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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 15/16] bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command.
Date: Tue, 27 Apr 2021 10:38:21 -0700	[thread overview]
Message-ID: <CAEf4BzaeG9XmJiWzRE3r5aKCD+ibiLsGLYx03Pgco1PSjn_L0A@mail.gmail.com> (raw)
In-Reply-To: <20210427032837.mtaqbbptczd3dvck@ast-mbp.dhcp.thefacebook.com>

On Mon, Apr 26, 2021 at 8:28 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Mon, Apr 26, 2021 at 03:35:16PM -0700, Andrii Nakryiko wrote:
> > On Thu, Apr 22, 2021 at 5:27 PM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
> > > From: Alexei Starovoitov <ast@kernel.org>
> > >
> > > Add -L flag to bpftool to use libbpf gen_trace facility and syscall/loader program
> > > for skeleton generation and program loading.
> > >
> > > "bpftool gen skeleton -L" command will generate a "light skeleton" or "loader skeleton"
> > > that is similar to existing skeleton, but has one major difference:
> > > $ bpftool gen skeleton lsm.o > lsm.skel.h
> > > $ bpftool gen skeleton -L lsm.o > lsm.lskel.h
> > > $ diff lsm.skel.h lsm.lskel.h
> > > @@ -5,34 +4,34 @@
> > >  #define __LSM_SKEL_H__
> > >
> > >  #include <stdlib.h>
> > > -#include <bpf/libbpf.h>
> > > +#include <bpf/bpf.h>
> > >
> > > The light skeleton does not use majority of libbpf infrastructure.
> > > It doesn't need libelf. It doesn't parse .o file.
> > > It only needs few sys_bpf wrappers. All of them are in bpf/bpf.h file.
> > > In future libbpf/bpf.c can be inlined into bpf.h, so not even libbpf.a would be
> > > needed to work with light skeleton.
> > >
> > > "bpftool prog load -L file.o" command is introduced for debugging of syscall/loader
> > > program generation. Just like the same command without -L it will try to load
> > > the programs from file.o into the kernel. It won't even try to pin them.
> > >
> > > "bpftool prog load -L -d file.o" command will provide additional debug messages
> > > on how syscall/loader program was generated.
> > > Also the execution of syscall/loader program will use bpf_trace_printk() for
> > > each step of loading BTF, creating maps, and loading programs.
> > > The user can do "cat /.../trace_pipe" for further debug.
> > >
> > > An example of fexit_sleep.lskel.h generated from progs/fexit_sleep.c:
> > > struct fexit_sleep {
> > >         struct bpf_loader_ctx ctx;
> > >         struct {
> > >                 struct bpf_map_desc bss;
> > >         } maps;
> > >         struct {
> > >                 struct bpf_prog_desc nanosleep_fentry;
> > >                 struct bpf_prog_desc nanosleep_fexit;
> > >         } progs;
> > >         struct {
> > >                 int nanosleep_fentry_fd;
> > >                 int nanosleep_fexit_fd;
> > >         } links;
> > >         struct fexit_sleep__bss {
> > >                 int pid;
> > >                 int fentry_cnt;
> > >                 int fexit_cnt;
> > >         } *bss;
> > > };
> > >
> > > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> > > ---
> > >  tools/bpf/bpftool/Makefile        |   2 +-
> > >  tools/bpf/bpftool/gen.c           | 313 +++++++++++++++++++++++++++---
> > >  tools/bpf/bpftool/main.c          |   7 +-
> > >  tools/bpf/bpftool/main.h          |   1 +
> > >  tools/bpf/bpftool/prog.c          |  80 ++++++++
> > >  tools/bpf/bpftool/xlated_dumper.c |   3 +
> > >  6 files changed, 382 insertions(+), 24 deletions(-)
> > >
> >
> > [...]
> >
> > > @@ -268,6 +269,254 @@ static void codegen(const char *template, ...)
> > >         free(s);
> > >  }
> > >
> > > +static void print_hex(const char *obj_data, int file_sz)
> > > +{
> > > +       int i, len;
> > > +
> > > +       /* embed contents of BPF object file */
> >
> > nit: this comment should have stayed at the original place
> >
> > > +       for (i = 0, len = 0; i < file_sz; i++) {
> > > +               int w = obj_data[i] ? 4 : 2;
> > > +
> >
> > [...]
> >
> > > +       bpf_object__for_each_map(map, obj) {
> > > +               const char * ident;
> > > +
> > > +               ident = get_map_ident(map);
> > > +               if (!ident)
> > > +                       continue;
> > > +
> > > +               if (!bpf_map__is_internal(map) ||
> > > +                   !(bpf_map__def(map)->map_flags & BPF_F_MMAPABLE))
> > > +                       continue;
> > > +
> > > +               printf("\tskel->%1$s =\n"
> > > +                      "\t\tmmap(NULL, %2$zd, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED,\n"
> > > +                      "\t\t\tskel->maps.%1$s.map_fd, 0);\n",
> > > +                      ident, bpf_map_mmap_sz(map));
> >
> > use codegen()?
>
> why?
> codegen() would add extra early \n for no good reason.

for consistency, seems like the rest of the code in that function uses
codegen(). But not critical.

