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    Subject[PATCH] arm64/kernel/entry: refine comment of stack overflow check
    Date
    Stack overflow checking can be done by testing
    sp & (1 << THREAD_SHIFT)
    only for the stacks are aligned to (2 << THREAD_SHIFT) with size of
    (1 << THREAD_SIZE), and this is the case when CONFIG_VMAP_STACK is
    set.

    Fix the code comment to avoid confusion.

    Signed-off-by: Heyi Guo <guoheyi@huawei.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Will Deacon <will@kernel.org>
    ---
    arch/arm64/kernel/entry.S | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
    index cf3bd2976e57..9e8ba507090f 100644
    --- a/arch/arm64/kernel/entry.S
    +++ b/arch/arm64/kernel/entry.S
    @@ -76,7 +76,8 @@ alternative_else_nop_endif
    #ifdef CONFIG_VMAP_STACK
    /*
    * Test whether the SP has overflowed, without corrupting a GPR.
    - * Task and IRQ stacks are aligned to (1 << THREAD_SHIFT).
    + * Task and IRQ stacks are aligned to (2 << THREAD_SHIFT) with size of
    + * (1 << THREAD_SHIFT).
    */
    add sp, sp, x0 // sp' = sp + x0
    sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp
    --
    2.19.1
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