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default since 2005, SKAS3/4 is obsolete and can be removed.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 <[e-mail]>

arch/um/include/shared/os.h

···
 
 /* start_up.c */
 extern void os_early_checks(void);
-extern void can_do_skas(void);
 extern void os_check_bugs(void);
 extern void check_host_supports_tls(int *supports_tls, int *tls_min);
 
···
 extern void os_stop_process(int pid);
 extern void os_kill_process(int pid, int reap_child);
 extern void os_kill_ptraced_process(int pid, int reap_child);
-extern long os_ptrace_ldt(long pid, long addr, long data);
 
 extern int os_getpid(void);
 extern int os_getpgrp(void);

arch/um/include/shared/skas/proc_mm.h

···
-/*
- * Copyright (C) 2002 Jeff Dike ([e-mail])
- * Licensed under the GPL
- */
-
-#ifndef __SKAS_PROC_MM_H
-#define __SKAS_PROC_MM_H
-
-#define MM_MMAP 54
-#define MM_MUNMAP 55
-#define MM_MPROTECT 56
-#define MM_COPY_SEGMENTS 57
-
-struct mm_mmap {
-	unsigned long addr;
-	unsigned long len;
-	unsigned long prot;
-	unsigned long flags;
-	unsigned long fd;
-	unsigned long offset;
-};
-
-struct mm_munmap {
-	unsigned long addr;
-	unsigned long len;
-};
-
-struct mm_mprotect {
-	unsigned long addr;
-	unsigned long len;
-	unsigned int prot;
-};
-
-struct proc_mm_op {
-	int op;
-	union {
-		struct mm_mmap mmap;
-		struct mm_munmap munmap;
-	        struct mm_mprotect mprotect;
-		int copy_segments;
-	} u;
-};
-
-#endif

arch/um/include/shared/skas/skas.h

···
 #include <sysdep/ptrace.h>
 
 extern int userspace_pid[];
-extern int proc_mm, ptrace_faultinfo, ptrace_ldt;
-extern int skas_needs_stub;
 
 extern int user_thread(unsigned long stack, int flags);
 extern void new_thread_handler(void);
 extern void handle_syscall(struct uml_pt_regs *regs);
-extern int new_mm(unsigned long stack);
 extern long execute_syscall_skas(void *r);
 extern unsigned long current_stub_stack(void);
 

arch/um/include/shared/skas_ptrace.h

···
-/* 
- * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
- * Licensed under the GPL
- */
-
-#ifndef __SKAS_PTRACE_H
-#define __SKAS_PTRACE_H
-
-#define PTRACE_FAULTINFO 52
-#define PTRACE_SWITCH_MM 55
-
-#include <sysdep/skas_ptrace.h>
-
-#endif

arch/um/kernel/ptrace.c

···
 #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)
 {
···
 		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)

arch/um/kernel/reboot.c

···
 
 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;
+	struct task_struct *p;
+	int pid;
 
-		read_lock(&tasklist_lock);
-		for_each_process(p) {
-			struct task_struct *t;
+	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);
+		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)

arch/um/kernel/skas/mmu.c

···
 	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 (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 (to_mm->id.u.pid < 0) {
+		ret = to_mm->id.u.pid;
+		goto out_free;
 	}
 
 	ret = init_new_ldt(to_mm, from_mm);
···
 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);
···
 {
 	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);
 }

arch/um/kernel/skas/process.c

···
 #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)
···
 {
 	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();
 

arch/um/kernel/trap.c

···
 		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 {

arch/um/kernel/um_arch.c

···
 	unsigned long stack;
 	unsigned int i;
 	int add;
-	char * mode;
 
 	for (i = 1; i < argc; i++) {
 		if ((i == 1) && (argv[i][0] == ' '))
···
 
 	/* 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);
 

arch/um/os-Linux/process.c

···
 #include <init.h>
 #include <longjmp.h>
 #include <os.h>
-#include <skas_ptrace.h>
 
 #define ARBITRARY_ADDR -1
 #define FAILURE_PID    -1
···
 	kill(pid, SIGKILL);
 	if (reap_child)
 		CATCH_EINTR(waitpid(pid, NULL, __WALL));
-}
-
-/* This is here uniquely to have access to the userspace errno, i.e. the one
- * used by ptrace in case of error.
- */
-
-long os_ptrace_ldt(long pid, long addr, long data)
-{
-	int ret;
-
-	ret = ptrace(PTRACE_LDT, pid, addr, data);
-
-	if (ret < 0)
-		return -errno;
-	return ret;
 }
 
