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396 lines
8.9 KiB
396 lines
8.9 KiB
/* |
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* Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <[email protected]> |
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* Licensed under the GPL |
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*/ |
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#include <linux/percpu.h> |
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#include <linux/sched.h> |
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#include <linux/syscalls.h> |
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#include <linux/uaccess.h> |
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#include <asm/ptrace-abi.h> |
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#include <os.h> |
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#include <skas.h> |
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#include <sysdep/tls.h> |
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/* |
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* If needed we can detect when it's uninitialized. |
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* |
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* These are initialized in an initcall and unchanged thereafter. |
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*/ |
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static int host_supports_tls = -1; |
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int host_gdt_entry_tls_min; |
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int do_set_thread_area(struct user_desc *info) |
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{ |
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int ret; |
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u32 cpu; |
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cpu = get_cpu(); |
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ret = os_set_thread_area(info, userspace_pid[cpu]); |
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put_cpu(); |
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if (ret) |
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printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, " |
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"index = %d\n", ret, info->entry_number); |
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return ret; |
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} |
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int do_get_thread_area(struct user_desc *info) |
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{ |
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int ret; |
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u32 cpu; |
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cpu = get_cpu(); |
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ret = os_get_thread_area(info, userspace_pid[cpu]); |
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put_cpu(); |
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if (ret) |
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printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, " |
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"index = %d\n", ret, info->entry_number); |
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return ret; |
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} |
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/* |
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* sys_get_thread_area: get a yet unused TLS descriptor index. |
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* XXX: Consider leaving one free slot for glibc usage at first place. This must |
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* be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else. |
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* |
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* Also, this must be tested when compiling in SKAS mode with dynamic linking |
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* and running against NPTL. |
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*/ |
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static int get_free_idx(struct task_struct* task) |
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{ |
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struct thread_struct *t = &task->thread; |
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int idx; |
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if (!t->arch.tls_array) |
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return GDT_ENTRY_TLS_MIN; |
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for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++) |
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if (!t->arch.tls_array[idx].present) |
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return idx + GDT_ENTRY_TLS_MIN; |
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return -ESRCH; |
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} |
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static inline void clear_user_desc(struct user_desc* info) |
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{ |
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/* Postcondition: LDT_empty(info) returns true. */ |
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memset(info, 0, sizeof(*info)); |
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/* |
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* Check the LDT_empty or the i386 sys_get_thread_area code - we obtain |
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* indeed an empty user_desc. |
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*/ |
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info->read_exec_only = 1; |
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info->seg_not_present = 1; |
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} |
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#define O_FORCE 1 |
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static int load_TLS(int flags, struct task_struct *to) |
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{ |
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int ret = 0; |
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int idx; |
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for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) { |
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struct uml_tls_struct* curr = |
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&to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN]; |
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/* |
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* Actually, now if it wasn't flushed it gets cleared and |
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* flushed to the host, which will clear it. |
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*/ |
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if (!curr->present) { |
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if (!curr->flushed) { |
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clear_user_desc(&curr->tls); |
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curr->tls.entry_number = idx; |
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} else { |
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WARN_ON(!LDT_empty(&curr->tls)); |
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continue; |
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} |
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} |
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if (!(flags & O_FORCE) && curr->flushed) |
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continue; |
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ret = do_set_thread_area(&curr->tls); |
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if (ret) |
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goto out; |
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curr->flushed = 1; |
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} |
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out: |
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return ret; |
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} |
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/* |
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* Verify if we need to do a flush for the new process, i.e. if there are any |
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* present desc's, only if they haven't been flushed. |
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*/ |
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static inline int needs_TLS_update(struct task_struct *task) |
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{ |
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int i; |
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int ret = 0; |
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for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) { |
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struct uml_tls_struct* curr = |
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&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN]; |
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/* |
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* Can't test curr->present, we may need to clear a descriptor |
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* which had a value. |
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*/ |
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if (curr->flushed) |
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continue; |
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ret = 1; |
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break; |
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} |
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return ret; |
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} |
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/* |
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* On a newly forked process, the TLS descriptors haven't yet been flushed. So |
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* we mark them as such and the first switch_to will do the job. |
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*/ |
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void clear_flushed_tls(struct task_struct *task) |
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{ |
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int i; |
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for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) { |
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struct uml_tls_struct* curr = |
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&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN]; |
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/* |
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* Still correct to do this, if it wasn't present on the host it |
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* will remain as flushed as it was. |
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*/ |
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if (!curr->present) |
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continue; |
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curr->flushed = 0; |
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} |
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} |
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/* |
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* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a |
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* common host process. So this is needed in SKAS0 too. |
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* |
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* However, if each thread had a different host process (and this was discussed |
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* for SMP support) this won't be needed. |
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* |
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* And this will not need be used when (and if) we'll add support to the host |
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* SKAS patch. |
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*/ |
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int arch_switch_tls(struct task_struct *to) |
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{ |
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if (!host_supports_tls) |
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return 0; |
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/* |
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* We have no need whatsoever to switch TLS for kernel threads; beyond |
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* that, that would also result in us calling os_set_thread_area with |
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* userspace_pid[cpu] == 0, which gives an error. |
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*/ |
