On Fri, Jul 12, 2024, flyingpenghao@xxxxxxxxx wrote:
> From: Peng Hao <flyingpeng@xxxxxxxxxxx>
>
> When KASAN is enabled and built with clang:
> clang report
> arch/x86/kvm/emulate.c:3022:5: error: stack frame size (2488) exceeds limit (2048) in 'emulator_task_switch' [-Werror,-Wframe-larger-than]
> int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
> ^
>
> since emulator_do_task_switch() consumes a lot of stack space, mark it as
> noinline_for_stack to prevent it from blowing up emulator_task_switch()'s
> stack size.
No, sprinkling noinline to combat KASAN stack frame sizes is not a maintainable
approach. Practically speaking, KASAN + -Werror + FRAME_WARN=2048 is not a sane
config.
> Signed-off-by: Peng Hao <flyingpeng@xxxxxxxxxxx>
> ---
> arch/x86/kvm/emulate.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 5d4c86133453..bbc185b9725d 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2918,7 +2918,7 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt, u16 old_tss_sel,
> return load_state_from_tss32(ctxt, &tss_seg);
> }
>
> -static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
> +static noinline_for_stack int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
> u16 tss_selector, int idt_index, int reason,
> bool has_error_code, u32 error_code)
> {
> --
> 2.27.0
>
