Re: [Qemu-devel] valgrind problem in sun4u_load_kernel()

[Artyom Tarasenko <atar4qemu@gmail.com>]

On Sun, Jun 17, 2018 at 12:22 PM, Mark Cave-Ayland
<mark.cave-ayland@ilande.co.uk> wrote:
> On 15/06/18 11:37, Thomas Huth wrote:
>
>>   Hi Mark, hi Artyom,
>>
>> while using valgrind to fix some issues with the rom_ptr() function
>> today, I noticed that there is one more problem in sun4u_load_kernel():
>> The kernel_top variable can be used uninitialized in some cases:
>> If load_elf() fails and the kernel is loaded via load_aout() or
>> load_image_targphys(), the kernel_top variable is never set to a valid
>> value. This could cause some trouble when loading the initrd later. When
>> you've got some spare time, could you please have a look?
>
>
> Hmmm that's an interesting one - I'm not immediately aware of any 64-bit
> kernels that are a.out rather than ELF, so I wonder if this has been used to
> run a.out executables on startup? Any thoughts, Artyom?

I think there are no Linux/SPARC64 kernels in the a.out format.
NetBSD should not be a problem either

> If this is the case then we can only have a valid kernel_top with an ELF
> kernel then maybe the following is a good enough solution:
>
>
> diff --git a/hw/sparc64/sun4u.c b/hw/sparc64/sun4u.c
> index 3975a7b65a..35acf8c96e 100644
> --- a/hw/sparc64/sun4u.c
> +++ b/hw/sparc64/sun4u.c
> @@ -139,7 +139,7 @@ static uint64_t sun4u_load_kernel(const char
> *kernel_filename,
>      unsigned int i;
>      long kernel_size;
>      uint8_t *ptr;
> -    uint64_t kernel_top;
> +    uint64_t kernel_top = 0;
>
>      linux_boot = (kernel_filename != NULL);
>
> @@ -172,7 +172,7 @@ static uint64_t sun4u_load_kernel(const char
> *kernel_filename,
>          }
>          /* load initrd above kernel */
>          *initrd_size = 0;
> -        if (initrd_filename) {
> +        if (initrd_filename && kernel_top) {
>              *initrd_addr = TARGET_PAGE_ALIGN(kernel_top);
>
>              *initrd_size = load_image_targphys(initrd_filename,
>
>
Looks good to me.
Acked-by: Artyom Tarasenko <atar4qemu@gmail.com>


-- 
Regards,
Artyom Tarasenko

SPARC and PPC PReP under qemu blog: http://tyom.blogspot.com/search/label/qemu