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[PATCH] uml: increase granularity of host capability checking
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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>
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Bodo Stroesser authored and Linus Torvalds committed Sep 5, 2005
1 parent 60d339f commit 8b51304
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Showing 4 changed files with 96 additions and 34 deletions.
2 changes: 1 addition & 1 deletion arch/um/kernel/skas/include/skas.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down
52 changes: 28 additions & 24 deletions arch/um/kernel/skas/mmu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand All @@ -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);
Expand All @@ -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;
}
Expand All @@ -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);
}
Expand Down
69 changes: 61 additions & 8 deletions arch/um/kernel/skas/process.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand All @@ -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;
Expand All @@ -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)
Expand Down Expand Up @@ -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))
{
Expand Down
7 changes: 6 additions & 1 deletion arch/um/kernel/skas/process_kern.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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);
}

Expand Down

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