>
> > > +       }
> > > +       codegen("\
> > > +               \n\
> > > +                       return 0;                                           \n\
> > > +               }                                                           \n\
> > > +                                                                           \n\
> > > +               static inline struct %1$s *                                 \n\
> >
> > [...]
> >
> > >  static int do_skeleton(int argc, char **argv)
> > >  {
> > >         char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")];
> > > @@ -277,7 +526,7 @@ static int do_skeleton(int argc, char **argv)
> > >         struct bpf_object *obj = NULL;
> > >         const char *file, *ident;
> > >         struct bpf_program *prog;
> > > -       int fd, len, err = -1;
> > > +       int fd, err = -1;
> > >         struct bpf_map *map;
> > >         struct btf *btf;
> > >         struct stat st;
> > > @@ -359,7 +608,25 @@ static int do_skeleton(int argc, char **argv)
> > >         }
> > >
> > >         get_header_guard(header_guard, obj_name);
> > > -       codegen("\
> > > +       if (use_loader)
> >
> > please use {} for such a long if/else, even if it's, technically, a
> > single-statement if
>
> I think it reads fine as-is, but, sure, I can add {}
>
> > > +               codegen("\
> > > +               \n\
> > > +               /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */   \n\
> > > +               /* THIS FILE IS AUTOGENERATED! */                           \n\
> > > +               #ifndef %2$s                                                \n\
> > > +               #define %2$s                                                \n\
> > > +                                                                           \n\
> > > +               #include <stdlib.h>                                         \n\
> > > +               #include <bpf/bpf.h>                                        \n\
> > > +               #include <bpf/skel_internal.h>                              \n\
> > > +                                                                           \n\
> > > +               struct %1$s {                                               \n\
> > > +                       struct bpf_loader_ctx ctx;                          \n\
> > > +               ",
> > > +               obj_name, header_guard
> > > +               );
> > > +       else
> > > +               codegen("\
> > >                 \n\
> > >                 /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */   \n\
> > >                                                                             \n\
> >
> > [...]
>
> --

  reply	other threads:[~2021-04-27 17:38 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-23  0:26 [PATCH v2 bpf-next 00/16] bpf: syscall program, FD array, loader program, light skeleton Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 01/16] bpf: Introduce bpf_sys_bpf() helper and program type Alexei Starovoitov
2021-04-23 18:15   ` Yonghong Song
2021-04-23 18:28     ` Alexei Starovoitov
2021-04-23 19:32       ` Yonghong Song
2021-04-26 16:51   ` Andrii Nakryiko
2021-04-27 18:45   ` John Fastabend
2021-04-23  0:26 ` [PATCH v2 bpf-next 02/16] bpf: Introduce bpfptr_t user/kernel pointer Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 03/16] bpf: Prepare bpf syscall to be used from kernel and user space Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 04/16] libbpf: Support for syscall program type Alexei Starovoitov
2021-04-26 22:24   ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 05/16] selftests/bpf: Test " Alexei Starovoitov
2021-04-26 17:02   ` Andrii Nakryiko
2021-04-27  2:43     ` Alexei Starovoitov
2021-04-27 16:28       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 06/16] bpf: Make btf_load command to be bpfptr_t compatible Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 07/16] selftests/bpf: Test for btf_load command Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 08/16] bpf: Introduce fd_idx Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 09/16] libbpf: Support for fd_idx Alexei Starovoitov
2021-04-26 17:14   ` Andrii Nakryiko
2021-04-27  2:53     ` Alexei Starovoitov
2021-04-27 16:36       ` Andrii Nakryiko
2021-04-28  1:32         ` Alexei Starovoitov
2021-04-28 18:40           ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 10/16] bpf: Add bpf_btf_find_by_name_kind() helper Alexei Starovoitov
2021-04-26 22:46   ` Andrii Nakryiko
2021-04-27  3:37     ` Alexei Starovoitov
2021-04-27 17:45       ` Andrii Nakryiko
2021-04-28  1:55         ` Alexei Starovoitov
2021-04-28 18:44           ` Andrii Nakryiko
2021-04-27 21:00   ` John Fastabend
2021-04-27 21:05     ` John Fastabend
2021-04-28  2:10     ` Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 11/16] bpf: Add bpf_sys_close() helper Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 12/16] libbpf: Change the order of data and text relocations Alexei Starovoitov
2021-04-26 17:29   ` Andrii Nakryiko
2021-04-27  3:00     ` Alexei Starovoitov
2021-04-27 16:47       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 13/16] libbpf: Add bpf_object pointer to kernel_supports() Alexei Starovoitov
2021-04-26 17:30   ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 14/16] libbpf: Generate loader program out of BPF ELF file Alexei Starovoitov
2021-04-26 22:22   ` Andrii Nakryiko
2021-04-27  3:25     ` Alexei Starovoitov
2021-04-27 17:34       ` Andrii Nakryiko
2021-04-28  1:42         ` Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 15/16] bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command Alexei Starovoitov
2021-04-26 22:35   ` Andrii Nakryiko
2021-04-27  3:28     ` Alexei Starovoitov
2021-04-27 17:38       ` Andrii Nakryiko [this message]
2021-04-23  0:26 ` [PATCH v2 bpf-next 16/16] selftests/bpf: Convert few tests to light skeleton Alexei Starovoitov
2021-04-23 21:36 ` [PATCH v2 bpf-next 00/16] bpf: syscall program, FD array, loader program, " Yonghong Song
2021-04-23 23:16   ` Alexei Starovoitov

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