ftrace: add ftrace_init_nop()

Architectures may need to perform special initialization of ftrace
callsites, and today they do so by special-casing ftrace_make_nop() when
the expected branch address is MCOUNT_ADDR. In some cases (e.g. for
patchable-function-entry), we don't have an mcount-like symbol and don't
want a synthetic MCOUNT_ADDR, but we may need to perform some
initialization of callsites.

To make it possible to separate initialization from runtime
modification, and to handle cases without an mcount-like symbol, this
patch adds an optional ftrace_init_nop() function that architectures can
implement, which does not pass a branch address.

Where an architecture does not provide ftrace_init_nop(), we will fall
back to the existing behaviour of calling ftrace_make_nop() with
MCOUNT_ADDR.

At the same time, ftrace_code_disable() is renamed to
ftrace_nop_initialize() to make it clearer that it is intended to
intialize a callsite into a disabled state, and is not for disabling a
callsite that has been runtime enabled. The kerneldoc description of rec
arguments is updated to cover non-mcount callsites.

Signed-off-by: Mark Rutland <[email protected]>
Reviewed-by: Amit Daniel Kachhap <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Miroslav Benes <[email protected]>
Reviewed-by: Steven Rostedt (VMware) <[email protected]>
Reviewed-by: Torsten Duwe <[email protected]>
Tested-by: Amit Daniel Kachhap <[email protected]>
Tested-by: Sven Schnelle <[email protected]>
Tested-by: Torsten Duwe <[email protected]>
Cc: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions