Messages in this thread | | | From | Guo Ren <> | Date | Thu, 1 Dec 2022 21:17:22 +0800 | Subject | Re: [PATCH 2/2] RISC-V: Add some comments about the shadow and overflow stacks |
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On Wed, Nov 30, 2022 at 10:35 AM Palmer Dabbelt <palmer@rivosinc.com> wrote: > > 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. > > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> > --- > arch/riscv/kernel/traps.c | 20 +++++++++++++------- > 1 file changed, 13 insertions(+), 7 deletions(-) > > diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c > index acdfcacd7e57..336d4aadadb1 100644 > --- a/arch/riscv/kernel/traps.c > +++ b/arch/riscv/kernel/traps.c > @@ -200,18 +200,18 @@ void __init trap_init(void) > } > > #ifdef CONFIG_VMAP_STACK > +/* > + * Extra stack space that allows us to provide panic messages when the kernel > + * has overflowed its stack. > + */ > static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], > overflow_stack)__aligned(16); > /* > - * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used > - * to get per-cpu overflow stack(get_overflow_stack). > + * A temporary stack for use by handle_kernel_stack_overflow. This is used so > + * we can call into C code to get the per-hart overflow stack. Usage of this > + * stack must be protected by spin_shadow_stack. Reviewed-by: Guo Ren <guoren@kernel.org>
> */ > long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16); > -asmlinkage unsigned long get_overflow_stack(void) > -{ > - return (unsigned long)this_cpu_ptr(overflow_stack) + > - OVERFLOW_STACK_SIZE; > -} > > /* > * A pseudo spinlock to protect the shadow stack from being used by multiple > @@ -222,6 +222,12 @@ asmlinkage unsigned long get_overflow_stack(void) > */ > unsigned long spin_shadow_stack; > > +asmlinkage unsigned long get_overflow_stack(void) > +{ > + return (unsigned long)this_cpu_ptr(overflow_stack) + > + OVERFLOW_STACK_SIZE; > +} > + > asmlinkage void handle_bad_stack(struct pt_regs *regs) > { > unsigned long tsk_stk = (unsigned long)current->stack; > -- > 2.38.1 >
-- Best Regards Guo Ren
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