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Groups > linux.kernel > #1268914
| From | Wang Nan <wangnan0@huawei.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 06/12] bpf tools: Load a program with different instances using preprocessor |
| Date | 2015-11-13 13:40 +0100 |
| Message-ID | <qulO2-6pf-17@gated-at.bofh.it> (permalink) |
| References | <qulEm-6kY-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
This patch is a preparation for BPF prologue support which allows
generating a series of BPF bytecode for fetching kernel data before
calling program code. With the newly introduced multiple instances
support, perf is able to create different prologues for different
kprobe points.
Before this patch, a bpf_program can be loaded into kernel only once,
and get the only resuling fd. What this patch done is to allow creating
and loading different variants of one bpf_program, then fetching their
fds.
Here describe the basic idea in this patch. The detail description of
the newly introduced APIs can be found in comment in the patch body.
The key of this patch is the new mechanism in bpf_program__load().
Instead of loading BPF program into kernel directly, it calls a
'pre-processor' to generate program instances which would be final
loaded into kernel based on the original code. To enable multiple
instances generation, libbpf passes an index to the pre-processor
so it know which instance is being loaded.
Pre-processor should be passed from libbpf's user (perf) using
bpf_program__set_prep(). The number of instances and the relationship
between indics and the target instance should be clear when calling
bpf_program__set_prep().
To retrive fd for a specific instance of a program,
bpf_program__nth_fd() is introduced. It return the resuling fd
according to index.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: He Kuang <hekuang@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
tools/lib/bpf/libbpf.c | 145 ++++++++++++++++++++++++++++++++++++++++++++++---
tools/lib/bpf/libbpf.h | 64 ++++++++++++++++++++++
2 files changed, 200 insertions(+), 9 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e176bad..fcfa39f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -152,7 +152,11 @@ struct bpf_program {
} *reloc_desc;
int nr_reloc;
- int fd;
+ struct {
+ int nr;
+ int *fds;
+ } instances;
+ bpf_program_prep_t preprocessor;
struct bpf_object *obj;
void *priv;
@@ -206,10 +210,24 @@ struct bpf_object {
static void bpf_program__unload(struct bpf_program *prog)
{
+ int i;
+
if (!prog)
return;
- zclose(prog->fd);
+ /*
+ * If the object is opened but the program is never loaded,
+ * it is possible that prog->instances.nr == -1.
+ */
+ if (prog->instances.nr > 0) {
+ for (i = 0; i < prog->instances.nr; i++)
+ zclose(prog->instances.fds[i]);
+ } else if (prog->instances.nr != -1)
+ pr_warning("Internal error: instances.nr is %d\n",
+ prog->instances.nr);
+
+ prog->instances.nr = -1;
+ zfree(&prog->instances.fds);
}
static void bpf_program__exit(struct bpf_program *prog)
@@ -260,7 +278,8 @@ bpf_program__init(void *data, size_t size, char *name, int idx,
memcpy(prog->insns, data,
prog->insns_cnt * sizeof(struct bpf_insn));
prog->idx = idx;
- prog->fd = -1;
+ prog->instances.fds = NULL;
+ prog->instances.nr = -1;
return 0;
errout:
@@ -860,13 +879,73 @@ static int
bpf_program__load(struct bpf_program *prog,
char *license, u32 kern_version)
{
- int err, fd;
+ int err = 0, fd, i;
+
+ if (prog->instances.nr < 0 || !prog->instances.fds) {
+ if (prog->preprocessor) {
+ pr_warning("Internal error: can't load program '%s'\n",
