Re: [PATCHv3 bpf-next 08/26] libbpf: Add elf_open/elf_close functions

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Jul 06, 2023 at 04:09:29PM -0700, Andrii Nakryiko wrote:
> On Fri, Jun 30, 2023 at 1:35 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding elf_open/elf_close functions and using it in
> > elf_find_func_offset_from_file function. It will be
> > used in following changes to save some common code.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  tools/lib/bpf/elf.c        | 59 +++++++++++++++++++++++++-------------
> >  tools/lib/bpf/libbpf_elf.h |  8 ++++++
> >  tools/lib/bpf/usdt.c       | 31 ++++++--------------
> >  3 files changed, 56 insertions(+), 42 deletions(-)
> >
> 
> one nit below
> 
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> 
> > diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> > index 2b62b4af28ce..74e35071d22e 100644
> > --- a/tools/lib/bpf/elf.c
> > +++ b/tools/lib/bpf/elf.c
> > @@ -11,6 +11,40 @@
> >
> >  #define STRERR_BUFSIZE  128
> >
> > +int elf_open(const char *binary_path, struct elf_fd *elf_fd)
> > +{
> > +       char errmsg[STRERR_BUFSIZE];
> > +       int fd, ret;
> > +       Elf *elf;
> > +
> > +       if (elf_version(EV_CURRENT) == EV_NONE) {
> > +               pr_warn("elf: failed to init libelf for %s\n", binary_path);
> > +               return -LIBBPF_ERRNO__LIBELF;
> > +       }
> > +       fd = open(binary_path, O_RDONLY | O_CLOEXEC);
> > +       if (fd < 0) {
> > +               ret = -errno;
> > +               pr_warn("elf: failed to open %s: %s\n", binary_path,
> > +                       libbpf_strerror_r(ret, errmsg, sizeof(errmsg)));
> > +               return ret;
> > +       }
> > +       elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
> > +       if (!elf) {
> > +               pr_warn("elf: could not read elf from %s: %s\n", binary_path, elf_errmsg(-1));
> > +               close(fd);
> > +               return -LIBBPF_ERRNO__FORMAT;
> > +       }
> > +       elf_fd->fd = fd;
> > +       elf_fd->elf = elf;
> > +       return 0;
> > +}
> > +
> > +void elf_close(struct elf_fd *elf_fd)
> > +{
> > +       elf_end(elf_fd->elf);
> > +       close(elf_fd->fd);
> 
> nit: I'd make elf_close() work correctly with a) NULL elf_fd and b)

right, ok

> NULL elf_fd->elf, just to never have to think about this

there's NULL check in elf_end

thanks,
jirka