linux-toradex.git/kernel/kcov.c, branch v5.9-rc5

kcov: make some symbols static

2020-08-12T17:58:02+00:00

Fix sparse build warnings:

kernel/kcov.c:99:1: warning:
 symbol '__pcpu_scope_kcov_percpu_data' was not declared. Should it be static?
kernel/kcov.c:778:6: warning:
 symbol 'kcov_remote_softirq_start' was not declared. Should it be static?
kernel/kcov.c:795:6: warning:
 symbol 'kcov_remote_softirq_stop' was not declared. Should it be static?

Reported-by: Hulk Robot 
Signed-off-by: Wei Yongjun 
Signed-off-by: Andrew Morton 
Reviewed-by: Andrey Konovalov 
Link: http://lkml.kernel.org/r/20200702115501.73077-1-weiyongjun1@huawei.com
Signed-off-by: Linus Torvalds

kcov: check kcov_softirq in kcov_remote_stop()

2020-06-11T02:14:17+00:00

kcov_remote_stop() should check that the corresponding kcov_remote_start()
actually found the specified remote handle and started collecting
coverage.  This is done by checking the per thread kcov_softirq flag.

A particular failure scenario where this was observed involved a softirq
with a remote coverage collection section coming between check_kcov_mode()
and the access to t->kcov_area in __sanitizer_cov_trace_pc().  In that
softirq kcov_remote_start() bailed out after kcov_remote_find() check, but
the matching kcov_remote_stop() didn't check if kcov_remote_start()
succeeded, and overwrote per thread kcov parameters with invalid (zero)
values.

Fixes: 5ff3b30ab57d ("kcov: collect coverage from interrupts")
Signed-off-by: Andrey Konovalov 
Signed-off-by: Andrew Morton 
Reviewed-by: Dmitry Vyukov 
Cc: Alexander Potapenko 
Cc: Marco Elver 
Cc: Tetsuo Handa 
Link: http://lkml.kernel.org/r/fcd1cd16eac1d2c01a66befd8ea4afc6f8d09833.1591576806.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds

kcov: collect coverage from interrupts

2020-06-05T02:06:20+00:00

This change extends kcov remote coverage support to allow collecting
coverage from soft interrupts in addition to kernel background threads.

To collect coverage from code that is executed in softirq context, a part
of that code has to be annotated with kcov_remote_start/stop() in a
similar way as how it is done for global kernel background threads.  Then
the handle used for the annotations has to be passed to the
KCOV_REMOTE_ENABLE ioctl.

Internally this patch adjusts the __sanitizer_cov_trace_pc() compiler
inserted callback to not bail out when called from softirq context.
kcov_remote_start/stop() are updated to save/restore the current per task
kcov state in a per-cpu area (in case the softirq came when the kernel was
already collecting coverage in task context).  Coverage from softirqs is
collected into pre-allocated per-cpu areas, whose size is controlled by
the new CONFIG_KCOV_IRQ_AREA_SIZE.

[andreyknvl@google.com: turn current->kcov_softirq into unsigned int to fix objtool warning]
  Link: http://lkml.kernel.org/r/841c778aa3849c5cb8c3761f56b87ce653a88671.1585233617.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov 
Signed-off-by: Andrew Morton 
Reviewed-by: Dmitry Vyukov 
Cc: Alan Stern 
Cc: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Link: http://lkml.kernel.org/r/469bd385c431d050bc38a593296eff4baae50666.1584655448.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds

kcov: use t->kcov_mode as enabled indicator

2020-06-05T02:06:20+00:00

Currently kcov_remote_start() and kcov_remote_stop() check t->kcov to find
out whether the coverage is already being collected by the current task.
Use t->kcov_mode for that instead.  This doesn't change the overall
behavior in any way, but serves as a preparation for the following softirq
coverage collection support patch.

Signed-off-by: Andrey Konovalov 
Signed-off-by: Andrew Morton 
Reviewed-by: Dmitry Vyukov 
Cc: Alan Stern 
Cc: Alexander Potapenko 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Cc: Andrey Konovalov 
Link: http://lkml.kernel.org/r/f70377945d1d8e6e4916cbce871a12303d6186b4.1585233617.git.andreyknvl@google.com
Link: http://lkml.kernel.org/r/ee1a1dec43059da5d7664c85c1addc89c4cd58de.1584655448.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds

kcov: move t->kcov_sequence assignment

2020-06-05T02:06:20+00:00

Move t->kcov_sequence assignment before assigning t->kcov_mode for
consistency.

