[PATCH v4 1/2] powerpc/irq: bring back ksp_limit management in C functions.

Christophe Leroy
2019-10-10T05:36:36Z

Commit cbc9565ee826 ("powerpc: Remove ksp_limit on ppc64") moved
PPC32 ksp_limit handling in assembly functions call_do_softirq()
and call_do_irq() as they are different for PPC32 and PPC64.

In preparation of replacing these functions by inline assembly,
partialy revert that commit to bring back ksp_limit assignment
in the callers.

To get and set ksp_limit without a forest of #ifdefs CONFIG_PPC32,
use helpers that will void on PPC64.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

---
v2: added forward declaration of struct task_struct to avoid build failure.
v3: included linux/sched.h, forward declaration is not enough.
v4: no change
---
arch/powerpc/include/asm/irq.h | 22 ++++++++++++++++++++++
arch/powerpc/kernel/irq.c | 14 +++++++++++++-
arch/powerpc/kernel/misc_32.S | 14 --------------
3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index 814dfab7e392..0c6469983c66 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -10,6 +10,7 @@
#include <linux/threads.h>
#include <linux/list.h>
#include <linux/radix-tree.h>
+#include <linux/sched.h>

#include <asm/types.h>
#include <linux/atomic.h>
@@ -64,5 +65,26 @@ extern void __do_irq(struct pt_regs *regs);

int irq_choose_cpu(const struct cpumask *mask);

+#ifdef CONFIG_PPC32
+static inline unsigned long get_ksp_limit(struct task_struct *tsk)
+{
+ return tsk->thread.ksp_limit;
+}
+
+static inline void set_ksp_limit(struct task_struct *tsk, unsigned long limit)
+{
+ tsk->thread.ksp_limit = limit;
+}
+#else
+static inline unsigned long get_ksp_limit(struct task_struct *tsk)
+{
+ return 0;
+}
+
+static inline void set_ksp_limit(struct task_struct *tsk, unsigned long limit)
+{
+}
+#endif
+
#endif /* _ASM_IRQ_H */
#endif /* __KERNEL__ */
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5645bc9cbc09..04204be49577 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -646,6 +646,7 @@ void do_IRQ(struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
void *cursp, *irqsp, *sirqsp;
+ unsigned long saved_ksp_limit = get_ksp_limit(current);

/* Switch to the irq stack to handle this */
cursp = (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
@@ -658,9 +659,15 @@ void do_IRQ(struct pt_regs *regs)
set_irq_regs(old_regs);
return;
}
+ /* Adjust the stack limit */
+ set_ksp_limit(current, (unsigned long)irqsp);
+
/* Switch stack and call */
call_do_irq(regs, irqsp);

+ /* Restore stack limit */
+ set_ksp_limit(current, saved_ksp_limit);
+
set_irq_regs(old_regs);
}

@@ -681,7 +688,12 @@ void *hardirq_ctx[NR_CPUS] __read_mostly;

void do_softirq_own_stack(void)
{
- call_do_softirq(softirq_ctx[smp_processor_id()]);
+ void *irqsp = softirq_ctx[smp_processor_id()];
+ unsigned long saved_ksp_limit = get_ksp_limit(current);
+
+ set_ksp_limit(current, (unsigned long)irqsp);
+ call_do_softirq(irqsp);
+ set_ksp_limit(current, saved_ksp_limit);
}

irq_hw_number_t virq_to_hw(unsigned int virq)
diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index 82df4b09e79f..a5422f7782b3 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -33,23 +33,14 @@

.text

-/*
- * We store the saved ksp_limit in the unused part
- * of the STACK_FRAME_OVERHEAD
- */
_GLOBAL(call_do_softirq)
mflr r0
stw r0,4(r1)
- lwz r10,THREAD+KSP_LIMIT(r2)
- stw r3, THREAD+KSP_LIMIT(r2)
stwu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
mr r1,r3
- stw r10,8(r1)
bl __do_softirq
- lwz r10,8(r1)
lwz r1,0(r1)
lwz r0,4(r1)
- stw r10,THREAD+KSP_LIMIT(r2)
mtlr r0
blr

@@ -59,16 +50,11 @@ _GLOBAL(call_do_softirq)
_GLOBAL(call_do_irq)
mflr r0
stw r0,4(r1)
- lwz r10,THREAD+KSP_LIMIT(r2)
- stw r4, THREAD+KSP_LIMIT(r2)
stwu r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r4)
mr r1,r4
- stw r10,8(r1)
bl __do_irq
- lwz r10,8(r1)
lwz r1,0(r1)
lwz r0,4(r1)
- stw r10,THREAD+KSP_LIMIT(r2)
mtlr r0
blr

--
2.13.3