[PATCH v2 1/3] powerpc/irq: don't use current_stack_pointer() in check_stack_overflow()

[PATCH v2 1/3] powerpc/irq: don't use current_stack_pointer() in check_stack_overflow()

[Christophe Leroy]

current_stack_pointer() doesn't return the stack pointer, but the
caller's stack frame. See commit bfe9a2cfe91a ("powerpc: Reimplement
__get_SP() as a function not a define") and commit acf620ecf56c
("powerpc: Rename __get_SP() to current_stack_pointer()") for details.

The purpose of check_stack_overflow() is to verify that the stack has
not overflowed.

To really know whether the stack pointer is still within boundaries,
the check must be done directly on the value of r1.

Define a get_sp() macro to get the value of r1 directly. (Adapted from
arch/powerpc/boot/reg.h)

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
v2: Define a get_sp() macro instead of using asm("r1") locally.
---
 arch/powerpc/include/asm/reg.h | 3 +++
 arch/powerpc/kernel/irq.c      | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 1aa46dff0957..d585f2566338 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1450,6 +1450,9 @@ static inline void mtsrin(u32 val, u32 idx)
 
 extern unsigned long current_stack_pointer(void);
 
+register unsigned long __stack_pointer asm("r1");
+#define get_sp()	(__stack_pointer)
+
 extern unsigned long scom970_read(unsigned int address);
 extern void scom970_write(unsigned int address, unsigned long value);
 
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index add67498c126..cd29c2eb2d8e 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -601,7 +601,7 @@ static inline void check_stack_overflow(void)
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
 	long sp;
 
-	sp = current_stack_pointer() & (THREAD_SIZE-1);
+	sp = get_sp() & (THREAD_SIZE - 1);
 
 	/* check for stack overflow: is there less than 2KB free? */
 	if (unlikely(sp < 2048)) {
-- 
2.25.0

[PATCH v2 2/3] powerpc/irq: use IS_ENABLED() in check_stack_overflow()

[Christophe Leroy]

Instead of #ifdef, use IS_ENABLED(CONFIG_DEBUG_STACKOVERFLOW).
This enable GCC to check for code validity even when the option
is not selected.
---
v2: rebased

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/irq.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index cd29c2eb2d8e..9333e115418f 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -598,9 +598,11 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
 
 static inline void check_stack_overflow(void)
 {
-#ifdef CONFIG_DEBUG_STACKOVERFLOW
 	long sp;
 
+	if (!IS_ENABLED(CONFIG_DEBUG_STACKOVERFLOW))
+		return;
+
 	sp = get_sp() & (THREAD_SIZE - 1);
 
 	/* check for stack overflow: is there less than 2KB free? */
@@ -608,7 +610,6 @@ static inline void check_stack_overflow(void)
 		pr_err("do_IRQ: stack overflow: %ld\n", sp);
 		dump_stack();
 	}
-#endif
 }
 
 void __do_irq(struct pt_regs *regs)
-- 
2.25.0

[PATCH v2 3/3] powerpc/irq: don't use current_stack_pointer() in do_IRQ()

[Christophe Leroy]

Until commit 7306e83ccf5c ("powerpc: Don't use CURRENT_THREAD_INFO to
find the stack"), the current stack base address was obtained by
calling current_thread_info(). That inline function was simply masking
out the value of r1.

In that commit, it was changed to using current_stack_pointer(), which
is an heavier function as it is an outline assembly function which
cannot be inlined and which reads the content of the stack at 0(r1)

Revert to just using get_sp() for geting r1 and masking out its value
to obtain the base address of the stack pointer as before.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Fixes: 7306e83ccf5c ("powerpc: Don't use CURRENT_THREAD_INFO to find the stack")
---
v2: New in this series. Using get_sp()
---
 arch/powerpc/kernel/irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 9333e115418f..193c2b64ce37 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -647,7 +647,7 @@ void do_IRQ(struct pt_regs *regs)
 	void *cursp, *irqsp, *sirqsp;
 
 	/* Switch to the irq stack to handle this */
-	cursp = (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1));
+	cursp = (void *)(get_sp() & ~(THREAD_SIZE - 1));
 	irqsp = hardirq_ctx[raw_smp_processor_id()];
 	sirqsp = softirq_ctx[raw_smp_processor_id()];
 
-- 
2.25.0