2020-07-15 22:29 UTC-0700 ~ Tony Ambardar <tony.ambardar@xxxxxxxxx>
> The bpftool sources include code to walk file trees, but use multiple
> frameworks to do so: nftw and fts. While nftw conforms to POSIX/SUSv3 and
> is widely available, fts is not conformant and less common, especially on
> non-glibc systems. The inconsistent framework usage hampers maintenance
> and portability of bpftool, in particular for embedded systems.
>
> Standardize code usage by rewriting one fts-based function to use nftw.
> Clean up related function warnings by using "const char *" arguments and
> fixing an unsafe call to dirname().
>
> These changes help in building bpftool against musl for OpenWrt.
Could you please add a line to the log about the reason for the path
copy in open_obj_pinned()?
>
> Signed-off-by: Tony Ambardar <Tony.Ambardar@xxxxxxxxx>
> ---
>
> V2:
> * use _GNU_SOURCE to pull in getpagesize(), getline(), nftw() definitions
> * use "const char *" in open_obj_pinned() and open_obj_pinned_any()
> * make dirname() safely act on a string copy
>
> ---
> tools/bpf/bpftool/common.c | 129 +++++++++++++++++++++----------------
> tools/bpf/bpftool/main.h | 4 +-
> 2 files changed, 76 insertions(+), 57 deletions(-)
>
> diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
> index 29f4e7611ae8..7c2e52fc5784 100644
> --- a/tools/bpf/bpftool/common.c
> +++ b/tools/bpf/bpftool/common.c
> @@ -1,10 +1,11 @@
> // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> /* Copyright (C) 2017-2018 Netronome Systems, Inc. */
>
> +#define _GNU_SOURCE
> #include <ctype.h>
> #include <errno.h>
> #include <fcntl.h>
> -#include <fts.h>
> +#include <ftw.h>
> #include <libgen.h>
> #include <mntent.h>
> #include <stdbool.h>
> @@ -160,24 +161,36 @@ int mount_tracefs(const char *target)
> return err;
> }
>
> -int open_obj_pinned(char *path, bool quiet)
> +int open_obj_pinned(const char *path, bool quiet)
> {
> - int fd;
> + char *pname;
> + int fd = -1;
> +
> + pname = strdup(path);
> + if (pname == NULL) {
Simply "if (!pname) {"
> + if (!quiet)
> + p_err("bpf obj get (%s): %s", path, strerror(errno));
Please update the error message, this one was for a failure on
bpf_obj_get().
> + goto out_ret;
> + }
> +
You're adding a second blank line here, please fix.
>
> - fd = bpf_obj_get(path);
> + fd = bpf_obj_get(pname);
> if (fd < 0) {
> if (!quiet)
> - p_err("bpf obj get (%s): %s", path,
> - errno == EACCES && !is_bpffs(dirname(path)) ?
> + p_err("bpf obj get (%s): %s", pname,
> + errno == EACCES && !is_bpffs(dirname(pname)) ?
> "directory not in bpf file system (bpffs)" :
> strerror(errno));
> - return -1;
> + goto out_free;
> }
>
> +out_free:
> + free(pname);
> +out_ret:
> return fd;
> }
>
> -int open_obj_pinned_any(char *path, enum bpf_obj_type exp_type)
> +int open_obj_pinned_any(const char *path, enum bpf_obj_type exp_type)
> {
> enum bpf_obj_type type;
> int fd;
> @@ -367,68 +380,74 @@ void print_hex_data_json(uint8_t *data, size_t len)
> jsonw_end_array(json_wtr);
> }
>
> -int build_pinned_obj_table(struct pinned_obj_table *tab,
> - enum bpf_obj_type type)
> +static struct pinned_obj_table *build_fn_table; /* params for nftw cb*/
> +static enum bpf_obj_type build_fn_type;
I would move the comments above the lines, since it applies to both of them.
> +
> +static int do_build_table_cb(const char *fpath, const struct stat *sb,
> + int typeflag, struct FTW *ftwbuf)
Please align the second line on the open parenthesis.
> {
> struct bpf_prog_info pinned_info = {};
A few suggestions on this code, even though I realise you simply moved
some parts. We can skip zero-initialising here (" = {}") because we
memset() it below before using it anyway.
> struct pinned_obj *obj_node = NULL;
> __u32 len = sizeof(pinned_info);
> - struct mntent *mntent = NULL;
> enum bpf_obj_type objtype;
> + int fd, err = 0;
> +
> + if (typeflag != FTW_F)
> + goto out_ret;
> + fd = open_obj_pinned(fpath, true);
> + if (fd < 0)
> + goto out_ret;
> +
> + objtype = get_fd_type(fd);
> + if (objtype != build_fn_type)
> + goto out_close;
> +
> + memset(&pinned_info, 0, sizeof(pinned_info));
> + if (bpf_obj_get_info_by_fd(fd, &pinned_info, &len)) {
> + p_err("can't get obj info: %s", strerror(errno));
We are simply building a table here to show the paths where objects are
pinned when listing progs/maps/etc., and I don't believe we want to
print an error in that case. And with such a message I would expect the
function to return and bpftool to stop, but again I don't believe this
is necessary here and we can just go on listing objects, even if we fail
to show their pinned paths.
> + goto out_close;
> + }
> +
> + obj_node = malloc(sizeof(*obj_node));
> + if (!obj_node) {
> + p_err("mem alloc failed");
Same here, let's not add an error message.
> + err = -1;
> + goto out_close;
> + }
> +
> + memset(obj_node, 0, sizeof(*obj_node));
Instead of malloc() + memset(), we could simply use calloc().
> + obj_node->id = pinned_info.id;
> + obj_node->path = strdup(fpath);
> + hash_add(build_fn_table->table, &obj_node->hash, obj_node->id);
> +
> +out_close:
> + close(fd);
> +out_ret:
> + return err;
> +}
> +
> +int build_pinned_obj_table(struct pinned_obj_table *tab,
> + enum bpf_obj_type type)
> +{
The end looks good.
Apart from the minor points mentioned above, the patch is good, copying
the string in open_obj_pinned() looks like the right approach. It does
compile (with no warnings) and works as intended on my machine :).
Thanks,
Quentin
