diff options
Diffstat (limited to 'arch/um/sys-i386/tls.c')
| -rw-r--r-- | arch/um/sys-i386/tls.c | 55 |
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); |