org/r/20190805001541.8096-1-peter@lekensteyn.nl
Hi,
Thanks to Jakub for observing that zlib is already used by libelf, this
simplifies the patch tremendously as the same API can be used for both
compressed and uncompressed files. No special case exists anymore for
fclose/pclose.
According to configure.ac in elfutils, zlib is mandatory, so I just
assume it to be available. For simplicity I also silently assume lines
to be less than 4096 characters. If that is not the case, then lines
will appear truncated, but that should not be an issue for the
CONFIG_xyz lines that we are scanning for.
Jakub requested the handle leak fix to be posted separately against the
bpf tree, but since the whole code is rewritten I am not sure if it is
worth it. It is an unusual edge case: /boot/config-$(uname -r) could be
opened, but starts with unexpected data.
Kind regards,
Peter
---
tools/bpf/bpftool/Makefile | 2 +-
tools/bpf/bpftool/feature.c | 105 ++++++++++++++++++------------------
2 files changed, 54 insertions(+), 53 deletions(-)
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index a7afea4dec47..078bd0dcfba5 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -52,7 +52,7 @@ ifneq ($(EXTRA_LDFLAGS),)
LDFLAGS += $(EXTRA_LDFLAGS)
endif
-LIBS = -lelf $(LIBBPF)
+LIBS = -lelf -lz $(LIBBPF)
INSTALL ?= install
RM ?= rm -f
diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index d672d9086fff..03bdc5b3ac49 100644
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -14,6 +14,7 @@
#include <bpf.h>
#include <libbpf.h>
+#include <zlib.h>
#include "main.h"
@@ -284,34 +285,32 @@ static void probe_jit_limit(void)
}
}
-static char *get_kernel_config_option(FILE *fd, const char *option)
+static bool read_next_kernel_config_option(gzFile file, char *buf, size_t n,
+ char **value)
{
- size_t line_n = 0, optlen = strlen(option);
- char *res, *strval, *line = NULL;
- ssize_t n;
+ char *sep;
- rewind(fd);
- while ((n = getline(&line, &line_n, fd)) > 0) {
- if (strncmp(line, option, optlen))
+ while (gzgets(file, buf, n)) {
+ if (strncmp(buf, "CONFIG_", 7))
continue;
- /* Check we have at least '=', value, and '\n' */
- if (strlen(line) < optlen + 3)
- continue;
- if (*(line + optlen) != '=')
+
+ sep = strchr(buf, '=');
+ if (!sep)
continue;
/* Trim ending '\n' */
- line[strlen(line) - 1] = '\0';
+ buf[strlen(buf) - 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)
@@ -386,59 +385,61 @@ static void probe_kernel_image_config(void)
/* test_bpf module for BPF tests */
"CONFIG_TEST_BPF",
};
- char *value, *buf = NULL;
+ char *values[ARRAY_SIZE(options)] = { };
struct utsname utsn;
char path[PATH_MAX];
- size_t i, n;
- ssize_t ret;
- FILE *fd;
+ gzFile file = NULL;
+ char buf[4096];
+ char *value;
+ size_t i;
- if (uname(&utsn))
- goto no_config;
+ if (!uname(&utsn)) {
+ snprintf(path, sizeof(path), "/boot/config-%s", utsn.release);
- snprintf(path, sizeof(path), "/boot/config-%s", utsn.release);
+ /* gzopen also accepts uncompressed files. */
+ file = gzopen(path, "r");
+ }
- 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.
+ if (!file) {
+ /* Some distributions build with CONFIG_IKCONFIG=y and put the
+ * config file at /proc/config.gz.
*/
- fd = fopen("/proc/config", "r");
+ file = gzopen("/proc/config.gz", "r");
}
- if (!fd) {
+ if (!file) {
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);
- ret = getline(&buf, &n, fd);
- if (!buf || !ret) {
+ if (!gzgets(file, buf, sizeof(buf)) ||
+ !gzgets(file, buf, sizeof(buf))) {
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;
}
- free(buf);
- for (i = 0; i < ARRAY_SIZE(options); i++) {
- value = get_kernel_config_option(fd, options[i]);
- print_kernel_option(options[i], value);
- free(value);
+ while (read_next_kernel_config_option(file, buf, sizeof(buf), &value)) {
+ for (i = 0; i < ARRAY_SIZE(options); i++) {
+ if (values[i] || strcmp(buf, options[i]))
+ continue;
+
+ values[i] = strdup(value);
+ }
}
- fclose(fd);
- return;
-no_config:
- for (i = 0; i < ARRAY_SIZE(options); i++)
- print_kernel_option(options[i], NULL);
+end_parse:
+ if (file)
+ gzclose(file);
+
+ for (i = 0; i < ARRAY_SIZE(options); i++) {
+ print_kernel_option(options[i], values[i]);
+ free(values[i]);
+ }
}
static bool probe_bpf_syscall(const char *define_prefix)
--
2.22.0
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