On Thu, 29 Oct 2026 16:53:58 +0000 "Jose Fernandez (Anthropic)" <[email protected]> wrote:
> sorttable hardcodes before_func to 8 bytes on arm64 (two prefix NOPs). > Make it configurable from CONFIG_ARM64_FUNCTION_PREFIX_NOPS instead. > kCFI kernels with CALL_OPS need three NOPs. The symbol does not exist > yet, so no functional change. > > Reviewed-by: Ben Cressey <[email protected]> > Reviewed-by: Florent Revest (Anthropic) <[email protected]> > Acked-by: Alexei Starovoitov <[email protected]> > Assisted-by: LLM > Signed-off-by: Jose Fernandez (Anthropic) <[email protected]> Reviewed-by: Steven Rostedt <[email protected]> -- Steve > --- > scripts/Makefile | 4 ++++ > scripts/sorttable.c | 7 ++++++- > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/scripts/Makefile b/scripts/Makefile > index d7fbb7ca098b..7ef1c84cf79d 100644 > --- a/scripts/Makefile > +++ b/scripts/Makefile > @@ -54,6 +54,10 @@ endif > > ifdef CONFIG_BUILDTIME_MCOUNT_SORT > HOSTCFLAGS_sorttable.o += -DMCOUNT_SORT_ENABLED > +# 0 or unset (no prefix NOPs) leaves sorttable's built-in default in place. > +ifneq ($(filter-out 0,$(CONFIG_ARM64_FUNCTION_PREFIX_NOPS)),) > +HOSTCFLAGS_sorttable.o += -DFUNCTION_PREFIX_BYTES=$(shell expr 4 \* > $(CONFIG_ARM64_FUNCTION_PREFIX_NOPS)) > +endif > endif > > hostprogs += gen_init_cpio > diff --git a/scripts/sorttable.c b/scripts/sorttable.c > index 88e49a5c4251..2e951f2f60e8 100644 > --- a/scripts/sorttable.c > +++ b/scripts/sorttable.c > @@ -281,6 +281,11 @@ static int add_field(uint64_t addr, uint64_t size) > /* Used for when mcount/fentry is before the function entry */ > static int before_func; > > +/* How far before the function entry a patchable entry may be recorded */ > +#ifndef FUNCTION_PREFIX_BYTES > +#define FUNCTION_PREFIX_BYTES 8 > +#endif > + > /* Only return match if the address lies inside the function size */ > static int cmp_func_addr(const void *K, const void *A) > { > @@ -912,7 +917,7 @@ static int do_file(char const *const fname, void *addr) > /* fallthrough */ > case EM_RISCV: > /* arm64 and RISC-V place patchable entries before the > function. */ > - before_func = 8; > + before_func = FUNCTION_PREFIX_BYTES; > #else > case EM_AARCH64: > case EM_RISCV: >