 /* Kill off a ptraced child by all means available.  kill it normally first,

arch/um/os-Linux/skas/mem.c

···
 #include <as-layout.h>
 #include <mm_id.h>
 #include <os.h>
-#include <proc_mm.h>
 #include <ptrace_user.h>
 #include <registers.h>
 #include <skas.h>
···
 
 __initcall(init_syscall_regs);
 
-extern int proc_mm;
-
 static inline long do_syscall_stub(struct mm_id * mm_idp, void **addr)
 {
 	int n, i;
···
 	unsigned long * data;
 	unsigned long * syscall;
 	int err, pid = mm_idp->u.pid;
-
-	if (proc_mm)
-		/* FIXME: Need to look up userspace_pid by cpu */
-		pid = userspace_pid[0];
 
 	n = ptrace_setregs(pid, syscall_regs);
 	if (n < 0) {
···
 	int phys_fd, unsigned long long offset, int done, void **data)
 {
 	int ret;
+	unsigned long args[] = { virt, len, prot,
+				 MAP_SHARED | MAP_FIXED, phys_fd,
+				 MMAP_OFFSET(offset) };
 
-	if (proc_mm) {
-		struct proc_mm_op map;
-		int fd = mm_idp->u.mm_fd;
-
-		map = ((struct proc_mm_op) { .op	= MM_MMAP,
-				       .u		=
-				       { .mmap	=
-					 { .addr	= virt,
-					   .len	= len,
-					   .prot	= prot,
-					   .flags	= MAP_SHARED |
-					   MAP_FIXED,
-					   .fd	= phys_fd,
-					   .offset= offset
-					 } } } );
-		CATCH_EINTR(ret = write(fd, &map, sizeof(map)));
-		if (ret != sizeof(map)) {
-			ret = -errno;
-			printk(UM_KERN_ERR "map : /proc/mm map failed, "
-			       "err = %d\n", -ret);
-		}
-		else ret = 0;
-	}
-	else {
-		unsigned long args[] = { virt, len, prot,
-					 MAP_SHARED | MAP_FIXED, phys_fd,
-					 MMAP_OFFSET(offset) };
-
-		ret = run_syscall_stub(mm_idp, STUB_MMAP_NR, args, virt,
-				       data, done);
-	}
+	ret = run_syscall_stub(mm_idp, STUB_MMAP_NR, args, virt,
+			       data, done);
 
 	return ret;
 }
···
 	  int done, void **data)
 {
 	int ret;
+	unsigned long args[] = { (unsigned long) addr, len, 0, 0, 0,
+				 0 };
 
-	if (proc_mm) {
-		struct proc_mm_op unmap;
-		int fd = mm_idp->u.mm_fd;
-
-		unmap = ((struct proc_mm_op) { .op	= MM_MUNMAP,
-					 .u	=
-					 { .munmap	=
-					   { .addr	=
-					     (unsigned long) addr,
-					     .len		= len } } } );
-		CATCH_EINTR(ret = write(fd, &unmap, sizeof(unmap)));
-		if (ret != sizeof(unmap)) {
-			ret = -errno;
-			printk(UM_KERN_ERR "unmap - proc_mm write returned "
-			       "%d\n", ret);
-		}
-		else ret = 0;
-	}
-	else {
-		unsigned long args[] = { (unsigned long) addr, len, 0, 0, 0,
-					 0 };
-
-		ret = run_syscall_stub(mm_idp, __NR_munmap, args, 0,
-				       data, done);
-	}
+	ret = run_syscall_stub(mm_idp, __NR_munmap, args, 0,
+			       data, done);
 
 	return ret;
 }
···
 int protect(struct mm_id * mm_idp, unsigned long addr, unsigned long len,
 	    unsigned int prot, int done, void **data)
 {
-	struct proc_mm_op protect;
 	int ret;
+	unsigned long args[] = { addr, len, prot, 0, 0, 0 };
 
