On Fri, May 28, 2021 at 04:45:31PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, May 27, 2021 at 01:41:13PM -0700, Andrii Nakryiko escreveu:
> > On Thu, May 27, 2021 at 12:57 PM Arnaldo <arnaldo.melo@xxxxxxxxx> wrote:
> > > On May 27, 2021 4:14:17 PM GMT-03:00, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote:
> > > >If we make 1.22 mandatory there will be no good reason to make 1.23
> > > >mandatory again. So I will have absolutely no inclination to work on
> > > >this, for example. So we are just wasting a chance to clean up the
> > > >Kbuild story w.r.t. pahole. And we are talking about just a few days
> > > >at most, while we do have a reasonable work around on the kernel side.
>
> > > So there were patches for stop using objcopy, which we thought could
> > > uncover some can of worms, were there patches for the detached BTF
> > > file?
>
> > No, there weren't, if I remember correctly. What's the concern,
> > though? That detached BTF file isn't even an ELF, so it's
> > btf__get_raw_data() and write it to the file. Done.
>
> See patch below, lightly tested, now working on making pahole accept raw
> BTF files out of /sys/kernel/btf/
>
> Please test, and if works as expected, try to bolt this into the kbuild
> process, as intended.
>
> - Arnaldo
>
> commit b579a18a1ea0ee84b90b5302f597dda2edf2f61b
> Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Date: Fri May 28 16:41:30 2021 -0300
>
> pahole: Allow encoding BTF into a detached file
>
> Previously the newly encoded BTF info was stored into a ELF section in
> the file where the DWARF info was obtained, but it is useful to just
> dump it into a separate file, do it.
>
> Requested-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>
> diff --git a/btf_encoder.c b/btf_encoder.c
> index 033c927b537dad1e..bc3ac72968cea826 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -21,6 +21,14 @@
> #include <stdlib.h> /* for qsort() and bsearch() */
> #include <inttypes.h>
>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +
> +#include <unistd.h>
> +
> +#include <errno.h>
> +
> /*
> * This corresponds to the same macro defined in
> * include/linux/kallsyms.h
> @@ -267,14 +275,62 @@ static struct btf_elf *btfe;
> static uint32_t array_index_id;
> static bool has_index_type;
>
> -int btf_encoder__encode()
> +static int btf_encoder__dump(struct btf *btf, const char *filename)
> +{
> + uint32_t raw_btf_size;
> + const void *raw_btf_data;
> + int fd, err;
> +
> + /* Empty file, nothing to do, so... done! */
> + if (btf__get_nr_types(btf) == 0)
> + return 0;
> +
> + if (btf__dedup(btf, NULL, NULL)) {
> + fprintf(stderr, "%s: btf__dedup failed!\n", __func__);
> + return -1;
> + }
> +
> + raw_btf_data = btf__get_raw_data(btf, &raw_btf_size);
> + if (raw_btf_data == NULL) {
> + fprintf(stderr, "%s: btf__get_raw_data failed!\n", __func__);
> + return -1;
> + }
> +
> + fd = open(filename, O_WRONLY | O_CREAT);
I think you need to specify file mode as 3rd param:
$ ./pahole -j krava vmlinux
$ ~/linux/tools/bpf/bpftool/bpftool btf dump file ./krava
Error: failed to load BTF from ./krava: Permission denied
$ ll krava
--w-r-Sr-T. 1 jolsa jolsa 4525734 May 30 23:38 krava
jirka
