Re: libc compile failure with new syscall.

On 6/29/15 4:33 PM, Julian Elischer wrote:
> Hi all,
>
> At $JOB we have a few extra syscalls that we have added to our kernel.
>
> After generating the new sysent files in /sys/kern, libc fails to 
> compile with:
>
> ===> lib/libc (obj,depend,all,install)
> building shared library libc.so.7
> [...]
> /usr/bin/ld: rlk_check_offline.So: relocation R_X86_64_32 against 
> `SYS_rlk_check_offline' can not be used when making a shared object; 
> recompile with -fPIC
> rlk_check_offline.So: could not read symbols: Bad value
> *** [libc.so.7] Error code 1
>
> this suggests that the code that generates the libc syscall stubs is 
> generating something the linker doesn't like.
>
>
> the definition of the syscall is:
>
> 588     AUE_NULL        NOSTD   { int rlk_check_offline(char 
> *localfs, char *path, \
>                                     int *is_offline, int rlk_flags, \
>                                     int *cache_status); }
> ------
> which generates (in various files):
>         { AS(rlk_check_offline_args), (sy_call_t *)lkmressys, 
> AUE_NULL, NULL, 0, 0, 0, SY_THR_ABSENT }, /* 588 = rlk_check_offline */
> ------
>         "rlk_check_offline",                    /* 588 = 
> rlk_check_offline */
> ------
>         /* rlk_check_offline */
>         case 588: {
>                 struct rlk_check_offline_args *p = params;
>                 uarg[0] = (intptr_t) p->localfs; /* char * */
>                 uarg[1] = (intptr_t) p->path; /* char * */
>                 uarg[2] = (intptr_t) p->is_offline; /* int * */
>                 iarg[3] = p->rlk_flags; /* int */
>                 uarg[4] = (intptr_t) p->cache_status; /* int * */
>                 *n_args = 5;
>                 break;
>         }
> -------
> #define SYS_rlk_check_offline   588
> -------
> struct rlk_check_offline_args {
>         char localfs_l_[PADL_(char *)]; char * localfs; char 
> localfs_r_[PADR_(char *)];
>         char path_l_[PADL_(char *)]; char * path; char 
> path_r_[PADR_(char *)];
>         char is_offline_l_[PADL_(int *)]; int * is_offline; char 
> is_offline_r_[PADR_(int *)];
>         char rlk_flags_l_[PADL_(int)]; int rlk_flags; char 
> rlk_flags_r_[PADR_(int)];
>         char cache_status_l_[PADL_(int *)]; int * cache_status; char 
> cache_status_r_[PADR_(int *)];
> };
> int     sys_rlk_check_offline(struct thread *, struct 
> rlk_check_offline_args *);
> #define SYS_AUE_rlk_check_offline       AUE_NULL
>
> -------
>
>
>
> the generated stub looks like:
> $ cat /usr/obj/usr/src/lib/libc/rlk_check_offline.S
>
> #include "compat.h"
> #include "SYS.h"
> RSYSCALL(rlk_check_offline)
>         .section .note.GNU-stack,"",%progbits
>
> --------
>
>
> nothing in this definition looks special, So I'm surprised that the 
> libc build doesn't like it.
> This is a (just) post 10.1 10-stable. But we plan to move to 11 soon 
> too.
>
> Any suggestions as to what I should change would be greatly 
> appreciated.. I'm running out of ideas.

Having looked at it I'm guessing it's to do with the NOSTD , which 
generates  lkmressys and RSYSCALL which generates the code,
but I'm still not seeing the part that causes the error. I will admit 
my understanding of the linking process is not extensive.

I do have other syscall that are NOSTD and do not give the error.



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