[PATCH] uml: maintain own LDT entries
Patch imlements full LDT handling in SKAS:
* UML holds it's own LDT table, used to deliver data on
modify_ldt(READ)
* UML disables the default_ldt, inherited from the host (SKAS3)
or resets LDT entries, set by host's clib and inherited in
SKAS0
* A new global variable skas_needs_stub is inserted, that
can be used to decide, whether stub-pages must be supported
or not.
* Uses the syscall-stub to replace missing PTRACE_LDT (therefore,
write_ldt_entry needs to be modified)
Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/sys-i386/ldt.c b/arch/um/sys-i386/ldt.c
index 36b5c2c..6360f1c 100644
--- a/arch/um/sys-i386/ldt.c
+++ b/arch/um/sys-i386/ldt.c
@@ -3,53 +3,26 @@
* Licensed under the GPL
*/
+#include "linux/stddef.h"
#include "linux/config.h"
#include "linux/sched.h"
#include "linux/slab.h"
#include "linux/types.h"
+#include "linux/errno.h"
#include "asm/uaccess.h"
-#include "asm/ptrace.h"
#include "asm/smp.h"
#include "asm/ldt.h"
+#include "asm/unistd.h"
#include "choose-mode.h"
#include "kern.h"
#include "mode_kern.h"
-#ifdef CONFIG_MODE_TT
-
extern int modify_ldt(int func, void *ptr, unsigned long bytecount);
-static int do_modify_ldt_tt(int func, void *ptr, unsigned long bytecount)
-{
- return modify_ldt(func, ptr, bytecount);
-}
+#ifdef CONFIG_MODE_TT
-#endif
-
-#ifdef CONFIG_MODE_SKAS
-
-#include "skas.h"
-#include "skas_ptrace.h"
-
-static int do_modify_ldt_skas(int func, void *ptr, unsigned long bytecount)
-{
- struct ptrace_ldt ldt;
- u32 cpu;
- int res;
-
- ldt = ((struct ptrace_ldt) { .func = func,
- .ptr = ptr,
- .bytecount = bytecount });
-
- cpu = get_cpu();
- res = ptrace(PTRACE_LDT, userspace_pid[cpu], 0, (unsigned long) &ldt);
- put_cpu();
-
- return res;
-}
-#endif
-
-int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
+static long do_modify_ldt_tt(int func, void __user *ptr,
+ unsigned long bytecount)
{
struct user_desc info;
int res = 0;
@@ -89,8 +62,7 @@
goto out;
}
- res = CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func,
- p, bytecount);
+ res = modify_ldt(func, p, bytecount);
if(res < 0)
goto out;
@@ -108,3 +80,467 @@
kfree(buf);
return res;
}
+
+#endif
+
+#ifdef CONFIG_MODE_SKAS
+
+#include "skas.h"
+#include "skas_ptrace.h"
+#include "asm/mmu_context.h"
+
+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_skas(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 unshure: should interrupts be disabled here?
+ */
+ if(!current->active_mm || current->active_mm == &init_mm ||
+ mm_idp != ¤t->active_mm->context.skas.id)
+ switch_mm_skas(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 = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
+ if(res)
+ res = errno;
+
+ 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 != ¤t->active_mm->context.skas.id)
+ switch_mm_skas(¤t->active_mm->context.skas.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 = (void *)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 = ptrace(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 = ¤t->mm->context.skas.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);
+ }
+
+ down(&ldt->semaphore);
+ 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->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->pages[i], size)){
+ err = -EFAULT;
+ break;
+ }
+ bytecount -= size;
+ ptr += size;
+ }
+ }
+ up(&ldt->semaphore);
+
+ 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 = ¤t->mm->context.skas.ldt;
+ struct mm_id * mm_idp = ¤t->mm->context.skas.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)
+ down(&ldt->semaphore);
+
+ 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->entries, sizeof(entry0));
+ ldt->pages[i] = (struct ldt_entry *)
+ __get_free_page(GFP_KERNEL|__GFP_ZERO);
+ if(!ldt->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->pages[0], &entry0, sizeof(entry0));
+ memcpy(ldt->pages[0]+1, ldt->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->entries + ldt_info.entry_number;
+ else
+ ldt_p = ldt->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:
+ up(&ldt->semaphore);
+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;
+}
+
+short dummy_list[9] = {0, -1};
+short * host_ldt_entries = NULL;
+
+void ldt_get_host_info(void)
+{
+ long ret;
+ struct ldt_entry * ldt;
+ int i, size, k, order;
+
+ host_ldt_entries = dummy_list+1;
+
+ 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("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("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 < sizeof(dummy_list)/sizeof(dummy_list[0])) {
+ host_ldt_entries = dummy_list;
+ }
+ else {
+ size = (size + 1) * sizeof(dummy_list[0]);
+ host_ldt_entries = (short *)kmalloc(size, GFP_KERNEL);
+ if(host_ldt_entries == NULL) {
+ printk("ldt_get_host_info: couldn't allocate host ldt list\n");
+ goto out_free;
+ }
+ }
+
+ 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 mmu_context_skas * new_mm,
+ struct mmu_context_skas * from_mm)
+{
+ struct user_desc desc;
+ short * num_p;
+ int i;
+ long page, err=0;
+ void *addr = NULL;
+
+ memset(&desc, 0, sizeof(desc));
+
+ if(!ptrace_ldt)
+ init_MUTEX(&new_mm->ldt.semaphore);
+
+ if(!from_mm){
+ /*
+ * 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
+ */
+ if(host_ldt_entries == NULL)
+ 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->ldt.entry_count = 0;
+ }
+ else 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.
+ */
+ down(&from_mm->ldt.semaphore);
+ if(from_mm->ldt.entry_count <= LDT_DIRECT_ENTRIES){
+ memcpy(new_mm->ldt.entries, from_mm->ldt.entries,
+ sizeof(new_mm->ldt.entries));
+ }
+ else{
+ i = from_mm->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->ldt.pages[i] = (struct ldt_entry*)page;
+ memcpy(new_mm->ldt.pages[i],
+ from_mm->ldt.pages[i], PAGE_SIZE);
+ }
+ }
+ new_mm->ldt.entry_count = from_mm->ldt.entry_count;
+ up(&from_mm->ldt.semaphore);
+ }
+
+ return err;
+}
+
+
+void free_ldt(struct mmu_context_skas * mm)
+{
+ int i;
+
+ if(!ptrace_ldt && mm->ldt.entry_count > LDT_DIRECT_ENTRIES){
+ i = mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
+ while(i-- > 0){
+ free_page((long )mm->ldt.pages[i]);
+ }
+ }
+ mm->ldt.entry_count = 0;
+}
+#endif
+
+int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
+{
+ return(CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func,
+ ptr, bytecount));
+}