+ prog->section_name);
+ return -LIBBPF_ERRNO__INTERNAL;
+ }
+
+ prog->instances.fds = malloc(sizeof(int));
+ if (!prog->instances.fds) {
+ pr_warning("No enough memory for fds\n");
+ return -ENOMEM;
+ }
+ prog->instances.nr = 1;
+ prog->instances.fds[0] = -1;
+ }
+
+ if (!prog->preprocessor) {
+ if (prog->instances.nr != 1)
+ pr_warning("Program '%s' inconsistent: nr(%d) not 1\n",
+ prog->section_name, prog->instances.nr);
- err = load_program(prog->insns, prog->insns_cnt,
- license, kern_version, &fd);
- if (!err)
- prog->fd = fd;
+ err = load_program(prog->insns, prog->insns_cnt,
+ license, kern_version, &fd);
+ if (!err)
+ prog->instances.fds[0] = fd;
+ goto out;
+ }
+
+ for (i = 0; i < prog->instances.nr; i++) {
+ struct bpf_prog_prep_result result;
+ bpf_program_prep_t preprocessor = prog->preprocessor;
+
+ bzero(&result, sizeof(result));
+ err = (*preprocessor)(prog, i, prog->insns,
+ prog->insns_cnt, &result);
+ if (err) {
+ pr_warning("Preprocessing %dth instance of program '%s' failed\n",
+ i, prog->section_name);
+ goto out;
+ }
+
+ if (!result.new_insn_ptr || !result.new_insn_cnt) {
+ pr_debug("Skip loading %dth instance of program '%s'\n",
+ i, prog->section_name);
+ prog->instances.fds[i] = -1;
+ if (result.pfd)
+ *result.pfd = -1;
+ continue;
+ }
+
+ err = load_program(result.new_insn_ptr,
+ result.new_insn_cnt,
+ license, kern_version, &fd);
+
+ if (err) {
+ pr_warning("Loading %dth instance of program '%s' failed\n",
+ i, prog->section_name);
+ goto out;
+ }
+ if (result.pfd)
+ *result.pfd = fd;
+ prog->instances.fds[i] = fd;
+ }
+out:
if (err)
pr_warning("failed to load program '%s'\n",
prog->section_name);
@@ -1121,5 +1200,53 @@ const char *bpf_program__title(struct bpf_program *prog, bool needs_copy)
int bpf_program__fd(struct bpf_program *prog)
{
- return prog->fd;
+ return bpf_program__nth_fd(prog, 0);
+}
+
+int bpf_program__set_prep(struct bpf_program *prog, int nr_instances,
+ bpf_program_prep_t prep)
+{
+ int *instances_fds;
+
+ if (nr_instances <= 0 || !prep)
+ return -EINVAL;
+
+ if (prog->instances.nr > 0 || prog->instances.fds) {
+ pr_warning("Can't set pre-processor after loading\n");
+ return -EINVAL;
+ }
+
+ instances_fds = malloc(sizeof(int) * nr_instances);
+ if (!instances_fds) {
+ pr_warning("alloc memory failed for fds\n");
+ return -ENOMEM;
+ }
+
+ /* fill all fd with -1 */
+ memset(instances_fds, 0xff, sizeof(int) * nr_instances);
+
+ prog->instances.nr = nr_instances;
+ prog->instances.fds = instances_fds;
+ prog->preprocessor = prep;
+ return 0;
+}
+
+int bpf_program__nth_fd(struct bpf_program *prog, int n)
+{
+ int fd;
+
+ if (n >= prog->instances.nr || n < 0) {
+ pr_warning("Can't get the %dth fd from program %s: only %d instances\n",
+ n, prog->section_name, prog->instances.nr);
+ return -EINVAL;
+ }
+
+ fd = prog->instances.fds[n];
+ if (fd < 0) {
+ pr_warning("%dth instance of program '%s' is invalid\n",
+ n, prog->section_name);
+ return -ENOENT;
+ }
+
+ return fd;
}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index c9a9aef..949df4b 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -88,6 +88,70 @@ const char *bpf_program__title(struct bpf_program *prog, bool needs_copy);
int bpf_program__fd(struct bpf_program *prog);
+struct bpf_insn;
+
+/*
+ * Libbpf allows callers to adjust BPF programs before being loaded
+ * into kernel. One program in an object file can be transform into
+ * multiple variants to be attached to different code.
+ *
+ * bpf_program_prep_t, bpf_program__set_prep and bpf_program__nth_fd
+ * are APIs for this propose.
