bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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
> 


  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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).