ff943683f8
Fix how selftests determine relative offset of a function that is
uprobed. Previously, there was an assumption that uprobed function is
always in the first executable region, which is not always the case
(libbpf CI hits this case now). So get_base_addr() approach in isolation
doesn't work anymore. So teach get_uprobe_offset() to determine correct
memory mapping and calculate uprobe offset correctly.
While at it, I merged together two implementations of
get_uprobe_offset() helper, moving powerpc64-specific logic inside (had
to add extra {} block to avoid unused variable error for insn).
Also ensured that uprobed functions are never inlined, but are still
static (and thus local to each selftest), by using a no-op asm volatile
block internally. I didn't want to keep them global __weak, because some
tests use uprobe's ref counter offset (to test USDT-like logic) which is
not compatible with non-refcounted uprobe. So it's nicer to have each
test uprobe target local to the file and guaranteed to not be inlined or
skipped by the compiler (which can happen with static functions,
especially if compiling selftests with -O2).
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220126193058.3390292-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
117 lines
3.9 KiB
C
117 lines
3.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <test_progs.h>
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#include "test_attach_probe.skel.h"
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/* this is how USDT semaphore is actually defined, except volatile modifier */
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volatile unsigned short uprobe_ref_ctr __attribute__((unused)) __attribute((section(".probes")));
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/* uprobe attach point */
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static void trigger_func(void)
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{
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asm volatile ("");
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}
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void test_attach_probe(void)
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{
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DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, uprobe_opts);
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int duration = 0;
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struct bpf_link *kprobe_link, *kretprobe_link;
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struct bpf_link *uprobe_link, *uretprobe_link;
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struct test_attach_probe* skel;
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ssize_t uprobe_offset, ref_ctr_offset;
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bool legacy;
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/* Check if new-style kprobe/uprobe API is supported.
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* Kernels that support new FD-based kprobe and uprobe BPF attachment
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* through perf_event_open() syscall expose
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* /sys/bus/event_source/devices/kprobe/type and
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* /sys/bus/event_source/devices/uprobe/type files, respectively. They
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* contain magic numbers that are passed as "type" field of
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* perf_event_attr. Lack of such file in the system indicates legacy
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* kernel with old-style kprobe/uprobe attach interface through
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* creating per-probe event through tracefs. For such cases
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* ref_ctr_offset feature is not supported, so we don't test it.
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*/
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legacy = access("/sys/bus/event_source/devices/kprobe/type", F_OK) != 0;
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uprobe_offset = get_uprobe_offset(&trigger_func);
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if (!ASSERT_GE(uprobe_offset, 0, "uprobe_offset"))
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return;
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ref_ctr_offset = get_rel_offset((uintptr_t)&uprobe_ref_ctr);
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if (!ASSERT_GE(ref_ctr_offset, 0, "ref_ctr_offset"))
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return;
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skel = test_attach_probe__open_and_load();
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if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
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return;
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if (CHECK(!skel->bss, "check_bss", ".bss wasn't mmap()-ed\n"))
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goto cleanup;
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kprobe_link = bpf_program__attach_kprobe(skel->progs.handle_kprobe,
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false /* retprobe */,
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SYS_NANOSLEEP_KPROBE_NAME);
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if (!ASSERT_OK_PTR(kprobe_link, "attach_kprobe"))
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goto cleanup;
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skel->links.handle_kprobe = kprobe_link;
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kretprobe_link = bpf_program__attach_kprobe(skel->progs.handle_kretprobe,
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true /* retprobe */,
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SYS_NANOSLEEP_KPROBE_NAME);
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if (!ASSERT_OK_PTR(kretprobe_link, "attach_kretprobe"))
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goto cleanup;
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skel->links.handle_kretprobe = kretprobe_link;
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if (!legacy)
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ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_before");
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uprobe_opts.retprobe = false;
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uprobe_opts.ref_ctr_offset = legacy ? 0 : ref_ctr_offset;
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uprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uprobe,
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0 /* self pid */,
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"/proc/self/exe",
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uprobe_offset,
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&uprobe_opts);
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if (!ASSERT_OK_PTR(uprobe_link, "attach_uprobe"))
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goto cleanup;
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skel->links.handle_uprobe = uprobe_link;
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if (!legacy)
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ASSERT_GT(uprobe_ref_ctr, 0, "uprobe_ref_ctr_after");
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/* if uprobe uses ref_ctr, uretprobe has to use ref_ctr as well */
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uprobe_opts.retprobe = true;
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uprobe_opts.ref_ctr_offset = legacy ? 0 : ref_ctr_offset;
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uretprobe_link = bpf_program__attach_uprobe_opts(skel->progs.handle_uretprobe,
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-1 /* any pid */,
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"/proc/self/exe",
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uprobe_offset, &uprobe_opts);
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if (!ASSERT_OK_PTR(uretprobe_link, "attach_uretprobe"))
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goto cleanup;
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skel->links.handle_uretprobe = uretprobe_link;
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/* trigger & validate kprobe && kretprobe */
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usleep(1);
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if (CHECK(skel->bss->kprobe_res != 1, "check_kprobe_res",
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"wrong kprobe res: %d\n", skel->bss->kprobe_res))
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goto cleanup;
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if (CHECK(skel->bss->kretprobe_res != 2, "check_kretprobe_res",
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"wrong kretprobe res: %d\n", skel->bss->kretprobe_res))
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goto cleanup;
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/* trigger & validate uprobe & uretprobe */
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trigger_func();
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if (CHECK(skel->bss->uprobe_res != 3, "check_uprobe_res",
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"wrong uprobe res: %d\n", skel->bss->uprobe_res))
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goto cleanup;
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if (CHECK(skel->bss->uretprobe_res != 4, "check_uretprobe_res",
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"wrong uretprobe res: %d\n", skel->bss->uretprobe_res))
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goto cleanup;
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cleanup:
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test_attach_probe__destroy(skel);
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ASSERT_EQ(uprobe_ref_ctr, 0, "uprobe_ref_ctr_cleanup");
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}
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