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KCSAN updates for v6.2

Browse source 
This series adds instrumentation for memcpy(), memset(), and memmove() for
 Clang v16+'s new function names that are used when the -fsanitize=thread
 argument is given.  It also fixes objtool warnings from KCSAN's volatile
 instrumentation, and fixes a pair of typos in a pair of Kconfig options'
 help clauses.
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Merge tag 'kcsan.2022.12.02a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull KCSAN updates from Paul McKenney:

 - Add instrumentation for memcpy(), memset(), and memmove() for Clang
   v16+'s new function names that are used when the -fsanitize=thread
   argument is given

 - Fix objtool warnings from KCSAN's volatile instrumentation, and typos
   in a pair of Kconfig options' help clauses

* tag 'kcsan.2022.12.02a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  kcsan: Fix trivial typo in Kconfig help comments
  objtool, kcsan: Add volatile read/write instrumentation to whitelist
  kcsan: Instrument memcpy/memset/memmove with newer Clang
This commit is contained in:
Linus Torvalds 2022-12-12 08:03:49 -08:00
commit f433cf2102
3 changed files with 63 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

50
kernel/kcsan/core.c
View file

@ -14,10 +14,12 @@
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/minmax.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/preempt.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/uaccess.h>
#include "encoding.h"
@ -1308,3 +1310,51 @@ noinline void __tsan_atomic_signal_fence(int memorder)
}
}
EXPORT_SYMBOL(__tsan_atomic_signal_fence);
#ifdef __HAVE_ARCH_MEMSET
void *__tsan_memset(void *s, int c, size_t count);
noinline void *__tsan_memset(void *s, int c, size_t count)
{
/*
* Instead of not setting up watchpoints where accessed size is greater
* than MAX_ENCODABLE_SIZE, truncate checked size to MAX_ENCODABLE_SIZE.
*/
size_t check_len = min_t(size_t, count, MAX_ENCODABLE_SIZE);
check_access(s, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
return memset(s, c, count);
}
#else
void *__tsan_memset(void *s, int c, size_t count) __alias(memset);
#endif
EXPORT_SYMBOL(__tsan_memset);
#ifdef __HAVE_ARCH_MEMMOVE
void *__tsan_memmove(void *dst, const void *src, size_t len);
noinline void *__tsan_memmove(void *dst, const void *src, size_t len)
{
size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
check_access(dst, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
check_access(src, check_len, 0, _RET_IP_);
return memmove(dst, src, len);
}
#else
void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove);
#endif
EXPORT_SYMBOL(__tsan_memmove);
#ifdef __HAVE_ARCH_MEMCPY
void *__tsan_memcpy(void *dst, const void *src, size_t len);
noinline void *__tsan_memcpy(void *dst, const void *src, size_t len)
{
size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
check_access(dst, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
check_access(src, check_len, 0, _RET_IP_);
return memcpy(dst, src, len);
}
#else
void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy);
#endif
EXPORT_SYMBOL(__tsan_memcpy);

6
lib/Kconfig.kcsan
View file

@ -125,7 +125,7 @@ config KCSAN_SKIP_WATCH
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
watchpoint is set up, i.e. one in KCSAN_SKIP_WATCH 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.
@ -135,8 +135,8 @@ config KCSAN_SKIP_WATCH_RANDOMIZE
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.
KCSAN_SKIP_WATCH. If false, the chosen value is always
KCSAN_SKIP_WATCH.
config KCSAN_INTERRUPT_WATCHER
bool "Interruptible watchers" if !KCSAN_STRICT

10
tools/objtool/check.c
View file

@ -999,6 +999,16 @@ static const char *uaccess_safe_builtin[] = {
"__tsan_read_write4",
"__tsan_read_write8",
"__tsan_read_write16",
"__tsan_volatile_read1",
"__tsan_volatile_read2",
"__tsan_volatile_read4",
"__tsan_volatile_read8",
"__tsan_volatile_read16",
"__tsan_volatile_write1",
"__tsan_volatile_write2",
"__tsan_volatile_write4",
"__tsan_volatile_write8",
"__tsan_volatile_write16",
"__tsan_atomic8_load",
"__tsan_atomic16_load",
"__tsan_atomic32_load",