399 lines
8.9 KiB
C
399 lines
8.9 KiB
C
/*
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* Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
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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 <asm/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_copy_tls(struct task_struct *new)
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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,
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(void __user *) UPT_SI(&new->thread.regs.regs),
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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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