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authorThomas Gleixner <tglx@linutronix.de>2020-06-11 20:02:46 +0200
committerThomas Gleixner <tglx@linutronix.de>2020-06-11 20:02:46 +0200
commit37d1a04b13a6d2fec91a6813fc034947a27db034 (patch)
treec6a8d7d0df96a6eb1ddb53a12885761cb72e0e92 /lib
parent37f8173dd84936ea78000ed1cad24f8b18d48ebb (diff)
parent97a9474aeb789183a1d0712e66a4283860279ac9 (diff)
downloadlinux-37d1a04b13a6d2fec91a6813fc034947a27db034.tar.bz2
Rebase locking/kcsan to locking/urgent
Merge the state of the locking kcsan branch before the read/write_once() and the atomics modifications got merged. Squash the fallout of the rebase on top of the read/write once and atomic fallback work into the merge. The history of the original branch is preserved in tag locking-kcsan-2020-06-02. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug2
-rw-r--r--lib/Kconfig.kcsan181
-rw-r--r--lib/Makefile4
-rw-r--r--lib/iov_iter.c7
-rw-r--r--lib/usercopy.c7
5 files changed, 195 insertions, 6 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cb98741601bd..90e16bfe27c7 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1570,6 +1570,8 @@ config PROVIDE_OHCI1394_DMA_INIT
source "samples/Kconfig"
+source "lib/Kconfig.kcsan"
+
config ARCH_HAS_DEVMEM_IS_ALLOWED
bool
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
new file mode 100644
index 000000000000..689b6b81f272
--- /dev/null
+++ b/lib/Kconfig.kcsan
@@ -0,0 +1,181 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config HAVE_ARCH_KCSAN
+ bool
+
+menuconfig KCSAN
+ bool "KCSAN: dynamic data race detector"
+ depends on HAVE_ARCH_KCSAN && DEBUG_KERNEL && !KASAN
+ select STACKTRACE
+ help
+ The Kernel Concurrency Sanitizer (KCSAN) is a dynamic
+ data-race detector that relies on compile-time instrumentation.
+ KCSAN uses a watchpoint-based sampling approach to detect races.
+
+ While KCSAN's primary purpose is to detect data races, it
+ also provides assertions to check data access constraints.
+ These assertions can expose bugs that do not manifest as
+ data races.
+
+ See <file:Documentation/dev-tools/kcsan.rst> for more details.
+
+if KCSAN
+
+config KCSAN_VERBOSE
+ bool "Show verbose reports with more information about system state"
+ depends on PROVE_LOCKING
+ help
+ If enabled, reports show more information about the system state that
+ may help better analyze and debug races. This includes held locks and
+ IRQ trace events.
+
+ While this option should generally be benign, we call into more
+ external functions on report generation; if a race report is
+ generated from any one of them, system stability may suffer due to
+ deadlocks or recursion. If in doubt, say N.
+
+config KCSAN_DEBUG
+ bool "Debugging of KCSAN internals"
+
+config KCSAN_SELFTEST
+ bool "Perform short selftests on boot"
+ default y
+ help
+ Run KCSAN selftests on boot. On test failure, causes the kernel to panic.
+
+config KCSAN_EARLY_ENABLE
+ bool "Early enable during boot"
+ default y
+ help
+ If KCSAN should be enabled globally as soon as possible. KCSAN can
+ later be enabled/disabled via debugfs.
+
+config KCSAN_NUM_WATCHPOINTS
+ int "Number of available watchpoints"
+ default 64
+ help
+ Total number of available watchpoints. An address range maps into a
+ specific watchpoint slot as specified in kernel/kcsan/encoding.h.
+ Although larger number of watchpoints may not be usable due to
+ limited number of CPUs, a larger value helps to improve performance
+ due to reducing cache-line contention. The chosen default is a
+ conservative value; we should almost never observe "no_capacity"
+ events (see /sys/kernel/debug/kcsan).
