kernel/linux.git/include/linux/kcov.h, branch v7.2-rc1

kcov: allow simultaneous KCOV_ENABLE/KCOV_REMOTE_ENABLE

2026-05-29T04:24:51+00:00

Allow the same userspace thread to simultaneously collect normal coverage in syscall context (KCOV_ENABLE) and remote coverage of asynchronous work created by the thread (KCOV_REMOTE_ENABLE). With this, remote KCOV coverage becomes useful for generic fuzzing and not just fuzzing of specific data injection interfaces. This requires that the task_struct::kcov_* fields are separated into ones that are used by the task that generates coverage, and ones that are used by the task that requested remote coverage. To split this up: - Split task_struct::kcov into kcov and kcov_remote. kcov_task_exit() now has to clean up both separately. - Only use task_struct::kcov_mode on the task that generates coverage. - Only reset task_struct::kcov_handle on the task that requested remote coverage. After this change, fields used by the task that generates coverage are: - kcov_mode - kcov_size - kcov_area - kcov - kcov_sequence - kcov_softirq Fields used by the task that requested remote coverage are: - kcov_remote - kcov_handle [jannh@google.com: remove unused constant KCOV_MODE_REMOTE, per Dmitry] Link: https://lore.kernel.org/20260515-kcov-simultaneous-remote-v2-1-56fde1cfa509@google.com [jannh@google.com: update documentation on remote coverage collection] Link: https://lore.kernel.org/20260519-kcov-docs-v1-1-5bb22f4cb20c@google.com [jannh@google.com: move and reword sentence on simultaneous normal/remote collection Link: https://lore.kernel.org/20260520-kcov-docs-v2-1-819f78778763@google.com Link: https://lore.kernel.org/20260505-kcov-simultaneous-remote-v1-1-a670ba7cefd2@google.com Signed-off-by: Jann Horn Reviewed-by: Dmitry Vyukov Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Marco Elver Signed-off-by: Andrew Morton

kcov: refactor common handle ID into kcov_common_handle_id

2026-05-29T04:24:45+00:00

Store common handle IDs in "struct kcov_common_handle_id", which consumes no space in non-KCOV builds. This cleanup removes #ifdef boilerplate code from subsystems that integrate with KCOV (in particular in usbip_common.h and skbuff.h, see the diffstat). This should also make it easier to add KCOV remote coverage to more subsystems in the future. Link: https://lore.kernel.org/20260430-kcov-refactor-common-handle-v1-1-23a0c7a0ba38@google.com Signed-off-by: Jann Horn Acked-by: Greg Kroah-Hartman Reviewed-by: Dmitry Vyukov Acked-by: Jakub Kicinski Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Eugenio Pérez Cc: Hongren (Zenithal) Zheng Cc: Jann Horn Cc: Jason Wang Cc: "Michael S. Tsirkin" Cc: Shuah Khan Cc: Valentina Manea Signed-off-by: Andrew Morton

kcov, usb: Don't disable interrupts in kcov_remote_start_usb_softirq()

2025-08-13T15:18:43+00:00

kcov_remote_start_usb_softirq() the begin of urb's completion callback. HCDs marked HCD_BH will invoke this function from the softirq and in_serving_softirq() will detect this properly. Root-HUB (RH) requests will not be delayed to softirq but complete immediately in IRQ context. This will confuse kcov because in_serving_softirq() will report true if the softirq is served after the hardirq and if the softirq got interrupted by the hardirq in which currently runs. This was addressed by simply disabling interrupts in kcov_remote_start_usb_softirq() which avoided the interruption by the RH while a regular completion callback was invoked. This not only changes the behaviour while kconv is enabled but also breaks PREEMPT_RT because now sleeping locks can no longer be acquired. Revert the previous fix. Address the issue by invoking kcov_remote_start_usb() only if the context is just "serving softirqs" which is identified by checking in_serving_softirq() and in_hardirq() must be false. Fixes: f85d39dd7ed89 ("kcov, usb: disable interrupts in kcov_remote_start_usb_softirq") Cc: stable Reported-by: Yunseong Kim Closes: https://lore.kernel.org/all/20250725201400.1078395-2-ysk@kzalloc.com/ Tested-by: Yunseong Kim Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20250811082745.ycJqBXMs@linutronix.de Signed-off-by: Greg Kroah-Hartman

Merge tag 'mm-hotfixes-stable-2024-06-17-11-43' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-06-17T19:30:07+00:00

