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author | David S. Miller <davem@davemloft.net> | 2010-02-17 06:09:29 (GMT) |
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committer | David S. Miller <davem@davemloft.net> | 2010-02-17 06:09:29 (GMT) |
commit | 2bb4646fce8d09916b351d1a62f98db7cec6fc41 (patch) | |
tree | c1f0d002e69868606eca9d1b919835f422892063 /Documentation/trace/ftrace-design.txt | |
parent | 6836b9bdd98e3b500cd49512484df68f46e14659 (diff) | |
parent | b0483e78e5c4c9871fc5541875b3bc006846d46b (diff) | |
download | linux-fsl-qoriq-2bb4646fce8d09916b351d1a62f98db7cec6fc41.tar.xz |
Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Diffstat (limited to 'Documentation/trace/ftrace-design.txt')
-rw-r--r-- | Documentation/trace/ftrace-design.txt | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt index 239f14b..6a5a579 100644 --- a/Documentation/trace/ftrace-design.txt +++ b/Documentation/trace/ftrace-design.txt @@ -1,5 +1,6 @@ function tracer guts ==================== + By Mike Frysinger Introduction ------------ @@ -173,14 +174,16 @@ void ftrace_graph_caller(void) 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 @@ void return_to_handler(void) #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 --------------------- |