+
+config KCSAN_UDELAY_TASK
+ int "Delay in microseconds (for tasks)"
+ default 80
+ help
+ For tasks, the microsecond delay after setting up a watchpoint.
+
+config KCSAN_UDELAY_INTERRUPT
+ int "Delay in microseconds (for interrupts)"
+ default 20
+ help
+ For interrupts, the microsecond delay after setting up a watchpoint.
+ Interrupts have tighter latency requirements, and their delay should
+ be lower than for tasks.
+
+config KCSAN_DELAY_RANDOMIZE
+ bool "Randomize above delays"
+ default y
+ help
+ If delays should be randomized, where the maximum is KCSAN_UDELAY_*.
+ If false, the chosen delays are always the KCSAN_UDELAY_* values
+ as defined above.
+
+config KCSAN_SKIP_WATCH
+ int "Skip instructions before setting up watchpoint"
+ default 4000
+ help
+ The number of per-CPU memory operations to skip, before another
+ watchpoint is set up, i.e. one in KCSAN_WATCH_SKIP per-CPU
+ memory operations are used to set up a watchpoint. A smaller value
+ results in more aggressive race detection, whereas a larger value
+ improves system performance at the cost of missing some races.
+
+config KCSAN_SKIP_WATCH_RANDOMIZE
+ bool "Randomize watchpoint instruction skip count"
+ default y
+ help
+ If instruction skip count should be randomized, where the maximum is
+ KCSAN_WATCH_SKIP. If false, the chosen value is always
+ KCSAN_WATCH_SKIP.
+
+config KCSAN_INTERRUPT_WATCHER
+ bool "Interruptible watchers"
+ help
+ If enabled, a task that set up a watchpoint may be interrupted while
+ delayed. This option will allow KCSAN to detect races between
+ interrupted tasks and other threads of execution on the same CPU.
+
+ Currently disabled by default, because not all safe per-CPU access
+ primitives and patterns may be accounted for, and therefore could
+ result in false positives.
+
+config KCSAN_REPORT_ONCE_IN_MS
+ int "Duration in milliseconds, in which any given race is only reported once"
+ default 3000
+ help
+ Any given race is only reported once in the defined time window.
+ Different races may still generate reports within a duration that is
+ smaller than the duration defined here. This allows rate limiting
+ reporting to avoid flooding the console with reports. Setting this
+ to 0 disables rate limiting.
+
+# The main purpose of the below options is to control reported data races (e.g.
+# in fuzzer configs), and are not expected to be switched frequently by other
+# users. We could turn some of them into boot parameters, but given they should
+# not be switched normally, let's keep them here to simplify configuration.
+#
+# The defaults below are chosen to be very conservative, and may miss certain
+# bugs.
+
+config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN
+ bool "Report races of unknown origin"
+ default y
+ help
+ If KCSAN should report races where only one access is known, and the
+ conflicting access is of unknown origin. This type of race is
+ reported if it was only possible to infer a race due to a data value
+ change while an access is being delayed on a watchpoint.
+
+config KCSAN_REPORT_VALUE_CHANGE_ONLY
+ bool "Only report races where watcher observed a data value change"
+ default y
+ help
+ If enabled and a conflicting write is observed via a watchpoint, but
+ the data value of the memory location was observed to remain
+ unchanged, do not report the data race.
+
+config KCSAN_ASSUME_PLAIN_WRITES_ATOMIC
+ bool "Assume that plain aligned writes up to word size are atomic"
+ default y
+ help
+ Assume that plain aligned writes up to word size are atomic by
+ default, and also not subject to other unsafe compiler optimizations
+ resulting in data races. This will cause KCSAN to not report data
+ races due to conflicts where the only plain accesses are aligned
+ writes up to word size: conflicts between marked reads and plain
+ aligned writes up to word size will not be reported as data races;
+ notice that data races between two conflicting plain aligned writes
+ will also not be reported.
