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Message-ID: <87pmcuw6f5.fsf@all.your.base.are.belong.to.us>
Date: Thu, 08 Dec 2022 11:12:14 +0100
From: Björn Töpel <bjorn@...nel.org>
To: guoren@...nel.org, arnd@...db.de, guoren@...nel.org,
palmer@...osinc.com, tglx@...utronix.de, peterz@...radead.org,
luto@...nel.org, conor.dooley@...rochip.com, heiko@...ech.de,
jszhang@...nel.org, lazyparser@...il.com, falcon@...ylab.org,
chenhuacai@...nel.org, apatel@...tanamicro.com,
atishp@...shpatra.org, palmer@...belt.com,
paul.walmsley@...ive.com, mark.rutland@....com,
zouyipeng@...wei.com, bigeasy@...utronix.de,
David.Laight@...lab.com, chenzhongjin@...wei.com,
greentime.hu@...ive.com, andy.chiu@...ive.com, ben@...adent.org.uk
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH -next V10 08/10] riscv: stack: Support
HAVE_IRQ_EXIT_ON_IRQ_STACK
guoren@...nel.org writes:
> From: Guo Ren <guoren@...ux.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.
>
I still would like to see this as a separate series, and that the
generic entry series ended with the previous patch. It's already a lot
of moving pieces in this series. Now add stack changes? Is this really
required for generic entry support?
Some comments below.
> Tested-by: Jisheng Zhang <jszhang@...nel.org>
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.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 518e8523d41d..0a9d4bdc0338 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -446,6 +446,14 @@ 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.
> +
Other archs uses CONFIG_IRQSTACKS. Let's use that for riscv as well, and
also use the same Kconfig wording as the other archs.
> 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");
This whole assembly thing will be C&P in later commits. Can we please do
something like x86 does here (call_on_stack --
arch/x86/include/asm/irq_stack.h), which will hurt our eyes a bit less,
and make it more maintainable?
Björn
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