Re: [PATCH v5 07/10] x86/asm/acpi: Fix asmvalidate warnings for wakeup_64.S

Pavel Machek
2015-06-10T13:19:25Z

Hi!

> Fix the following asmvalidate warnings:
>
> asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: wakeup_long64()+0x15: unsupported jump to outside of function
> asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: wakeup_long64()+0x55: unsupported jump to outside of function
> asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: wakeup_long64(): unsupported fallthrough at end of function
> asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel()+0x9a: unsupported jump to outside of function
> asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel()+0x116: unsupported jump to outside of function
> asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel(): unsupported fallthrough at end of function
> asmvalidate: arch/x86/kernel/acpi/wakeup_64.o: do_suspend_lowlevel(): missing FP_SAVE/RESTORE macros
>
> 1. wakeup_long64() isn't a function that can be called. It's actually
> redirected to via a return instruction in the entry code. It
> shouldn't be annotated as a callable function. Change ENDPROC ->
> PROC accordingly.

But I see -> END.

> 2. do_suspend_lowlevel() is a non-leaf callable function, so
> save/restore the frame pointer with FP_SAVE/RESTORE.

It does not work with the frame pointer itself. Is FP_SAVE/RESTORE
still neccessary? Will you need FP_RESTORE to wakeup_long64, then?

> 3. Remove the unnecessary jump to .Lresume_point, as it just results in
> jumping to the next instruction (which is a nop because of the
> align). Otherwise asmvalidate gets confused by the jump.

It also results in flushing the pipeline. Ok, I guess this one is unneccessary.

> 4. Change the "jmp restore_processor_state" to a call instruction,
> because jumping outside the function's boundaries isn't allowed. Now
> restore_processor_state() will return back to do_suspend_lowlevel()
> instead of do_suspend_lowlevel()'s caller.
>
> 5. Remove superfluous rsp changes.

Did you test the changes?

Do you plan to make similar changes to wakeup_32.S?

> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> index 8c35df4..7e442be 100644
> --- a/arch/x86/kernel/acpi/wakeup_64.S
> +++ b/arch/x86/kernel/acpi/wakeup_64.S
> @@ -5,6 +5,7 @@
> #include <asm/page_types.h>
> #include <asm/msr.h>
> #include <asm/asm-offsets.h>
> +#include <asm/func.h>
>
> # Copyright 2003 Pavel Machek <pavel@suse.cz>, distribute under GPLv2
>
> @@ -33,13 +34,13 @@ ENTRY(wakeup_long64)
>
> movq saved_rip, %rax
> jmp *%rax
> -ENDPROC(wakeup_long64)
> +END(wakeup_long64)
>

This should result in no binary code changes, so that's ok with me...

> ENTRY(do_suspend_lowlevel)
> - subq $8, %rsp
> + FP_SAVE
> xorl %eax, %eax
> call save_processor_state
>

Are you sure? Stuff like
movq $saved_context, %rax
movq %rsp, pt_regs_sp(%rax)

follows. And you did not modify wakeup_long64, which now receives
different value in saved_rsp.

> @@ -108,8 +108,9 @@ ENTRY(do_suspend_lowlevel)
> movq pt_regs_r15(%rax), %r15
>
> xorl %eax, %eax
> - addq $8, %rsp
> - jmp restore_processor_state
> + call restore_processor_state
> + FP_RESTORE
> + ret
> ENDPROC(do_suspend_lowlevel)

Umm. I rather liked the direct jump.

Pavel
--
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