On Wed, 3 Jun 2009, Wang Liming wrote: > wu zhangjin wrote: > > hi, > > > > sorry, I'm so late to reply your E-mail, a little busy these days. > > > > > > } > > > > > > ----------arch/mips/kernel/module.c:apply_r_mips_26_rel()------------------- > > > > > > v is kernel _mcount's address, location is the address of the instrution > > > that should be relocated; > > > > > > To resolve this problem, we may need to do more work, either on gcc or on > > > the kernel. So I want to hear your test result and if you have solution, > > > please let me know. > > > > > > > yes, current version of mips-specific dynamic ftrace not support modules > > yet. > > > > there is similar solution implemented in PowerPC(something named > > trampoline), > > although I did not look into it, but I'm sure we can implement the > > mips-specific one > > via imitating it. > Good hit. I may have a look on Powerpc implementation. Note, PowerPC uses a trampoline from modules to kernel core. I think MIPS just calls mcount differently. That is, it does a full 32bit address call (64 bit for 64 bit archs?). Something like: lui v1, _mcount addiu v1, v1, _mcount jalr v1 addiu sp, sp, -8 Then a nop would not do. Due to preemption, we can not modify more than one line. But you could modify it to: b 1f addiu v1, v1, _mcount jalr v1 addiu sp, sp, -8 1: Clobbering v1 should not be an issue since it is already used to store _mcount. That is, we still do the addiu v1,v1,_mcount with that branch. But v1 should be ignored. -- Steve
