Eric (eric_begot@yahoo.fr) wrote: > Christophe Lucas wrote: > >Bijoy (bijoyjth@gwu.edu) wrote: > > > >>>You are probably confusing the user-space and the kernel-space side of > >>>the thing. On the user-side, the wrapper takes arguments from the stack > >>>and loads them to the registers. And calls the trap. Now the kernel > >>>parts comes to play. It does some setup and calls the sys_* function. > >>>But the arguments are still in registers. So the asmlinkage tells the > >>>compiler, that the function will have the args in registers and not on > >>>the stack, as would be expected for C function. > >> > >>Isnt it the other way around .... when the sys_* function is called .. > >>the arguments are on the stack .... the syscall handler saves the > >>register arguments (SAVE_ALL) and then invokes the actual syscall .... > >>asmlinkage means that the arguments are on the stack and not in registers > >>.... plz correct me if i am wrong. > > > > > >Hi, > > > >As I can understand about syscall and asmlinkage: > >From user space, syscall's arguments are stored in registers, and number > >of syscall are in eax. > >x80 int are launched, and arch/i386/entry.S come to ENTRY(system_call) > >and arguments are pushed on stack. > >sys_ functions are called from address stored in sys_call_table. > >Then the sys_ function is executed and asmlinkage say to not optimized > >the arguments and to take arguments from stack. > > > >If I make a mistake, I will happy you give me the right way. > > > >Regards, > > > Ok, > > I believe that I effictively made a confusion between user and kernel > space, more precisely between the wrapper C funtion and the real system > call. > It's the real system call which has the tag asmlinkage, right ? Like > "asmlinkage long sys_open(...)". Yes, see linux/arch/i386/kernel/sys_i386.c HTH -- Amicalement Christophe * GNU/Linux & UNIX developer and network administrator * Membre RotomaLUG (http://www.rotomalug.org) * Registered User #271267 * Email: c.lucas@ifrance.com * Web Site: http://odie.mcom.fr/~clucas/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
