This patch set reports two issues with captured stack traces.
First issue, fixed in patch #2, deals with fixing up uretprobe trampoline
addresses in captured stack trace. This issue happens when there are pending
return probes, for which kernel hijacks some of the return addresses on user
stacks. The code is matching those special uretprobe trampoline addresses with
the list of pending return probe instances and replaces them with actual
return addresses. This is the same fixup logic that fprobe/kretprobe has for
kernel stack traces.
Second issue, which patch #3 is fixing with the help of heuristic, is having
to do with capturing user stack traces in entry uprobes. At the very entrance
to user function, frame pointer in rbp register is not yet setup, so actual
caller return address is still pointed to by rsp. Patch is using a simple
heuristic, looking for `push %rbp` instruction, to fetch this extra direct
caller return address, before proceeding to unwind the stack using rbp.
Patch #4 adds tests into BPF selftests, that validate that captured stack
traces at various points is what we expect to get. This patch, while being BPF
selftests, is isolated from any other BPF selftests changes and can go in
through non-BPF tree without the risk of merge conflicts.
Patches are based on latest linux-trace/probes/for-next.
v1->v2:
- fixed GCC aggressively inlining test_uretprobe_stack() function (BPF CI);
- fixed comments (Peter).
Andrii Nakryiko (4):
uprobes: rename get_trampoline_vaddr() and make it global
perf,uprobes: fix user stack traces in the presence of pending
uretprobes
perf,x86: avoid missing caller address in stack traces captured in
uprobe
selftests/bpf: add test validating uprobe/uretprobe stack traces
arch/x86/events/core.c | 20 ++
include/linux/uprobes.h | 3 +
kernel/events/callchain.c | 43 +++-
kernel/events/uprobes.c | 17 +-
.../bpf/prog_tests/uretprobe_stack.c | 186 ++++++++++++++++++
.../selftests/bpf/progs/uretprobe_stack.c | 96 +++++++++
6 files changed, 361 insertions(+), 4 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/uretprobe_stack.c
create mode 100644 tools/testing/selftests/bpf/progs/uretprobe_stack.c
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2.43.0