+
+config KCSAN_IGNORE_ATOMICS
+ bool "Do not instrument marked atomic accesses"
+ help
+ Never instrument marked atomic accesses. This option can be used for
+ additional filtering. Conflicting marked atomic reads and plain
+ writes will never be reported as a data race, however, will cause
+ plain reads and marked writes to result in "unknown origin" reports.
+ If combined with CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n, data
+ races where at least one access is marked atomic will never be
+ reported.
+
+ Similar to KCSAN_ASSUME_PLAIN_WRITES_ATOMIC, but including unaligned
+ accesses, conflicting marked atomic reads and plain writes will not
+ be reported as data races; however, unlike that option, data races
+ due to two conflicting plain writes will be reported (aligned and
+ unaligned, if CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n).
+
+endif # KCSAN
diff --git a/lib/Makefile b/lib/Makefile
index 315516fa4ef4..b1c42c10073b 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -25,6 +25,9 @@ KASAN_SANITIZE_string.o := n
CFLAGS_string.o := $(call cc-option, -fno-stack-protector)
endif
+# Used by KCSAN while enabled, avoid recursion.
+KCSAN_SANITIZE_random32.o := n
+
lib-y := ctype.o string.o vsprintf.o cmdline.o \
rbtree.o radix-tree.o timerqueue.o xarray.o \
idr.o extable.o sha1.o irq_regs.o argv_split.o \
@@ -296,6 +299,7 @@ endif
UBSAN_SANITIZE_ubsan.o := n
KASAN_SANITIZE_ubsan.o := n
+KCSAN_SANITIZE_ubsan.o := n
CFLAGS_ubsan.o := $(call cc-option, -fno-stack-protector) $(DISABLE_STACKLEAK_PLUGIN)
obj-$(CONFIG_SBITMAP) += sbitmap.o
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 51595bf3af85..bf538c2bec77 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -8,6 +8,7 @@
#include <linux/splice.h>
#include <net/checksum.h>
#include <linux/scatterlist.h>
+#include <linux/instrumented.h>
#define PIPE_PARANOIA /* for now */
@@ -138,7 +139,7 @@
static int copyout(void __user *to, const void *from, size_t n)
{
if (access_ok(to, n)) {
- kasan_check_read(from, n);
+ instrument_copy_to_user(to, from, n);
n = raw_copy_to_user(to, from, n);
}
return n;
@@ -147,7 +148,7 @@ static int copyout(void __user *to, const void *from, size_t n)
static int copyin(void *to, const void __user *from, size_t n)
{
if (access_ok(from, n)) {
- kasan_check_write(to, n);
+ instrument_copy_from_user(to, from, n);
n = raw_copy_from_user(to, from, n);
}
return n;
@@ -639,7 +640,7 @@ EXPORT_SYMBOL(_copy_to_iter);
static int copyout_mcsafe(void __user *to, const void *from, size_t n)
{
if (access_ok(to, n)) {
- kasan_check_read(from, n);
+ instrument_copy_to_user(to, from, n);
n = copy_to_user_mcsafe((__force void *) to, from, n);
}
return n;
diff --git a/lib/usercopy.c b/lib/usercopy.c
index ca2a697a2061..b26509f112f9 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0
-#include <linux/uaccess.h>
#include <linux/bitops.h>
+#include <linux/instrumented.h>
+#include <linux/uaccess.h>
/* out-of-line parts */
@@ -10,7 +11,7 @@ unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n
unsigned long res = n;
might_fault();
if (likely(access_ok(from, n))) {
- kasan_check_write(to, n);
+ instrument_copy_from_user(to, from, n);
res = raw_copy_from_user(to, from, n);
}
if (unlikely(res))
@@ -25,7 +26,7 @@ unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
{
might_fault();
if (likely(access_ok(to, n))) {
- kasan_check_read(from, n);
+ instrument_copy_to_user(to, from, n);
n = raw_copy_to_user(to, from, n);
}
return n;