-	if (proc_mm) {
-		int fd = mm_idp->u.mm_fd;
-
-		protect = ((struct proc_mm_op) { .op	= MM_MPROTECT,
-					   .u	=
-					   { .mprotect	=
-					     { .addr	=
-					       (unsigned long) addr,
-					       .len	= len,
-					       .prot	= prot } } } );
-
-		CATCH_EINTR(ret = write(fd, &protect, sizeof(protect)));
-		if (ret != sizeof(protect)) {
-			ret = -errno;
-			printk(UM_KERN_ERR "protect failed, err = %d", -ret);
-		}
-		else ret = 0;
-	}
-	else {
-		unsigned long args[] = { addr, len, prot, 0, 0, 0 };
-
-		ret = run_syscall_stub(mm_idp, __NR_mprotect, args, 0,
-				       data, done);
-	}
+	ret = run_syscall_stub(mm_idp, __NR_mprotect, args, 0,
+			       data, done);
 
 	return ret;
 }

arch/um/os-Linux/skas/process.c

···
 #include <kern_util.h>
 #include <mem.h>
 #include <os.h>
-#include <proc_mm.h>
 #include <ptrace_user.h>
 #include <registers.h>
 #include <skas.h>
-#include <skas_ptrace.h>
 #include <sysdep/stub.h>
 
 int is_skas_winch(int pid, int fd, void *data)
···
 static void get_skas_faultinfo(int pid, struct faultinfo *fi)
 {
 	int err;
+	unsigned long fpregs[FP_SIZE];
 
-	if (ptrace_faultinfo) {
-		err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
-		if (err) {
-			printk(UM_KERN_ERR "get_skas_faultinfo - "
-			       "PTRACE_FAULTINFO failed, errno = %d\n", errno);
-			fatal_sigsegv();
-		}
-
-		/* Special handling for i386, which has different structs */
-		if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
-			memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
-			       sizeof(struct faultinfo) -
-			       sizeof(struct ptrace_faultinfo));
+	err = get_fp_registers(pid, fpregs);
+	if (err < 0) {
+		printk(UM_KERN_ERR "save_fp_registers returned %d\n",
+		       err);
+		fatal_sigsegv();
 	}
-	else {
-		unsigned long fpregs[FP_SIZE];
+	err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
+	if (err) {
+		printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
+		       "errno = %d\n", pid, errno);
+		fatal_sigsegv();
+	}
+	wait_stub_done(pid);
 
-		err = get_fp_registers(pid, fpregs);
-		if (err < 0) {
-			printk(UM_KERN_ERR "save_fp_registers returned %d\n",
-			       err);
-			fatal_sigsegv();
-		}
-		err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
-		if (err) {
-			printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
-			       "errno = %d\n", pid, errno);
-			fatal_sigsegv();
-		}
-		wait_stub_done(pid);
+	/*
+	 * faultinfo is prepared by the stub-segv-handler at start of
+	 * the stub stack page. We just have to copy it.
+	 */
+	memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
 
-		/*
-		 * faultinfo is prepared by the stub-segv-handler at start of
-		 * the stub stack page. We just have to copy it.
-		 */
-		memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
-
-		err = put_fp_registers(pid, fpregs);
-		if (err < 0) {
-			printk(UM_KERN_ERR "put_fp_registers returned %d\n",
-			       err);
-			fatal_sigsegv();
-		}
+	err = put_fp_registers(pid, fpregs);
+	if (err < 0) {
+		printk(UM_KERN_ERR "put_fp_registers returned %d\n",
+		       err);
+		fatal_sigsegv();
 	}
 }
 
···
 static int userspace_tramp(void *stack)
 {
 	void *addr;
-	int err;
+	int err, fd;
+	unsigned long long offset;
 
 	ptrace(PTRACE_TRACEME, 0, 0, 0);
 
