Re: [Xen-devel] [PATCH v2 04/23] x86/boot: call reloc() using cdecl calling convention

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Jul 20, 2015 at 04:28:59PM +0200, Daniel Kiper wrote:
> Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

> ---
>  xen/arch/x86/boot/head.S  |    4 +++-
>  xen/arch/x86/boot/reloc.c |   20 ++++++++++++++++----
>  2 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index ed42782..3cbb2e6 100644
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -119,8 +119,10 @@ __start:
>  
>          /* Save the Multiboot info struct (after relocation) for later use. 
> */
>          mov     $sym_phys(cpu0_stack)+1024,%esp
> -        push    %ebx
> +        push    %ebx                /* Multiboot information address. */
> +        push    %eax                /* Boot trampoline address. */
>          call    reloc
> +        add     $8,%esp             /* Remove reloc() args from stack. */
>          mov     %eax,sym_phys(multiboot_ptr)
>  
>          /* Initialize BSS (no nasty surprises!). */
> diff --git a/xen/arch/x86/boot/reloc.c b/xen/arch/x86/boot/reloc.c
> index 63045c0..708898f 100644
> --- a/xen/arch/x86/boot/reloc.c
> +++ b/xen/arch/x86/boot/reloc.c
> @@ -10,15 +10,27 @@
>   *    Keir Fraser <keir@xxxxxxx>
>   */
>  
> -/* entered with %eax = BOOT_TRAMPOLINE */
> +/*
> + * This entry point is entered from xen/arch/x86/boot/head.S with:
> + *   - 0x4(%esp) = BOOT_TRAMPOLINE_ADDRESS,
> + *   - 0x8(%esp) = MULTIBOOT_INFORMATION_ADDRESS.
> + */
>  asm (
>      "    .text                         \n"
>      "    .globl _start                 \n"
>      "_start:                           \n"
> +    "    push %ebp                     \n"
> +    "    mov  %esp,%ebp                \n"
>      "    call 1f                       \n"
> -    "1:  pop  %ebx                     \n"
> -    "    mov  %eax,alloc-1b(%ebx)      \n"
> -    "    jmp  reloc                    \n"
> +    "1:  pop  %ecx                     \n"
> +    "    mov  0x8(%ebp),%eax           \n"
> +    "    mov  %eax,alloc-1b(%ecx)      \n"
> +    "    mov  0xc(%ebp),%eax           \n"
> +    "    push %eax                     \n"
> +    "    call reloc                    \n"
> +    "    add  $4,%esp                  \n"
> +    "    pop  %ebp                     \n"
> +    "    ret                           \n"
>      );
>  
>  /*
> -- 
> 1.7.10.4
> 
> 
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