On Thu, 16 Jul 2020 at 02:14, Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote:
>
> 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()?
Good point, will do.
> >
> > 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.
You're right. I just realized those aren't pre-existing messages; I
added them but then forgot.
> > + 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);
I should check for failed allocation here too.
> > + 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 :).
Glad to hear it! I'll update the patch based on your comments above
and resend shortly. Thanks again for the testing and feedback.
Regards,
Tony
> Thanks,
> Quentin