···
 		exit(1);
 	}
 
-	if (!proc_mm) {
-		/*
-		 * This has a pte, but it can't be mapped in with the usual
-		 * tlb_flush mechanism because this is part of that mechanism
-		 */
-		int fd;
-		unsigned long long offset;
-		fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
-		addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
-			      PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
+	/*
+	 * This has a pte, but it can't be mapped in with the usual
+	 * tlb_flush mechanism because this is part of that mechanism
+	 */
+	fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
+	addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
+		      PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
+	if (addr == MAP_FAILED) {
+		printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
+		       "errno = %d\n", STUB_CODE, errno);
+		exit(1);
+	}
+
+	if (stack != NULL) {
+		fd = phys_mapping(to_phys(stack), &offset);
+		addr = mmap((void *) STUB_DATA,
+			    UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
+			    MAP_FIXED | MAP_SHARED, fd, offset);
 		if (addr == MAP_FAILED) {
-			printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
-			       "errno = %d\n", STUB_CODE, errno);
+			printk(UM_KERN_ERR "mapping segfault stack "
+			       "at 0x%lx failed, errno = %d\n",
+			       STUB_DATA, errno);
 			exit(1);
 		}
-
-		if (stack != NULL) {
-			fd = phys_mapping(to_phys(stack), &offset);
-			addr = mmap((void *) STUB_DATA,
-				    UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
-				    MAP_FIXED | MAP_SHARED, fd, offset);
-			if (addr == MAP_FAILED) {
-				printk(UM_KERN_ERR "mapping segfault stack "
-				       "at 0x%lx failed, errno = %d\n",
-				       STUB_DATA, errno);
-				exit(1);
-			}
-		}
 	}
-	if (!ptrace_faultinfo && (stack != NULL)) {
+	if (stack != NULL) {
 		struct sigaction sa;
 
 		unsigned long v = STUB_CODE +
···
 
 	sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 
-	flags = CLONE_FILES;
-	if (proc_mm)
-		flags |= CLONE_VM;
-	else
-		flags |= SIGCHLD;
+	flags = CLONE_FILES | SIGCHLD;
 
 	pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
 	if (pid < 0) {
···
 
 			switch (sig) {
 			case SIGSEGV:
-				if (PTRACE_FULL_FAULTINFO ||
-				    !ptrace_faultinfo) {
+				if (PTRACE_FULL_FAULTINFO) {
 					get_skas_faultinfo(pid,
 							   &regs->faultinfo);
 					(*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si,
···
 	return err;
 }
 
-/*
- * This is used only, if stub pages are needed, while proc_mm is
- * available. Opening /proc/mm creates a new mm_context, which lacks
- * the stub-pages. Thus, we map them using /proc/mm-fd
- */
-int map_stub_pages(int fd, unsigned long code, unsigned long data,
-		   unsigned long stack)
-{
-	struct proc_mm_op mmop;
-	int n;
-	unsigned long long code_offset;
-	int code_fd = phys_mapping(to_phys((void *) &__syscall_stub_start),
-				   &code_offset);
-
-	mmop = ((struct proc_mm_op) { .op        = MM_MMAP,
-				      .u         =
-				      { .mmap    =
-					{ .addr    = code,
-					  .len     = UM_KERN_PAGE_SIZE,
-					  .prot    = PROT_EXEC,
-					  .flags   = MAP_FIXED | MAP_PRIVATE,
-					  .fd      = code_fd,
-					  .offset  = code_offset
-	} } });
-	CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
-	if (n != sizeof(mmop)) {
-		n = errno;
-		printk(UM_KERN_ERR "mmap args - addr = 0x%lx, fd = %d, "
-		       "offset = %llx\n", code, code_fd,
-		       (unsigned long long) code_offset);
-		printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for code "
-		       "failed, err = %d\n", n);
-		return -n;
-	}
-
-	if (stack) {
-		unsigned long long map_offset;
-		int map_fd = phys_mapping(to_phys((void *)stack), &map_offset);
-		mmop = ((struct proc_mm_op)
-				{ .op        = MM_MMAP,
-				  .u         =
-				  { .mmap    =
-				    { .addr    = data,
-				      .len     = UM_KERN_PAGE_SIZE,
-				      .prot    = PROT_READ | PROT_WRITE,
-				      .flags   = MAP_FIXED | MAP_SHARED,
-				      .fd      = map_fd,
-				      .offset  = map_offset
-		} } });
-		CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
-		if (n != sizeof(mmop)) {
-			n = errno;
-			printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for "
-			       "data failed, err = %d\n", n);
-			return -n;
-		}
-	}
-
-	return 0;
-}
-
 void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 {
 	(*buf)[0].JB_IP = (unsigned long) handler;
···
 
