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Groups > linux.kernel > #1179819
| From | Wang Nan <wangnan0@huawei.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v11 14/39] bpf tools: Record map accessing instructions for each program |
| Date | 2015-07-08 15:30 +0200 |
| Message-ID | <pJXAf-3fG-33@gated-at.bofh.it> (permalink) |
| References | <pJXqx-3bZ-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
This patch records the indices of instructions which are needed to be
relocated. That information is saved in the 'reloc_desc' field in
'struct bpf_program'. In the loading phase (this patch takes effect in
the opening phase), the collected instructions will be replaced by map
loading instructions.
Since we are going to close the ELF file and clear all data at the end
of the 'opening' phase, the ELF information will no longer be valid in
the 'loading' phase. We have to locate the instructions before maps are
loaded, instead of directly modifying the instruction.
'struct bpf_map_def' is introduced in this patch to let us know how many
maps are defined in the object.
This is the third part of map relocation. The principle of map relocation
is described in commit message of 'bpf tools: Collect symbol table from
SHT_SYMTAB section'.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1435716878-189507-15-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/lib/bpf/libbpf.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/libbpf.h | 13 ++++++
2 files changed, 137 insertions(+)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5f12fa6..4f13772 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9,6 +9,7 @@
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
+#include <inttypes.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
@@ -88,6 +89,12 @@ struct bpf_program {
char *section_name;
struct bpf_insn *insns;
size_t insns_cnt;
+
+ struct {
+ int insn_idx;
+ int map_idx;
+ } *reloc_desc;
+ int nr_reloc;
};
struct bpf_object {
@@ -127,6 +134,9 @@ static void bpf_program__clear(struct bpf_program *prog)
zfree(&prog->section_name);
zfree(&prog->insns);
+ zfree(&prog->reloc_desc);
+
+ prog->nr_reloc = 0;
prog->insns_cnt = 0;
prog->idx = -1;
}
@@ -484,6 +494,118 @@ out:
return err;
}
+static struct bpf_program *
+bpf_object__find_prog_by_idx(struct bpf_object *obj, int idx)
+{
+ struct bpf_program *prog;
+ size_t i;
+
+ for (i = 0; i < obj->nr_programs; i++) {
+ prog = &obj->programs[i];
+ if (prog->idx == idx)
+ return prog;
+ }
+ return NULL;
+}
+
+static int
+bpf_program__collect_reloc(struct bpf_program *prog,
+ size_t nr_maps, GElf_Shdr *shdr,
+ Elf_Data *data, Elf_Data *symbols)
+{
+ int i, nrels;
+
+ pr_debug("collecting relocating info for: '%s'\n",
+ prog->section_name);
+ nrels = shdr->sh_size / shdr->sh_entsize;
+
+ prog->reloc_desc = malloc(sizeof(*prog->reloc_desc) * nrels);
+ if (!prog->reloc_desc) {
+ pr_warning("failed to alloc memory in relocation\n");
+ return -ENOMEM;
+ }
+ prog->nr_reloc = nrels;
+
+ for (i = 0; i < nrels; i++) {
+ GElf_Sym sym;
+ GElf_Rel rel;
+ unsigned int insn_idx;
+ struct bpf_insn *insns = prog->insns;
+ size_t map_idx;
+
+ if (!gelf_getrel(data, i, &rel)) {
+ pr_warning("relocation: failed to get %d reloc\n", i);
+ return -EINVAL;
+ }
+
+ insn_idx = rel.r_offset / sizeof(struct bpf_insn);
+ pr_debug("relocation: insn_idx=%u\n", insn_idx);
+
+ if (!gelf_getsym(symbols,
+ GELF_R_SYM(rel.r_info),
+ &sym)) {
+ pr_warning("relocation: symbol %"PRIx64" not found\n",
+ GELF_R_SYM(rel.r_info));
+ return -EINVAL;
+ }
+
+ if (insns[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
+ pr_warning("bpf: relocation: invalid relo for insns[%d].code 0x%x\n",
+ insn_idx, insns[insn_idx].code);
+ return -EINVAL;
+ }
+
+ map_idx = sym.st_value / sizeof(struct bpf_map_def);
+ if (map_idx >= nr_maps) {
+ pr_warning("bpf relocation: map_idx %d large than %d\n",
+ (int)map_idx, (int)nr_maps - 1);
+ return -EINVAL;
+ }
+
+ prog->reloc_desc[i].insn_idx = insn_idx;
+ prog->reloc_desc[i].map_idx = map_idx;
+ }
+ return 0;
+}
+
+static int bpf_object__collect_reloc(struct bpf_object *obj)
+{
+ int i, err;
+
+ if (!obj_elf_valid(obj)) {
+ pr_warning("Internal error: elf object is closed\n");
+ return -EINVAL;
+ }
+
+ for (i = 0; i < obj->efile.nr_reloc; i++) {
+ GElf_Shdr *shdr = &obj->efile.reloc[i].shdr;
+ Elf_Data *data = obj->efile.reloc[i].data;
+ int idx = shdr->sh_info;
+ struct bpf_program *prog;
+ size_t nr_maps = obj->maps_buf_sz /
+ sizeof(struct bpf_map_def);
+
+ if (shdr->sh_type != SHT_REL) {
+ pr_warning("internal error at %d\n", __LINE__);
+ return -EINVAL;
+ }
+
+ prog = bpf_object__find_prog_by_idx(obj, idx);
+ if (!prog) {
+ pr_warning("relocation failed: no %d section\n",
+ idx);
+ return -ENOENT;
+ }
+
+ err = bpf_program__collect_reloc(prog, nr_maps,
+ shdr, data,
+ obj->efile.symbols);
+ if (err)
+ return -EINVAL;
+ }
+ return 0;
+}
+
static int bpf_object__validate(struct bpf_object *obj)
{
if (obj->kern_version == 0) {
@@ -514,6 +636,8 @@ __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
goto out;
if (bpf_object__elf_collect(obj))
goto out;
