summaryrefslogtreecommitdiffstats
path: root/kernel
diff options
context:
space:
mode:
authorThomas Gleixner <tglx@linutronix.de>2020-03-04 11:05:22 +0100
committerThomas Gleixner <tglx@linutronix.de>2020-06-11 15:14:36 +0200
commit0372007f5a79d61d3cb48a507717b9afb5d6addd (patch)
tree6c24f01600b47cf9a89e58d3a740f9064ebee299 /kernel
parent20355e5f73a75e58cee4c80d4cd92ce0d1628023 (diff)
downloadlinux-0372007f5a79d61d3cb48a507717b9afb5d6addd.tar.bz2
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 'kernel')
-rw-r--r--kernel/context_tracking.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index ce430885c26c..36a98c48aedc 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(context_tracking_key);
DEFINE_PER_CPU(struct context_tracking, context_tracking);
EXPORT_SYMBOL_GPL(context_tracking);
-static bool context_tracking_recursion_enter(void)
+static noinstr bool context_tracking_recursion_enter(void)
{
int recursion;
@@ -45,7 +45,7 @@ static bool context_tracking_recursion_enter(void)
return false;
}
-static void context_tracking_recursion_exit(void)
+static __always_inline void context_tracking_recursion_exit(void)
{
__this_cpu_dec(context_tracking.recursion);
}
@@ -59,7 +59,7 @@ static void context_tracking_recursion_exit(void)
* instructions to execute won't use any RCU read side critical section
* because this function sets RCU in extended quiescent state.
*/
-void __context_tracking_enter(enum ctx_state state)
+void noinstr __context_tracking_enter(enum ctx_state state)
{
/* Kernel threads aren't supposed to go to userspace */
WARN_ON_ONCE(!current->mm);
@@ -77,8 +77,10 @@ void __context_tracking_enter(enum ctx_state state)
* on the tick.
*/
if (state == CONTEXT_USER) {
+ instrumentation_begin();
trace_user_enter(0);
vtime_user_enter(current);
+ instrumentation_end();
}
rcu_user_enter();
}
@@ -99,7 +101,6 @@ void __context_tracking_enter(enum ctx_state state)
}
context_tracking_recursion_exit();
}
-NOKPROBE_SYMBOL(__context_tracking_enter);
EXPORT_SYMBOL_GPL(__context_tracking_enter);
void context_tracking_enter(enum ctx_state state)
@@ -142,7 +143,7 @@ NOKPROBE_SYMBOL(context_tracking_user_enter);
* This call supports re-entrancy. This way it can be called from any exception
* handler without needing to know if we came from userspace or not.
*/
-void __context_tracking_exit(enum ctx_state state)
+void noinstr __context_tracking_exit(enum ctx_state state)
{
if (!context_tracking_recursion_enter())
return;
@@ -155,15 +156,16 @@ void __context_tracking_exit(enum ctx_state state)
*/
rcu_user_exit();
if (state == CONTEXT_USER) {
+ instrumentation_begin();
vtime_user_exit(current);
trace_user_exit(0);
+ instrumentation_end();
}
}
__this_cpu_write(context_tracking.state, CONTEXT_KERNEL);
}
context_tracking_recursion_exit();
}
-NOKPROBE_SYMBOL(__context_tracking_exit);
EXPORT_SYMBOL_GPL(__context_tracking_exit);
void context_tracking_exit(enum ctx_state state)