On Fri, May 28, 2021 at 12:45 PM Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> 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/ btf__parse() handles both ELF and raw BTF transparently. Then there is btf__parse_elf() and btf__parse_raw() for specifically ELF or raw. See all APIs at: https://github.com/libbpf/libbpf/blob/master/src/btf.h#L40 > > Please test, and if works as expected, try to bolt this into the kbuild > process, as intended. I'm on PTO today, will try to get to this soon-ish. > > - 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); > + if (fd < 0) { > + fprintf(stderr, "%s: Couldn't open %s for writing the raw BTF info: %s\n", __func__, filename, strerror(errno)); > + return -1; > + } > + err = write(fd, raw_btf_data, raw_btf_size); > + if (err < 0) > + fprintf(stderr, "%s: Couldn't open %s for writing the raw BTF info: %s\n", __func__, filename, strerror(errno)); > + > + close(fd); > + > + if (err != raw_btf_size) { > + fprintf(stderr, "%s: Could only write %d bytes to %s of raw BTF info out of %d, aborting\n", __func__, err, filename, raw_btf_size); > + unlink(filename); > + err = -1; > + } else { > + /* go from bytes written == raw_btf_size to an indication that all went fine */ > + err = 0; > + } > + > + return err; > +} > + > +int btf_encoder__encode(const char *filename) > { > int err; > > if (gobuffer__size(&btfe->percpu_secinfo) != 0) > btf_elf__add_datasec_type(btfe, PERCPU_SECTION, &btfe->percpu_secinfo); > > - err = btf_elf__encode(btfe, 0); > + if (filename == NULL) > + err = btf_elf__encode(btfe, 0); > + else > + err = btf_encoder__dump(btfe->btf, filename); > + > delete_functions(); > btf_elf__delete(btfe); > btfe = NULL; > @@ -412,7 +468,7 @@ static bool has_arg_names(struct cu *cu, struct ftype *ftype) > } > > int cu__encode_btf(struct cu *cu, int verbose, bool force, > - bool skip_encoding_vars) > + bool skip_encoding_vars, const char *detached_btf_filename) > { > uint32_t type_id_off; > uint32_t core_id; > @@ -425,7 +481,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > btf_elf__force = force; > > if (btfe && strcmp(btfe->filename, cu->filename)) { > - err = btf_encoder__encode(); > + err = btf_encoder__encode(detached_btf_filename); > if (err) > goto out; > > diff --git a/btf_encoder.h b/btf_encoder.h > index 46fb2312fc0eea9b..bfc6085092028adc 100644 > --- a/btf_encoder.h > +++ b/btf_encoder.h > @@ -11,9 +11,9 @@ > > struct cu; > > -int btf_encoder__encode(); > +int btf_encoder__encode(const char *filename); > > int cu__encode_btf(struct cu *cu, int verbose, bool force, > - bool skip_encoding_vars); > + bool skip_encoding_vars, const char *detached_btf_filename); > > #endif /* _BTF_ENCODER_H_ */ > diff --git a/man-pages/pahole.1 b/man-pages/pahole.1 > index 2659fe6f231405d8..6e7ded59595f5ea7 100644 > --- a/man-pages/pahole.1 > +++ b/man-pages/pahole.1 > @@ -189,6 +189,10 @@ features such as BPF CO-RE (Compile Once - Run Everywhere). > > See \fIhttps://nakryiko.com/posts/bpf-portability-and-co-re/\fR. > > +.TP > +.B \-j, \-\-btf_encode_detached=FILENAME > +Same thing as -J/--btf_encode, but storing the raw BTF info into a separate file. > + > .TP > .B \-\-btf_encode_force > Ignore those symbols found invalid when encoding BTF. > diff --git a/pahole.c b/pahole.c > index 24659e2969c8fb85..1cbff6175b60af51 100644 > --- a/pahole.c > +++ b/pahole.c > @@ -26,6 +26,7 @@ > #include "lib/bpf/src/libbpf.h" > #include "pahole_strings.h" > > +static char *detached_btf_filename; > static bool btf_encode; > static bool ctf_encode; > static bool first_obj_only; > @@ -1152,6 +1153,12 @@ static const struct argp_option pahole__options[] = { > .key = 'J', > .doc = "Encode as BTF", > }, > + { > + .name = "btf_encode_detached", > + .key = 'j', > + .arg = "FILENAME", > + .doc = "Encode as BTF in a detached file", > + }, > { > .name = "skip_encoding_btf_vars", > .key = ARGP_skip_encoding_btf_vars, > @@ -1223,6 +1230,7 @@ static error_t pahole__options_parser(int key, char *arg, > conf_load.extra_dbg_info = 1; break; > case 'i': find_containers = 1; > class_name = arg; break; > + case 'j': detached_btf_filename = arg; // fallthru > case 'J': btf_encode = 1; > conf_load.get_addr_info = true; > no_bitfield_type_recode = true; break; > @@ -2458,7 +2466,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu, > > if (btf_encode) { > if (cu__encode_btf(cu, global_verbose, btf_encode_force, > - skip_encoding_btf_vars)) { > + skip_encoding_btf_vars, detached_btf_filename)) { > fprintf(stderr, "Encountered error while encoding BTF.\n"); > exit(1); > } > @@ -2872,7 +2880,7 @@ try_sole_arg_as_class_names: > header = NULL; > > if (btf_encode) { > - err = btf_encoder__encode(); > + err = btf_encoder__encode(detached_btf_filename); > if (err) { > fputs("Failed to encode BTF\n", stderr); > goto out_cus_delete;
