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authorPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>2006-03-31 02:30:25 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-31 12:18:52 -0800
commit3feb88562d149f078319e5a1b2f7acaa10251a5c (patch)
tree73fb00f0ecb9ed0c4cf8eec24c84253ce9620464 /arch/um/sys-i386
parent54d8d3b5a0ce1cdbad1d3154c9ea9732d394e9c7 (diff)
[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>
Diffstat (limited to 'arch/um/sys-i386')
-rw-r--r--arch/um/sys-i386/tls.c55
1 files changed, 53 insertions, 2 deletions
diff --git a/arch/um/sys-i386/tls.c b/arch/um/sys-i386/tls.c
index 2251654c6b4..a3188e861cc 100644
--- a/arch/um/sys-i386/tls.c
+++ b/arch/um/sys-i386/tls.c
@@ -24,6 +24,10 @@
#include "skas.h"
#endif
+/* If needed we can detect when it's uninitialized. */
+static int host_supports_tls = -1;
+int host_gdt_entry_tls_min = -1;
+
#ifdef CONFIG_MODE_SKAS
int do_set_thread_area_skas(struct user_desc *info)
{
@@ -157,11 +161,20 @@ void clear_flushed_tls(struct task_struct *task)
}
}
-/* This in SKAS0 does not need to be used, since we have different host
- * processes. Nor will this need to be used when we'll add support to the host
+/* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
+ * common host process. So this is needed in SKAS0 too.
+ *
+ * However, if each thread had a different host process (and this was discussed
+ * for SMP support) this won't be needed.
+ *
+ * And this will not need be used when (and if) we'll add support to the host
* SKAS patch. */
+
int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to)
{
+ if (!host_supports_tls)
+ return 0;
+
/* We have no need whatsoever to switch TLS for kernel threads; beyond
* that, that would also result in us calling os_set_thread_area with
* userspace_pid[cpu] == 0, which gives an error. */
@@ -173,6 +186,9 @@ int arch_switch_tls_skas(struct task_struct *from, struct task_struct *to)
int arch_switch_tls_tt(struct task_struct *from, struct task_struct *to)
{
+ if (!host_supports_tls)
+ return 0;
+
if (needs_TLS_update(to))
return load_TLS(0, to);
@@ -256,6 +272,9 @@ asmlinkage int sys_set_thread_area(struct user_desc __user *user_desc)
struct user_desc info;
int idx, ret;
+ if (!host_supports_tls)
+ return -ENOSYS;
+
if (copy_from_user(&info, user_desc, sizeof(info)))
return -EFAULT;
@@ -287,6 +306,9 @@ int ptrace_set_thread_area(struct task_struct *child, int idx,
{
struct user_desc info;
+ if (!host_supports_tls)
+ return -EIO;
+
if (copy_from_user(&info, user_desc, sizeof(info)))
return -EFAULT;
@@ -298,6 +320,9 @@ asmlinkage int sys_get_thread_area(struct user_desc __user *user_desc)
struct user_desc info;
int idx, ret;
+ if (!host_supports_tls)
+ return -ENOSYS;
+
if (get_user(idx, &user_desc->entry_number))
return -EFAULT;
@@ -321,6 +346,9 @@ int ptrace_get_thread_area(struct task_struct *child, int idx,
struct user_desc info;
int ret;
+ if (!host_supports_tls)
+ return -EIO;
+
ret = get_tls_entry(child, &info, idx);
if (ret < 0)
goto out;
@@ -331,3 +359,26 @@ out:
return ret;
}
+
+/* XXX: This part is probably common to i386 and x86-64. Don't create a common
+ * file for now, do that when implementing x86-64 support.*/
+static int __init __setup_host_supports_tls(void) {
+ check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
+ if (host_supports_tls) {
+ printk(KERN_INFO "Host TLS support detected\n");
+ printk(KERN_INFO "Detected host type: ");
+ switch (host_gdt_entry_tls_min) {
+ case GDT_ENTRY_TLS_MIN_I386:
+ printk("i386\n");
+ break;
+ case GDT_ENTRY_TLS_MIN_X86_64:
+ printk("x86_64\n");
+ break;
+ }
+ } else
+ printk(KERN_ERR " Host TLS support NOT detected! "
+ "TLS support inside UML will not work\n");
+ return 1;
+}
+
+__initcall(__setup_host_supports_tls);