Le 24/05/2022 à 12:15, Naveen N. Rao a écrit :
Christophe Leroy wrote:
Le 23/05/2022 à 19:55, Sathvika Vasireddy a écrit :
Architectures can select HAVE_NOP_MCOUNT if they choose
to nop out mcount call sites. If that config option is
selected, then --mnop is passed as an option to objtool,
along with --mcount.
Is there a reason not to nop out mcount call sites on powerpc as well ?
Yes, if there are functions that are out of range of _mcount(), then the linker would have inserted long branch trampolines. We detect such cases during boot. But, if we nop out the _mcount call sites during build time, we will need some other way to identify these.
But does it really matter whether _mcount is reachable or not ?
_mcount is never used, and the function we want to call in lieu of _mcount might be reachable while _mcount is not or might be unreachable while _mcount is.