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Date: Thu, 14 Mar 2019 14:05:04 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Daniel Borkmann <daniel@...earbox.net>
Cc: Alexei Starovoitov <ast@...nel.org>, bpf@...r.kernel.org,
Networking <netdev@...r.kernel.org>,
Joe Stringer <joe@...d.net.nz>,
john fastabend <john.fastabend@...il.com>,
Yonghong Song <yhs@...com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>, tgraf@...g.ch,
lmb@...udflare.com
Subject: Re: [PATCH rfc v3 bpf-next 6/9] bpf, libbpf: refactor relocation handling
On Mon, Mar 11, 2019 at 2:51 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> From: Joe Stringer <joe@...d.net.nz>
>
> Adjust the code for relocations slightly with no functional changes,
> so that upcoming patches that will introduce support for relocations
> into the .data, .rodata and .bss sections can be added independent
> of these changes.
>
> Signed-off-by: Joe Stringer <joe@...d.net.nz>
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
lgtm
Acked-by: Andrii Nakryiko <andriin@...com>
> ---
> tools/lib/bpf/libbpf.c | 62 ++++++++++++++++++++++--------------------
> 1 file changed, 32 insertions(+), 30 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index f5eb60379c8d..0afdb8914386 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -851,20 +851,20 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
> obj->efile.symbols = data;
> obj->efile.strtabidx = sh.sh_link;
> }
> - } else if ((sh.sh_type == SHT_PROGBITS) &&
> - (sh.sh_flags & SHF_EXECINSTR) &&
> - (data->d_size > 0)) {
> - if (strcmp(name, ".text") == 0)
> - obj->efile.text_shndx = idx;
> - err = bpf_object__add_program(obj, data->d_buf,
> - data->d_size, name, idx);
> - if (err) {
> - char errmsg[STRERR_BUFSIZE];
> - char *cp = libbpf_strerror_r(-err, errmsg,
> - sizeof(errmsg));
> -
> - pr_warning("failed to alloc program %s (%s): %s",
> - name, obj->path, cp);
> + } else if (sh.sh_type == SHT_PROGBITS && data->d_size > 0) {
> + if (sh.sh_flags & SHF_EXECINSTR) {
> + if (strcmp(name, ".text") == 0)
> + obj->efile.text_shndx = idx;
> + err = bpf_object__add_program(obj, data->d_buf,
> + data->d_size, name, idx);
> + if (err) {
> + char errmsg[STRERR_BUFSIZE];
> + char *cp = libbpf_strerror_r(-err, errmsg,
> + sizeof(errmsg));
> +
> + pr_warning("failed to alloc program %s (%s): %s",
> + name, obj->path, cp);
> + }
> }
> } else if (sh.sh_type == SHT_REL) {
> void *reloc = obj->efile.reloc;
> @@ -1026,24 +1026,26 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,
> return -LIBBPF_ERRNO__RELOC;
> }
>
> - /* TODO: 'maps' is sorted. We can use bsearch to make it faster. */
> - for (map_idx = 0; map_idx < nr_maps; map_idx++) {
> - if (maps[map_idx].offset == sym.st_value) {
> - pr_debug("relocation: find map %zd (%s) for insn %u\n",
> - map_idx, maps[map_idx].name, insn_idx);
> - break;
> + if (sym.st_shndx == maps_shndx) {
> + /* TODO: 'maps' is sorted. We can use bsearch to make it faster. */
> + for (map_idx = 0; map_idx < nr_maps; map_idx++) {
> + if (maps[map_idx].offset == sym.st_value) {
> + pr_debug("relocation: find map %zd (%s) for insn %u\n",
> + map_idx, maps[map_idx].name, insn_idx);
> + break;
> + }
> }
> - }
>
> - if (map_idx >= nr_maps) {
> - pr_warning("bpf relocation: map_idx %d large than %d\n",
> - (int)map_idx, (int)nr_maps - 1);
> - return -LIBBPF_ERRNO__RELOC;
> - }
> + if (map_idx >= nr_maps) {
> + pr_warning("bpf relocation: map_idx %d large than %d\n",
> + (int)map_idx, (int)nr_maps - 1);
> + return -LIBBPF_ERRNO__RELOC;
> + }
>
> - prog->reloc_desc[i].type = RELO_LD64;
> - prog->reloc_desc[i].insn_idx = insn_idx;
> - prog->reloc_desc[i].map_idx = map_idx;
> + prog->reloc_desc[i].type = RELO_LD64;
> + prog->reloc_desc[i].insn_idx = insn_idx;
> + prog->reloc_desc[i].map_idx = map_idx;
> + }
> }
> return 0;
> }
> @@ -1405,7 +1407,7 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
> }
> insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
> insns[insn_idx].imm = obj->maps[map_idx].fd;
> - } else {
> + } else if (prog->reloc_desc[i].type == RELO_CALL) {
> err = bpf_program__reloc_text(prog, obj,
> &prog->reloc_desc[i]);
> if (err)
> --
> 2.17.1
>
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