On 11/20/23 9:56 AM, Jiri Olsa wrote:
Adding fill_link_info test for uprobe_multi link.
Setting up uprobes with bogus ref_ctr_offsets and cookie values
to test all the bpf_link_info::uprobe_multi fields.
Acked-by: Song Liu <song@xxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/fill_link_info.c | 191 ++++++++++++++++++
.../selftests/bpf/progs/test_fill_link_info.c | 6 +
2 files changed, 197 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
index 9294cb8d7743..fdf2c6b8c0cf 100644
--- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
+++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
@@ -7,6 +7,7 @@
#include <test_progs.h>
#include "trace_helpers.h"
#include "test_fill_link_info.skel.h"
+#include "bpf/libbpf_internal.h"
#define TP_CAT "sched"
#define TP_NAME "sched_switch"
@@ -300,6 +301,189 @@ static void test_kprobe_multi_fill_link_info(struct test_fill_link_info *skel,
bpf_link__destroy(link);
}
+/* Initialize semaphore variables so they don't end up in bss
+ * section and we could get retrieve their offsets.
+ */
+static short uprobe_link_info_sema_1 = 1;
+static short uprobe_link_info_sema_2 = 1;
+static short uprobe_link_info_sema_3 = 1;
I guess The typical sema value starting value should be 0, right?
If this is the case, the above is not a good example.
So the issue is that current libbpf does not support
retrieving offset from .bss section? Do you know why?
In selftest udst.c, we have semaphore defined as
usdt.c:unsigned short test_usdt0_semaphore SEC(".probes");
usdt.c:unsigned short test_usdt3_semaphore SEC(".probes");
usdt.c:unsigned short test_usdt12_semaphore SEC(".probes");
Will the following work?
static short uprobe_link_info_sema_1 SEC(".probes");
...
+
+noinline void uprobe_link_info_func_1(void)
+{
+ uprobe_link_info_sema_1++;
+ asm volatile ("");
The 'asm volatile' above intends to prevent compiler from
doing 'implicit' inlining. So as a convention let us
switch statement order to
asm volatile ("");
uprobe_link_info_sema_1++;
Similarly for below.
+}
+
+noinline void uprobe_link_info_func_2(void)
+{
+ uprobe_link_info_sema_2++;
+ asm volatile ("");
+}
+
+noinline void uprobe_link_info_func_3(void)
+{
+ uprobe_link_info_sema_3++;
+ asm volatile ("");
+}
+
+static int
+verify_umulti_link_info(int fd, bool retprobe, __u64 *offsets,
+ __u64 *cookies, __u64 *ref_ctr_offsets)
+{
+ char path[PATH_MAX], path_buf[PATH_MAX];
+ struct bpf_link_info info;
+ __u32 len = sizeof(info);
+ __u64 ref_ctr_offsets_buf[3];
+ __u64 offsets_buf[3];
+ __u64 cookies_buf[3];
+ int i, err, bit;
+ __u32 count = 0;
+
+ memset(path, 0, sizeof(path));
+ err = readlink("/proc/self/exe", path, sizeof(path));
+ if (!ASSERT_NEQ(err, -1, "readlink"))
+ return -1;
+
+ for (bit = 0; bit < 8; bit++) {
+ memset(&info, 0, sizeof(info));
+ info.uprobe_multi.path = ptr_to_u64(path_buf);
+ info.uprobe_multi.path_size = sizeof(path_buf);
+ info.uprobe_multi.count = count;
+
+ if (bit & 0x1)
+ info.uprobe_multi.offsets = ptr_to_u64(offsets_buf);
+ if (bit & 0x2)
+ info.uprobe_multi.cookies = ptr_to_u64(cookies_buf);
+ if (bit & 0x4)
+ info.uprobe_multi.ref_ctr_offsets = ptr_to_u64(ref_ctr_offsets_buf);
+
+ err = bpf_link_get_info_by_fd(fd, &info, &len);
+ if (!ASSERT_OK(err, "bpf_link_get_info_by_fd"))
+ return -1;
+
+ if (!ASSERT_EQ(info.type, BPF_LINK_TYPE_UPROBE_MULTI, "info.type"))
+ return -1;
+
+ ASSERT_EQ(info.uprobe_multi.pid, getpid(), "info.uprobe_multi.pid");
+ ASSERT_EQ(info.uprobe_multi.count, 3, "info.uprobe_multi.count");
+ ASSERT_EQ(info.uprobe_multi.flags & BPF_F_KPROBE_MULTI_RETURN,
