um: Remove SKAS3/4 support

Before we had SKAS0 UML had two modes of operation
TT (tracing thread) and SKAS3/4 (separated kernel address space).
TT was known to be insecure and got removed a long time ago.
SKAS3/4 required a few (3 or 4) patches on the host side which never went
mainline. The last host patch is 10 years old.

With SKAS0 mode (separated kernel address space using 0 host patches),
default since 2005, SKAS3/4 is obsolete and can be removed.

Signed-off-by: Richard Weinberger <richard@nod.at>

6 files changed, 38 insertions, 136 deletions

diff --git a/arch/um/kernel/ptrace.c b/arch/um/kernel/ptrace.c
index 62435ef003d9..174ee5017264 100644
--- a/arch/um/kernel/ptrace.c
+++ b/arch/um/kernel/ptrace.c
@@ -8,9 +8,6 @@
 #include <linux/sched.h>
 #include <linux/tracehook.h>
 #include <asm/uaccess.h>
-#include <skas_ptrace.h>
-
-
 
 void user_enable_single_step(struct task_struct *child)
 {
@@ -104,35 +101,6 @@ long arch_ptrace(struct task_struct *child, long request,
                 ret = ptrace_set_thread_area(child, addr, vp);
                 break;
 
-        case PTRACE_FAULTINFO: {
-                /*
-                 * Take the info from thread->arch->faultinfo,
-                 * but transfer max. sizeof(struct ptrace_faultinfo).
-                 * On i386, ptrace_faultinfo is smaller!
-                 */
-                ret = copy_to_user(p, &child->thread.arch.faultinfo,
-                                   sizeof(struct ptrace_faultinfo)) ?
-                        -EIO : 0;
-                break;
-        }
-
-#ifdef PTRACE_LDT
-        case PTRACE_LDT: {
-                struct ptrace_ldt ldt;
-
-                if (copy_from_user(&ldt, p, sizeof(ldt))) {
-                        ret = -EIO;
-                        break;
-                }
-
-                /*
-                 * This one is confusing, so just punt and return -EIO for
-                 * now
-                 */
-                ret = -EIO;
-                break;
-        }
-#endif
         default:
                 ret = ptrace_request(child, request, addr, data);
                 if (ret == -EIO)
diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c
index ced8903921ae..9bdf67a092a5 100644
--- a/arch/um/kernel/reboot.c
+++ b/arch/um/kernel/reboot.c
@@ -15,28 +15,21 @@ void (*pm_power_off)(void);
 
 static void kill_off_processes(void)
 {
-        if (proc_mm)
-                /*
-                 * FIXME: need to loop over userspace_pids
-                 */
-                os_kill_ptraced_process(userspace_pid[0], 1);
-        else {
-                struct task_struct *p;
-                int pid;
-
-                read_lock(&tasklist_lock);
-                for_each_process(p) {
-                        struct task_struct *t;
-
-                        t = find_lock_task_mm(p);
-                        if (!t)
-                                continue;
-                        pid = t->mm->context.id.u.pid;
-                        task_unlock(t);
-                        os_kill_ptraced_process(pid, 1);
-                }
-                read_unlock(&tasklist_lock);
+        struct task_struct *p;
+        int pid;
+
+        read_lock(&tasklist_lock);
+        for_each_process(p) {
+                struct task_struct *t;
+
+                t = find_lock_task_mm(p);
+                if (!t)
+                        continue;
+                pid = t->mm->context.id.u.pid;
+                task_unlock(t);
+                os_kill_ptraced_process(pid, 1);
         }
+        read_unlock(&tasklist_lock);
 }
 
 void uml_cleanup(void)
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 007d5503f49b..94abdcc1d6ad 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -54,35 +54,22 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
         unsigned long stack = 0;
         int ret = -ENOMEM;
 
-        if (skas_needs_stub) {
-                stack = get_zeroed_page(GFP_KERNEL);
-                if (stack == 0)
-                        goto out;
-        }
+        stack = get_zeroed_page(GFP_KERNEL);
+        if (stack == 0)
+                goto out;
 
         to_mm->id.stack = stack;
         if (current->mm != NULL && current->mm != &init_mm)
                 from_mm = &current->mm->context;
 
