Date: Mon, 29 Jun 2015 17:04:01 +0800 From: Julian Elischer <julian@freebsd.org> To: "hackers@freebsd.org" <hackers@freebsd.org>, freebsd-current <freebsd-current@freebsd.org> Subject: Re: libc compile failure with new syscall. Message-ID: <55910A01.60206@freebsd.org> In-Reply-To: <559102DB.4050902@freebsd.org> References: <559102DB.4050902@freebsd.org>
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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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