Pull misc fixes from Andrew Morton: "Mainly MM singleton fixes. And a couple of ocfs2 regression fixes" * tag 'mm-hotfixes-stable-2024-06-17-11-43' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: kcov: don't lose track of remote references during softirqs mm: shmem: fix getting incorrect lruvec when replacing a shmem folio mm/debug_vm_pgtable: drop RANDOM_ORVALUE trick mm: fix possible OOB in numa_rebuild_large_mapping() mm/migrate: fix kernel BUG at mm/compaction.c:2761! selftests: mm: make map_fixed_noreplace test names stable mm/memfd: add documentation for MFD_NOEXEC_SEAL MFD_EXEC mm: mmap: allow for the maximum number of bits for randomizing mmap_base by default gcov: add support for GCC 14 zap_pid_ns_processes: clear TIF_NOTIFY_SIGNAL along with TIF_SIGPENDING mm: huge_memory: fix misused mapping_large_folio_support() for anon folios lib/alloc_tag: fix RCU imbalance in pgalloc_tag_get() lib/alloc_tag: do not register sysctl interface when CONFIG_SYSCTL=n MAINTAINERS: remove Lorenzo as vmalloc reviewer Revert "mm: init_mlocked_on_free_v3" mm/page_table_check: fix crash on ZONE_DEVICE gcc: disable '-Warray-bounds' for gcc-9 ocfs2: fix NULL pointer dereference in ocfs2_abort_trigger() ocfs2: fix NULL pointer dereference in ocfs2_journal_dirty()

kcov: don't lose track of remote references during softirqs

2024-06-15T17:43:08+00:00

In kcov_remote_start()/kcov_remote_stop(), we swap the previous KCOV metadata of the current task into a per-CPU variable. However, the kcov_mode_enabled(mode) check is not sufficient in the case of remote KCOV coverage: current->kcov_mode always remains KCOV_MODE_DISABLED for remote KCOV objects. If the original task that has invoked the KCOV_REMOTE_ENABLE ioctl happens to get interrupted and kcov_remote_start() is called, it ultimately leads to kcov_remote_stop() NOT restoring the original KCOV reference. So when the task exits, all registered remote KCOV handles remain active forever. The most uncomfortable effect (at least for syzkaller) is that the bug prevents the reuse of the same /sys/kernel/debug/kcov descriptor. If we obtain it in the parent process and then e.g. drop some capabilities and continuously fork to execute individual programs, at some point current->kcov of the forked process is lost, kcov_task_exit() takes no action, and all KCOV_REMOTE_ENABLE ioctls calls from subsequent forks fail. And, yes, the efficiency is also affected if we keep on losing remote kcov objects. a) kcov_remote_map keeps on growing forever. b) (If I'm not mistaken), we're also not freeing the memory referenced by kcov->area. Fix it by introducing a special kcov_mode that is assigned to the task that owns a KCOV remote object. It makes kcov_mode_enabled() return true and yet does not trigger coverage collection in __sanitizer_cov_trace_pc() and write_comp_data(). [nogikh@google.com: replace WRITE_ONCE() with an ordinary assignment] Link: https://lkml.kernel.org/r/20240614171221.2837584-1-nogikh@google.com Link: https://lkml.kernel.org/r/20240611133229.527822-1-nogikh@google.com Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts") Signed-off-by: Aleksandr Nogikh Reviewed-by: Dmitry Vyukov Reviewed-by: Andrey Konovalov Tested-by: Andrey Konovalov Cc: Alexander Potapenko Cc: Arnd Bergmann Cc: Marco Elver Cc: Signed-off-by: Andrew Morton

kcov, usb: disable interrupts in kcov_remote_start_usb_softirq

2024-06-04T13:34:44+00:00

After commit 8fea0c8fda30 ("usb: core: hcd: Convert from tasklet to BH workqueue"), usb_giveback_urb_bh() runs in the BH workqueue with interrupts enabled. Thus, the remote coverage collection section in usb_giveback_urb_bh()-> __usb_hcd_giveback_urb() might be interrupted, and the interrupt handler might invoke __usb_hcd_giveback_urb() again. This breaks KCOV, as it does not support nested remote coverage collection sections within the same context (neither in task nor in softirq). Update kcov_remote_start/stop_usb_softirq() to disable interrupts for the duration of the coverage collection section to avoid nested sections in the softirq context (in addition to such in the task context, which are already handled). Reported-by: Tetsuo Handa Closes: https://lore.kernel.org/linux-usb/0f4d1964-7397-485b-bc48-11c01e2fcbca@I-love.SAKURA.ne.jp/ Closes: https://syzkaller.appspot.com/bug?extid=0438378d6f157baae1a2 Suggested-by: Alan Stern Fixes: 8fea0c8fda30 ("usb: core: hcd: Convert from tasklet to BH workqueue") Cc: stable@vger.kernel.org Acked-by: Dmitry Vyukov Signed-off-by: Andrey Konovalov Link: https://lore.kernel.org/r/20240527173538.4989-1-andrey.konovalov@linux.dev Signed-off-by: Greg Kroah-Hartman

