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authorThomas Gleixner <tglx@linutronix.de>2020-03-04 13:05:22 +0300
committerThomas Gleixner <tglx@linutronix.de>2020-06-11 16:14:36 +0300
commit0372007f5a79d61d3cb48a507717b9afb5d6addd (patch)
tree6c24f01600b47cf9a89e58d3a740f9064ebee299 /include/linux/context_tracking_state.h
parent20355e5f73a75e58cee4c80d4cd92ce0d1628023 (diff)
downloadlinux-0372007f5a79d61d3cb48a507717b9afb5d6addd.tar.xz
context_tracking: Ensure that the critical path cannot be instrumented
context tracking lacks a few protection mechanisms against instrumentation: - While the core functions are marked NOKPROBE they lack protection against function tracing which is required as the function entry/exit points can be utilized by BPF. - static functions invoked from the protected functions need to be marked as well as they can be instrumented otherwise. - using plain inline allows the compiler to emit traceable and probable functions. Fix this by marking the functions noinstr and converting the plain inlines to __always_inline. The NOKPROBE_SYMBOL() annotations are removed as the .noinstr.text section is already excluded from being probed. Cures the following objtool warnings: vmlinux.o: warning: objtool: enter_from_user_mode()+0x34: call to __context_tracking_exit() leaves .noinstr.text section vmlinux.o: warning: objtool: prepare_exit_to_usermode()+0x29: call to __context_tracking_enter() leaves .noinstr.text section vmlinux.o: warning: objtool: syscall_return_slowpath()+0x29: call to __context_tracking_enter() leaves .noinstr.text section vmlinux.o: warning: objtool: do_syscall_64()+0x7f: call to __context_tracking_enter() leaves .noinstr.text section vmlinux.o: warning: objtool: do_int80_syscall_32()+0x3d: call to __context_tracking_enter() leaves .noinstr.text section vmlinux.o: warning: objtool: do_fast_syscall_32()+0x9c: call to __context_tracking_enter() leaves .noinstr.text section and generates new ones... Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200505134340.811520478@linutronix.de
Diffstat (limited to 'include/linux/context_tracking_state.h')
-rw-r--r--include/linux/context_tracking_state.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index e7fe6678b7ad..65a60d3313b0 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -26,12 +26,12 @@ struct context_tracking {
extern struct static_key_false context_tracking_key;
DECLARE_PER_CPU(struct context_tracking, context_tracking);
-static inline bool context_tracking_enabled(void)
+static __always_inline bool context_tracking_enabled(void)
{
return static_branch_unlikely(&context_tracking_key);
}
-static inline bool context_tracking_enabled_cpu(int cpu)
+static __always_inline bool context_tracking_enabled_cpu(int cpu)
{
return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
}
@@ -41,7 +41,7 @@ static inline bool context_tracking_enabled_this_cpu(void)
return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
}
-static inline bool context_tracking_in_user(void)
+static __always_inline bool context_tracking_in_user(void)
{
return __this_cpu_read(context_tracking.state) == CONTEXT_USER;
}