Messages in this thread | | | Subject | Re: [PATCH bpf-next 3/3] bpf: btf: json print map dump with btf info | From | Quentin Monnet <> | Date | Thu, 21 Jun 2018 11:24:59 +0100 |
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Hi Okash,
Thanks for the patch! Please find some nitpicks inline below.
2018-06-20 13:30 UTC-0700 ~ Okash Khawaja <osk@fb.com> > This patch modifies `bpftool map dump [-j|-p] id <map-id>` to json- > print and pretty-json-print map dump. It calls btf_dumper introduced in > previous patch to accomplish this. > > The patch only prints debug info when -j or -p flags are supplied. Then > too, if the map has associated btf data loaded. Otherwise the usual > debug-less output is printed. > > Signed-off-by: Okash Khawaja <osk@fb.com> > Acked-by: Martin KaFai Lau <kafai@fb.com> > > --- > tools/bpf/bpftool/map.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 91 insertions(+), 3 deletions(-) > > --- a/tools/bpf/bpftool/map.c > +++ b/tools/bpf/bpftool/map.c > @@ -43,9 +43,13 @@ > #include <unistd.h> > #include <sys/types.h> > #include <sys/stat.h> > +#include <linux/err.h> > > #include <bpf.h> > > +#include "json_writer.h" > +#include "btf.h" > +#include "btf_dumper.h" > #include "main.h" > > static const char * const map_type_name[] = { > @@ -508,6 +512,83 @@ static int do_show(int argc, char **argv > return errno == ENOENT ? 0 : -1; > } > > + > +static int do_dump_btf(struct btf *btf, struct bpf_map_info *map_info, > + void *key, void *value)
Nit: Please align the second line on the opening parenthesis.
> +{ > + int ret; > + > + jsonw_start_object(json_wtr); > + jsonw_name(json_wtr, "key"); > + > + ret = btf_dumper_type(btf, json_wtr, map_info->btf_key_type_id, key); > + if (ret) > + goto out; > + > + jsonw_end_object(json_wtr); > + > + jsonw_start_object(json_wtr); > + jsonw_name(json_wtr, "value"); > + > + ret = btf_dumper_type(btf, json_wtr, map_info->btf_value_type_id, > + value);
Same comment.
> + > +out: > + /* end of root object */ > + jsonw_end_object(json_wtr);
This is not the root JSON object, which is not produced in that function, so I find the comment misleading.
I also find it confusing that it closes the first JSON object of this function if there is an error, but the second if "btf_dumper_type()" succeeds. What about the following: closing the first object in all cases, before evaluating the value of "ret", and if "ret" is non-null returning immediately; and completely removing the "goto" from this function?
> + > + return ret; > +} > + > +static struct btf *get_btf(struct bpf_map_info *map_info) > +{ > + int btf_fd = bpf_btf_get_fd_by_id(map_info->btf_id); > + struct bpf_btf_info btf_info = { 0 }; > + __u32 len = sizeof(btf_info); > + uint32_t last_size; > + int err; > + struct btf *btf = NULL; > + void *ptr = NULL, *temp_ptr;
Nit: please sort declarations in reverse-Christmas-tree order.
> + > + if (btf_fd < 0) > + return NULL; > + > + btf_info.btf_size = 4096; > + do { > + last_size = btf_info.btf_size; > + temp_ptr = realloc(ptr, last_size); > + if (!temp_ptr) { > + p_err("unable allocate memory for debug info.");
"unable *to* allocate"? (Also most other error messages do not end with a period, but here this is just me being fussy.)
> + goto exit_free; > + } > + > + ptr = temp_ptr; > + bzero(ptr, last_size); > + btf_info.btf = ptr_to_u64(ptr); > + err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len); > + } while (!err && btf_info.btf_size > last_size && last_size == 4096);
If I understand correctly, the first time you try to retrieve up to 4096 bytes, and if the btf_info is larger than this, you try a second time with the size returned in btf_info.btf_size instead. I don't find it intuitive (but maybe this is just me?), do you think you could add a comment above this bloc maybe?
> + > + if (err || btf_info.btf_size > last_size) { > + p_info("can't get btf info. debug info won't be displayed. error: %s", > + err ? strerror(errno) : "exceeds size retry");
Nit: Please align the second line on the opening parenthesis.
> + goto exit_free; > + } > + > + btf = btf__new((uint8_t *) btf_info.btf,
Nit: No space between the cast and the name of the variable.
> + btf_info.btf_size, NULL);
Same remark on parenthesis here...
> + if (IS_ERR(btf)) { > + printf("error when initialising btf: %s\n", > + strerror(PTR_ERR(btf)));
... and here.
> + btf = NULL; > + } > + > +exit_free: > + close(btf_fd); > + free(ptr); > + > + return btf; > +} > + > static int do_dump(int argc, char **argv) > { > void *key, *value, *prev_key; > @@ -516,6 +597,7 @@ static int do_dump(int argc, char **argv > __u32 len = sizeof(info); > int err; > int fd; > + struct btf *btf = NULL;
Reverse-Christmas-tree order, please.
> > if (argc != 2) > usage(); > @@ -538,6 +620,8 @@ static int do_dump(int argc, char **argv > goto exit_free; > } > > + btf = get_btf(&info); > + > prev_key = NULL; > if (json_output) > jsonw_start_array(json_wtr); > @@ -550,9 +634,12 @@ static int do_dump(int argc, char **argv > } > > if (!bpf_map_lookup_elem(fd, key, value)) { > - if (json_output) > - print_entry_json(&info, key, value); > - else > + if (json_output) { > + if (btf) > + do_dump_btf(btf, &info, key, value); > + else > + print_entry_json(&info, key, value); > + } else > print_entry_plain(&info, key, value);
Please add brackets around "print_entry_plain()" (to harmonise with the "if" of the same bloc).
> } else { > if (json_output) { > @@ -584,6 +671,7 @@ exit_free: > free(key); > free(value); > close(fd); > + btf__free(btf); > > return err; > } >
Thanks, Quentin
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