-        if (proc_mm) {
-                ret = new_mm(stack);
-                if (ret < 0) {
-                        printk(KERN_ERR "init_new_context_skas - "
-                               "new_mm failed, errno = %d\n", ret);
-                        goto out_free;
-                }
-                to_mm->id.u.mm_fd = ret;
-        }
-        else {
-                if (from_mm)
-                        to_mm->id.u.pid = copy_context_skas0(stack,
-                                                             from_mm->id.u.pid);
-                else to_mm->id.u.pid = start_userspace(stack);
-
-                if (to_mm->id.u.pid < 0) {
-                        ret = to_mm->id.u.pid;
-                        goto out_free;
-                }
+        if (from_mm)
+                to_mm->id.u.pid = copy_context_skas0(stack,
+                                                     from_mm->id.u.pid);
+        else to_mm->id.u.pid = start_userspace(stack);
+
+        if (to_mm->id.u.pid < 0) {
+                ret = to_mm->id.u.pid;
+                goto out_free;
         }
 
         ret = init_new_ldt(to_mm, from_mm);
@@ -105,9 +92,6 @@ void uml_setup_stubs(struct mm_struct *mm)
 {
         int err, ret;
 
-        if (!skas_needs_stub)
-                return;
-
         ret = init_stub_pte(mm, STUB_CODE,
                             (unsigned long) &__syscall_stub_start);
         if (ret)
@@ -154,25 +138,19 @@ void destroy_context(struct mm_struct *mm)
 {
         struct mm_context *mmu = &mm->context;
 
-        if (proc_mm)
-                os_close_file(mmu->id.u.mm_fd);
-        else {
-                /*
-                 * If init_new_context wasn't called, this will be
-                 * zero, resulting in a kill(0), which will result in the
-                 * whole UML suddenly dying.  Also, cover negative and
-                 * 1 cases, since they shouldn't happen either.
-                 */
-                if (mmu->id.u.pid < 2) {
-                        printk(KERN_ERR "corrupt mm_context - pid = %d\n",
-                               mmu->id.u.pid);
-                        return;
-                }
-                os_kill_ptraced_process(mmu->id.u.pid, 1);
+        /*
+         * If init_new_context wasn't called, this will be
+         * zero, resulting in a kill(0), which will result in the
+         * whole UML suddenly dying.  Also, cover negative and
+         * 1 cases, since they shouldn't happen either.
+         */
+        if (mmu->id.u.pid < 2) {
+                printk(KERN_ERR "corrupt mm_context - pid = %d\n",
+                       mmu->id.u.pid);
+                return;
         }
+        os_kill_ptraced_process(mmu->id.u.pid, 1);
 
-        if (skas_needs_stub)
-                free_page(mmu->id.stack);
-
+        free_page(mmu->id.stack);
         free_ldt(mmu);
 }
diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index 4da11b3c8ddb..082955d694f3 100644
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -10,25 +10,6 @@
 #include <os.h>
 #include <skas.h>
 
-int new_mm(unsigned long stack)
-{
-        int fd, err;
-
-        fd = os_open_file("/proc/mm", of_cloexec(of_write(OPENFLAGS())), 0);
-        if (fd < 0)
-                return fd;
-
-        if (skas_needs_stub) {
-                err = map_stub_pages(fd, STUB_CODE, STUB_DATA, stack);
-                if (err) {
-                        os_close_file(fd);
-                        return err;
-                }
-        }
-
-        return fd;
-}
-
 extern void start_kernel(void);
 
 static int __init start_kernel_proc(void *unused)
@@ -55,14 +36,6 @@ int __init start_uml(void)
 {
         stack_protections((unsigned long) &cpu0_irqstack);
         set_sigstack(cpu0_irqstack, THREAD_SIZE);
-        if (proc_mm) {
-                userspace_pid[0] = start_userspace(0);
-                if (userspace_pid[0] < 0) {
-                        printf("start_uml - start_userspace returned %d\n",
-                               userspace_pid[0]);
-                        exit(1);
-                }
-        }
 
         init_new_thread_signals();
 
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index 209617302df8..8e4daf44e980 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -220,7 +220,7 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
                 panic("Segfault with no mm");
         }
 
-        if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
+        if (SEGV_IS_FIXABLE(&fi))
                 err = handle_page_fault(address, ip, is_write, is_user,
                                         &si.si_code);
         else {
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 9274eae6ae7b..dbd5bda1f184 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -268,7 +268,6 @@ int __init linux_main(int argc, char **argv)
         unsigned long stack;
         unsigned int i;
         int add;
-        char * mode;
 
         for (i = 1; i < argc; i++) {
                 if ((i == 1) && (argv[i][0] == ' '))
@@ -291,15 +290,6 @@ int __init linux_main(int argc, char **argv)
         /* OS sanity checks that need to happen before the kernel runs */
         os_early_checks();
 
-        can_do_skas();
-
-        if (proc_mm && ptrace_faultinfo)
-                mode = "SKAS3";
-        else
-                mode = "SKAS0";
-
-        printf("UML running in %s mode\n", mode);
-
         brk_start = (unsigned long) sbrk(0);
 
         /*