[PATCH] uml: check for differences in host support

If running on a host not supporting TLS (for instance 2.4) we should report
that cleanly to the user, instead of printing not comprehensible "error 5" for
that.

Additionally, i386 and x86_64 support different ranges for
user_desc->entry_number, and we must account for that; we couldn't pass
ourselves -1 because we need to override previously existing TLS descriptors
which glibc has possibly set, so test at startup the range to use.

x86 and x86_64 existing ranges are hardcoded.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 8 insertions, 0 deletions

diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index 1b780b5dacb..f88856c28a6 100644
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -173,6 +173,7 @@ extern int os_fchange_dir(int fd);
 extern void os_early_checks(void);
 extern int can_do_skas(void);
 extern void os_check_bugs(void);
+extern void check_host_supports_tls(int *supports_tls, int *tls_min);
 
 /* Make sure they are clear when running in TT mode. Required by
  * SEGV_MAYBE_FIXABLE */
diff --git a/arch/um/include/sysdep-i386/tls.h b/arch/um/include/sysdep-i386/tls.h
index 938f953b26c..918fd3c5ff9 100644
--- a/arch/um/include/sysdep-i386/tls.h
+++ b/arch/um/include/sysdep-i386/tls.h
@@ -25,4 +25,8 @@ typedef struct um_dup_user_desc {
 typedef struct user_desc user_desc_t;
 
 # endif /* __KERNEL__ */
+
+#define GDT_ENTRY_TLS_MIN_I386 6
+#define GDT_ENTRY_TLS_MIN_X86_64 12
+
 #endif /* _SYSDEP_TLS_H */
diff --git a/arch/um/include/user_util.h b/arch/um/include/user_util.h
index 615f2f0a32d..fe0c29b5144 100644
--- a/arch/um/include/user_util.h
+++ b/arch/um/include/user_util.h
@@ -8,6 +8,9 @@
 
 #include "sysdep/ptrace.h"
 
+/* Copied from kernel.h */
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
 #define CATCH_EINTR(expr) while ((errno = 0, ((expr) < 0)) && (errno == EINTR))
 
 extern int mode_tt;