 void __switch_mm(struct mm_id *mm_idp)
 {
-	int err;
-
-	/* FIXME: need cpu pid in __switch_mm */
-	if (proc_mm) {
-		err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
-			     mm_idp->u.mm_fd);
-		if (err) {
-			printk(UM_KERN_ERR "__switch_mm - PTRACE_SWITCH_MM "
-			       "failed, errno = %d\n", errno);
-			fatal_sigsegv();
-		}
-	}
-	else userspace_pid[0] = mm_idp->u.pid;
+	userspace_pid[0] = mm_idp->u.pid;
 }

arch/um/os-Linux/start_up.c

···
 #include <ptrace_user.h>
 #include <registers.h>
 #include <skas.h>
-#include <skas_ptrace.h>
 
 static void ptrace_child(void)
 {
···
 
 	return ret;
 }
-
-/* Changed only during early boot */
-int ptrace_faultinfo;
-static int disable_ptrace_faultinfo;
-
-int ptrace_ldt;
-static int disable_ptrace_ldt;
-
-int proc_mm;
-static int disable_proc_mm;
-
-int have_switch_mm;
-static int disable_switch_mm;
-
-int skas_needs_stub;
-
-static int __init skas0_cmd_param(char *str, int* add)
-{
-	disable_ptrace_faultinfo = 1;
-	disable_ptrace_ldt = 1;
-	disable_proc_mm = 1;
-	disable_switch_mm = 1;
-
-	return 0;
-}
-
-/* The two __uml_setup would conflict, without this stupid alias. */
-
-static int __init mode_skas0_cmd_param(char *str, int* add)
-	__attribute__((alias("skas0_cmd_param")));
-
-__uml_setup("skas0", skas0_cmd_param,
-"skas0\n"
-"    Disables SKAS3 and SKAS4 usage, so that SKAS0 is used\n\n");
-
-__uml_setup("mode=skas0", mode_skas0_cmd_param,
-"mode=skas0\n"
-"    Disables SKAS3 and SKAS4 usage, so that SKAS0 is used.\n\n");
 
 /* Changed only during early boot */
 static int force_sysemu_disabled = 0;
···
 	if (init_registers(pid))
 		fatal("Failed to initialize default registers");
 	stop_ptraced_child(pid, 1, 1);
-}
-
-static int __init noprocmm_cmd_param(char *str, int* add)
-{
-	disable_proc_mm = 1;
-	return 0;
-}
-
-__uml_setup("noprocmm", noprocmm_cmd_param,
-"noprocmm\n"
-"    Turns off usage of /proc/mm, even if host supports it.\n"
-"    To support /proc/mm, the host needs to be patched using\n"
-"    the current skas3 patch.\n\n");
-
-static int __init noptracefaultinfo_cmd_param(char *str, int* add)
-{
-	disable_ptrace_faultinfo = 1;
-	return 0;
-}
-
-__uml_setup("noptracefaultinfo", noptracefaultinfo_cmd_param,
-"noptracefaultinfo\n"
-"    Turns off usage of PTRACE_FAULTINFO, even if host supports\n"
-"    it. To support PTRACE_FAULTINFO, the host needs to be patched\n"
-"    using the current skas3 patch.\n\n");
-
-static int __init noptraceldt_cmd_param(char *str, int* add)
-{
-	disable_ptrace_ldt = 1;
-	return 0;
-}
-
-__uml_setup("noptraceldt", noptraceldt_cmd_param,
-"noptraceldt\n"
-"    Turns off usage of PTRACE_LDT, even if host supports it.\n"
-"    To support PTRACE_LDT, the host needs to be patched using\n"
-"    the current skas3 patch.\n\n");
-
-static inline void check_skas3_ptrace_faultinfo(void)
-{
-	struct ptrace_faultinfo fi;
-	int pid, n;
-
-	non_fatal("  - PTRACE_FAULTINFO...");
-	pid = start_ptraced_child();
-
-	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
-	if (n < 0) {
-		if (errno == EIO)
-			non_fatal("not found\n");
-		else
-			perror("not found");
-	} else if (disable_ptrace_faultinfo)
-		non_fatal("found but disabled on command line\n");
-	else {
-		ptrace_faultinfo = 1;
-		non_fatal("found\n");
-	}
-
-	stop_ptraced_child(pid, 1, 1);
-}
-
-static inline void check_skas3_ptrace_ldt(void)
-{
-#ifdef PTRACE_LDT
-	int pid, n;
-	unsigned char ldtbuf[40];
-	struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
-		.func = 2, /* read default ldt */
-		.ptr = ldtbuf,
-		.bytecount = sizeof(ldtbuf)};
-
-	non_fatal("  - PTRACE_LDT...");
-	pid = start_ptraced_child();
-
-	n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
-	if (n < 0) {
-		if (errno == EIO)
-			non_fatal("not found\n");
-		else
-			perror("not found");
-	} else if (disable_ptrace_ldt)
-		non_fatal("found, but use is disabled\n");
-	else {
-		ptrace_ldt = 1;
-		non_fatal("found\n");
-	}
-
-	stop_ptraced_child(pid, 1, 1);
-#endif
-}
-
-static inline void check_skas3_proc_mm(void)
-{
-	non_fatal("  - /proc/mm...");
-	if (access("/proc/mm", W_OK) < 0)
-		perror("not found");
-	else if (disable_proc_mm)
-		non_fatal("found but disabled on command line\n");
-	else {
-		proc_mm = 1;
-		non_fatal("found\n");
-	}
-}
-
-void can_do_skas(void)
-{
-	non_fatal("Checking for the skas3 patch in the host:\n");
-
-	check_skas3_proc_mm();
-	check_skas3_ptrace_faultinfo();
-	check_skas3_ptrace_ldt();
-
-	if (!proc_mm || !ptrace_faultinfo || !ptrace_ldt)
-		skas_needs_stub = 1;
 }
 
