Add get_mm and switch_mm support to UML.

Index: linux-2.6-skas4/arch/um/include/skas/mm_id.h
===================================================================
--- linux-2.6-skas4.orig/arch/um/include/skas/mm_id.h   2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/include/skas/mm_id.h        2008-01-09 
16:24:45.000000000 -0500
@@ -7,7 +7,7 @@
 #define __MM_ID_H
 
 struct mm_id {
-       union {
+       struct {
                int mm_fd;
                int pid;
        } u;
Index: linux-2.6-skas4/arch/um/include/skas/skas.h
===================================================================
--- linux-2.6-skas4.orig/arch/um/include/skas/skas.h    2008-01-09 
16:22:57.000000000 -0500
+++ linux-2.6-skas4/arch/um/include/skas/skas.h 2008-01-09 16:25:47.000000000 
-0500
@@ -6,12 +6,40 @@
 #ifndef __SKAS_H
 #define __SKAS_H
 
+#ifndef __KERNEL__
+#include <unistd.h>
+#include <sys/syscall.h>
+#endif
+#include "uml-config.h"
+
+#ifdef UML_CONFIG_X86_32
+#define __NR_new_mm             325
+#define __NR_switch_mm          326
+#else
+#define __NR_new_mm             286
+#define __NR_switch_mm          287
+#endif
+
+#define MM_COPY 0
+
+#define MM_ALL_REGS 0
+#define MM_SP_IP 1
+#define MM_SAME 2
+
+#define PTRACE_SWITCH_MM 33
+
+#ifndef __ASSEMBLY__
+
 #include "sysdep/ptrace.h"
 
 extern int userspace_pid[];
 extern int proc_mm, ptrace_faultinfo, ptrace_ldt;
 extern int skas_needs_stub;
 
+extern int have_switch_mm;
+extern int self_mm_fd;
+extern int have_ptrace_switch_mm;
+
 extern int user_thread(unsigned long stack, int flags);
 extern void new_thread_handler(void);
 extern void handle_syscall(struct uml_pt_regs *regs);
@@ -20,4 +48,19 @@ extern void get_skas_faultinfo(int pid, 
 extern long execute_syscall_skas(void *r);
 extern unsigned long current_stub_stack(void);
 
+#ifndef __KERNEL__
+static inline long new_mm(int flags)
+{
+       return syscall(__NR_new_mm, MM_COPY, 0, 0, 0, 0, 0, 0);
+}
+
+static inline long switch_mm(int mm_fd, unsigned long flags,
+                            unsigned long *new_regs, unsigned long *save_regs)
+{
+       return syscall(__NR_switch_mm, mm_fd, flags, new_regs, save_regs, 0, 0);
+}
+#endif
+
+#endif
+
 #endif
Index: linux-2.6-skas4/arch/um/kernel/reboot.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/kernel/reboot.c        2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/kernel/reboot.c     2008-01-09 16:24:45.000000000 
-0500
@@ -11,7 +11,7 @@ void (*pm_power_off)(void);
 
 static void kill_off_processes(void)
 {
-       if(proc_mm)
+       if(proc_mm || have_switch_mm)
                /*
                 * FIXME: need to loop over userspace_pids
                 */
Index: linux-2.6-skas4/arch/um/kernel/skas/mmu.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/kernel/skas/mmu.c      2008-01-09 
16:24:05.000000000 -0500
+++ linux-2.6-skas4/arch/um/kernel/skas/mmu.c   2008-01-09 16:24:45.000000000 
-0500
@@ -65,6 +65,9 @@ static int init_stub_pte(struct mm_struc
        return -ENOMEM;
 }
 
