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0104607288
When KCOV runs its boot selftest with whole-kernel instrumentation enabled, it sets current->kcov_mode to KCOV_MODE_TRACE_PC without installing a coverage area. Any instrumented code accepted as task-context coverage in that window dereferences current->kcov_area and crashes. On ARMv5 Versatile PB with CONFIG_KCOV_SELFTEST=y, CONFIG_KCOV_INSTRUMENT_ALL=y and CONFIG_IRQSOFF_TRACER=y, boot hits a NULL pointer fault during the selftest: kcov: running self test Internal error: Oops: 5 [#1] ARM PC is at __sanitizer_cov_trace_pc+0x4c/0x90 Kernel panic - not syncing: Fatal exception A diagnostic run showed the unwanted coverage comes from the IRQs-off tracer callbacks reached from ARM IRQ entry before hardirq context is visible to KCOV: __sanitizer_cov_trace_pc from tracer_hardirqs_off+0x18/0x1cc tracer_hardirqs_off from trace_hardirqs_off+0x34/0x54 trace_hardirqs_off from __irq_svc+0x58/0xb0 __irq_svc from kcov_init+0x7c/0xdc and similarly through tracer_hardirqs_on(). trace_preemptirq.o is already excluded because this tracing path can run from early interrupt code and produce coverage unrelated to syscall inputs. Exclude trace_irqsoff.o as well, instead of requiring users to turn off CONFIG_KCOV_INSTRUMENT_ALL=y, which is the default whole-kernel KCOV mode. With the exclusion in place, the same ARMv5 Versatile PB QEMU test boots through the KCOV selftest and reaches userspace. Tested on ARMv5 Versatile PB QEMU with CONFIG_KCOV_SELFTEST=y, CONFIG_KCOV_INSTRUMENT_ALL=y and CONFIG_IRQSOFF_TRACER=y. Link: https://patch.msgid.link/20260525170428.67211-1-kmehltretter@gmail.com Assisted-by: Codex:gpt-5 Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> |
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| .. | ||
| rv | ||
| blktrace.c | ||
| bpf_trace.c | ||
| bpf_trace.h | ||
| error_report-traces.c | ||
| fgraph.c | ||
| fprobe.c | ||
| ftrace_internal.h | ||
| ftrace.c | ||
| Kconfig | ||
| kprobe_event_gen_test.c | ||
| Makefile | ||
| pid_list.c | ||
| pid_list.h | ||
| power-traces.c | ||
| preemptirq_delay_test.c | ||
| remote_test_events.h | ||
| remote_test.c | ||
| rethook.c | ||
| ring_buffer_benchmark.c | ||
| ring_buffer.c | ||
| rpm-traces.c | ||
| simple_ring_buffer.c | ||
| synth_event_gen_test.c | ||
| trace_benchmark.c | ||
| trace_benchmark.h | ||
| trace_boot.c | ||
| trace_branch.c | ||
| trace_btf.c | ||
| trace_btf.h | ||
| trace_clock.c | ||
| trace_dynevent.c | ||
| trace_dynevent.h | ||
| trace_entries.h | ||
| trace_eprobe.c | ||
| trace_event_perf.c | ||
| trace_events_filter_test.h | ||
| trace_events_filter.c | ||
| trace_events_hist.c | ||
| trace_events_inject.c | ||
| trace_events_synth.c | ||
| trace_events_trigger.c | ||
| trace_events_user.c | ||
| trace_events.c | ||
| trace_export.c | ||
| trace_fprobe.c | ||
| trace_functions_graph.c | ||
| trace_functions.c | ||
| trace_hwlat.c | ||
| trace_irqsoff.c | ||
| trace_kdb.c | ||
| trace_kprobe_selftest.c | ||
| trace_kprobe_selftest.h | ||
| trace_kprobe.c | ||
| trace_mmiotrace.c | ||
| trace_nop.c | ||
| trace_osnoise.c | ||
| trace_output.c | ||
| trace_output.h | ||
| trace_pid.c | ||
| trace_preemptirq.c | ||
| trace_printk.c | ||
| trace_probe_kernel.h | ||
| trace_probe_tmpl.h | ||
| trace_probe.c | ||
| trace_probe.h | ||
| trace_recursion_record.c | ||
| trace_remote.c | ||
| trace_sched_switch.c | ||
| trace_sched_wakeup.c | ||
| trace_selftest_dynamic.c | ||
| trace_selftest.c | ||
| trace_seq.c | ||
| trace_snapshot.c | ||
| trace_stack.c | ||
| trace_stat.c | ||
| trace_stat.h | ||
| trace_synth.h | ||
| trace_syscalls.c | ||
| trace_uprobe.c | ||
| trace.c | ||
| trace.h | ||
| tracing_map.c | ||
| tracing_map.h | ||
| undefsyms_base.c | ||