diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2016-08-19 13:52:57 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-08-24 12:15:14 +0200 |
| commit | 9a7c348ba6a46f6270d4fe49577649dad5664fe7 (patch) | |
| tree | 747a399fc9f6f3f1e234e27a164b9bb5e6ac015a /Documentation/trace | |
| parent | ftrace: Only allocate the ret_stack 'fp' field when needed (diff) | |
| download | linux-9a7c348ba6a46f6270d4fe49577649dad5664fe7.tar.xz linux-9a7c348ba6a46f6270d4fe49577649dad5664fe7.zip | |
ftrace: Add return address pointer to ftrace_ret_stack
Storing this value will help prevent unwinders from getting out of sync
with the function graph tracer ret_stack. Now instead of needing a
stateful iterator, they can compare the return address pointer to find
the right ret_stack entry.
Note that an array of 50 ftrace_ret_stack structs is allocated for every
task. So when an arch implements this, it will add either 200 or 400
bytes of memory usage per task (depending on whether it's a 32-bit or
64-bit platform).
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a95cfcc39e8f26b89a430c56926af0bb217bc0a1.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace-design.txt | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt index dd5f916b351d..a273dd0bbaaa 100644 --- a/Documentation/trace/ftrace-design.txt +++ b/Documentation/trace/ftrace-design.txt @@ -203,6 +203,17 @@ 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_FUNCTION_GRAPH_RET_ADDR_PTR +-------------------------------- + +An arch may pass in a pointer to the return address on the stack. This +prevents potential stack unwinding issues where the unwinder gets out of +sync with ret_stack and the wrong addresses are reported by +ftrace_graph_ret_addr(). + +Adding support for it is easy: just define the macro in asm/ftrace.h and +pass the return address pointer as the 'retp' argument to +ftrace_push_return_trace(). HAVE_FTRACE_NMI_ENTER --------------------- |