diff options
Diffstat (limited to 'arch/xtensa/kernel/process.c')
-rw-r--r-- | arch/xtensa/kernel/process.c | 147 |
1 files changed, 90 insertions, 57 deletions
diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c index bc020825cce..09ae7bfab9a 100644 --- a/arch/xtensa/kernel/process.c +++ b/arch/xtensa/kernel/process.c @@ -45,6 +45,7 @@ #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, }; @@ -158,64 +159,123 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) /* * 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) @@ -311,32 +371,5 @@ long xtensa_clone(unsigned long clone_flags, unsigned long newsp, 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; -} - |