From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Wang Nan <wangnan0@huawei.com>
Cc: namhyung@kernel.org, alexei.starovoitov@gmail.com,
masami.hiramatsu.pt@hitachi.com, paulus@samba.org,
a.p.zijlstra@chello.nl, mingo@redhat.com, jolsa@kernel.org,
dsahern@gmail.com, daniel@iogearbox.net,
brendan.d.gregg@gmail.com, lizefan@huawei.com,
hekuang@huawei.com, xiakaixu@huawei.com,
linux-kernel@vger.kernel.org, pi3orama@163.com
Subject: Re: [RFC PATCH v5 07/30] bpf tools: Check endianess and make libbpf fail early
Date: Wed, 3 Jun 2015 18:52:40 -0300 [thread overview]
Message-ID: <20150603215240.GE32707@kernel.org> (raw)
In-Reply-To: <1433144296-74992-8-git-send-email-wangnan0@huawei.com>
Em Mon, Jun 01, 2015 at 07:37:53AM +0000, Wang Nan escreveu:
> Check endianess according to EHDR. Code is taken from
> tools/perf/util/symbol-elf.c.
>
> Libbpf doesn't magically convert missmatched endianess. See discussion
> on https://lkml.org/lkml/2015/5/18/650 that, even if we swap
Please don't use URLs like this, I tried accessing this link and it
seems lkml.org is not accessible now :-\
Simply avoid having URLs like this, but if you insist, then follow the
Link: standard and use:
http://lkml.kernel.org/r/MESSAGE-ID
This way I can click on it to redirect me to some archive and if it
still doesn't work, then I can google for that message-id, but the way
you did I can't even google for the subject of that message :-\
BTW: this is what I get for lkml.org now:
504 Gateway Time-out
nginx/1.4.6 (Ubuntu)
- Arnaldo
> eBPF instructions to correct byte order, we are unable to deal with
> endianess in code logical generated by LLVM.
>
> Therefore, libbpf should simply reject missmatched ELF object, and let
> LLVM to create good code.
>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Acked-by: Alexei Starovoitov <ast@plumgrid.com>
> ---
> tools/lib/bpf/libbpf.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 0824822..5d56c40 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -166,6 +166,34 @@ errout:
> return err;
> }
>
> +static int
> +bpf_object__check_endianess(struct bpf_object *obj)
> +{
> + static unsigned int const endian = 1;
> +
> + switch (obj->efile.ehdr.e_ident[EI_DATA]) {
> + case ELFDATA2LSB:
> + /* We are big endian, BPF obj is little endian. */
> + if (*(unsigned char const *)&endian != 1)
> + goto mismatch;
> + break;
> +
> + case ELFDATA2MSB:
> + /* We are little endian, BPF obj is big endian. */
> + if (*(unsigned char const *)&endian != 0)
> + goto mismatch;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return 0;
> +
> +mismatch:
> + pr_warning("Error: endianess mismatch.\n");
> + return -EINVAL;
> +}
> +
> struct bpf_object *bpf_object__open(const char *path)
> {
> struct bpf_object *obj;
> @@ -187,6 +215,8 @@ struct bpf_object *bpf_object__open(const char *path)
>
> if (bpf_object__elf_init(obj))
> goto out;
> + if (bpf_object__check_endianess(obj))
> + goto out;
>
> bpf_object__elf_finish(obj);
> return obj;
> --
> 1.8.3.4
next prev parent reply other threads:[~2015-06-03 21:52 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-01 7:37 [RFC PATCH v5 00/30] perf tools: filtering events using eBPF programs Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 01/30] perf tools: Move linux/kernel.h to tools/include Wang Nan
2015-06-04 14:11 ` [tip:perf/core] " tip-bot for Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 02/30] perf tools: Move linux/{list.h,poison.h} " Wang Nan
2015-06-04 14:11 ` [tip:perf/core] tools: Move tools/perf/util/include/linux/{list.h ,poison.h} " tip-bot for Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 03/30] tools build: Add feature check for eBPF API Wang Nan
2015-06-02 22:11 ` Arnaldo Carvalho de Melo
2015-06-03 1:15 ` Wangnan (F)
2015-06-03 13:47 ` Arnaldo Carvalho de Melo
2015-06-01 7:37 ` [RFC PATCH v5 04/30] bpf tools: Introduce 'bpf' library to tools Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 05/30] bpf tools: Allow caller to set printing function Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 06/30] bpf tools: Open eBPF object file and do basic validation Wang Nan
2015-06-03 21:33 ` Arnaldo Carvalho de Melo
2015-06-03 21:35 ` Arnaldo Carvalho de Melo
2015-06-04 2:18 ` Wangnan (F)
2015-06-01 7:37 ` [RFC PATCH v5 07/30] bpf tools: Check endianess and make libbpf fail early Wang Nan
2015-06-03 21:52 ` Arnaldo Carvalho de Melo [this message]
2015-06-01 7:37 ` [RFC PATCH v5 08/30] bpf tools: Iterate over ELF sections to collect information Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 09/30] bpf tools: Collect version and license from ELF sections Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 10/30] bpf tools: Collect map definitions from 'maps' section Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 11/30] bpf tools: Collect symbol table from SHT_SYMTAB section Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 12/30] bpf tools: Collect eBPF programs from their own sections Wang Nan
2015-06-01 7:37 ` [RFC PATCH v5 13/30] bpf tools: Collect relocation sections from SHT_REL sections Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 14/30] bpf tools: Record map accessing instructions for each program Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 15/30] bpf tools: Add bpf.c/h for common bpf operations Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 16/30] bpf tools: Create eBPF maps defined in an object file Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 17/30] bpf tools: Relocate eBPF programs Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 18/30] bpf tools: Introduce bpf_load_program() to bpf.c Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 19/30] bpf tools: Load eBPF programs in object files into kernel Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 20/30] bpf tools: Introduce accessors for struct bpf_program Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 21/30] bpf tools: Introduce accessors for struct bpf_object Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 22/30] bpf tools: Link all bpf objects onto a list Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 23/30] perf tools: Make perf depend on libbpf Wang Nan
2015-06-03 2:45 ` [RFC PATCH v6 " Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 24/30] perf record: Enable passing bpf object file to --event Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 25/30] perf tools: Parse probe points of eBPF programs during preparation Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 26/30] perf probe: Attach trace_probe_event with perf_probe_event Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 27/30] perf record: Probe at kprobe points Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 28/30] perf record: Load all eBPF object into kernel Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 29/30] perf tools: Add bpf_fd field to evsel and config it Wang Nan
2015-06-01 7:38 ` [RFC PATCH v5 30/30] perf tools: Attach eBPF program to perf event Wang Nan
2015-06-02 0:48 ` [RFC PATCH v5 00/30] perf tools: filtering events using eBPF programs Alexei Starovoitov
2015-06-02 1:15 ` Arnaldo Carvalho de Melo
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