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authorLinus Torvalds <torvalds@linux-foundation.org>2010-02-01 13:43:01 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2010-02-01 13:43:01 -0500
commit935cc9323ac33bb9b6cb853815e5c86f77e50607 (patch)
tree6b48024b35b2d166de592ab3238e80c3e763f46a /Documentation
parent4ca5ded2bdc09259ad89915bac2d218e72cda351 (diff)
parent03688970347bfea32823953a7ce5886d1713205f (diff)
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
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/trace/ftrace-design.txt26
-rw-r--r--Documentation/trace/ftrace.txt2
2 files changed, 24 insertions, 4 deletions
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index 239f14b2b55a..6a5a579126b0 100644
--- a/Documentation/trace/ftrace-design.txt
+++ b/Documentation/trace/ftrace-design.txt
@@ -1,5 +1,6 @@
1 function tracer guts 1 function tracer guts
2 ==================== 2 ====================
3 By Mike Frysinger
3 4
4Introduction 5Introduction
5------------ 6------------
@@ -173,14 +174,16 @@ void ftrace_graph_caller(void)
173 174
174 unsigned long *frompc = &...; 175 unsigned long *frompc = &...;
175 unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE; 176 unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
176 prepare_ftrace_return(frompc, selfpc); 177 /* passing frame pointer up is optional -- see below */
178 prepare_ftrace_return(frompc, selfpc, frame_pointer);
177 179
178 /* restore all state needed by the ABI */ 180 /* restore all state needed by the ABI */
179} 181}
180#endif 182#endif
181 183
182For information on how to implement prepare_ftrace_return(), simply look at 184For information on how to implement prepare_ftrace_return(), simply look at the
183the x86 version. The only architecture-specific piece in it is the setup of 185x86 version (the frame pointer passing is optional; see the next section for
186more information). The only architecture-specific piece in it is the setup of
184the fault recovery table (the asm(...) code). The rest should be the same 187the fault recovery table (the asm(...) code). The rest should be the same
185across architectures. 188across architectures.
186 189
@@ -205,6 +208,23 @@ void return_to_handler(void)
205#endif 208#endif
206 209
207 210
211HAVE_FUNCTION_GRAPH_FP_TEST
212---------------------------
213
214An arch may pass in a unique value (frame pointer) to both the entering and
215exiting of a function. On exit, the value is compared and if it does not
216match, then it will panic the kernel. This is largely a sanity check for bad
217code generation with gcc. If gcc for your port sanely updates the frame
218pointer under different opitmization levels, then ignore this option.
219
220However, adding support for it isn't terribly difficult. In your assembly code
221that calls prepare_ftrace_return(), pass the frame pointer as the 3rd argument.
222Then in the C version of that function, do what the x86 port does and pass it
223along to ftrace_push_return_trace() instead of a stub value of 0.
224
225Similarly, when you call ftrace_return_to_handler(), pass it the frame pointer.
226
227
208HAVE_FTRACE_NMI_ENTER 228HAVE_FTRACE_NMI_ENTER
209--------------------- 229---------------------
210 230
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 8179692fbb90..bab3040da548 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1625,7 +1625,7 @@ If I am only interested in sys_nanosleep and hrtimer_interrupt:
1625 1625
1626 # echo sys_nanosleep hrtimer_interrupt \ 1626 # echo sys_nanosleep hrtimer_interrupt \
1627 > set_ftrace_filter 1627 > set_ftrace_filter
1628 # echo ftrace > current_tracer 1628 # echo function > current_tracer
1629 # echo 1 > tracing_enabled 1629 # echo 1 > tracing_enabled
1630 # usleep 1 1630 # usleep 1
1631 # echo 0 > tracing_enabled 1631 # echo 0 > tracing_enabled