summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--arch/xtensa/kernel/process.c26
1 files changed, 25 insertions, 1 deletions
diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c
index 1908f6642d31..341c151af919 100644
--- a/arch/xtensa/kernel/process.c
+++ b/arch/xtensa/kernel/process.c
@@ -220,8 +220,32 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
if (user_mode(regs)) {
childregs->areg[1] = usp;
+
+ /* 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) {
- childregs->wmask = 1; /* can't share live windows */
+ /* 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],