On Thu, Aug 18, 2022 at 11:32:55PM +0200, Jiri Olsa wrote: > On Thu, Aug 18, 2022 at 02:00:21PM -0700, Alexei Starovoitov wrote: > > On Thu, Aug 18, 2022 at 1:50 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > > > On Thu, 18 Aug 2022 22:27:07 +0200 > > > Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > > > > > > > ok, so the problem with __attribute__((patchable_function_entry(5))) is that > > > > it puts function address into __patchable_function_entries section, which is > > > > one of ftrace locations source: > > > > > > > > #define MCOUNT_REC() . = ALIGN(8); \ > > > > __start_mcount_loc = .; \ > > > > KEEP(*(__mcount_loc)) \ > > > > KEEP(*(__patchable_function_entries)) \ > > > > __stop_mcount_loc = .; \ > > > > ... > > > > > > > > > > > > it looks like __patchable_function_entries is used for other than x86 archs, > > > > so we perhaps we could have x86 specific MCOUNT_REC macro just with > > > > __mcount_loc section? > > > > > > So something like this: > > > > > > #ifdef CONFIG_X86 > > > # define NON_MCOUNT_PATCHABLE KEEP(*(__patchable_function_entries)) > > > # define MCOUNT_PATCHABLE > > > #else > > > # define NON_MCOUNT_PATCHABLE > > > # define MCOUNT_PATCHABLE KEEP(*(__patchable_function_entries)) > > > #endif > > > > > > #define MCOUNT_REC() . = ALIGN(8); \ > > > __start_mcount_loc = .; \ > > > KEEP(*(__mcount_loc)) \ > > > MCOUNT_PATCHABLE \ > > > __stop_mcount_loc = .; \ > > > NON_MCOUNT_PATCHABLE \ > > > ... > > > > > > ?? > > > > That's what more or less Peter's patch is doing: > > Here it is again for reference: > > https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?id=8d075bdf11193f1d276bf19fa56b4b8dfe24df9e > > ah nice, and discards the __patchable_function_entries section, great > tested change below with Peter's change above and it seems to work, once it get merged I'll send full patch thanks, jirka --- diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 39bd36359c1e..39b6807058e9 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -924,6 +924,8 @@ int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs); } #define DEFINE_BPF_DISPATCHER(name) \ + __attribute__((__no_instrument_function__)) \ + __attribute__((patchable_function_entry(5))) \ noinline __nocfi unsigned int bpf_dispatcher_##name##_func( \ const void *ctx, \ const struct bpf_insn *insnsi, \
