[PATCH V4 6/8] riscv: Support HAVE_IRQ_EXIT_ON_IRQ_STACK

guoren
2022-09-08T02:26:46Z

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/irq.h | 3 ++
arch/riscv/include/asm/thread_info.h | 2 ++
arch/riscv/include/asm/vmap_stack.h | 28 ++++++++++++++++
arch/riscv/kernel/entry.S | 27 ++++++++++++++++
arch/riscv/kernel/irq.c | 48 ++++++++++++++++++++++++++--
6 files changed, 114 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..a8a12b4ba1a9 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"
+ 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/irq.h b/arch/riscv/include/asm/irq.h
index e4c435509983..205e1c693dfd 100644
--- a/arch/riscv/include/asm/irq.h
+++ b/arch/riscv/include/asm/irq.h
@@ -13,5 +13,8 @@
#include <asm-generic/irq.h>

extern void __init init_IRQ(void);
+asmlinkage void call_on_stack(struct pt_regs *regs, ulong *sp,
+ void (*fn)(struct pt_regs *), ulong tmp);
+asmlinkage void noinstr do_riscv_irq(struct pt_regs *regs);

#endif /* _ASM_RISCV_IRQ_H */
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/entry.S b/arch/riscv/kernel/entry.S
index 5f49517cd3a2..426529b84db0 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -332,6 +332,33 @@ ENTRY(ret_from_kernel_thread)
tail syscall_exit_to_user_mode
ENDPROC(ret_from_kernel_thread)

+#ifdef CONFIG_IRQ_STACKS
+ENTRY(call_on_stack)
+ /* Create a frame record to save our ra and fp */
+ addi sp, sp, -RISCV_SZPTR
+ REG_S ra, (sp)
+ addi sp, sp, -RISCV_SZPTR
+ REG_S fp, (sp)
+
+ /* Save sp in fp */
+ move fp, sp
+
+ /* Move to the new stack and call the function there */
+ li a3, IRQ_STACK_SIZE
+ add sp, a1, a3
+ jalr a2
+
+ /*
+ * Restore sp from prev fp, and fp, ra from the frame
+ */
+ move sp, fp
+ REG_L fp, (sp)
+ addi sp, sp, RISCV_SZPTR
+ REG_L ra, (sp)
+ addi sp, sp, RISCV_SZPTR
+ ret
+ENDPROC(call_on_stack)
+#endif

/*
* Integer register context switch
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index 24c2e1bd756a..5ad4952203c5 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 +50,34 @@ 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
+ ulong *sp = per_cpu(irq_stack_ptr, smp_processor_id());
+
+ if (on_thread_stack())
+ call_on_stack(regs, sp, handle_riscv_irq, 0);
+ else
+#endif
+ handle_riscv_irq(regs);

irqentry_exit(regs, state);
}
--
2.36.1