Signed-off-by: Andrey Konovalov 
Signed-off-by: Andrew Morton 
Reviewed-by: Dmitry Vyukov 
Cc: Alan Stern 
Cc: Alexander Potapenko 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Cc: Andrey Konovalov 
Link: http://lkml.kernel.org/r/5889efe35e0b300e69dba97216b1288d9c2428a8.1585233617.git.andreyknvl@google.com
Link: http://lkml.kernel.org/r/f0283c676bab3335cb48bfe12d375a3da4719f59.1584655448.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds

kcov: move t->kcov assignments into kcov_start/stop

2020-06-05T02:06:20+00:00

Every time kcov_start/stop() is called, t->kcov is also assigned, so move
the assignment into the functions.

Signed-off-by: Andrey Konovalov 
Signed-off-by: Andrew Morton 
Reviewed-by: Dmitry Vyukov 
Cc: Alan Stern 
Cc: Alexander Potapenko 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Cc: Andrey Konovalov 
Link: http://lkml.kernel.org/r/6644839d3567df61ade3c4b246a46cacbe4f9e11.1585233617.git.andreyknvl@google.com
Link: http://lkml.kernel.org/r/82625ef3ff878f0b585763cc31d09d9b08ca37d6.1584655448.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds

kcov: fix potential use-after-free in kcov_remote_start

2020-06-05T02:06:20+00:00

If vmalloc() fails in kcov_remote_start() we'll access remote->kcov
without holding kcov_remote_lock, so remote might potentially be freed at
that point.  Cache kcov pointer in a local variable.

Signed-off-by: Andrey Konovalov 
Signed-off-by: Andrew Morton 
Reviewed-by: Dmitry Vyukov 
Cc: Alan Stern 
Cc: Alexander Potapenko 
Cc: Greg Kroah-Hartman 
Cc: Marco Elver 
Cc: Andrey Konovalov 
Link: http://lkml.kernel.org/r/9d9134359725a965627b7e8f2652069f86f1d1fa.1585233617.git.andreyknvl@google.com
Link: http://lkml.kernel.org/r/de0d3d30ff90776a2a509cc34c7c1c7521bda125.1584655448.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds

kcov: cleanup debug messages

2020-06-05T02:06:20+00:00

Patch series "kcov: collect coverage from usb soft interrupts", v4.

This patchset extends kcov to allow collecting coverage from soft
interrupts and then uses the new functionality to collect coverage from
USB code.

This has allowed to find at least one new HID bug [1], which was recently
fixed by Alan [2].

[1] https://syzkaller.appspot.com/bug?extid=09ef48aa58261464b621
[2] https://patchwork.kernel.org/patch/11283319/

Any subsystem that uses softirqs (e.g. timers) can make use of this in
the future. Looking at the recent syzbot reports, an obvious candidate
is the networking subsystem [3, 4, 5 and many more].

[3] https://syzkaller.appspot.com/bug?extid=522ab502c69badc66ab7
[4] https://syzkaller.appspot.com/bug?extid=57f89d05946c53dbbb31
[5] https://syzkaller.appspot.com/bug?extid=df358e65d9c1b9d3f5f4

This pach (of 7):

Previous commit left a lot of excessive debug messages, clean them up.

Link; http://lkml.kernel.org/r/cover.1585233617.git.andreyknvl@google.com
Link; http://lkml.kernel.org/r/ab5e2885ce674ba6e04368551e51eeb6a2c11baf.1585233617.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov 
Signed-off-by: Andrew Morton 
Reviewed-by: Dmitry Vyukov 
Cc: Greg Kroah-Hartman 
Cc: Alan Stern 
Cc: Alexander Potapenko 
Cc: Marco Elver 
Cc: Andrey Konovalov 
Link: http://lkml.kernel.org/r/4a497134b2cf7a9d306d28e3dd2746f5446d1605.1584655448.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds

kernel/kcov.c: fix typos in kcov_remote_start documentation

2020-05-08T02:27:20+00:00

Signed-off-by: Maciej Grochowski 
Signed-off-by: Andrew Morton 
Reviewed-by: Andrey Konovalov 
Link: http://lkml.kernel.org/r/20200420030259.31674-1-maciek.grochowski@gmail.com
Signed-off-by: Linus Torvalds

kcov: remote coverage support

2019-12-05T03:44:14+00:00

Patch series " kcov: collect coverage from usb and vhost", v3.