+extern int copy_context_skas4(struct mm_id *id);
+extern int get_new_mm(void);
+
 int init_new_context(struct task_struct *task, struct mm_struct *mm)
 {
        struct mm_context *from_mm = NULL;
@@ -109,6 +112,20 @@ int init_new_context(struct task_struct 
                }
                to_mm->id.u.mm_fd = ret;
        }
+       else if (have_switch_mm) {
+               to_mm->id.u.mm_fd = get_new_mm();
+               if(to_mm->id.u.mm_fd < 0) {
+                       ret = to_mm->id.u.mm_fd;
+                       goto out_free;
+               }
+
+               ret = copy_context_skas4(&to_mm->id);
+               if (ret < 0) {
+                       os_close_file(to_mm->id.u.mm_fd);
+                       to_mm->id.u.mm_fd = -1;
+                       goto out_free;
+               }
+       }
        else {
                if (from_mm)
                        to_mm->id.u.pid = copy_context_skas0(stack,
@@ -136,11 +153,15 @@ void destroy_context(struct mm_struct *m
 {
        struct mm_context *mmu = &mm->context;
 
-       if (proc_mm)
+       if (proc_mm || have_switch_mm)
                os_close_file(mmu->id.u.mm_fd);
-       else
+       else {
                os_kill_ptraced_process(mmu->id.u.pid, 1);
 
+               if (have_switch_mm)
+                       os_close_file(mmu->id.u.mm_fd);
+       }
+
        if (!proc_mm || !ptrace_faultinfo) {
                free_page(mmu->id.stack);
                pte_lock_deinit(virt_to_page(mmu->last_page_table));
Index: linux-2.6-skas4/arch/um/kernel/skas/process.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/kernel/skas/process.c  2008-01-09 
16:24:05.000000000 -0500
+++ linux-2.6-skas4/arch/um/kernel/skas/process.c       2008-01-09 
16:24:45.000000000 -0500
@@ -49,7 +49,7 @@ int __init start_uml(void)
 {
        stack_protections((unsigned long) &cpu0_irqstack);
        set_sigstack(cpu0_irqstack, THREAD_SIZE);
-       if (proc_mm)
+       if (proc_mm || have_switch_mm)
                userspace_pid[0] = start_userspace(0);
 
        init_new_thread_signals();
Index: linux-2.6-skas4/arch/um/kernel/um_arch.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/kernel/um_arch.c       2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/kernel/um_arch.c    2008-01-09 16:24:45.000000000 
-0500
@@ -271,7 +271,9 @@ int __init linux_main(int argc, char **a
 
        can_do_skas();
 
-       if (proc_mm && ptrace_faultinfo)
+       if (have_switch_mm)
+               mode = "SKAS4";
+       else if (proc_mm && ptrace_faultinfo)
                mode = "SKAS3";
        else
                mode = "SKAS0";
Index: linux-2.6-skas4/arch/um/os-Linux/skas/mem.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/os-Linux/skas/mem.c    2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/os-Linux/skas/mem.c 2008-01-09 16:24:45.000000000 
-0500
@@ -6,6 +6,7 @@
 #include <stddef.h>
 #include <unistd.h>
 #include <errno.h>
+#include <signal.h>
 #include <string.h>
 #include <sys/mman.h>
 #include "init.h"
@@ -22,7 +23,7 @@
 #include "sysdep/stub.h"
 #include "uml-config.h"
 
-extern unsigned long batch_syscall_stub, __syscall_stub_start;
+extern unsigned long batch_syscall_stub, switch_mm_stub, __syscall_stub_start;
 
 extern void wait_stub_done(int pid);
 
@@ -43,7 +44,10 @@ static int __init init_syscall_regs(void
        unsigned long *stub_entry;
 
        get_safe_registers(syscall_regs);
-       stub_entry = &batch_syscall_stub;
+       if (have_switch_mm)
+               stub_entry = &switch_mm_stub;
+       else
+               stub_entry = &batch_syscall_stub;
 
        syscall_regs[REGS_IP_INDEX] = STUB_CODE +
                ((unsigned long) stub_entry -
@@ -126,6 +130,32 @@ static long do_syscall_stub(struct mm_id
        return ret;
 }
 
