#include <asm/regs.h>
extern void ret_from_fork(void);
+extern void ret_from_kernel_thread(void);
struct task_struct *current_set[NR_CPUS] = {&init_task, };
/*
* Copy thread.
*
+ * There are two modes in which this function is called:
+ * 1) Userspace thread creation,
+ * regs != NULL, usp_thread_fn is userspace stack pointer.
+ * It is expected to copy parent regs (in case CLONE_VM is not set
+ * in the clone_flags) and set up passed usp in the childregs.
+ * 2) Kernel thread creation,
+ * regs == NULL, usp_thread_fn is the function to run in the new thread
+ * and thread_fn_arg is its parameter.
+ * childregs are not used for the kernel threads.
+ *
* The stack layout for the new thread looks like this:
*
- * +------------------------+ <- sp in childregs (= tos)
+ * +------------------------+
* | childregs |
* +------------------------+ <- thread.sp = sp in dummy-frame
* | dummy-frame | (saved in dummy-frame spill-area)
* +------------------------+
*
- * We create a dummy frame to return to ret_from_fork:
- * a0 points to ret_from_fork (simulating a call4)
+ * We create a dummy frame to return to either ret_from_fork or
+ * ret_from_kernel_thread:
+ * a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
* sp points to itself (thread.sp)
- * a2, a3 are unused.
+ * a2, a3 are unused for userspace threads,
+ * a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
*
* Note: This is a pristine frame, so we don't need any spill region on top of
* childregs.
+ *
+ * The fun part: if we're keeping the same VM (i.e. cloning a thread,
+ * not an entire process), we're normally given a new usp, and we CANNOT share
+ * any live address register windows. If we just copy those live frames over,
+ * the two threads (parent and child) will overflow the same frames onto the
+ * parent stack at different times, likely corrupting the parent stack (esp.
+ * if the parent returns from functions that called clone() and calls new
+ * ones, before the child overflows its now old copies of its parent windows).
+ * One solution is to spill windows to the parent stack, but that's fairly
+ * involved. Much simpler to just not copy those live frames across.
*/
-int copy_thread(unsigned long clone_flags, unsigned long usp,
- unsigned long unused,
- struct task_struct * p, struct pt_regs * regs)
+int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
+ unsigned long thread_fn_arg,
+ struct task_struct *p, struct pt_regs *unused)
{
- struct pt_regs *childregs;
- struct thread_info *ti;
- unsigned long tos;
- int user_mode = user_mode(regs);
-
- /* Set up new TSS. */
- tos = (unsigned long)task_stack_page(p) + THREAD_SIZE;
- if (user_mode)
- childregs = (struct pt_regs*)(tos - PT_USER_SIZE);
- else
- childregs = (struct pt_regs*)tos - 1;
+ struct pt_regs *childregs = task_pt_regs(p);
- *childregs = *regs;
+#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
+ struct thread_info *ti;
+#endif
/* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
*((int*)childregs - 3) = (unsigned long)childregs;
*((int*)childregs - 4) = 0;
- childregs->areg[1] = tos;
- childregs->areg[2] = 0;
- p->set_child_tid = p->clear_child_tid = NULL;
- p->thread.ra = MAKE_RA_FOR_CALL((unsigned long)ret_from_fork, 0x1);
p->thread.sp = (unsigned long)childregs;
- if (user_mode(regs)) {
+ if (!(p->flags & PF_KTHREAD)) {
+ struct pt_regs *regs = current_pt_regs();
+ unsigned long usp = usp_thread_fn ?
+ usp_thread_fn : regs->areg[1];
- int len = childregs->wmask & ~0xf;
+ p->thread.ra = MAKE_RA_FOR_CALL(
+ (unsigned long)ret_from_fork, 0x1);
+
+ /* This does not copy all the regs.
+ * In a bout of brilliance or madness,
+ * ARs beyond a0-a15 exist past the end of the struct.
+ */
+ *childregs = *regs;
childregs->areg[1] = usp;
- memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
- ®s->areg[XCHAL_NUM_AREGS - len/4], len);
+ childregs->areg[2] = 0;
+
+ /* When sharing memory with the parent thread, the child
+ usually starts on a pristine stack, so we have to reset
+ windowbase, windowstart and wmask.
+ (Note that such a new thread is required to always create
+ an initial call4 frame)
+ The exception is vfork, where the new thread continues to
+ run on the parent's stack until it calls execve. This could
+ be a call8 or call12, which requires a legal stack frame
+ of the previous caller for the overflow handlers to work.
+ (Note that it's always legal to overflow live registers).
+ In this case, ensure to spill at least the stack pointer
+ of that frame. */
+
+ if (clone_flags & CLONE_VM) {
+ /* check that caller window is live and same stack */
+ int len = childregs->wmask & ~0xf;
+ if (regs->areg[1] == usp && len != 0) {
+ int callinc = (regs->areg[0] >> 30) & 3;
+ int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
+ put_user(regs->areg[caller_ars+1],
+ (unsigned __user*)(usp - 12));
+ }
+ childregs->wmask = 1;
+ childregs->windowstart = 1;
+ childregs->windowbase = 0;
+ } else {
+ int len = childregs->wmask & ~0xf;
+ memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
+ ®s->areg[XCHAL_NUM_AREGS - len/4], len);
+ }
// FIXME: we need to set THREADPTR in thread_info...
if (clone_flags & CLONE_SETTLS)
childregs->areg[2] = childregs->areg[6];
-
} else {
- /* In kernel space, we start a new thread with a new stack. */
- childregs->wmask = 1;
+ p->thread.ra = MAKE_RA_FOR_CALL(
+ (unsigned long)ret_from_kernel_thread, 1);
+
+ /* pass parameters to ret_from_kernel_thread:
+ * a2 = thread_fn, a3 = thread_fn arg
+ */
+ *((int *)childregs - 1) = thread_fn_arg;
+ *((int *)childregs - 2) = usp_thread_fn;
+
+ /* Childregs are only used when we're going to userspace
+ * in which case start_thread will set them up.
+ */
}
#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
void __user *child_tid, long a5,
struct pt_regs *regs)
{
- if (!newsp)
- newsp = regs->areg[1];
return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
}
-
-/*
- * xtensa_execve() executes a new program.
- */
-
-asmlinkage
-long xtensa_execve(const char __user *name,
- const char __user *const __user *argv,
- const char __user *const __user *envp,
- long a3, long a4, long a5,
- struct pt_regs *regs)
-{
- long error;
- struct filename *filename;
-
- filename = getname(name);
- error = PTR_ERR(filename);
- if (IS_ERR(filename))
- goto out;
- error = do_execve(filename->name, argv, envp, regs);
- putname(filename);
-out:
- return error;
-}
-
projects / ~andy / linux / blobdiff