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if (likely(to->mm)) |
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return load_TLS(O_FORCE, to); |
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return 0; |
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} |
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static int set_tls_entry(struct task_struct* task, struct user_desc *info, |
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int idx, int flushed) |
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{ |
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struct thread_struct *t = &task->thread; |
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if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) |
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return -EINVAL; |
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t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info; |
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t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1; |
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t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed; |
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return 0; |
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} |
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int arch_set_tls(struct task_struct *new, unsigned long tls) |
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{ |
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struct user_desc info; |
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int idx, ret = -EFAULT; |
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if (copy_from_user(&info, (void __user *) tls, sizeof(info))) |
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goto out; |
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ret = -EINVAL; |
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if (LDT_empty(&info)) |
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goto out; |
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idx = info.entry_number; |
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ret = set_tls_entry(new, &info, idx, 0); |
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out: |
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return ret; |
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} |
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/* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */ |
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static int get_tls_entry(struct task_struct *task, struct user_desc *info, |
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int idx) |
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{ |
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struct thread_struct *t = &task->thread; |
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if (!t->arch.tls_array) |
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goto clear; |
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if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) |
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return -EINVAL; |
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if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present) |
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goto clear; |
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*info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls; |
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out: |
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/* |
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* Temporary debugging check, to make sure that things have been |
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* flushed. This could be triggered if load_TLS() failed. |
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*/ |
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if (unlikely(task == current && |
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!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) { |
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printk(KERN_ERR "get_tls_entry: task with pid %d got here " |
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"without flushed TLS.", current->pid); |
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} |
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return 0; |
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clear: |
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/* |
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* When the TLS entry has not been set, the values read to user in the |
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* tls_array are 0 (because it's cleared at boot, see |
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* arch/i386/kernel/head.S:cpu_gdt_table). Emulate that. |
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*/ |
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clear_user_desc(info); |
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info->entry_number = idx; |
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goto out; |
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} |
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SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc) |
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{ |
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struct user_desc info; |
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int idx, ret; |
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if (!host_supports_tls) |
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return -ENOSYS; |
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if (copy_from_user(&info, user_desc, sizeof(info))) |
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return -EFAULT; |
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idx = info.entry_number; |
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if (idx == -1) { |
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idx = get_free_idx(current); |
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if (idx < 0) |
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return idx; |
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info.entry_number = idx; |
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/* Tell the user which slot we chose for him.*/ |
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if (put_user(idx, &user_desc->entry_number)) |
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return -EFAULT; |
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} |
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ret = do_set_thread_area(&info); |
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if (ret) |
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return ret; |
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return set_tls_entry(current, &info, idx, 1); |
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} |
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/* |
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* Perform set_thread_area on behalf of the traced child. |
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* Note: error handling is not done on the deferred load, and this differ from |
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* i386. However the only possible error are caused by bugs. |
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*/ |
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int ptrace_set_thread_area(struct task_struct *child, int idx, |
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struct user_desc __user *user_desc) |
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{ |
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struct user_desc info; |
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if (!host_supports_tls) |
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return -EIO; |
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if (copy_from_user(&info, user_desc, sizeof(info))) |
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return -EFAULT; |
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return set_tls_entry(child, &info, idx, 0); |
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} |
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SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc) |
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{ |
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struct user_desc info; |
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int idx, ret; |
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if (!host_supports_tls) |
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return -ENOSYS; |
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if (get_user(idx, &user_desc->entry_number)) |
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return -EFAULT; |
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ret = get_tls_entry(current, &info, idx); |
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if (ret < 0) |
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goto out; |
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if (copy_to_user(user_desc, &info, sizeof(info))) |
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ret = -EFAULT; |
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out: |
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return ret; |
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} |
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/* |
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* Perform get_thread_area on behalf of the traced child. |
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*/ |
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int ptrace_get_thread_area(struct task_struct *child, int idx, |
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struct user_desc __user *user_desc) |
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{ |
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struct user_desc info; |
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int ret; |
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if (!host_supports_tls) |
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return -EIO; |
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ret = get_tls_entry(child, &info, idx); |
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if (ret < 0) |
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goto out; |
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if (copy_to_user(user_desc, &info, sizeof(info))) |
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ret = -EFAULT; |
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out: |
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return ret; |
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} |
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/* |
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* This code is really i386-only, but it detects and logs x86_64 GDT indexes |
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* if a 32-bit UML is running on a 64-bit host. |
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*/ |
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static int __init __setup_host_supports_tls(void) |
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{ |
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check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min); |
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if (host_supports_tls) { |
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printk(KERN_INFO "Host TLS support detected\n"); |
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printk(KERN_INFO "Detected host type: "); |
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switch (host_gdt_entry_tls_min) { |
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case GDT_ENTRY_TLS_MIN_I386: |
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printk(KERN_CONT "i386"); |
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break; |
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case GDT_ENTRY_TLS_MIN_X86_64: |
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printk(KERN_CONT "x86_64"); |
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break; |
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} |
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printk(KERN_CONT " (GDT indexes %d to %d)\n", |
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host_gdt_entry_tls_min, |
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host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES); |
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} else |
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printk(KERN_ERR " Host TLS support NOT detected! " |
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"TLS support inside UML will not work\n"); |
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return 0; |
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} |
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__initcall(__setup_host_supports_tls);
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