[PATCH] uml: increase granularity of host capability checking

This change enables SKAS0/SKAS3 to work with all combinations of /proc/mm and
PTRACE_FAULTINFO being available or not.

Also it changes the initialization of proc_mm and ptrace_faultinfo slightly,
to ease forcing SKAS0 on a patched host.  Forcing UML to run without /proc/mm
or PTRACE_FAULTINFO by cmdline parameter can be implemented with a setup
resetting the related variable.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/um/kernel/skas/include/skas.h b/arch/um/kernel/skas/include/skas.h
index e91064b..03c9d99 100644 (file)
--- a/arch/um/kernel/skas/include/skas.h
+++ b/arch/um/kernel/skas/include/skas.h
@@ -33,7 +33,7 @@ extern void *protect(struct mm_id * mm_idp, unsigned long addr,
                     unsigned long len, int r, int w, int x, int done,
                     void *data);
 extern void user_signal(int sig, union uml_pt_regs *regs, int pid);
-extern int new_mm(int from);
+extern int new_mm(int from, unsigned long stack);
 extern int start_userspace(unsigned long stub_stack);
 extern int copy_context_skas0(unsigned long stack, int pid);
 extern void get_skas_faultinfo(int pid, struct faultinfo * fi);

diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index d232daa..d837223 100644 (file)
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -77,23 +77,14 @@ int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
        struct mm_struct *cur_mm = current->mm;
        struct mm_id *cur_mm_id = &cur_mm->context.skas.id;
        struct mm_id *mm_id = &mm->context.skas.id;
-       unsigned long stack;
-       int from, ret;
+       unsigned long stack = 0;
+       int from, ret = -ENOMEM;
 
-       if(proc_mm){
-               if((cur_mm != NULL) && (cur_mm != &init_mm))
-                       from = cur_mm->context.skas.id.u.mm_fd;
-               else from = -1;
+       if(!proc_mm || !ptrace_faultinfo){
+               stack = get_zeroed_page(GFP_KERNEL);
+               if(stack == 0)
+                       goto out;
 
-               ret = new_mm(from);
-               if(ret < 0){
-                       printk("init_new_context_skas - new_mm failed, "
-                              "errno = %d\n", ret);
-                       return ret;
-               }
-               mm_id->u.mm_fd = ret;
-       }
-       else {
                /* This zeros the entry that pgd_alloc didn't, needed since
                 * we are about to reinitialize it, and want mm.nr_ptes to
                 * be accurate.
@@ -103,20 +94,30 @@ int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
                ret = init_stub_pte(mm, CONFIG_STUB_CODE,
                                    (unsigned long) &__syscall_stub_start);
                if(ret)
-                       goto out;
-
-               ret = -ENOMEM;
-               stack = get_zeroed_page(GFP_KERNEL);
-               if(stack == 0)
-                       goto out;
-               mm_id->stack = stack;
+                       goto out_free;
 
                ret = init_stub_pte(mm, CONFIG_STUB_DATA, stack);
                if(ret)
                        goto out_free;
 
                mm->nr_ptes--;
+       }
+       mm_id->stack = stack;
 
+       if(proc_mm){
+               if((cur_mm != NULL) && (cur_mm != &init_mm))
+                       from = cur_mm_id->u.mm_fd;
+               else from = -1;
+
+               ret = new_mm(from, stack);
+               if(ret < 0){
+                       printk("init_new_context_skas - new_mm failed, "
+                              "errno = %d\n", ret);
+                       goto out_free;
+               }
+               mm_id->u.mm_fd = ret;
+       }
+       else {
                if((cur_mm != NULL) && (cur_mm != &init_mm))
                        mm_id->u.pid = copy_context_skas0(stack,
                                                          cur_mm_id->u.pid);
@@ -126,7 +127,8 @@ int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
        return 0;
 
  out_free:
-       free_page(mm_id->stack);
+       if(mm_id->stack != 0)
+               free_page(mm_id->stack);
  out:
        return ret;
 }
@@ -137,8 +139,10 @@ void destroy_context_skas(struct mm_struct *mm)
 
        if(proc_mm)
                os_close_file(mmu->id.u.mm_fd);
-       else {
+       else
                os_kill_ptraced_process(mmu->id.u.pid, 1);
+
+       if(!proc_mm || !ptrace_faultinfo){
                free_page(mmu->id.stack);
                free_page(mmu->last_page_table);
        }

diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index f228f8b..5cd0e99 100644 (file)
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -138,6 +138,8 @@ static void handle_trap(int pid, union uml_pt_regs *regs, int local_using_sysemu
 }
 
 extern int __syscall_stub_start;
+int stub_code_fd = -1;
+__u64 stub_code_offset;
 
