For ppc64, it's not sufficient to merely align the stack pointer
(clone_args->child_stack); we must also set up a stack frame (48
bytes). Encapsulate the stack setup details in a helper function
(stack_setup_frame) which makes appropriate adjustments.
Although the genstack implementation provides zeroed stack pages, it's
best not to rely on that implementation detail, so explicitly zero the
back chain pointer in stack_setup_frame as well.
Signed-off-by: Nathan Lynch <ntl@xxxxxxxxx>
---
clone_ppc.c | 26 ++++++++++++++++++--------
1 files changed, 18 insertions(+), 8 deletions(-)
diff --git a/clone_ppc.c b/clone_ppc.c
index f047a9e..2d8b0f8 100644
--- a/clone_ppc.c
+++ b/clone_ppc.c
@@ -31,6 +31,22 @@ extern int __eclone(int (*fn)(void *arg),
size_t args_size,
pid_t *pids);
+#ifdef __powerpc64__
+#define MIN_STACK_FRAME 48
+#else
+#define MIN_STACK_FRAME 16
+#endif
+
+static unsigned long stack_setup_frame(unsigned long base, unsigned long size)
+{
+ unsigned long *sp;
+
+ sp = (unsigned long *)(((base + size - 1) & ~0xf) - MIN_STACK_FRAME);
+ *sp = 0;
+
+ return (unsigned long)sp;
+}
+
int eclone(int (*fn)(void *), void *fn_arg, int clone_flags_low,
struct clone_args *clone_args, pid_t *pids)
{
@@ -38,15 +54,9 @@ int eclone(int (*fn)(void *), void *fn_arg, int clone_flags_low,
unsigned long child_sp;
int newpid;
- /* The stack pointer for the child is communicated to the
- * kernel via clone_args.child_stack, and to the __eclone
- * assembly wrapper via the child_sp argument [r4]. So we
- * need to align child_sp here and ensure that the wrapper and
- * the kernel receive the same value.
- */
if (clone_args->child_stack)
- child_sp = (clone_args->child_stack +
- clone_args->child_stack_size - 1) & ~0xf;
+ child_sp = stack_setup_frame(clone_args->child_stack,
+ clone_args->child_stack_size);
else
child_sp = 0;
--
1.6.0.6
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