Re: [PATCH 02/39] bpf tools: Collect eBPF programs from their own sections
From: Wangnan (F)
Date: Thu Jul 09 2015 - 23:16:59 EST
On 2015/7/9 23:58, Arnaldo Carvalho de Melo wrote:
Em Thu, Jul 09, 2015 at 12:35:05PM +0000, Wang Nan escreveu:
This patch collects all programs in an object file into an array of
'struct bpf_program' for further processing. That structure is for
representing each eBPF program. 'bpf_prog' should be a better name, but
it has been used by linux/filter.h. Although it is a kernel space name,
I still prefer to call it 'bpf_program' to prevent possible confusion.
bpf_program__new() creates a new 'struct bpf_program' object. It first
init a variable in stack using __bpf_program__new(), then if success,
enlarges obj->programs array and copy the new object in.
Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Brendan Gregg <brendan.d.gregg@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kaixu Xia <xiakaixu@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
Link: http://lkml.kernel.org/r/1435716878-189507-13-git-send-email-wangnan0@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 117 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 117 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9b016c0..3b717de 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -78,12 +78,27 @@ void libbpf_set_print(libbpf_print_fn_t warn,
# define LIBBPF_ELF_C_READ_MMAP ELF_C_READ
#endif
+/*
+ * bpf_prog should be a better name but it has been used in
+ * linux/filter.h.
+ */
+struct bpf_program {
+ /* Index in elf obj file, for relocation use. */
+ int idx;
+ char *section_name;
+ struct bpf_insn *insns;
+ size_t insns_cnt;
+};
+
struct bpf_object {
char license[64];
u32 kern_version;
void *maps_buf;
size_t maps_buf_sz;
+ struct bpf_program *programs;
+ size_t nr_programs;
+
/*
* Information when doing elf related work. Only valid if fd
* is valid.
@@ -100,6 +115,84 @@ struct bpf_object {
};
#define obj_elf_valid(o) ((o)->efile.elf)
+static void bpf_program__clear(struct bpf_program *prog)
+{
+ if (!prog)
+ return;
+
+ zfree(&prog->section_name);
+ zfree(&prog->insns);
+ prog->insns_cnt = 0;
+ prog->idx = -1;
+}
So in perf land we use 'bpf_program__exit()' as the counterpart of
bpf_program__init(), i.e. one just initializes fields, allocating
memory for 'struct bpf_program' members, but does not allocates the
struct bpf_program itself, because sometimes we embed it inside other
structs, or we have it in arrays, as you do.
So, to keep that convention, please rename bpf_program__clear() to
bpf_program__exit() and the next function, __bpf_program__new() to
bpf_program__init(), with 'struct bpf_program *prog' as the first
parameter.
To speed things up, from now on, when I see such stuff, I will do the
changes, put them in a branch with a commiter note, and wait for your
Ack (or not, if you disagree with something).
One more comment below.
+
+static int
+__bpf_program__new(void *data, size_t size, char *name, int idx,
+ struct bpf_program *prog)
+{
+ if (size < sizeof(struct bpf_insn)) {
+ pr_warning("corrupted section '%s'\n", name);
+ return -EINVAL;
+ }
+
+ bzero(prog, sizeof(*prog));
+
+ prog->section_name = strdup(name);
+ if (!prog->section_name) {
+ pr_warning("failed to alloc name for prog %s\n",
+ name);
+ goto errout;
+ }
+
+ prog->insns = malloc(size);
+ if (!prog->insns) {
+ pr_warning("failed to alloc insns for %s\n", name);
+ goto errout;
+ }
+ prog->insns_cnt = size / sizeof(struct bpf_insn);
+ memcpy(prog->insns, data,
+ prog->insns_cnt * sizeof(struct bpf_insn));
+ prog->idx = idx;
+
+ return 0;
+errout:
+ bpf_program__clear(prog);
+ return -ENOMEM;
+}
+
+static struct bpf_program *
+bpf_program__new(struct bpf_object *obj, void *data, size_t size,
+ char *name, int idx)
This, as well, is not a 'bpf_program' method, it is a 'struct
bpf_object' one, that will manipulate 'struct bpf_object' internal
state, changing its struct members to get space for an extra bpf_program
that was initialized on the stack, if the initialization of such
bpf_program went well, or bail out otherwise.
So I suggest you rename this to:
int bpf_object__add_program(struct bpf_object *obj, void *data, size_t size, char *name, int idx)
And probably move that debug that uses prog->section_name to just after
the realloc, here in this function.
I will look at the other patches after lunch, thanks for providing the
git tree, I will try and use it before looking at the patches
individually, to get a feel of the whole thing.
I didn't find your code, so I updated my git tree. Please see:
https://github.com/WangNan0/linux/commit/e5ffa4f070ee36cce5130d08622dc305ad9cdb31
And I also resolved a confliction in the next patch.
I think you can comment on current patchset since the modification is
too small to
send again.
And following is new pull request:
The following changes since commit 3381a29cbec5447086c0f726ee9a88c02e60becc:
bpf tools: Collect map definitions from 'maps' section (2015-07-07
13:41:45 -0300)
are available in the git repository at:
https://github.com/WangNan0/linux.git perf/ebpf-for-acme
for you to fetch changes up to ecc453e27f60ff59e0c2d1cdf64fb595b72d2f68:
perf tools: Support attach BPF program on uprobe events (2015-07-10
02:52:57 +0000)
Thank you.
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