+ retprobe, "info.uprobe_multi.flags.retprobe");
+ ASSERT_EQ(info.uprobe_multi.path_size, strlen(path), "info.uprobe_multi.path_size");
+ ASSERT_STREQ(path_buf, path, "info.uprobe_multi.path");
+
+ for (i = 0; i < info.uprobe_multi.count; i++) {
+ if (info.uprobe_multi.offsets)
+ ASSERT_EQ(offsets_buf[i], offsets[i], "info.uprobe_multi.offsets");
+ if (info.uprobe_multi.cookies)
+ ASSERT_EQ(cookies_buf[i], cookies[i], "info.uprobe_multi.cookies");
+ if (info.uprobe_multi.ref_ctr_offsets) {
+ ASSERT_EQ(ref_ctr_offsets_buf[i], ref_ctr_offsets[i],
+ "info.uprobe_multi.ref_ctr_offsets");
+ }
+ }
+ count = count ?: info.uprobe_multi.count;
+ }
+
+ return 0;
+}
+
+static void verify_umulti_invalid_user_buffer(int fd)
+{
+ struct bpf_link_info info;
+ __u32 len = sizeof(info);
+ __u64 buf[3];
+ int err;
+
+ /* upath_size defined, not path */
+ memset(&info, 0, sizeof(info));
+ info.uprobe_multi.path_size = 3;
+ err = bpf_link_get_info_by_fd(fd, &info, &len);
+ ASSERT_EQ(err, -EINVAL, "failed_upath_size");
+
+ /* path has wrong pointer */
+ memset(&info, 0, sizeof(info));
+ info.uprobe_multi.path_size = PATH_MAX;
+ info.uprobe_multi.path = 123;
+ err = bpf_link_get_info_by_fd(fd, &info, &len);
+ ASSERT_EQ(err, -EFAULT, "failed_bad_path_ptr");
+
+ /* count zero, with offsets */
+ memset(&info, 0, sizeof(info));
+ info.uprobe_multi.offsets = ptr_to_u64(buf);
+ err = bpf_link_get_info_by_fd(fd, &info, &len);
+ ASSERT_EQ(err, -EINVAL, "failed_count");
+
+ /* offsets not big enough */
+ memset(&info, 0, sizeof(info));
+ info.uprobe_multi.offsets = ptr_to_u64(buf);
+ info.uprobe_multi.count = 2;
+ err = bpf_link_get_info_by_fd(fd, &info, &len);
+ ASSERT_EQ(err, -ENOSPC, "failed_small_count");
+
+ /* offsets has wrong pointer */
+ memset(&info, 0, sizeof(info));
+ info.uprobe_multi.offsets = 123;
+ info.uprobe_multi.count = 3;
+ err = bpf_link_get_info_by_fd(fd, &info, &len);
+ ASSERT_EQ(err, -EFAULT, "failed_wrong_offsets");
+}
+
+static void test_uprobe_multi_fill_link_info(struct test_fill_link_info *skel,
+ bool retprobe, bool invalid)
+{
+ LIBBPF_OPTS(bpf_uprobe_multi_opts, opts,
+ .retprobe = retprobe,
+ );
+ const char *syms[3] = {
+ "uprobe_link_info_func_1",
+ "uprobe_link_info_func_2",
+ "uprobe_link_info_func_3",
+ };
+ __u64 cookies[3] = {
+ 0xdead,
+ 0xbeef,
+ 0xcafe,
+ };
+ const char *sema[3] = {
+ "uprobe_link_info_sema_1",
+ "uprobe_link_info_sema_2",
+ "uprobe_link_info_sema_3",
+ };
+ __u64 *offsets, *ref_ctr_offsets;
+ struct bpf_link *link;
+ int link_fd, err;
+
+ err = elf_resolve_syms_offsets("/proc/self/exe", 3, sema,
+ (unsigned long **) &ref_ctr_offsets, STT_OBJECT);
+ if (!ASSERT_OK(err, "elf_resolve_syms_offsets_object"))
+ return;
+
+ err = elf_resolve_syms_offsets("/proc/self/exe", 3, syms,
+ (unsigned long **) &offsets, STT_FUNC);
+ if (!ASSERT_OK(err, "elf_resolve_syms_offsets_func"))
+ return;
potential leak of ref_ctr_offsets?
+
+ opts.syms = syms;
+ opts.cookies = &cookies[0];
+ opts.ref_ctr_offsets = (unsigned long *) &ref_ctr_offsets[0];
+ opts.cnt = ARRAY_SIZE(syms);
+
+ link = bpf_program__attach_uprobe_multi(skel->progs.umulti_run, 0,
+ "/proc/self/exe", NULL, &opts);
+ if (!ASSERT_OK_PTR(link, "bpf_program__attach_uprobe_multi"))
+ goto out;
+
+ link_fd = bpf_link__fd(link);
+ if (invalid)
+ verify_umulti_invalid_user_buffer(link_fd);
+ else
+ verify_umulti_link_info(link_fd, retprobe, offsets, cookies, ref_ctr_offsets);
+
+ bpf_link__destroy(link);
+out:
+ free(offsets);
Should we free ref_ctr_offsets here?
+}
+
[...]
