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RISC-V: Add some comments about the shadow and overflow stacks
It took me a while to page all this back in when trying to review the recent spin_shadow_stack, so I figured I'd just write up some comments. Reviewed-by: Guo Ren <guoren@kernel.org> Reviewed-by: Jisheng Zhang <jszhang@kernel.org> Link: https://lore.kernel.org/r/20221130023515.20217-2-palmer@rivosinc.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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1 changed files with 13 additions and 7 deletions
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@ -200,18 +200,18 @@ void __init trap_init(void)
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}
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}
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#ifdef CONFIG_VMAP_STACK
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#ifdef CONFIG_VMAP_STACK
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/*
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* Extra stack space that allows us to provide panic messages when the kernel
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* has overflowed its stack.
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*/
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static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
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static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
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overflow_stack)__aligned(16);
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overflow_stack)__aligned(16);
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/*
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/*
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* shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used
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* A temporary stack for use by handle_kernel_stack_overflow. This is used so
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* to get per-cpu overflow stack(get_overflow_stack).
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* we can call into C code to get the per-hart overflow stack. Usage of this
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* stack must be protected by spin_shadow_stack.
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*/
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*/
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long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16);
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long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16);
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asmlinkage unsigned long get_overflow_stack(void)
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{
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return (unsigned long)this_cpu_ptr(overflow_stack) +
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OVERFLOW_STACK_SIZE;
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}
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/*
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/*
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* A pseudo spinlock to protect the shadow stack from being used by multiple
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* A pseudo spinlock to protect the shadow stack from being used by multiple
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@ -222,6 +222,12 @@ asmlinkage unsigned long get_overflow_stack(void)
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*/
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*/
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unsigned long spin_shadow_stack;
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unsigned long spin_shadow_stack;
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asmlinkage unsigned long get_overflow_stack(void)
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{
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return (unsigned long)this_cpu_ptr(overflow_stack) +
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OVERFLOW_STACK_SIZE;
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}
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asmlinkage void handle_bad_stack(struct pt_regs *regs)
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asmlinkage void handle_bad_stack(struct pt_regs *regs)
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{
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{
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unsigned long tsk_stk = (unsigned long)current->stack;
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unsigned long tsk_stk = (unsigned long)current->stack;
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