kcov: add prototypes for helper functions

2023-06-10T00:44:17+00:00

A number of internal functions in kcov are only called from generated code and don't technically need a declaration, but 'make W=1' warns about global symbols without a prototype: kernel/kcov.c:199:14: error: no previous prototype for '__sanitizer_cov_trace_pc' [-Werror=missing-prototypes] kernel/kcov.c:264:14: error: no previous prototype for '__sanitizer_cov_trace_cmp1' [-Werror=missing-prototypes] kernel/kcov.c:270:14: error: no previous prototype for '__sanitizer_cov_trace_cmp2' [-Werror=missing-prototypes] kernel/kcov.c:276:14: error: no previous prototype for '__sanitizer_cov_trace_cmp4' [-Werror=missing-prototypes] kernel/kcov.c:282:14: error: no previous prototype for '__sanitizer_cov_trace_cmp8' [-Werror=missing-prototypes] kernel/kcov.c:288:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp1' [-Werror=missing-prototypes] kernel/kcov.c:295:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp2' [-Werror=missing-prototypes] kernel/kcov.c:302:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp4' [-Werror=missing-prototypes] kernel/kcov.c:309:14: error: no previous prototype for '__sanitizer_cov_trace_const_cmp8' [-Werror=missing-prototypes] kernel/kcov.c:316:14: error: no previous prototype for '__sanitizer_cov_trace_switch' [-Werror=missing-prototypes] Adding prototypes for these in a header solves that problem, but now there is a mismatch between the built-in type and the prototype on 64-bit architectures because they expect some functions to take a 64-bit 'unsigned long' argument rather than an 'unsigned long long' u64 type: include/linux/kcov.h:84:6: error: conflicting types for built-in function '__sanitizer_cov_trace_switch'; expected 'void(long long unsigned int, void *)' [-Werror=builtin-declaration-mismatch] 84 | void __sanitizer_cov_trace_switch(u64 val, u64 *cases); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ Avoid this as well with a custom type definition. Link: https://lkml.kernel.org/r/20230517124944.929997-1-arnd@kernel.org Signed-off-by: Arnd Bergmann Cc: Andrey Konovalov Cc: Dmitry Vyukov Cc: Rong Tao Signed-off-by: Andrew Morton

kcov: fix spelling typos in comments

2022-12-12T03:30:20+00:00

Fix the typo of 'suport' in kcov.h Link: https://lkml.kernel.org/r/tencent_922CA94B789587D79FD154445D035AA19E07@qq.com Signed-off-by: Rong Tao Reviewed-by: Dmitry Vyukov Cc: Andrey Konovalov Signed-off-by: Andrew Morton

kcov: Remove kcov include from sched.h and move it to its users.

2021-03-06T11:40:21+00:00

The recent addition of in_serving_softirq() to kconv.h results in compile failure on PREEMPT_RT because it requires task_struct::softirq_disable_cnt. This is not available if kconv.h is included from sched.h. It is not needed to include kconv.h from sched.h. All but the net/ user already include the kconv header file. Move the include of the kconv.h header from sched.h it its users. Additionally include sched.h from kconv.h to ensure that everything task_struct related is available. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Acked-by: Johannes Berg Acked-by: Andrey Konovalov Link: https://lkml.kernel.org/r/20210218173124.iy5iyqv3a4oia4vv@linutronix.de

kcov, usb: hide in_serving_softirq checks in __usb_hcd_giveback_urb

2021-01-07T13:17:29+00:00

Done opencode in_serving_softirq() checks in in_serving_softirq() to avoid cluttering the code, hide them in kcov helpers instead. Fixes: aee9ddb1d371 ("kcov, usb: only collect coverage from __usb_hcd_giveback_urb in softirq") Signed-off-by: Andrey Konovalov Link: https://lore.kernel.org/r/aeb430c5bb90b0ccdf1ec302c70831c1a47b9c45.1609876340.git.andreyknvl@google.com Signed-off-by: Greg Kroah-Hartman