This patchset extends kcov to allow collecting coverage from backgound
kernel threads.  This extension requires custom annotations for each of
the places where coverage collection is desired.  This patchset
implements this for hub events in the USB subsystem and for vhost
workers.  See the first patch description for details about the kcov
extension.  The other two patches apply this kcov extension to USB and
vhost.

Examples of other subsystems that might potentially benefit from this
when custom annotations are added (the list is based on
process_one_work() callers for bugs recently reported by syzbot):

1. fs: writeback wb_workfn() worker,
2. net: addrconf_dad_work()/addrconf_verify_work() workers,
3. net: neigh_periodic_work() worker,
4. net/p9: p9_write_work()/p9_read_work() workers,
5. block: blk_mq_run_work_fn() worker.

These patches have been used to enable coverage-guided USB fuzzing with
syzkaller for the last few years, see the details here:

  https://github.com/google/syzkaller/blob/master/docs/linux/external_fuzzing_usb.md

This patchset has been pushed to the public Linux kernel Gerrit
instance:

  https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/1524

This patch (of 3):

Add background thread coverage collection ability to kcov.

With KCOV_ENABLE coverage is collected only for syscalls that are issued
from the current process.  With KCOV_REMOTE_ENABLE it's possible to
collect coverage for arbitrary parts of the kernel code, provided that
those parts are annotated with kcov_remote_start()/kcov_remote_stop().

This allows to collect coverage from two types of kernel background
threads: the global ones, that are spawned during kernel boot in a
limited number of instances (e.g.  one USB hub_event() worker thread is
spawned per USB HCD); and the local ones, that are spawned when a user
interacts with some kernel interface (e.g.  vhost workers).

To enable collecting coverage from a global background thread, a unique
global handle must be assigned and passed to the corresponding
kcov_remote_start() call.  Then a userspace process can pass a list of
such handles to the KCOV_REMOTE_ENABLE ioctl in the handles array field
of the kcov_remote_arg struct.  This will attach the used kcov device to
the code sections, that are referenced by those handles.

Since there might be many local background threads spawned from
different userspace processes, we can't use a single global handle per
annotation.  Instead, the userspace process passes a non-zero handle
through the common_handle field of the kcov_remote_arg struct.  This
common handle gets saved to the kcov_handle field in the current
task_struct and needs to be passed to the newly spawned threads via
custom annotations.  Those threads should in turn be annotated with
kcov_remote_start()/kcov_remote_stop().

Internally kcov stores handles as u64 integers.  The top byte of a
handle is used to denote the id of a subsystem that this handle belongs
to, and the lower 4 bytes are used to denote the id of a thread instance
within that subsystem.  A reserved value 0 is used as a subsystem id for
common handles as they don't belong to a particular subsystem.  The
bytes 4-7 are currently reserved and must be zero.  In the future the
number of bytes used for the subsystem or handle ids might be increased.

When a particular userspace process collects coverage by via a common
handle, kcov will collect coverage for each code section that is
annotated to use the common handle obtained as kcov_handle from the
current task_struct.  However non common handles allow to collect
coverage selectively from different subsystems.

Link: http://lkml.kernel.org/r/e90e315426a384207edbec1d6aa89e43008e4caf.1572366574.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov 
Cc: Dmitry Vyukov 
Cc: Greg Kroah-Hartman 
Cc: Alan Stern 
Cc: "Michael S. Tsirkin" 
Cc: Jason Wang 
Cc: Arnd Bergmann 
Cc: Steven Rostedt 
Cc: David Windsor 
Cc: Elena Reshetova 
Cc: Anders Roxell 
Cc: Alexander Potapenko 
Cc: Marco Elver 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds