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Diffstat (limited to 'arch/x86/um/ldt.c')
-rw-r--r--arch/x86/um/ldt.c502
1 files changed, 502 insertions, 0 deletions
diff --git a/arch/x86/um/ldt.c b/arch/x86/um/ldt.c
new file mode 100644
index 00000000000..8e08176f0bc
--- /dev/null
+++ b/arch/x86/um/ldt.c
@@ -0,0 +1,502 @@
+/*
+ * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <asm/unistd.h>
+#include <os.h>
+#include <proc_mm.h>
+#include <skas.h>
+#include <skas_ptrace.h>
+#include <sysdep/tls.h>
+
+extern int modify_ldt(int func, void *ptr, unsigned long bytecount);
+
+static long write_ldt_entry(struct mm_id *mm_idp, int func,
+ struct user_desc *desc, void **addr, int done)
+{
+ long res;
+
+ if (proc_mm) {
+ /*
+ * This is a special handling for the case, that the mm to
+ * modify isn't current->active_mm.
+ * If this is called directly by modify_ldt,
+ * (current->active_mm->context.skas.u == mm_idp)
+ * will be true. So no call to __switch_mm(mm_idp) is done.
+ * If this is called in case of init_new_ldt or PTRACE_LDT,
+ * mm_idp won't belong to current->active_mm, but child->mm.
+ * So we need to switch child's mm into our userspace, then
+ * later switch back.
+ *
+ * Note: I'm unsure: should interrupts be disabled here?
+ */
+ if (!current->active_mm || current->active_mm == &init_mm ||
+ mm_idp != &current->active_mm->context.id)
+ __switch_mm(mm_idp);
+ }
+
+ if (ptrace_ldt) {
+ struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
+ .func = func,
+ .ptr = desc,
+ .bytecount = sizeof(*desc)};
+ u32 cpu;
+ int pid;
+
+ if (!proc_mm)
+ pid = mm_idp->u.pid;
+ else {
+ cpu = get_cpu();
+ pid = userspace_pid[cpu];
+ }
+
+ res = os_ptrace_ldt(pid, 0, (unsigned long) &ldt_op);
+
+ if (proc_mm)
+ put_cpu();
+ }
+ else {
+ void *stub_addr;
+ res = syscall_stub_data(mm_idp, (unsigned long *)desc,
+ (sizeof(*desc) + sizeof(long) - 1) &
+ ~(sizeof(long) - 1),
+ addr, &stub_addr);
+ if (!res) {
+ unsigned long args[] = { func,
+ (unsigned long)stub_addr,
+ sizeof(*desc),
+ 0, 0, 0 };
+ res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
+ 0, addr, done);
+ }
+ }
+
+ if (proc_mm) {
+ /*
+ * This is the second part of special handling, that makes
+ * PTRACE_LDT possible to implement.
+ */
+ if (current->active_mm && current->active_mm != &init_mm &&
+ mm_idp != &current->active_mm->context.id)
+ __switch_mm(&current->active_mm->context.id);
+ }
+
+ return res;
+}
+
+static long read_ldt_from_host(void __user * ptr, unsigned long bytecount)
+{
+ int res, n;
+ struct ptrace_ldt ptrace_ldt = (struct ptrace_ldt) {
+ .func = 0,
+ .bytecount = bytecount,
+ .ptr = kmalloc(bytecount, GFP_KERNEL)};
+ u32 cpu;
+
+ if (ptrace_ldt.ptr == NULL)
+ return -ENOMEM;
+
+ /*
+ * This is called from sys_modify_ldt only, so userspace_pid gives
+ * us the right number
+ */
+
+ cpu = get_cpu();
+ res = os_ptrace_ldt(userspace_pid[cpu], 0, (unsigned long) &ptrace_ldt);
+ put_cpu();
+ if (res < 0)
+ goto out;
+
+ n = copy_to_user(ptr, ptrace_ldt.ptr, res);
+ if (n != 0)
+ res = -EFAULT;
+
+ out:
+ kfree(ptrace_ldt.ptr);
+
+ return res;
+}
+
+/*
+ * In skas mode, we hold our own ldt data in UML.
+ * Thus, the code implementing sys_modify_ldt_skas
+ * is very similar to (and mostly stolen from) sys_modify_ldt
+ * for arch/i386/kernel/ldt.c
+ * The routines copied and modified in part are:
+ * - read_ldt
+ * - read_default_ldt
+ * - write_ldt
+ * - sys_modify_ldt_skas
+ */
+
+static int read_ldt(void __user * ptr, unsigned long bytecount)
+{
+ int i, err = 0;
+ unsigned long size;
+ uml_ldt_t *ldt = &current->mm->context.arch.ldt;
+
+ if (!ldt->entry_count)
+ goto out;
+ if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
+ bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
+ err = bytecount;
+
+ if (ptrace_ldt)
+ return read_ldt_from_host(ptr, bytecount);
+
+ mutex_lock(&ldt->lock);
+ if (ldt->entry_count <= LDT_DIRECT_ENTRIES) {
+ size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
+ if (size > bytecount)
+ size = bytecount;
+ if (copy_to_user(ptr, ldt->u.entries, size))
+ err = -EFAULT;
+ bytecount -= size;
+ ptr += size;
+ }
+ else {
+ for (i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
+ i++) {
+ size = PAGE_SIZE;
+ if (size > bytecount)
+ size = bytecount;
+ if (copy_to_user(ptr, ldt->u.pages[i], size)) {
+ err = -EFAULT;
+ break;
+ }
+ bytecount -= size;
+ ptr += size;
+ }
+ }
+ mutex_unlock(&ldt->lock);
+
+ if (bytecount == 0 || err == -EFAULT)
+ goto out;
+
+ if (clear_user(ptr, bytecount))
+ err = -EFAULT;
+
+out:
+ return err;
+}
+
+static int read_default_ldt(void __user * ptr, unsigned long bytecount)
+{
+ int err;
+
+ if (bytecount > 5*LDT_ENTRY_SIZE)
+ bytecount = 5*LDT_ENTRY_SIZE;
+
+ err = bytecount;
+ /*
+ * UML doesn't support lcall7 and lcall27.
+ * So, we don't really have a default ldt, but emulate
+ * an empty ldt of common host default ldt size.
+ */
+ if (clear_user(ptr, bytecount))
+ err = -EFAULT;
+
+ return err;
+}
+
+static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
+{
+ uml_ldt_t *ldt = &current->mm->context.arch.ldt;
+ struct mm_id * mm_idp = &current->mm->context.id;
+ int i, err;
+ struct user_desc ldt_info;
+ struct ldt_entry entry0, *ldt_p;
+ void *addr = NULL;
+
+ err = -EINVAL;
+ if (bytecount != sizeof(ldt_info))
+ goto out;
+ err = -EFAULT;
+ if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
+ goto out;
+
+ err = -EINVAL;
+ if (ldt_info.entry_number >= LDT_ENTRIES)
+ goto out;
+ if (ldt_info.contents == 3) {
+ if (func == 1)
+ goto out;
+ if (ldt_info.seg_not_present == 0)
+ goto out;
+ }
+
+ if (!ptrace_ldt)
+ mutex_lock(&ldt->lock);
+
+ err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
+ if (err)
+ goto out_unlock;
+ else if (ptrace_ldt) {
+ /* With PTRACE_LDT available, this is used as a flag only */
+ ldt->entry_count = 1;
+ goto out;
+ }
+
+ if (ldt_info.entry_number >= ldt->entry_count &&
+ ldt_info.entry_number >= LDT_DIRECT_ENTRIES) {
+ for (i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
+ i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
+ i++) {
+ if (i == 0)
+ memcpy(&entry0, ldt->u.entries,
+ sizeof(entry0));
+ ldt->u.pages[i] = (struct ldt_entry *)
+ __get_free_page(GFP_KERNEL|__GFP_ZERO);
+ if (!ldt->u.pages[i]) {
+ err = -ENOMEM;
+ /* Undo the change in host */
+ memset(&ldt_info, 0, sizeof(ldt_info));
+ write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
+ goto out_unlock;
+ }
+ if (i == 0) {
+ memcpy(ldt->u.pages[0], &entry0,
+ sizeof(entry0));
+ memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
+ sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
+ }
+ ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
+ }
+ }
+ if (ldt->entry_count <= ldt_info.entry_number)
+ ldt->entry_count = ldt_info.entry_number + 1;
+
+ if (ldt->entry_count <= LDT_DIRECT_ENTRIES)
+ ldt_p = ldt->u.entries + ldt_info.entry_number;
+ else
+ ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
+ ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
+
+ if (ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
+ (func == 1 || LDT_empty(&ldt_info))) {
+ ldt_p->a = 0;
+ ldt_p->b = 0;
+ }
+ else{
+ if (func == 1)
+ ldt_info.useable = 0;
+ ldt_p->a = LDT_entry_a(&ldt_info);
+ ldt_p->b = LDT_entry_b(&ldt_info);
+ }
+ err = 0;
+
+out_unlock:
+ mutex_unlock(&ldt->lock);
+out:
+ return err;
+}
+
+static long do_modify_ldt_skas(int func, void __user *ptr,
+ unsigned long bytecount)
+{
+ int ret = -ENOSYS;
+
+ switch (func) {
+ case 0:
+ ret = read_ldt(ptr, bytecount);
+ break;
+ case 1:
+ case 0x11:
+ ret = write_ldt(ptr, bytecount, func);
+ break;
+ case 2:
+ ret = read_default_ldt(ptr, bytecount);
+ break;
+ }
+ return ret;
+}
+
+static DEFINE_SPINLOCK(host_ldt_lock);
+static short dummy_list[9] = {0, -1};
+static short * host_ldt_entries = NULL;
+
+static void ldt_get_host_info(void)
+{
+ long ret;
+ struct ldt_entry * ldt;
+ short *tmp;
+ int i, size, k, order;
+
+ spin_lock(&host_ldt_lock);
+
+ if (host_ldt_entries != NULL) {
+ spin_unlock(&host_ldt_lock);
+ return;
+ }
+ host_ldt_entries = dummy_list+1;
+
+ spin_unlock(&host_ldt_lock);
+
+ for (i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++)
+ ;
+
+ ldt = (struct ldt_entry *)
+ __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
+ if (ldt == NULL) {
+ printk(KERN_ERR "ldt_get_host_info: couldn't allocate buffer "
+ "for host ldt\n");
+ return;
+ }
+
+ ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
+ if (ret < 0) {
+ printk(KERN_ERR "ldt_get_host_info: couldn't read host ldt\n");
+ goto out_free;
+ }
+ if (ret == 0) {
+ /* default_ldt is active, simply write an empty entry 0 */
+ host_ldt_entries = dummy_list;
+ goto out_free;
+ }
+
+ for (i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++) {
+ if (ldt[i].a != 0 || ldt[i].b != 0)
+ size++;
+ }
+
+ if (size < ARRAY_SIZE(dummy_list))
+ host_ldt_entries = dummy_list;
+ else {
+ size = (size + 1) * sizeof(dummy_list[0]);
+ tmp = kmalloc(size, GFP_KERNEL);
+ if (tmp == NULL) {
+ printk(KERN_ERR "ldt_get_host_info: couldn't allocate "
+ "host ldt list\n");
+ goto out_free;
+ }
+ host_ldt_entries = tmp;
+ }
+
+ for (i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++) {
+ if (ldt[i].a != 0 || ldt[i].b != 0)
+ host_ldt_entries[k++] = i;
+ }
+ host_ldt_entries[k] = -1;
+
+out_free:
+ free_pages((unsigned long)ldt, order);
+}
+
+long init_new_ldt(struct mm_context *new_mm, struct mm_context *from_mm)
+{
+ struct user_desc desc;
+ short * num_p;
+ int i;
+ long page, err=0;
+ void *addr = NULL;
+ struct proc_mm_op copy;
+
+
+ if (!ptrace_ldt)
+ mutex_init(&new_mm->arch.ldt.lock);
+
+ if (!from_mm) {
+ memset(&desc, 0, sizeof(desc));
+ /*
+ * We have to initialize a clean ldt.
