patchable-function-entry

The -Z patchable-function-entry=total_nops,prefix_nops,record_section, -Z patchable-function-entry=total_nops,prefix_nops, or -Z patchable-function-entry=total_nops compiler flag enables nop padding of function entries with ‘total_nops’ nops, with an offset for the entry of the function at ‘prefix_nops’ nops. In the third form, ‘prefix_nops’ defaults to 0. record_section can specify a specific linker section to place entry record in, the default is __patchable_function_entries.

As an illustrative example, -Z patchable-function-entry=3,2 would produce:

nop
nop
function_label:
nop
//Actual function code begins here

This flag is used for hotpatching, especially in the Linux kernel. The flag arguments are modeled after the -fpatchable-function-entry flag as defined for both Clang and gcc and is intended to provide the same effect.