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This includes two fixes
- Bring back context level recursive protection in ring buffer. The simpler counter protection failed, due to a path when tracing with trace_clock_global() as it could not be reentrant and depended on the ring buffer recursive protection to keep that from happening. - Prevent branch profiling when FORTIFY_SOURCE is enabled. It causes 50 - 60 MB in warning messages. Branch profiling should never be run on production systems, so there's no reason that it needs to be enabled with FORTIFY_SOURCE. -----BEGIN PGP SIGNATURE----- iQHIBAABCgAyFiEEPm6V/WuN2kyArTUe1a05Y9njSUkFAlpdXGsUHHJvc3RlZHRA Z29vZG1pcy5vcmcACgkQ1a05Y9njSUmTIwv+JZPXGYdzZs2nAdCNKfC0bR0sM+MQ sqBN9En1UVOWn60LEt1lULTWh2AXzUKEDU3CkiDWwY44z9U3HZ4i/gbxIuxFLBUt oNKxIGkAz9F1yqqH5oZN+YeAgwc5XijglkrxmTUuSodW9ezCVT8gMr3sQpmnR9nk Jz2P/3XK2pbjLQQD8cmW4ZlWF2LMAnDGck8bWA1nFfe3TsZVCs56FK5vvAW+cUdF +cJHbfa3xfj93xHbUcpPJwdNjK8e14qsmNA56ukFp2zlq62Jnh8kDz3MXpOYGkYO fbXuPsopjtAZET3iQZEcwD5NygFF8E2cxB1qGbATXWTXYWbTO7GKQuUGSHrZGxnY DyWkEFSvL1oS3X54sGbnTiyE7iaSwWS2QAMeC/JkmsAQjgQ4H8KqxKLsyMpdZSEK IcoKGeLXqcSmu1mjrZ2PK+EKdKdONRm0bJXmjwkSTSQ12KXa5ubE3ahv3xpo7WD7 Lye2b1FupNPZc6sjq0iyx83t0yfaUl01AOWm =qWqD -----END PGP SIGNATURE----- Merge tag 'trace-v4.15-rc4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing fixes from Steven Rostedt: - Bring back context level recursive protection in ring buffer. The simpler counter protection failed, due to a path when tracing with trace_clock_global() as it could not be reentrant and depended on the ring buffer recursive protection to keep that from happening. - Prevent branch profiling when FORTIFY_SOURCE is enabled. It causes 50 - 60 MB in warning messages. Branch profiling should never be run on production systems, so there's no reason that it needs to be enabled with FORTIFY_SOURCE. * tag 'trace-v4.15-rc4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Prevent PROFILE_ALL_BRANCHES when FORTIFY_SOURCE=y ring-buffer: Bring back context level recursive checks
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commit
921d4f67bf
@ -355,7 +355,7 @@ config PROFILE_ANNOTATED_BRANCHES
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on if you need to profile the system's use of these macros.
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config PROFILE_ALL_BRANCHES
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bool "Profile all if conditionals"
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bool "Profile all if conditionals" if !FORTIFY_SOURCE
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select TRACE_BRANCH_PROFILING
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help
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This tracer profiles all branch conditions. Every if ()
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@ -2534,29 +2534,59 @@ rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
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* The lock and unlock are done within a preempt disable section.
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* The current_context per_cpu variable can only be modified
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* by the current task between lock and unlock. But it can
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* be modified more than once via an interrupt. There are four
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* different contexts that we need to consider.
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* be modified more than once via an interrupt. To pass this
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* information from the lock to the unlock without having to
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* access the 'in_interrupt()' functions again (which do show
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* a bit of overhead in something as critical as function tracing,
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* we use a bitmask trick.
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*
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* Normal context.
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* SoftIRQ context
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* IRQ context
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* NMI context
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* bit 0 = NMI context
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* bit 1 = IRQ context
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* bit 2 = SoftIRQ context
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* bit 3 = normal context.
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*
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* If for some reason the ring buffer starts to recurse, we
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* only allow that to happen at most 4 times (one for each
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* context). If it happens 5 times, then we consider this a
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* recusive loop and do not let it go further.
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* This works because this is the order of contexts that can
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* preempt other contexts. A SoftIRQ never preempts an IRQ
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* context.
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*
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* When the context is determined, the corresponding bit is
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* checked and set (if it was set, then a recursion of that context
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* happened).
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*
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* On unlock, we need to clear this bit. To do so, just subtract
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* 1 from the current_context and AND it to itself.
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*
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* (binary)
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* 101 - 1 = 100
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* 101 & 100 = 100 (clearing bit zero)
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*
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* 1010 - 1 = 1001
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* 1010 & 1001 = 1000 (clearing bit 1)
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*
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* The least significant bit can be cleared this way, and it
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* just so happens that it is the same bit corresponding to
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* the current context.
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*/
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static __always_inline int
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trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
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{
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if (cpu_buffer->current_context >= 4)
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unsigned int val = cpu_buffer->current_context;
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unsigned long pc = preempt_count();
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int bit;
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if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
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bit = RB_CTX_NORMAL;
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else
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bit = pc & NMI_MASK ? RB_CTX_NMI :
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pc & HARDIRQ_MASK ? RB_CTX_IRQ :
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pc & SOFTIRQ_OFFSET ? 2 : RB_CTX_SOFTIRQ;
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if (unlikely(val & (1 << bit)))
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return 1;
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cpu_buffer->current_context++;
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/* Interrupts must see this update */
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barrier();
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val |= (1 << bit);
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cpu_buffer->current_context = val;
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return 0;
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}
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@ -2564,9 +2594,7 @@ trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
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static __always_inline void
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trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
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{
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/* Don't let the dec leak out */
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barrier();
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cpu_buffer->current_context--;
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cpu_buffer->current_context &= cpu_buffer->current_context - 1;
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}
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/**
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