90 lines
3.2 KiB
ReStructuredText
90 lines
3.2 KiB
ReStructuredText
The Undefined Behavior Sanitizer - UBSAN
|
|
========================================
|
|
|
|
UBSAN is a runtime undefined behaviour checker.
|
|
|
|
UBSAN uses compile-time instrumentation to catch undefined behavior (UB).
|
|
Compiler inserts code that perform certain kinds of checks before operations
|
|
that may cause UB. If check fails (i.e. UB detected) __ubsan_handle_*
|
|
function called to print error message.
|
|
|
|
GCC has that feature since 4.9.x [1_] (see ``-fsanitize=undefined`` option and
|
|
its suboptions). GCC 5.x has more checkers implemented [2_].
|
|
|
|
Report example
|
|
--------------
|
|
|
|
::
|
|
|
|
================================================================================
|
|
UBSAN: Undefined behaviour in ../include/linux/bitops.h:110:33
|
|
shift exponent 32 is to large for 32-bit type 'unsigned int'
|
|
CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.0-rc1+ #26
|
|
0000000000000000 ffffffff82403cc8 ffffffff815e6cd6 0000000000000001
|
|
ffffffff82403cf8 ffffffff82403ce0 ffffffff8163a5ed 0000000000000020
|
|
ffffffff82403d78 ffffffff8163ac2b ffffffff815f0001 0000000000000002
|
|
Call Trace:
|
|
[<ffffffff815e6cd6>] dump_stack+0x45/0x5f
|
|
[<ffffffff8163a5ed>] ubsan_epilogue+0xd/0x40
|
|
[<ffffffff8163ac2b>] __ubsan_handle_shift_out_of_bounds+0xeb/0x130
|
|
[<ffffffff815f0001>] ? radix_tree_gang_lookup_slot+0x51/0x150
|
|
[<ffffffff8173c586>] _mix_pool_bytes+0x1e6/0x480
|
|
[<ffffffff83105653>] ? dmi_walk_early+0x48/0x5c
|
|
[<ffffffff8173c881>] add_device_randomness+0x61/0x130
|
|
[<ffffffff83105b35>] ? dmi_save_one_device+0xaa/0xaa
|
|
[<ffffffff83105653>] dmi_walk_early+0x48/0x5c
|
|
[<ffffffff831066ae>] dmi_scan_machine+0x278/0x4b4
|
|
[<ffffffff8111d58a>] ? vprintk_default+0x1a/0x20
|
|
[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
|
|
[<ffffffff830b2240>] setup_arch+0x405/0xc2c
|
|
[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
|
|
[<ffffffff830ae053>] start_kernel+0x83/0x49a
|
|
[<ffffffff830ad120>] ? early_idt_handler_array+0x120/0x120
|
|
[<ffffffff830ad386>] x86_64_start_reservations+0x2a/0x2c
|
|
[<ffffffff830ad4f3>] x86_64_start_kernel+0x16b/0x17a
|
|
================================================================================
|
|
|
|
Usage
|
|
-----
|
|
|
|
To enable UBSAN configure kernel with::
|
|
|
|
CONFIG_UBSAN=y
|
|
|
|
and to check the entire kernel::
|
|
|
|
CONFIG_UBSAN_SANITIZE_ALL=y
|
|
|
|
To enable instrumentation for specific files or directories, add a line
|
|
similar to the following to the respective kernel Makefile:
|
|
|
|
- For a single file (e.g. main.o)::
|
|
|
|
UBSAN_SANITIZE_main.o := y
|
|
|
|
- For all files in one directory::
|
|
|
|
UBSAN_SANITIZE := y
|
|
|
|
To exclude files from being instrumented even if
|
|
``CONFIG_UBSAN_SANITIZE_ALL=y``, use::
|
|
|
|
UBSAN_SANITIZE_main.o := n
|
|
|
|
and::
|
|
|
|
UBSAN_SANITIZE := n
|
|
|
|
Detection of unaligned accesses controlled through the separate option -
|
|
CONFIG_UBSAN_ALIGNMENT. It's off by default on architectures that support
|
|
unaligned accesses (CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y). One could
|
|
still enable it in config, just note that it will produce a lot of UBSAN
|
|
reports.
|
|
|
|
References
|
|
----------
|
|
|
|
.. _1: https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html
|
|
.. _2: https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
|
|
.. _3: https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html
|