commit 152d523e6307 ("powerpc: Create context switch helpers save_sprs()
and restore_sprs()") has an issue with newly created processes and
kernel threads. These do not call back through __switch_to(), instead
returning straight to ret_from_fork() or ret_from_kernel_thread().
This means restore_sprs() is not getting called. Add a call to it
in ret_from_fork() and ret_from_kernel_thread().
Signed-off-by: Anton Blanchard <an...@samba.org>
Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and
restore_sprs()")
---
arch/powerpc/kernel/entry_32.S | 20 ++++++++++++++++++++
arch/powerpc/kernel/entry_64.S | 20 ++++++++++++++++++++
arch/powerpc/kernel/process.c | 19 ++++++++++++-------
3 files changed, 52 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 2405631..64802a1 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -423,6 +423,16 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
.globl ret_from_fork
ret_from_fork:
REST_NVGPRS(r1)
+ /*
+ * The first context switch for a process doesn't return through
+ * __switch_to(), so we need to call restore_sprs() here.
+ */
+ mr r4,r2
+ bl restore_sprs
+ /*
+ * restore_sprs() returns a pointer to the previous task struct,
+ * which is what schedule_tail() expects to be passed.
+ */
bl schedule_tail
li r3,0
b ret_from_syscall
@@ -430,6 +440,16 @@ ret_from_fork:
.globl ret_from_kernel_thread
ret_from_kernel_thread:
REST_NVGPRS(r1)
+ /*
+ * The first context switch for a kernel thread doesn't return through
+ * __switch_to(), so we need to call restore_sprs() here.
+ */
+ mr r4,r2
+ bl restore_sprs
+ /*
+ * restore_sprs() returns a pointer to the previous task struct,
+ * which is what schedule_tail() expects to be passed.
+ */
bl schedule_tail
mtlr r14
mr r3,r15
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index c8b4225..a21a861 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -409,12 +409,32 @@ _GLOBAL(ppc_switch_endian)
b .Lsyscall_exit
_GLOBAL(ret_from_fork)
+ /*
+ * The first context switch for a process doesn't return through
+ * __switch_to(), so we need to call restore_sprs() here.
+ */
+ ld r4,PACACURRENT(r13)
+ bl restore_sprs
+ /*
+ * restore_sprs() returns a pointer to the previous task struct,
+ * which is what schedule_tail() expects to be passed.
+ */
bl schedule_tail
REST_NVGPRS(r1)
li r3,0
b .Lsyscall_exit
_GLOBAL(ret_from_kernel_thread)
+ /*
+ * The first context switch for a kernel thread doesn't return through
+ * __switch_to(), so we need to call restore_sprs() here.
+ */
+ ld r4,PACACURRENT(r13)
+ bl restore_sprs
+ /*
+ * restore_sprs() returns a pointer to the previous task struct,
+ * which is what schedule_tail() expects to be passed.
+ */
bl schedule_tail
REST_NVGPRS(r1)
mtlr r14
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 73d5ac0..ec10250 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -854,9 +854,12 @@ static inline void save_sprs(struct thread_struct *t)
#endif
}
-static inline void restore_sprs(struct thread_struct *old_thread,
- struct thread_struct *new_thread)
+struct task_struct *restore_sprs(struct task_struct *old,
+ struct task_struct *new)
{
+ struct thread_struct *old_thread = &old->thread;
+ struct thread_struct *new_thread = &new->thread;
+
#ifdef CONFIG_ALTIVEC
if (cpu_has_feature(CPU_FTR_ALTIVEC) &&
old_thread->vrsave != new_thread->vrsave)
@@ -891,6 +894,12 @@ static inline void restore_sprs(struct thread_struct
*old_thread,
mtspr(SPRN_TAR, new_thread->tar);
}
#endif
+
+ /*
+ * ret_from_fork and ret_from_kernel_thread expect us to
+ * return a pointer to the previous task struct.
+ */
+ return old;
}
struct task_struct *__switch_to(struct task_struct *prev,
@@ -966,11 +975,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
last = _switch(old_thread, new_thread);
- /* Need to recalculate these after calling _switch() */
- old_thread = &last->thread;
- new_thread = ¤t->thread;
-
- restore_sprs(old_thread, new_thread);
+ restore_sprs(last, current);
#ifdef CONFIG_PPC_BOOK3S_64
if (current_thread_info()->local_flags & _TLF_LAZY_MMU) {
--
2.5.0
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