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Commit 8b51304e authored by Bodo Stroesser's avatar Bodo Stroesser Committed by Linus Torvalds
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[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: default avatarBodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: default avatarJeff Dike <jdike@addtoit.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 60d339f6

arch/um/kernel/skas/include/skas.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

arch/um/kernel/skas/mmu.c

+28 −24
Original line number Diff line number Diff line
@@ -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);
@@ -126,6 +127,7 @@ int init_new_context_skas(struct task_struct *task, struct mm_struct *mm) 
	return 0;



 out_free:

	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);

	}

arch/um/kernel/skas/process.c

+61 −8
Original line number Diff line number Diff line
@@ -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))

{

arch/um/kernel/skas/process_kern.c

+6 −1
Original line number Diff line number Diff line
@@ -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);

}