user/sven/linux.git/kernel/kcsan, branch v5.10.100

kcsan: Fix debugfs initcall return type

2021-05-26T10:06:54Z

commit 976aac5f882989e4f6c1b3a7224819bf0e801c6a upstream. clang with CONFIG_LTO_CLANG points out that an initcall function should return an 'int' due to the changes made to the initcall macros in commit 3578ad11f3fb ("init: lto: fix PREL32 relocations"): kernel/kcsan/debugfs.c:274:15: error: returning 'void' from a function with incompatible result type 'int' late_initcall(kcsan_debugfs_init); ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~ include/linux/init.h:292:46: note: expanded from macro 'late_initcall' #define late_initcall(fn) __define_initcall(fn, 7) Fixes: e36299efe7d7 ("kcsan, debugfs: Move debugfs file creation out of early init") Cc: stable Reviewed-by: Greg Kroah-Hartman Reviewed-by: Marco Elver Reviewed-by: Nathan Chancellor Reviewed-by: Miguel Ojeda Signed-off-by: Arnd Bergmann Signed-off-by: Paul E. McKenney Signed-off-by: Greg Kroah-Hartman

kcsan, debugfs: Move debugfs file creation out of early init

2021-05-11T12:47:33Z

commit e36299efe7d749976fbdaaf756dee6ef32543c2c upstream. Commit 56348560d495 ("debugfs: do not attempt to create a new file before the filesystem is initalized") forbids creating new debugfs files until debugfs is fully initialized. This means that KCSAN's debugfs file creation, which happened at the end of __init(), no longer works. And was apparently never supposed to work! However, there is no reason to create KCSAN's debugfs file so early. This commit therefore moves its creation to a late_initcall() callback. Cc: "Rafael J. Wysocki" Cc: stable Fixes: 56348560d495 ("debugfs: do not attempt to create a new file before the filesystem is initalized") Reviewed-by: Greg Kroah-Hartman Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney Signed-off-by: Greg Kroah-Hartman

kcsan: Rewrite kcsan_prandom_u32_max() without prandom_u32_state()

2021-03-04T10:37:37Z

[ Upstream commit 71a076f4a61a6c779794ad286f356b39725edc3b ] Rewrite kcsan_prandom_u32_max() to not depend on code that might be instrumented, removing any dependency on lib/random32.c. The rewrite implements a simple linear congruential generator, that is sufficient for our purposes (for udelay() and skip_watch counter randomness). The initial motivation for this was to allow enabling KCSAN for kernel/sched (remove KCSAN_SANITIZE := n from kernel/sched/Makefile), with CONFIG_DEBUG_PREEMPT=y. Without this change, we could observe recursion: check_access() [via instrumentation] kcsan_setup_watchpoint() reset_kcsan_skip() kcsan_prandom_u32_max() get_cpu_var() preempt_disable() preempt_count_add() [in kernel/sched/core.c] check_access() [via instrumentation] Note, while this currently does not affect an unmodified kernel, it'd be good to keep a KCSAN kernel working when KCSAN_SANITIZE := n is removed from kernel/sched/Makefile to permit testing scheduler code with KCSAN if desired. Fixes: cd290ec24633 ("kcsan: Use tracing-safe version of prandom") Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin

kernel/: fix repeated words in comments

2020-10-16T18:11:19Z

Fix multiple occurrences of duplicated words in kernel/. Fix one typo/spello on the same line as a duplicate word. Change one instance of "the the" to "that the". Otherwise just drop one of the repeated words. Signed-off-by: Randy Dunlap Signed-off-by: Andrew Morton Link: https://lkml.kernel.org/r/98202fa6-8919-ef63-9efe-c0fad5ca7af1@infradead.org Signed-off-by: Linus Torvalds

kcsan: Use tracing-safe version of prandom

2020-08-31T04:50:13Z

In the core runtime, we must minimize any calls to external library functions to avoid any kind of recursion. This can happen even though instrumentation is disabled for called functions, but tracing is enabled. Most recently, prandom_u32() added a tracepoint, which can cause problems for KCSAN even if the rcuidle variant is used. For example: kcsan -> prandom_u32() -> trace_prandom_u32_rcuidle -> srcu_read_lock_notrace -> __srcu_read_lock -> kcsan ... While we could disable KCSAN in kcsan_setup_watchpoint(), this does not solve other unexpected behaviour we may get due recursing into functions that may not be tolerant to such recursion: __srcu_read_lock -> kcsan -> ... -> __srcu_read_lock Therefore, switch to using prandom_u32_state(), which is uninstrumented, and does not have a tracepoint. Link: https://lkml.kernel.org/r/20200821063043.1949509-1-elver@google.com Link: https://lkml.kernel.org/r/20200820172046.GA177701@elver.google.com Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney

kcsan: Optimize debugfs stats counters

2020-08-24T22:10:23Z

Remove kcsan_counter_inc/dec() functions, as they perform no other logic, and are no longer needed. This avoids several calls in kcsan_setup_watchpoint() and kcsan_found_watchpoint(), as well as lets the compiler warn us about potential out-of-bounds accesses as the array's size is known at all usage sites at compile-time. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney

kcsan: Use pr_fmt for consistency

2020-08-24T22:10:23Z

Use the same pr_fmt throughout for consistency. [ The only exception is report.c, where the format must be kept precisely as-is. ] Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney

kcsan: Show message if enabled early

2020-08-24T22:10:22Z

Show a message in the kernel log if KCSAN was enabled early. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney

kcsan: Remove debugfs test command

2020-08-24T22:10:22Z

Remove the debugfs test command, as it is no longer needed now that we have the KUnit+Torture based kcsan-test module. This is to avoid confusion around how KCSAN should be tested, as only the kcsan-test module is maintained. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney

kcsan: Simplify constant string handling

2020-08-24T22:10:22Z

Simplify checking prefixes and length calculation of constant strings. For the former, the kernel provides str_has_prefix(), and the latter we should just use strlen("..") because GCC and Clang have optimizations that optimize these into constants. No functional change intended. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney