On Tue, 30 Apr 2019 11:33:21 -0700 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Apr 30, 2019 at 10:49 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > + > > +asm( > > + ".text\n" > > + > > + /* Trampoline for function update with interrupts enabled */ > > + ".global ftrace_emulate_call_irqoff\n" > > + ".type ftrace_emulate_call_irqoff, @function\n" > > + "ftrace_emulate_call_irqoff:\n\t" > > + "push %gs:ftrace_bp_call_return\n\t" > > Well, as mentioned in my original suggestion, this won't work on > 32-bit, or on UP. They have different models for per-cpu data (32-bti > uses %fs, and UP doesn't use a segment override at all). Ah, yeah, I forgot about 32-bit. I could easily make this use fs as well, and for UP, just use a static variable. > > Maybe we just don't care about UP at all for this code, of course. > > And maybe we can make the decision to also make 32-bit just not use > this either - so maybe the code is ok per se, just needs to make sure > it never triggers for the cases that it's not written for.. > > > + "ftrace_emulate_call_update_irqoff:\n\t" > > + "push %gs:ftrace_bp_call_return\n\t" > > + "sti\n\t" > > + "jmp *ftrace_update_func_call\n" > > .. and this should then use the "push push sti ret" model instead. > > Plus get updated for objtool complaints. Yeah, I see that now. Somehow it disappeared when I looked for it after making some other changes. I can update it. > > Anyway, since Andy really likes the entry code change, can we have > that patch in parallel and judge the difference that way? Iirc, that > was x86-64 specific too. Note, I don't think live kernel patching supports 32 bit anyway, so that may not be an issue. Josh, When you come back to the office, can you look into that method? -- Steve
