On Wed, 01 May 2019 10:26:32 +0200 Nicolai Stange nstange@suse.de wrote:
+extern asmlinkage void ftrace_emulate_call_irqon(void); +extern asmlinkage void ftrace_emulate_call_irqoff(void); +extern asmlinkage void ftrace_emulate_call_nmi(void); +extern asmlinkage void ftrace_emulate_call_update_irqoff(void); +extern asmlinkage void ftrace_emulate_call_update_irqon(void); +extern asmlinkage void ftrace_emulate_call_update_nmi(void);
+static DEFINE_PER_CPU(void *, ftrace_bp_call_return); +static DEFINE_PER_CPU(void *, ftrace_bp_call_nmi_return);
Andy mentioned #DB and #MC exceptions here: https://lkml.kernel.org/r/C55DED25-C60D-4731-9A6B-92BDA8771766@amacapital.ne...
I think that #DB won't be possible, provided the trampolines below get tagged as NOKPROBE (do_int3() and ftrace_int3_handler() already have it).
It's highly theoretic, but tracing do_machine_check() could clobber ftrace_bp_call_return or ftrace_bp_call_nmi_return?
Probably shouldn't trace do_machine_check() then ;-)
+#ifdef CONFIG_SMP +#ifdef CONFIG_X86_64 +# define BP_CALL_RETURN "%gs:ftrace_bp_call_return" +# define BP_CALL_NMI_RETURN "%gs:ftrace_bp_call_nmi_return" +#else +# define BP_CALL_RETURN "%fs:ftrace_bp_call_return" +# define BP_CALL_NMI_RETURN "%fs:ftrace_bp_call_nmi_return" +#endif +#else /* SMP */ +# define BP_CALL_RETURN "ftrace_bp_call_return" +# define BP_CALL_NMI_RETURN "ftrace_bp_call_nmi_return" +#endif
+/* To hold the ftrace_caller address to push on the stack */ +void *ftrace_caller_func = (void *)ftrace_caller;
The live patching ftrace_ops need ftrace_regs_caller.
Ah, you're right. Luckily ftrace_regs_caller is a superset of ftrace_caller. That is, those only needing ftrace_caller can do fine with ftrace_regs_caller (but not vice versa).
Easy enough to fix.
+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 "BP_CALL_RETURN"\n\t""push ftrace_caller_func\n""sti\n\t""ret\n\t"- ".size ftrace_emulate_call_irqoff, .-ftrace_emulate_call_irqoff\n"
- /* Trampoline for function update with interrupts disabled*/
- ".global ftrace_emulate_call_irqon\n"
The naming is perhaps a bit confusing, i.e. "update with interrupts disabled" vs. "irqon"... How about swapping irqoff<->irqon?
I just used the terminology Linus used. It is confusing. Perhaps just call it ftrace_emulate_call (for non sti case) and ftrace_emulate_call_sti for the sti case. That should remove the confusion.
-- Steve