[PATCH AUTOSEL 6.0 18/46] arm64: run softirqs on the per-CPU IRQ stack

Sasha Levin
2022-10-11T14:51:48Z

From: Qi Zheng <zhengqi.arch@bytedance.com>

[ Upstream commit 8eb858c44b98e0326bb32fca34ae671995cd73bb ]

Currently arm64 supports per-CPU IRQ stack, but softirqs
are still handled in the task context.

Since any call to local_bh_enable() at any level in the task's
call stack may trigger a softirq processing run, which could
potentially cause a task stack overflow if the combined stack
footprints exceed the stack's size, let's run these softirqs
on the IRQ stack as well.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220815124739.15948-1-zhengqi.arch@bytedance.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/irq.c | 14 ++++++++++++++
2 files changed, 15 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1ce7685ad5de..68ee7146bdb9 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -230,6 +230,7 @@ config ARM64
select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
select TRACE_IRQFLAGS_SUPPORT
select TRACE_IRQFLAGS_NMI_SUPPORT
+ select HAVE_SOFTIRQ_ON_OWN_STACK
help
ARM 64-bit (AArch64) Linux support.

diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index bda49430c9ea..38dbd3828f13 100644
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -21,7 +21,9 @@
#include <linux/seq_file.h>
#include <linux/vmalloc.h>
#include <asm/daifflags.h>
+#include <asm/exception.h>
#include <asm/vmap_stack.h>
+#include <asm/softirq_stack.h>

/* Only access this in an NMI enter/exit */
DEFINE_PER_CPU(struct nmi_ctx, nmi_contexts);
@@ -71,6 +73,18 @@ static void init_irq_stacks(void)
}
#endif

+#ifndef CONFIG_PREEMPT_RT
+static void ____do_softirq(struct pt_regs *regs)
+{
+ __do_softirq();
+}
+
+void do_softirq_own_stack(void)
+{
+ call_on_irq_stack(NULL, ____do_softirq);
+}
+#endif
+
static void default_handle_irq(struct pt_regs *regs)
{
panic("IRQ taken without a root IRQ handler\n");
--
2.35.1