On Wed, 5 Nov 2014 11:42:07 +0100
Borislav Petkov <b...@alien8.de> wrote:
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> > index e4d48f6cad86..ca17c20a1010 100644
> > --- a/arch/x86/kernel/ftrace.c
> > +++ b/arch/x86/kernel/ftrace.c
> > @@ -48,7 +48,7 @@ int ftrace_arch_code_modify_post_process(void)
> > union ftrace_code_union {
> > char code[MCOUNT_INSN_SIZE];
> > struct {
> > - char e8;
> > + unsigned char e8;
>
> u8?
>
> "u8 e8;" looks supa dupa though :-)
And compete with PowerPC's eieio command.
>
> > int offset;
> > } __attribute__((packed));
> > };
> > @@ -797,12 +797,26 @@ static unsigned long create_trampoline(struct
> > ftrace_ops *ops)
> > return (unsigned long)trampoline;
> > }
> >
> > +static unsigned long calc_trampoline_call_offset(bool save_regs)
> > +{
> > + unsigned long start_offset;
> > + unsigned long call_offset;
> > +
> > + if (save_regs) {
> > + start_offset = (unsigned long)ftrace_regs_caller;
> > + call_offset = (unsigned long)ftrace_regs_call;
> > + } else {
> > + start_offset = (unsigned long)ftrace_caller;
> > + call_offset = (unsigned long)ftrace_call;
> > + }
> > +
> > + return call_offset - start_offset;
> > +}
> > +
> > void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
> > {
> > ftrace_func_t func;
> > unsigned char *new;
> > - unsigned long start_offset;
> > - unsigned long call_offset;
> > unsigned long offset;
> > unsigned long ip;
> > int ret;
> > @@ -820,15 +834,7 @@ void arch_ftrace_update_trampoline(struct ftrace_ops
> > *ops)
> > return;
> > }
> >
> > - if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
> > - start_offset = (unsigned long)ftrace_regs_caller;
> > - call_offset = (unsigned long)ftrace_regs_call;
> > - } else {
> > - start_offset = (unsigned long)ftrace_caller;
> > - call_offset = (unsigned long)ftrace_call;
> > - }
> > -
> > - offset = call_offset - start_offset;
> > + offset = calc_trampoline_call_offset(ops->flags &
> > FTRACE_OPS_FL_SAVE_REGS);
> > ip = ops->trampoline + offset;
> >
> > func = ftrace_ops_get_func(ops);
> > @@ -840,6 +846,74 @@ void arch_ftrace_update_trampoline(struct ftrace_ops
> > *ops)
> > /* The update should never fail */
> > WARN_ON(ret);
> > }
> > +
> > +/* Return the address of the function the trampoline calls */
> > +static void *addr_from_call(void *ptr)
> > +{
> > + union ftrace_code_union calc;
> > + int ret;
> > +
> > + ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
> > + if (WARN_ON_ONCE(ret < 0))
> > + return NULL;
> > +
> > + /* Make sure this is a call */
> > + if (WARN_ON_ONCE(calc.e8 != 0xe8)) {
> > + pr_warn("Expected e8, got %x\n", calc.e8);
>
> Simply WARN_ONCE gives you both.
Ah, could do that.
>
> > + return NULL;
> > + }
> > +
> > + return ptr + MCOUNT_INSN_SIZE + calc.offset;
> > +}
> > +
> > +void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
> > + unsigned long frame_pointer);
> > +
> > +/*
> > + * If the ops->trampoline was not allocated, then it probably
> > + * has a static trampoline func, or is the ftrace caller itself.
> > + */
> > +static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace
> > *rec)
>
> I guess you can merge this one into its only caller below - it is not
> that huge... yet! :-)
>
Hmm, it's big enough not to be in that function as a if statement that
will return anyway.
gcc will just make it inlined anyway. I think it's better separate for
readability.
-- Steve
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