+ *
+ * - bpf_program_prep_t:
+ * It defines 'preprocessor', which is a caller defined function
+ * passed to libbpf through bpf_program__set_prep(), and will be
+ * called before program is loaded. The processor should adjust
+ * the program one time for each instances according to the number
+ * passed to it.
+ *
+ * - bpf_program__set_prep:
+ * Attachs a preprocessor to a BPF program. The number of instances
+ * whould be created is also passed through this function.
+ *
+ * - bpf_program__nth_fd:
+ * After the program is loaded, get resuling fds from bpf program for
+ * each instances.
+ *
+ * If bpf_program__set_prep() is not used, the program whould be loaded
+ * without adjustment during bpf_object__load(). The program has only
+ * one instance. In this case bpf_program__fd(prog) is equal to
+ * bpf_program__nth_fd(prog, 0).
+ */
+
+struct bpf_prog_prep_result {
+ /*
+ * If not NULL, load new instruction array.
+ * If set to NULL, don't load this instance.
+ */
+ struct bpf_insn *new_insn_ptr;
+ int new_insn_cnt;
+
+ /* If not NULL, result fd is set to it */
+ int *pfd;
+};
+
+/*
+ * Parameters of bpf_program_prep_t:
+ * - prog: The bpf_program being loaded.
+ * - n: Index of instance being generated.
+ * - insns: BPF instructions array.
+ * - insns_cnt:Number of instructions in insns.
+ * - res: Output parameter, result of transformation.
+ *
+ * Return value:
+ * - Zero: pre-processing success.
+ * - Non-zero: pre-processing, stop loading.
+ */
+typedef int (*bpf_program_prep_t)(struct bpf_program *prog, int n,
+ struct bpf_insn *insns, int insns_cnt,
+ struct bpf_prog_prep_result *res);
+
+int bpf_program__set_prep(struct bpf_program *prog, int nr_instance,
+ bpf_program_prep_t prep);
+
+int bpf_program__nth_fd(struct bpf_program *prog, int n);
+
/*
* We don't need __attribute__((packed)) now since it is
* unnecessary for 'bpf_map_def' because they are all aligned.
--
1.8.3.4
--
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Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH 00/12] perf tools: bpf: Improve BPF program ability Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:30 +0100
[PATCH 08/12] perf tools: Compile dwarf-regs.c if CONFIG_BPF_PROLOGUE is on Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
[PATCH 07/12] perf tools: Add BPF_PROLOGUE config options for further patches Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
[PATCH 09/12] perf tools: Add prologue for BPF programs for fetching arguments Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
[PATCH 06/12] bpf tools: Load a program with different instances using preprocessor Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
[PATCH 03/12] perf tools: Allow BPF program attach to uprobe events Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
Re: [PATCH 03/12] perf tools: Allow BPF program attach to uprobe events Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-11-13 16:40 +0100
[PATCH 11/12] perf test: Test BPF prologue Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
[PATCH 04/12] perf tools: Allow BPF program attach to modules Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
Re: [PATCH 04/12] perf tools: Allow BPF program attach to modules Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-11-13 16:50 +0100
[PATCH 10/12] perf tools: Generate prologue for BPF programs Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
[PATCH 05/12] perf tools: Allow BPF program config probing options Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
Re: [PATCH 05/12] perf tools: Allow BPF program config probing options Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-11-13 16:50 +0100
Re: [PATCH 05/12] perf tools: Allow BPF program config probing options "Wangnan (F)" <wangnan0@huawei.com> - 2015-11-16 10:20 +0100
[PATCH 01/12] perf probe: Fix memory leaking on faiulre by clearing all probe_trace_events Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
[PATCH 02/12] perf probe: Clear probe_trace_event when add_probe_trace_event() fails Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
Re: [PATCH 02/12] perf probe: Clear probe_trace_event when add_probe_trace_event() fails Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-11-13 17:00 +0100
[PATCH 12/12] perf tools: Use same BPF program if arguments are identical Wang Nan <wangnan0@huawei.com> - 2015-11-13 13:40 +0100
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