+static long do_syscall_stub_skas4(struct mm_id *mm_idp, void **addr)
+{
+       long ret;
+       unsigned long *return_regs;
+       int err;
+       sigset_t sigs, old;
+
+       return_regs = (unsigned long *) (mm_idp->stack + UM_KERN_PAGE_SIZE) -
+               MAX_REG_NR;
+       *(return_regs - 1) = self_mm_fd;
+
+       return_regs = (unsigned long *) (STUB_DATA + UM_KERN_PAGE_SIZE) -
+               MAX_REG_NR;
+
+       sigfillset(&sigs);
+       sigprocmask(SIG_SETMASK, &sigs, &old);
+       err = switch_mm(mm_idp->u.mm_fd, MM_SP_IP, syscall_regs, return_regs);
+       sigprocmask(SIG_SETMASK, &old, NULL);
+
+       ret = syscall_stub_done(mm_idp->stack);
+
+       *addr = check_init_stack(mm_idp, NULL);
+
+       return ret;
+}
+
 static int flush_syscalls(struct mm_id *mm_idp, void **addr, int extra)
 {
        unsigned long *stack = check_init_stack(mm_idp, *addr);
@@ -137,7 +167,10 @@ static int flush_syscalls(struct mm_id *
        if (current + (10 + extra) * sizeof(long) < end)
                return 0;
 
-       return do_syscall_stub(mm_idp, addr);
+       if (have_switch_mm)
+               return do_syscall_stub_skas4(mm_idp, addr);
+       else
+               return do_syscall_stub(mm_idp, addr);
 }
 
 long run_syscall_stub(struct mm_id *mm_idp, int syscall,
@@ -166,8 +199,12 @@ long run_syscall_stub(struct mm_id *mm_i
        *stack++ = expected;
        *stack = 0;
 
-       if (done)
-               return do_syscall_stub(mm_idp, addr);
+       if (done) {
+               if (have_switch_mm)
+                       return do_syscall_stub_skas4(mm_idp, addr);
+               else
+                       return do_syscall_stub(mm_idp, addr);
+       }
 
        *addr = stack;
 
Index: linux-2.6-skas4/arch/um/os-Linux/skas/process.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/os-Linux/skas/process.c        2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/os-Linux/skas/process.c     2008-01-09 
16:24:45.000000000 -0500
@@ -331,7 +331,7 @@ static int userspace_tramp(void *stack)
                        }
                }
        }
-       if (!ptrace_faultinfo && (stack != NULL)) {
+       if (!ptrace_faultinfo) {
                struct sigaction sa;
 
                unsigned long v = STUB_CODE +
@@ -375,7 +375,7 @@ int start_userspace(unsigned long stub_s
        sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
 
        flags = CLONE_FILES;
-       if (proc_mm)
+       if (proc_mm || have_switch_mm)
                flags |= CLONE_VM;
        else
                flags |= SIGCHLD;
@@ -488,8 +488,14 @@ void userspace(struct uml_pt_regs *regs)
                                printk(UM_KERN_ERR "userspace - child stopped "
                                       "with signal %d\n", sig);
                        }
-                       pid = userspace_pid[0];
+
+                       /*
+                        * userspace_pid can change in in_interrupt since
+                        * PTRACE_SWITCH_MM can cause a process to change
+                        * address spaces
+                        */
                        interrupt_end();
+                       pid = userspace_pid[0];
 
                        /* Avoid -ERESTARTSYS handling in host */
                        if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
@@ -577,6 +583,69 @@ int copy_context_skas0(unsigned long new
        return pid;
 }
 