 static int userspace_tramp(void *stack)
 {
@@ -152,31 +154,31 @@ static int userspace_tramp(void *stack)
                /* 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;
-               __u64 offset;
-
-               fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
                addr = mmap64((void *) UML_CONFIG_STUB_CODE, page_size(),
-                             PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
+                             PROT_EXEC, MAP_FIXED | MAP_PRIVATE,
+                             stub_code_fd, stub_code_offset);
                if(addr == MAP_FAILED){
-                       printk("mapping mmap stub failed, errno = %d\n",
+                       printk("mapping stub code failed, errno = %d\n",
                               errno);
                        exit(1);
                }
 
                if(stack != NULL){
+                       int fd;
+                       __u64 offset;
+
                        fd = phys_mapping(to_phys(stack), &offset);
                        addr = mmap((void *) UML_CONFIG_STUB_DATA, page_size(),
                                    PROT_READ | PROT_WRITE,
                                    MAP_FIXED | MAP_SHARED, fd, offset);
                        if(addr == MAP_FAILED){
-                               printk("mapping segfault stack failed, "
+                               printk("mapping stub stack failed, "
                                       "errno = %d\n", errno);
                                exit(1);
                        }
                }
        }
-       if(!ptrace_faultinfo && (stack != NULL)){
+       if(!ptrace_faultinfo){
                unsigned long v = UML_CONFIG_STUB_CODE +
                                  (unsigned long) stub_segv_handler -
                                  (unsigned long) &__syscall_stub_start;
@@ -202,6 +204,10 @@ int start_userspace(unsigned long stub_stack)
        unsigned long sp;
        int pid, status, n, flags;
 
+       if ( stub_code_fd == -1 )
+               stub_code_fd = phys_mapping(to_phys(&__syscall_stub_start),
+                                           &stub_code_offset);
+
        stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
        if(stack == MAP_FAILED)
@@ -363,6 +369,53 @@ int copy_context_skas0(unsigned long new_stack, int pid)
        return pid;
 }
 
+/*
+ * This is used only, if proc_mm is available, while PTRACE_FAULTINFO
+ * isn't. Opening /proc/mm creates a new mm_context, which lacks the stub-pages
+ * Thus, we map them using /proc/mm-fd
+ */
+void map_stub_pages(int fd, unsigned long code,
+                   unsigned long data, unsigned long stack)
+{
+       struct proc_mm_op mmop;
+       int n;
+
+       mmop = ((struct proc_mm_op) { .op        = MM_MMAP,
+                                     .u         =
+                                     { .mmap    =
+                                       { .addr    = code,
+                                         .len     = PAGE_SIZE,
+                                         .prot    = PROT_EXEC,
+                                         .flags   = MAP_FIXED | MAP_PRIVATE,
+                                         .fd      = stub_code_fd,
+                                         .offset  = stub_code_offset
+       } } });
+       n = os_write_file(fd, &mmop, sizeof(mmop));
+       if(n != sizeof(mmop))
+               panic("map_stub_pages : /proc/mm map for code failed, "
+                     "err = %d\n", -n);
+
+       if ( stack ) {
+               __u64 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     = PAGE_SIZE,
+                                     .prot    = PROT_READ | PROT_WRITE,
+                                     .flags   = MAP_FIXED | MAP_SHARED,
+                                     .fd      = map_fd,
+                                     .offset  = map_offset
+               } } });
+               n = os_write_file(fd, &mmop, sizeof(mmop));
+               if(n != sizeof(mmop))
+                       panic("map_stub_pages : /proc/mm map for data failed, "
+                             "err = %d\n", -n);
+       }
+}
+
 void new_thread(void *stack, void **switch_buf_ptr, void **fork_buf_ptr,
                void (*handler)(int))
 {

diff --git a/arch/um/kernel/skas/process_kern.c b/arch/um/kernel/skas/process_kern.c
index cbabab1..3d1b227 100644 (file)
--- a/arch/um/kernel/skas/process_kern.c
+++ b/arch/um/kernel/skas/process_kern.c
@@ -129,7 +129,9 @@ int copy_thread_skas(int nr, unsigned long clone_flags, unsigned long sp,
        return(0);
 }
 
-int new_mm(int from)
+extern void map_stub_pages(int fd, unsigned long code,
+                          unsigned long data, unsigned long stack);
+int new_mm(int from, unsigned long stack)
 {
        struct proc_mm_op copy;
        int n, fd;
@@ -148,6 +150,9 @@ int new_mm(int from)
                               "err = %d\n", -n);
        }
 
+       if(!ptrace_faultinfo)
+               map_stub_pages(fd, CONFIG_STUB_CODE, CONFIG_STUB_DATA, stack);
+
        return(fd);
 }