[PATCH kvm-unit-tests] x86: fix stack pointer after call

[PATCH kvm-unit-tests] x86: fix stack pointer after call

[Paolo Bonzini]

Since setup_multiboot has a C calling convention, the stack pointer must
be adjusted after the call.  Without this change, the bottom of the
percpu area would be 4 bytes below the bottom of the stack.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 x86/cstart.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/x86/cstart.S b/x86/cstart.S
index deb08b7..409cb00 100644
--- a/x86/cstart.S
+++ b/x86/cstart.S
@@ -116,6 +116,7 @@ start:
 
         push %ebx
         call setup_multiboot
+        addl $4, %esp
         call setup_libcflat
         mov mb_cmdline(%ebx), %eax
         mov %eax, __args
-- 
2.26.2

Re: [PATCH kvm-unit-tests] x86: fix stack pointer after call

[Thomas Huth]

On 25/06/2020 13.15, Paolo Bonzini wrote:
> Since setup_multiboot has a C calling convention, the stack pointer must
> be adjusted after the call.  Without this change, the bottom of the
> percpu area would be 4 bytes below the bottom of the stack.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   x86/cstart.S | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/x86/cstart.S b/x86/cstart.S
> index deb08b7..409cb00 100644
> --- a/x86/cstart.S
> +++ b/x86/cstart.S
> @@ -116,6 +116,7 @@ start:
>   
>           push %ebx
>           call setup_multiboot
> +        addl $4, %esp
>           call setup_libcflat
>           mov mb_cmdline(%ebx), %eax
>           mov %eax, __args

Looks right.

Reviewed-by: Thomas Huth <thuth@redhat.com>