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Merge branch 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: tracing/documentation: Cover new frame pointer semantics tracing/documentation: Fix a typo in ftrace.txt ring-buffer: Check for end of page in iterator ring-buffer: Check if ring buffer iterator has stale data tracing: Prevent kernel oops with corrupted buffer
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commit
935cc9323a
5 changed files with 51 additions and 10 deletions
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@ -1,5 +1,6 @@
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function tracer guts
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====================
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By Mike Frysinger
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Introduction
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------------
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@ -173,14 +174,16 @@ void ftrace_graph_caller(void)
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unsigned long *frompc = &...;
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unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
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prepare_ftrace_return(frompc, selfpc);
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/* passing frame pointer up is optional -- see below */
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prepare_ftrace_return(frompc, selfpc, frame_pointer);
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/* restore all state needed by the ABI */
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}
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#endif
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For information on how to implement prepare_ftrace_return(), simply look at
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the x86 version. The only architecture-specific piece in it is the setup of
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For information on how to implement prepare_ftrace_return(), simply look at the
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x86 version (the frame pointer passing is optional; see the next section for
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more information). The only architecture-specific piece in it is the setup of
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the fault recovery table (the asm(...) code). The rest should be the same
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across architectures.
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@ -205,6 +208,23 @@ void return_to_handler(void)
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#endif
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HAVE_FUNCTION_GRAPH_FP_TEST
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---------------------------
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An arch may pass in a unique value (frame pointer) to both the entering and
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exiting of a function. On exit, the value is compared and if it does not
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match, then it will panic the kernel. This is largely a sanity check for bad
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code generation with gcc. If gcc for your port sanely updates the frame
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pointer under different opitmization levels, then ignore this option.
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However, adding support for it isn't terribly difficult. In your assembly code
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that calls prepare_ftrace_return(), pass the frame pointer as the 3rd argument.
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Then in the C version of that function, do what the x86 port does and pass it
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along to ftrace_push_return_trace() instead of a stub value of 0.
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Similarly, when you call ftrace_return_to_handler(), pass it the frame pointer.
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HAVE_FTRACE_NMI_ENTER
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---------------------
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@ -1625,7 +1625,7 @@ If I am only interested in sys_nanosleep and hrtimer_interrupt:
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# echo sys_nanosleep hrtimer_interrupt \
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> set_ftrace_filter
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# echo ftrace > current_tracer
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# echo function > current_tracer
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# echo 1 > tracing_enabled
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# usleep 1
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# echo 0 > tracing_enabled
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@ -27,9 +27,7 @@ config HAVE_FUNCTION_GRAPH_TRACER
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config HAVE_FUNCTION_GRAPH_FP_TEST
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bool
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help
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An arch may pass in a unique value (frame pointer) to both the
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entering and exiting of a function. On exit, the value is compared
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and if it does not match, then it will panic the kernel.
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See Documentation/trace/ftrace-design.txt
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config HAVE_FUNCTION_TRACE_MCOUNT_TEST
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bool
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@ -464,6 +464,8 @@ struct ring_buffer_iter {
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struct ring_buffer_per_cpu *cpu_buffer;
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unsigned long head;
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struct buffer_page *head_page;
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struct buffer_page *cache_reader_page;
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unsigned long cache_read;
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u64 read_stamp;
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};
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@ -2716,6 +2718,8 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
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iter->read_stamp = cpu_buffer->read_stamp;
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else
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iter->read_stamp = iter->head_page->page->time_stamp;
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iter->cache_reader_page = cpu_buffer->reader_page;
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iter->cache_read = cpu_buffer->read;
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}
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/**
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@ -3060,13 +3064,22 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
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struct ring_buffer_event *event;
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int nr_loops = 0;
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if (ring_buffer_iter_empty(iter))
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return NULL;
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cpu_buffer = iter->cpu_buffer;
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buffer = cpu_buffer->buffer;
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/*
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* Check if someone performed a consuming read to
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* the buffer. A consuming read invalidates the iterator
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* and we need to reset the iterator in this case.
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*/
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if (unlikely(iter->cache_read != cpu_buffer->read ||
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iter->cache_reader_page != cpu_buffer->reader_page))
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rb_iter_reset(iter);
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again:
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if (ring_buffer_iter_empty(iter))
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return NULL;
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/*
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* We repeat when a timestamp is encountered.
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* We can get multiple timestamps by nested interrupts or also
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@ -3081,6 +3094,11 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
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if (rb_per_cpu_empty(cpu_buffer))
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return NULL;
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if (iter->head >= local_read(&iter->head_page->page->commit)) {
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rb_inc_iter(iter);
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goto again;
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}
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event = rb_iter_head_event(iter);
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switch (event->type_len) {
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@ -951,6 +951,11 @@ void trace_find_cmdline(int pid, char comm[])
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return;
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}
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if (WARN_ON_ONCE(pid < 0)) {
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strcpy(comm, "<XXX>");
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return;
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}
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if (pid > PID_MAX_DEFAULT) {
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strcpy(comm, "<...>");
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return;
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