+extern unsigned long switch_mm_stub;
+extern long task_size;
+
+static void unmap_new_as(void)
+{
+       void (*p)(void);
+       void *addr;
+       unsigned long stack = (unsigned long) &stack & ~(UM_KERN_PAGE_SIZE - 1);
+       unsigned long long data_offset, code_offset;
+       int fd = phys_mapping(to_phys((void *) stack), &data_offset);
+
+       addr = mmap((void *) STUB_DATA, UM_KERN_PAGE_SIZE,
+                   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd,
+                   data_offset);
+       if (addr == MAP_FAILED)
+               panic("Failed to remap stack");
+
+       fd = phys_mapping(to_phys(&__syscall_stub_start), &code_offset);
+       addr = mmap((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
+                   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd,
+                   code_offset);
+       if (addr == MAP_FAILED)
+               panic("Failed to remap code");
+
+       p = (void (*)(void)) (STUB_CODE +
+                             ((unsigned long) &switch_mm_stub -
+                              (unsigned long) &__syscall_stub_start));
+       (*p)();
+}
+
+int copy_context_skas4(struct mm_id *id)
+{
+       void *data = NULL;
+       unsigned long *return_regs, *fd_ptr, regs[MAX_REG_NR];
+       sigset_t sigs, old;
+       int err;
+
+       err = unmap(id, 0, STUB_START, 0, &data);
+       if (err)
+               return err;
+
+       err = unmap(id, STUB_END, task_size - STUB_END, 0, &data);
+       if (err)
+               return err;
+
+       return_regs = (unsigned long *) (id->stack + UM_KERN_PAGE_SIZE -
+                                        MAX_REG_NR * sizeof(long));
+       fd_ptr = return_regs - 1;
+       *fd_ptr = self_mm_fd;
+
+       regs[REGS_IP_INDEX] = (unsigned long) unmap_new_as;
+       regs[REGS_SP_INDEX] = id->stack + UM_KERN_PAGE_SIZE / 2;
+
+       sigfillset(&sigs);
+       sigprocmask(SIG_SETMASK, &sigs, &old);
+
+       err = switch_mm(id->u.mm_fd, MM_SP_IP, regs, return_regs);
+
+       sigprocmask(SIG_SETMASK, &old, NULL);
+
+       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
@@ -737,5 +806,12 @@ void __switch_mm(struct mm_id *mm_idp)
                        panic("__switch_mm - PTRACE_SWITCH_MM failed, "
                              "errno = %d\n", errno);
        }
+       else if (have_ptrace_switch_mm) {
+               err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
+                            mm_idp->u.mm_fd);
+               if (err)
+                       panic("__switch_mm - PTRACE_SWITCH_MM "
+                              "failed, errno = %d\n", errno);
+       }
        else userspace_pid[0] = mm_idp->u.pid;
 }
Index: linux-2.6-skas4/arch/um/os-Linux/start_up.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/os-Linux/start_up.c    2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/os-Linux/start_up.c 2008-01-09 16:24:45.000000000 
-0500
@@ -475,13 +475,208 @@ static inline void check_skas3_proc_mm(v
        }
 }
 
-void can_do_skas(void)
+static void can_do_skas3(void)
 {
        non_fatal("Checking for the skas3 patch in the host:\n");
 
