libselinux does not build on Blackfin

[tpetazzoni]

The libselinux library fails to build on the Blackfin architecture, with the following error message:

mapping.lo: In function `_selinux_set_mapping':
mapping.c:(.text+0x25a): undefined reference to `_avc_reset'
callbacks.lo: In function `_default_selinux_validate':
callbacks.c:(.text+0x82): undefined reference to `_security_check_context'
callbacks.lo: In function `_default_selinux_log':
callbacks.c:(.text+0x92): undefined reference to `_is_selinux_enabled'
label_media.lo: In function `_selabel_media_init':
label_media.c:(.text+0xf2): undefined reference to `_selinux_media_context_path'
label_file.lo: In function `_init':
label_file.c:(.text+0xa24): undefined reference to `_selinux_file_context_subs_dist_path'
label_file.c:(.text+0xa38): undefined reference to `_selinux_file_context_subs_path'
label_file.c:(.text+0xa4c): undefined reference to `_selinux_file_context_path'
label.lo: In function `_selabel_lookup_common':
label.c:(.text+0x172): undefined reference to `_selinux_raw_to_trans_context'
label_db.lo: In function `_selabel_db_init':
label_db.c:(.text+0xe4): undefined reference to `_selinux_sepgsql_context_path'
sestatus.lo: In function `_selinux_status_open':
sestatus.c:(.text+0x17e): undefined reference to `_security_getenforce'
sestatus.lo: In function `_selinux_status_deny_unknown':
sestatus.c:(.text+0x214): undefined reference to `_security_deny_unknown'
label_x.lo: In function `_selabel_x_init':
label_x.c:(.text+0xee): undefined reference to `_selinux_x_context_path'
collect2: ld returned 1 exit status
Makefile:119: recipe for target 'libselinux.so.1' failed
make[2]: *** [libselinux.so.1] Error 1

This is due to the fact that Blackfin has a special handling of symbols: a symbol called foo in C is called _foo in assembly. This apparently defeats the hidden_ref and hidden_proto logic in dso.h, which doesn't have explicit support for the Blackfin architecture. I tried a bit to change the assembly code to cope with the Blackfin specificities, but didn't manage to get something working. So far, the only solution I found is to simply not use this logic to hide symbols:

diff --git a/libselinux/src/dso.h b/libselinux/src/dso.h
index 12c3d11..f21d088 100644
--- a/libselinux/src/dso.h
+++ b/libselinux/src/dso.h
@@ -1,7 +1,7 @@
 #ifndef _SELINUX_DSO_H
 #define _SELINUX_DSO_H 1

-#ifdef SHARED
+#if defined(SHARED) && !defined(__bfin__)
 # define hidden __attribute__ ((visibility ("hidden")))
 # define hidden_proto(fct) __hidden_proto (fct, fct##_internal)
 # define __hidden_proto(fct, internal) \

But a real solution would be more appropriate.

[tpetazzoni]

To reproduce the issue:

git clone git://git.busybox.net/buildroot
cd buildroot
wget -O .config http://code.bulix.org/wjfzad-87798?raw
make

[stephensmalley]

I would prefer that these kinds of discussions occur on selinux@tycho.nsa.gov mailing list, not hidden away in github issues (far more people subscribed to selinux list, and better to archive all such discussions there). With regard to your specific issue, I was wondering whether glibc supports blackfin; if so, then there should be a fix for this issue in the glibc sources as the hidden_def/hidden_proto support for libselinux came from the glibc maintainers.

[tpetazzoni]

Unfortunately, I am not subscribed on the SELinux mailing list, though I understand your concern. I'll try to subscribe and ask there.

Blackfin is a non-MMU architecture, so it cannot be supported by the glibc C library. It is supported by the uClibc C library. It also has some hidden_proto definitions. I'll try to have a look. Thanks for the hint!