On Mon, 12 Nov 2018 at 12:01, Torsten Duwe <d...@lst.de> wrote: > > On Thu, Nov 08, 2018 at 01:42:35PM +0100, Ard Biesheuvel wrote: > > On 26 October 2018 at 16:21, Torsten Duwe <d...@lst.de> wrote: > > > /* The program counter just after the ftrace call site */ > > > str lr, [x9, #S_PC] > > > + > > > /* The stack pointer as it was on ftrace_caller entry... */ > > > add x28, fp, #16 > > > str x28, [x9, #S_SP] > > > > Please drop this hunk > > Sure. I missed that one during cleanup. > > > > @@ -233,6 +234,10 @@ ftrace_common: > ^^^^^^^^^^^^^^ > > > ldr x28, [fp, 8] > > > str x28, [x9, #S_LR] /* to pt_regs.r[30] */ > > > > > > +#if defined(CONFIG_LIVEPATCH) && defined(CONFIG_FUNCTION_GRAPH_TRACER) > > > + mov x28, lr /* remember old return address */ > > > +#endif > > > + > > > ldr_l x2, function_trace_op, x0 > > > ldr x1, [fp, #8] > > > sub x0, lr, #8 /* function entry == IP */ > > > @@ -245,6 +250,17 @@ ftrace_call: > > > > > > bl ftrace_stub > > > > > > +#if defined(CONFIG_LIVEPATCH) && defined(CONFIG_FUNCTION_GRAPH_TRACER) > > > + /* Is the trace function a live patcher an has messed with > > > + * the return address? > > > + */ > > > + add x9, sp, #16 /* advance to pt_regs for restore */ > > > + ldr x0, [x9, #S_PC] > > > + cmp x0, x28 /* compare with the value we remembered */ > > > + /* to not call graph tracer's "call" mechanism twice! */ > > > + b.ne ftrace_common_return > > > > Is ftrace_common_return guaranteed to be in range? Conditional > > branches have only -/+ 1 MB range IIRC. > > It's the same function. A "1f" would do the same job, but the long label > is a talking identifier that saves a comment. I'd more be worried about > the return from the graph trace caller, which happens to be the _next_ > function ;-) > > If ftrace_caller or graph_caller grow larger than a meg, something else is > _very_ wrong. >
Ah ok. I confused myself into thinking that ftrace_common_return() was defined in another compilation unit > > > +#endif > > > + > > > #ifdef CONFIG_FUNCTION_GRAPH_TRACER > > > > Can we fold these #ifdef blocks together (i.e, incorporate the > > conditional livepatch sequence here) > > I'll see how to make it fit. But remember some people might want ftrace > but no live patching capability. > Sure. I simply mean turning this #if defined(CONFIG_LIVEPATCH) && defined(CONFIG_FUNCTION_GRAPH_TRACER) <bla> #endif #ifdef CONFIG_FUNCTION_GRAPH_TRACER <bla bla> #endif into #ifdef CONFIG_FUNCTION_GRAPH_TRACER #ifdef CONFIG_LIVEPATCH <bla> #endif <bla bla> #endif
