[PATCH V6 07/11] riscv: Support HAVE_IRQ_EXIT_ON_IRQ_STACK

[guoren@kernel.org]

From: Guo Ren <guoren@linux.alibaba.com>

Add independent irq stacks for percpu to prevent kernel stack overflows.
It is also compatible with VMAP_STACK by implementing
arch_alloc_vmap_stack.  Many architectures have supported
HAVE_IRQ_EXIT_ON_IRQ_STACK, riscv should follow up.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
---
 arch/riscv/Kconfig                   |  8 ++++
 arch/riscv/include/asm/thread_info.h |  2 +
 arch/riscv/include/asm/vmap_stack.h  | 28 ++++++++++++
 arch/riscv/kernel/irq.c              | 66 +++++++++++++++++++++++++++-
 4 files changed, 102 insertions(+), 2 deletions(-)
 create mode 100644 arch/riscv/include/asm/vmap_stack.h

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a07bb3b73b5b..75db47a983f2 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -433,6 +433,14 @@ config FPU
 
 	  If you don't know what to do here, say Y.
 
+config IRQ_STACKS
+	bool "Independent irq stacks" if EXPERT
+	default y
+	select HAVE_IRQ_EXIT_ON_IRQ_STACK
+	help
+	  Add independent irq stacks for percpu to prevent kernel stack overflows.
+	  We may save some memory footprint by disabling IRQ_STACKS.
+
 endmenu # "Platform type"
 
 menu "Kernel features"
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 7de4fb96f0b5..043da8ccc7e6 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -40,6 +40,8 @@
 #define OVERFLOW_STACK_SIZE     SZ_4K
 #define SHADOW_OVERFLOW_STACK_SIZE (1024)
 
+#define IRQ_STACK_SIZE		THREAD_SIZE
+
 #ifndef __ASSEMBLY__
 
 extern long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE / sizeof(long)];
diff --git a/arch/riscv/include/asm/vmap_stack.h b/arch/riscv/include/asm/vmap_stack.h
new file mode 100644
index 000000000000..3fbf481abf4f
--- /dev/null
+++ b/arch/riscv/include/asm/vmap_stack.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copied from arch/arm64/include/asm/vmap_stack.h.
+#ifndef _ASM_RISCV_VMAP_STACK_H
+#define _ASM_RISCV_VMAP_STACK_H
+
+#include <linux/bug.h>
+#include <linux/gfp.h>
+#include <linux/kconfig.h>
+#include <linux/vmalloc.h>
+#include <linux/pgtable.h>
+#include <asm/thread_info.h>
+
+/*
+ * To ensure that VMAP'd stack overflow detection works correctly, all VMAP'd
+ * stacks need to have the same alignment.
+ */
+static inline unsigned long *arch_alloc_vmap_stack(size_t stack_size, int node)
+{
+	void *p;
+
+	BUILD_BUG_ON(!IS_ENABLED(CONFIG_VMAP_STACK));
+
+	p = __vmalloc_node(stack_size, THREAD_ALIGN, THREADINFO_GFP, node,
+			__builtin_return_address(0));
+	return kasan_reset_tag(p);
+}
+
+#endif /* _ASM_RISCV_VMAP_STACK_H */
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 24c2e1bd756a..5d77f692b198 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -10,6 +10,37 @@
 #include <linux/irqchip.h>
 #include <linux/seq_file.h>
 #include <asm/smp.h>
+#include <asm/vmap_stack.h>
+
+#ifdef CONFIG_IRQ_STACKS
+static DEFINE_PER_CPU(ulong *, irq_stack_ptr);
+
+#ifdef CONFIG_VMAP_STACK
+static void init_irq_stacks(void)
+{
+	int cpu;
+	ulong *p;
+
+	for_each_possible_cpu(cpu) {
+		p = arch_alloc_vmap_stack(IRQ_STACK_SIZE, cpu_to_node(cpu));
+		per_cpu(irq_stack_ptr, cpu) = p;
+	}
+}
+#else
+/* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned. */
+DEFINE_PER_CPU_ALIGNED(ulong [IRQ_STACK_SIZE/sizeof(ulong)], irq_stack);
+
+static void init_irq_stacks(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		per_cpu(irq_stack_ptr, cpu) = per_cpu(irq_stack, cpu);
+}
+#endif /* CONFIG_VMAP_STACK */
+#else
+static void init_irq_stacks(void) {}
+#endif /* CONFIG_IRQ_STACKS */
 
 int arch_show_interrupts(struct seq_file *p, int prec)
 {
@@ -19,21 +50,52 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 
 void __init init_IRQ(void)
 {
+	init_irq_stacks();
 	irqchip_init();
 	if (!handle_arch_irq)
 		panic("No interrupt controller found.");
 }
 
-asmlinkage void noinstr do_riscv_irq(struct pt_regs *regs)
+static void noinstr handle_riscv_irq(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs;
-	irqentry_state_t state = irqentry_enter(regs);
 
 	irq_enter_rcu();
 	old_regs = set_irq_regs(regs);
 	handle_arch_irq(regs);
 	set_irq_regs(old_regs);
 	irq_exit_rcu();
+}
+
+asmlinkage void noinstr do_riscv_irq(struct pt_regs *regs)
+{
+	irqentry_state_t state = irqentry_enter(regs);
+#ifdef CONFIG_IRQ_STACKS
+	if (on_thread_stack()) {
+		ulong *sp = per_cpu(irq_stack_ptr, smp_processor_id())
+					+ IRQ_STACK_SIZE/sizeof(ulong);
+		__asm__ __volatile(
+		"addi	sp, sp, -"RISCV_SZPTR  "\n"
+		REG_S"  ra, (sp)		\n"
+		"addi	sp, sp, -"RISCV_SZPTR  "\n"
+		REG_S"  s0, (sp)		\n"
+		"addi	s0, sp, 2*"RISCV_SZPTR "\n"
+		"move	sp, %[sp]		\n"
+		"move	a0, %[regs]		\n"
+		"call	handle_riscv_irq	\n"
+		"addi	sp, s0, -2*"RISCV_SZPTR"\n"
+		REG_L"  s0, (sp)		\n"
+		"addi	sp, sp, "RISCV_SZPTR   "\n"
+		REG_L"  ra, (sp)		\n"
+		"addi	sp, sp, "RISCV_SZPTR   "\n"
+		:
+		: [sp] "r" (sp), [regs] "r" (regs)
+		: "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
+		  "t0", "t1", "t2", "t3", "t4", "t5", "t6",
+		  "memory");
+	} else
+#endif
+		handle_riscv_irq(regs);
 
 	irqentry_exit(regs, state);
 }
-- 
2.36.1