Title: [8244] trunk: ftrace: cover new frame pointer semantics
- Revision
- 8244
- Author
- vapier
- Date
- 2010-01-27 19:30:42 -0500 (Wed, 27 Jan 2010)
Log Message
ftrace: cover new frame pointer semantics
Modified Paths
Diff
Modified: trunk/Documentation/trace/ftrace-design.txt (8243 => 8244)
--- trunk/Documentation/trace/ftrace-design.txt 2010-01-27 11:16:32 UTC (rev 8243)
+++ trunk/Documentation/trace/ftrace-design.txt 2010-01-28 00:30:42 UTC (rev 8244)
@@ -1,5 +1,6 @@
function tracer guts
====================
+ By Mike Frysinger
Introduction
------------
@@ -173,14 +174,16 @@
unsigned long *frompc = &...;
unsigned long selfpc = <return address> - MCOUNT_INSN_SIZE;
- prepare_ftrace_return(frompc, selfpc);
+ /* passing frame pointer up is optional -- see below */
+ prepare_ftrace_return(frompc, selfpc, frame_pointer);
/* restore all state needed by the ABI */
}
#endif
-For information on how to implement prepare_ftrace_return(), simply look at
-the x86 version. The only architecture-specific piece in it is the setup of
+For information on how to implement prepare_ftrace_return(), simply look at the
+x86 version (the frame pointer passing is optional; see the next section for
+more information). The only architecture-specific piece in it is the setup of
the fault recovery table (the asm(...) code). The rest should be the same
across architectures.
@@ -205,6 +208,23 @@
#endif
+HAVE_FUNCTION_GRAPH_FP_TEST
+---------------------------
+
+An arch may pass in a unique value (frame pointer) to both the entering and
+exiting of a function. On exit, the value is compared and if it does not
+match, then it will panic the kernel. This is largely a sanity check for bad
+code generation with gcc. If gcc for your port sanely updates the frame
+pointer under different opitmization levels, then ignore this option.
+
+However, adding support for it isn't terribly difficult. In your assembly code
+that calls prepare_ftrace_return(), pass the frame pointer as the 3rd argument.
+Then in the C version of that function, do what the x86 port does and pass it
+along to ftrace_push_return_trace() instead of a stub value of 0.
+
+Similarly, when you call ftrace_return_to_handler(), pass it the frame pointer.
+
+
HAVE_FTRACE_NMI_ENTER
---------------------
Modified: trunk/kernel/trace/Kconfig (8243 => 8244)
--- trunk/kernel/trace/Kconfig 2010-01-27 11:16:32 UTC (rev 8243)
+++ trunk/kernel/trace/Kconfig 2010-01-28 00:30:42 UTC (rev 8244)
@@ -12,39 +12,37 @@
config HAVE_FTRACE_NMI_ENTER
bool
help
- See Documentation/trace/ftrace-implementation.txt
+ See Documentation/trace/ftrace-design.txt
config HAVE_FUNCTION_TRACER
bool
help
- See Documentation/trace/ftrace-implementation.txt
+ See Documentation/trace/ftrace-design.txt
config HAVE_FUNCTION_GRAPH_TRACER
bool
help
- See Documentation/trace/ftrace-implementation.txt
+ See Documentation/trace/ftrace-design.txt
config HAVE_FUNCTION_GRAPH_FP_TEST
bool
help
- An arch may pass in a unique value (frame pointer) to both the
- entering and exiting of a function. On exit, the value is compared
- and if it does not match, then it will panic the kernel.
+ See Documentation/trace/ftrace-design.txt
config HAVE_FUNCTION_TRACE_MCOUNT_TEST
bool
help
- See Documentation/trace/ftrace-implementation.txt
+ See Documentation/trace/ftrace-design.txt
config HAVE_DYNAMIC_FTRACE
bool
help
- See Documentation/trace/ftrace-implementation.txt
+ See Documentation/trace/ftrace-design.txt
config HAVE_FTRACE_MCOUNT_RECORD
bool
help
- See Documentation/trace/ftrace-implementation.txt
+ See Documentation/trace/ftrace-design.txt
config HAVE_HW_BRANCH_TRACER
bool
@@ -52,7 +50,7 @@
config HAVE_SYSCALL_TRACEPOINTS
bool
help
- See Documentation/trace/ftrace-implementation.txt
+ See Documentation/trace/ftrace-design.txt
config TRACER_MAX_TRACE
bool
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