+ */
+ if (proc_mm) {
+ /*
+ * If the new mm was created using proc_mm, host's
+ * default-ldt currently is assigned, which normally
+ * contains the call-gates for lcall7 and lcall27.
+ * To remove these gates, we simply write an empty
+ * entry as number 0 to the host.
+ */
+ err = write_ldt_entry(&new_mm->id, 1, &desc, &addr, 1);
+ }
+ else{
+ /*
+ * Now we try to retrieve info about the ldt, we
+ * inherited from the host. All ldt-entries found
+ * will be reset in the following loop
+ */
+ ldt_get_host_info();
+ for (num_p=host_ldt_entries; *num_p != -1; num_p++) {
+ desc.entry_number = *num_p;
+ err = write_ldt_entry(&new_mm->id, 1, &desc,
+ &addr, *(num_p + 1) == -1);
+ if (err)
+ break;
+ }
+ }
+ new_mm->arch.ldt.entry_count = 0;
+
+ goto out;
+ }
+
+ if (proc_mm) {
+ /*
+ * We have a valid from_mm, so we now have to copy the LDT of
+ * from_mm to new_mm, because using proc_mm an new mm with
+ * an empty/default LDT was created in new_mm()
+ */
+ copy = ((struct proc_mm_op) { .op = MM_COPY_SEGMENTS,
+ .u =
+ { .copy_segments =
+ from_mm->id.u.mm_fd } } );
+ i = os_write_file(new_mm->id.u.mm_fd, &copy, sizeof(copy));
+ if (i != sizeof(copy))
+ printk(KERN_ERR "new_mm : /proc/mm copy_segments "
+ "failed, err = %d\n", -i);
+ }
+
+ if (!ptrace_ldt) {
+ /*
+ * Our local LDT is used to supply the data for
+ * modify_ldt(READLDT), if PTRACE_LDT isn't available,
+ * i.e., we have to use the stub for modify_ldt, which
+ * can't handle the big read buffer of up to 64kB.
+ */
+ mutex_lock(&from_mm->arch.ldt.lock);
+ if (from_mm->arch.ldt.entry_count <= LDT_DIRECT_ENTRIES)
+ memcpy(new_mm->arch.ldt.u.entries, from_mm->arch.ldt.u.entries,
+ sizeof(new_mm->arch.ldt.u.entries));
+ else {
+ i = from_mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
+ while (i-->0) {
+ page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
+ if (!page) {
+ err = -ENOMEM;
+ break;
+ }
+ new_mm->arch.ldt.u.pages[i] =
+ (struct ldt_entry *) page;
+ memcpy(new_mm->arch.ldt.u.pages[i],
+ from_mm->arch.ldt.u.pages[i], PAGE_SIZE);
+ }
+ }
+ new_mm->arch.ldt.entry_count = from_mm->arch.ldt.entry_count;
+ mutex_unlock(&from_mm->arch.ldt.lock);
+ }
+
+ out:
+ return err;
+}
+
+
+void free_ldt(struct mm_context *mm)
+{
+ int i;
+
+ if (!ptrace_ldt && mm->arch.ldt.entry_count > LDT_DIRECT_ENTRIES) {
+ i = mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
+ while (i-- > 0)
+ free_page((long) mm->arch.ldt.u.pages[i]);
+ }
+ mm->arch.ldt.entry_count = 0;
+}
+
+int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
+{
+ return do_modify_ldt_skas(func, ptr, bytecount);
+}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-04 13:18:04 +0000