From: Song Liu <songliubraving@fb.com>
To: Andrii Nakryiko <andriin@fb.com>
Cc: bpf <bpf@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Alexei Starovoitov <ast@fb.com>,
"daniel@iogearbox.net" <daniel@iogearbox.net>,
"andrii.nakryiko@gmail.com" <andrii.nakryiko@gmail.com>,
Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next] libbpf: provide more helpful message on uninitialized global var
Date: Tue, 23 Jul 2019 22:03:35 +0000 [thread overview]
Message-ID: <08DD65ED-34B4-47C0-B5ED-9A354CF5BA35@fb.com> (raw)
In-Reply-To: <20190723211133.1666218-1-andriin@fb.com>
> On Jul 23, 2019, at 2:11 PM, Andrii Nakryiko <andriin@fb.com> wrote:
>
> When BPF program defines uninitialized global variable, it's put into
> a special COMMON section. Libbpf will reject such programs, but will
> provide very unhelpful message with garbage-looking section index.
>
> This patch detects special section cases and gives more explicit error
> message.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
> ---
> tools/lib/bpf/libbpf.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 794dd5064ae8..8741c39adb1c 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -1760,15 +1760,22 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,
> (long long) sym.st_value, sym.st_name, name);
>
> shdr_idx = sym.st_shndx;
> + insn_idx = rel.r_offset / sizeof(struct bpf_insn);
> + pr_debug("relocation: insn_idx=%u, shdr_idx=%u\n",
> + insn_idx, shdr_idx);
> +
> + if (shdr_idx >= SHN_LORESERVE) {
> + pr_warning("relocation: not yet supported relo for non-static global \'%s\' variable in special section (0x%x) found in insns[%d].code 0x%x\n",
> + name, shdr_idx, insn_idx,
> + insns[insn_idx].code);
> + return -LIBBPF_ERRNO__RELOC;
> + }
> if (!bpf_object__relo_in_known_section(obj, shdr_idx)) {
> pr_warning("Program '%s' contains unrecognized relo data pointing to section %u\n",
> prog->section_name, shdr_idx);
> return -LIBBPF_ERRNO__RELOC;
> }
>
> - insn_idx = rel.r_offset / sizeof(struct bpf_insn);
> - pr_debug("relocation: insn_idx=%u\n", insn_idx);
> -
> if (insns[insn_idx].code == (BPF_JMP | BPF_CALL)) {
> if (insns[insn_idx].src_reg != BPF_PSEUDO_CALL) {
> pr_warning("incorrect bpf_call opcode\n");
> --
> 2.17.1
>
next prev parent reply other threads:[~2019-07-23 22:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 21:11 [PATCH v2 bpf-next] libbpf: provide more helpful message on uninitialized global var Andrii Nakryiko
2019-07-23 22:03 ` Song Liu [this message]
2019-07-23 23:00 ` Alexei Starovoitov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=08DD65ED-34B4-47C0-B5ED-9A354CF5BA35@fb.com \
--to=songliubraving@fb.com \
--cc=Kernel-team@fb.com \
--cc=andrii.nakryiko@gmail.com \
--cc=andriin@fb.com \
--cc=ast@fb.com \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.