        check_skas3_proc_mm();
        check_skas3_ptrace_faultinfo();
        check_skas3_ptrace_ldt();
+}
+
+int get_new_mm(void)
+{
+       int err;
+
+       err = new_mm(MM_COPY);
+       if (err < 0)
+               err = -errno;
+
+       return err;
+}
+
+static char *mm_stack;
+static unsigned long return_regs[MAX_REG_NR];
+int self_mm_fd;
+
+static int switch_mm_works;
+
+static void after_switch(void)
+{
+       switch_mm_works = 0;
+
+       switch_mm(self_mm_fd, MM_ALL_REGS, return_regs, NULL);
+}
+
+static int check_switch_mm(void)
+{
+       unsigned long regs[MAX_REG_NR];
+       int err, there = -1;
+
+       non_fatal("\t/proc/self/mm ... ");
+       self_mm_fd = open("/proc/self/mm", O_RDONLY);
+       if (self_mm_fd < 0)
+               goto bad;
+       non_fatal("OK\n");
+
+       mm_stack = mmap(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
+                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+       if(mm_stack == MAP_FAILED)
+               goto bad;
+
+       non_fatal("\tnew_mm ... ");
+       there = new_mm(MM_COPY);
+       if(there < 0)
+               goto bad;
+       non_fatal("OK\n");
+
+       regs[REGS_IP_INDEX] = (unsigned long) after_switch;
+       regs[REGS_SP_INDEX] = ((unsigned long) &mm_stack[UM_KERN_PAGE_SIZE]) -
+               sizeof(void *);
+
+       non_fatal("\tswitching over ... ");
+       err = switch_mm(there, MM_SP_IP, regs, return_regs);
+       if (err < 0)
+               goto bad;
+       non_fatal("switched back ... ");
+       switch_mm_works = 1;
+       if(!switch_mm_works)
+               goto bad;
+       else
+               non_fatal("OK\n");
+
+       munmap(mm_stack, UM_KERN_PAGE_SIZE);
+       close(there);
+
+       if (disable_switch_mm)
+               non_fatal("SKAS4 support disabled on command line\n");
+       else
+               have_switch_mm = 1;
+
+       return 1;
+ bad:
+       if (there > 0)
+               close(there);
+       munmap(mm_stack, UM_KERN_PAGE_SIZE);
+       non_fatal("Failed - \n");
+       perror("");
+       return 0;
+}
+
+int have_ptrace_switch_mm;
+static int disable_ptrace_switch_mm;
+
+static int ptrace_switch_mm_works;
+
+static int after_ptrace_switch(void)
+{
+       ptrace_switch_mm_works = 1;
+       exit(0);
+}
+
+static int check_ptrace_switch_mm(void)
+{
+       void *stack;
+       unsigned long regs[MAX_REG_NR];
+       int pid, here, err, status;
+
+       non_fatal("\tPTRACE_SWITCH_MM ... ");
+       pid = fork();
+       if(pid == 0){
+               ptrace(PTRACE_TRACEME, 0, 0, 0);
+               kill(getpid(), SIGSTOP);
+
+               exit(0);
+       }
+       else if(pid < 0)
+               goto bad;
+
+       stack = mmap(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
+                    MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+       if(stack == MAP_FAILED)
+               goto bad;
+
+       here = open("/proc/self/mm", O_RDONLY);
+       if(here < 0)
+               goto bad_unmap;
+
+       err = waitpid(pid, &status, WUNTRACED);
+       if (err < 0)
+               goto bad_close;
+       else if (err != pid) {
+               non_fatal("waitpid returned %d, expected %d\n", err, pid);
+               goto bad_close;
+       }
+       else if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
+               non_fatal("waitpid returned status 0x%d\n", status);
+               goto bad_close;
+       }
+
+       err = ptrace(PTRACE_GETREGS, pid, 0, regs);
+       if (err < 0)
+               goto bad_close;
+
+       regs[REGS_IP_INDEX] = (unsigned long) after_ptrace_switch;
+       regs[REGS_SP_INDEX] = (unsigned long) stack + UM_KERN_PAGE_SIZE -
+               sizeof(void *);
+
+       if (ptrace(PTRACE_SETREGS, pid, 0, regs) < 0)
+               goto bad_close;
+
+       if (ptrace(PTRACE_SWITCH_MM, pid, NULL, here) < 0)
+               goto bad_close;
+
+       if (ptrace(PTRACE_CONT, pid, NULL, 0) < 0)
+               goto bad_close;
+
+       err = waitpid(pid, &status, WUNTRACED);
+       if (err < 0)
+               goto bad_close;
+       else if(err != pid) {
+               non_fatal("waitpid returned %d, expected %d\n", err, pid);
+               goto bad_close;
+       }
+       else if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0)) {
+               non_fatal("waitpid returned status 0x%d\n", status);
+               goto bad_close;
+       }
+
+       if (!ptrace_switch_mm_works)
+               goto bad_close;
+       else non_fatal("OK\n");
+
+       if (disable_ptrace_switch_mm)
+               non_fatal("PTRACE_SWITCH_MM support disabled on command "
+                         "line\n");
+       else
+               have_ptrace_switch_mm = 1;
+
+       close(here);
+       munmap(stack, UM_KERN_PAGE_SIZE);
+
+       return 1;
+
+ bad_close:
+       close(here);
+ bad_unmap:
+       munmap(stack, UM_KERN_PAGE_SIZE);
+ bad:
+       non_fatal("Failed - \n");
+       perror("");
+       return 0;
+}
+
+static int can_do_skas4(void)
+{
+       non_fatal("Checking for new_mm and switch_mm support in the host:\n");
+
+       return check_switch_mm() && check_ptrace_switch_mm();
+}
+
+void can_do_skas(void)
+{
+       if(!can_do_skas4())
+               can_do_skas3();
 
