diff options
Diffstat (limited to 'arch/xtensa/kernel/process.c')
| -rw-r--r-- | arch/xtensa/kernel/process.c | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c index bc020825cce5..7901ee76b9be 100644 --- a/arch/xtensa/kernel/process.c +++ b/arch/xtensa/kernel/process.c @@ -173,6 +173,16 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) * * 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, @@ -191,13 +201,14 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, else childregs = (struct pt_regs*)tos - 1; + /* 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; /* 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); @@ -205,10 +216,14 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, if (user_mode(regs)) { - int len = childregs->wmask & ~0xf; childregs->areg[1] = usp; - memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4], - ®s->areg[XCHAL_NUM_AREGS - len/4], len); + if (clone_flags & CLONE_VM) { + childregs->wmask = 1; /* can't share live windows */ + } 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]; @@ -216,6 +231,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, } else { /* In kernel space, we start a new thread with a new stack. */ childregs->wmask = 1; + childregs->areg[1] = tos; } #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS) |