+ if (bpf_object__collect_reloc(obj))
+ goto out;
if (bpf_object__validate(obj))
goto out;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index dc966dd..6e75acd 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -30,4 +30,17 @@ struct bpf_object *bpf_object__open_buffer(void *obj_buf,
size_t obj_buf_sz);
void bpf_object__close(struct bpf_object *object);
+/*
+ * We don't need __attribute__((packed)) now since it is
+ * unnecessary for 'bpf_map_def' because they are all aligned.
+ * In addition, using it will trigger -Wpacked warning message,
+ * and will be treated as an error due to -Werror.
+ */
+struct bpf_map_def {
+ unsigned int type;
+ unsigned int key_size;
+ unsigned int value_size;
+ unsigned int max_entries;
+};
+
#endif
--
1.8.3.4
--
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[PATCH v11 00/39] perf tools: filtering events using eBPF programs - part1 Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 03/39] bpf tools: Introduce 'bpf' library and add bpf feature check Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 35/39] perf tools: Add bpf_fd field to evsel and config it Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 28/39] perf tools: Make perf depend on libbpf Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 34/39] perf record: Load all eBPF object into kernel Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 13/39] bpf tools: Collect relocation sections from SHT_REL sections Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 22/39] bpf tools: Link all bpf objects onto a list Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 02/39] tracing, perf: Implement BPF programs attached to uprobes Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 07/39] bpf tools: Check endianness and make libbpf fail early Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 38/39] perf record: Add clang options for compiling BPF scripts Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 33/39] perf record: Probe at kprobe points Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 32/39] perf probe: Attach trace_probe_event with perf_probe_event Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 36/39] perf tools: Attach eBPF program to perf event Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 23/39] perf tools: Introduce llvm config options Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 11/39] bpf tools: Collect symbol table from SHT_SYMTAB section Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 10/39] bpf tools: Collect map definitions from 'maps' section Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:20 +0200 [PATCH v11 19/39] bpf tools: Load eBPF programs in object files into kernel Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 18/39] bpf tools: Introduce bpf_load_program() to bpf.c Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 15/39] bpf tools: Add bpf.c/h for common bpf operations Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 29/39] perf record: Enable passing bpf object file to --event Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 05/39] bpf tools: Open eBPF object file and do basic validation Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 27/39] perf tests: Add LLVM test for eBPF on-the-fly compiling Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 09/39] bpf tools: Collect version and license from ELF sections Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 31/39] perf tools: Parse probe points of eBPF programs during preparation Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 17/39] bpf tools: Relocate eBPF programs Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 16/39] bpf tools: Create eBPF maps defined in an object file Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 14/39] bpf tools: Record map accessing instructions for each program Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 25/39] perf tools: Auto detecting kernel build directory Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 39/39] bpf tools: Load a program with different instance using preprocessor Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 04/39] bpf tools: Allow caller to set printing function Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 21/39] bpf tools: Introduce accessors for struct bpf_object Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 06/39] bpf tools: Read eBPF object from buffer Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 24/39] perf tools: Call clang to compile C source to object code Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 20/39] bpf tools: Introduce accessors for struct bpf_program Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 37/39] perf tools: Suppress probing messages when probing by BPF loading Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 [PATCH v11 26/39] perf tools: Auto detecting kernel include options Wang Nan <wangnan0@huawei.com> - 2015-07-08 15:30 +0200 Re: [PATCH v11 00/39] perf tools: filtering events using eBPF programs - part1 Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-07-08 16:10 +0200
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