[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>
This commit is contained in:
Paolo 'Blaisorblade' Giarrusso 2006-03-31 02:30:25 -08:00 committed by Linus Torvalds
parent 54d8d3b5a0
commit 3feb88562d
8 changed files with 102 additions and 6 deletions

View File

@ -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 */

View File

@ -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 */

View File

@ -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;

View File

@ -3,7 +3,7 @@
# Licensed under the GPL
#
obj-$(CONFIG_MODE_SKAS) = registers.o
obj-$(CONFIG_MODE_SKAS) = registers.o tls.o
USER_OBJS := $(obj-y)

View File

@ -0,0 +1,33 @@
#include <linux/unistd.h>
#include "sysdep/tls.h"
#include "user_util.h"
static _syscall1(int, get_thread_area, user_desc_t *, u_info);
/* Checks whether host supports TLS, and sets *tls_min according to the value
* valid on the host.
* i386 host have it == 6; x86_64 host have it == 12, for i386 emulation. */
void check_host_supports_tls(int *supports_tls, int *tls_min) {
/* Values for x86 and x86_64.*/
int val[] = {GDT_ENTRY_TLS_MIN_I386, GDT_ENTRY_TLS_MIN_X86_64};
int i;
for (i = 0; i < ARRAY_SIZE(val); i++) {
user_desc_t info;
info.entry_number = val[i];
if (get_thread_area(&info) == 0) {
*tls_min = val[i];
*supports_tls = 1;
return;
} else {
if (errno == EINVAL)
continue;
else if (errno == ENOSYS)
*supports_tls = 0;
return;
}
}
*supports_tls = 0;
}

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@ -48,8 +48,8 @@ int os_get_thread_area(user_desc_t *info, int pid)
#ifdef UML_CONFIG_MODE_TT
#include "linux/unistd.h"
_syscall1(int, get_thread_area, user_desc_t *, u_info);
_syscall1(int, set_thread_area, user_desc_t *, u_info);
static _syscall1(int, get_thread_area, user_desc_t *, u_info);
static _syscall1(int, set_thread_area, user_desc_t *, u_info);
int do_set_thread_area_tt(user_desc_t *info)
{

View File

@ -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);

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@ -1,6 +1,10 @@
#ifndef __UM_SEGMENT_H
#define __UM_SEGMENT_H
#include "asm/arch/segment.h"
extern int host_gdt_entry_tls_min;
#define GDT_ENTRY_TLS_ENTRIES 3
#define GDT_ENTRY_TLS_MIN host_gdt_entry_tls_min
#define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
#endif