 int __init parse_iomem(char *str, int *add)

arch/x86/um/ldt.c

···
 #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);
···
 		     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);
+	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 (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;
 }
···
 	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) {
···
 			goto out;
 	}
 
-	if (!ptrace_ldt)
-		mutex_lock(&ldt->lock);
+	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) {
···
 	int i;
 	long page, err=0;
 	void *addr = NULL;
-	struct proc_mm_op copy;
 
 
-	if (!ptrace_ldt)
-		mutex_init(&new_mm->arch.ldt.lock);
+	mutex_init(&new_mm->arch.ldt.lock);
 
 	if (!from_mm) {
 		memset(&desc, 0, sizeof(desc));
 		/*
-		 * We have to initialize a clean ldt.
+		 * 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 (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;
-			}
+		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);
+	/*
+	 * 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);
 	}
+	new_mm->arch.ldt.entry_count = from_mm->arch.ldt.entry_count;
+	mutex_unlock(&from_mm->arch.ldt.lock);
 
     out:
 	return err;
···
 {
 	int i;
 
-	if (!ptrace_ldt && mm->arch.ldt.entry_count > LDT_DIRECT_ENTRIES) {
+	if (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]);

arch/x86/um/shared/sysdep/faultinfo_32.h

···
 /* This is Page Fault */
 #define SEGV_IS_FIXABLE(fi)	((fi)->trap_no == 14)
 
-/* SKAS3 has no trap_no on i386, but get_skas_faultinfo() sets it to 0. */
-#define SEGV_MAYBE_FIXABLE(fi)	((fi)->trap_no == 0 && ptrace_faultinfo)
-
 #define PTRACE_FULL_FAULTINFO 0
 
 #endif

arch/x86/um/shared/sysdep/faultinfo_64.h

···
 /* This is Page Fault */
 #define SEGV_IS_FIXABLE(fi)	((fi)->trap_no == 14)
 
-/* No broken SKAS API, which doesn't pass trap_no, here. */
-#define SEGV_MAYBE_FIXABLE(fi)	0
-
 #define PTRACE_FULL_FAULTINFO 1
 
 #endif

arch/x86/um/shared/sysdep/skas_ptrace.h

···
-/*
- * Copyright (C) 2000, 2001, 2002 Jeff Dike ([e-mail])
- * Licensed under the GPL
- */
-
-#ifndef __SYSDEP_X86_SKAS_PTRACE_H
-#define __SYSDEP_X86_SKAS_PTRACE_H
-
-struct ptrace_faultinfo {
-        int is_write;
-        unsigned long addr;
-};
-
-struct ptrace_ldt {
-        int func;
-        void *ptr;
-        unsigned long bytecount;
-};
-
-#define PTRACE_LDT 54
-
-#endif