        if (!proc_mm || !ptrace_faultinfo || !ptrace_ldt)
                skas_needs_stub = 1;
Index: linux-2.6-skas4/arch/um/sys-i386/stub.S
===================================================================
--- linux-2.6-skas4.orig/arch/um/sys-i386/stub.S        2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/sys-i386/stub.S     2008-01-09 16:24:45.000000000 
-0500
@@ -1,5 +1,8 @@
 #include "uml-config.h"
 #include "as-layout.h"
+#include "skas/skas.h"
+
+#define MAX_REG_NR 17
 
 #define PROCESS_LIST \
        /* load pointer to first operation */ \
@@ -43,3 +46,16 @@ batch_syscall_stub:
        PROCESS_LIST
        /* stop */
        int3
+
+       .globl switch_mm_stub
+switch_mm_stub:
+       PROCESS_LIST
+
+       mov     $__NR_switch_mm, %eax
+       mov     ASM_STUB_DATA + UM_KERN_PAGE_SIZE - MAX_REG_NR * 4 - 4, %ebx
+       mov     $MM_ALL_REGS, %ecx
+       mov     $(ASM_STUB_DATA + UM_KERN_PAGE_SIZE - MAX_REG_NR * 4), %edx
+       xor     %esi, %esi
+       int     $0x80
+
+       int3
Index: linux-2.6-skas4/arch/um/sys-x86_64/stub.S
===================================================================
--- linux-2.6-skas4.orig/arch/um/sys-x86_64/stub.S      2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/sys-x86_64/stub.S   2008-01-09 16:24:45.000000000 
-0500
@@ -1,5 +1,8 @@
 #include "uml-config.h"
 #include "as-layout.h"
+#include "skas/skas.h"
+
+#define MAX_REG_NR 27
 
 #define PROCESS_LIST \
        mov     $(ASM_STUB_DATA >> 32), %rbx; \
@@ -46,3 +49,21 @@ batch_syscall_stub:
        PROCESS_LIST
        /* stop */
        int3
+
+       .globl switch_mm_stub
+switch_mm_stub:
+       PROCESS_LIST
+
+       mov     $__NR_switch_mm, %rax
+       mov     $(ASM_STUB_DATA >> 32), %rdi
+       sal     $32, %rdi
+       mov     $(ASM_STUB_DATA & 0xffffffff), %rsi
+       add     %rsi, %rdi
+       add     $(UM_KERN_PAGE_SIZE - MAX_REG_NR * 8 - 8), %rdi
+       mov     (%rdi), %rdi
+       mov     $MM_ALL_REGS, %rsi
+       mov     $(ASM_STUB_DATA + UM_KERN_PAGE_SIZE - MAX_REG_NR * 8), %rdx
+       xor     %r10, %r10
+       syscall
+
+       int3
Index: linux-2.6-skas4/arch/um/sys-x86_64/syscalls.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/sys-x86_64/syscalls.c  2008-01-09 
16:22:13.000000000 -0500
+++ linux-2.6-skas4/arch/um/sys-x86_64/syscalls.c       2008-01-09 
16:24:45.000000000 -0500
@@ -30,7 +30,7 @@ long arch_prctl(struct task_struct *task
 {
        unsigned long *ptr = addr, tmp;
        long ret;
-       int pid = task->mm->context.id.u.pid;
+       int pid = userspace_pid[0];
 
        /*
         * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to

-------------------------------------------------------------------------
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