Re: [PATCH v1 5/5] xsplice: Use ld-embedded build-ids

["Jan Beulich" <JBeulich@suse.com>]

>>> On 16.09.15 at 23:01, <konrad.wilk@oracle.com> wrote:
> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -108,11 +108,11 @@ $(TARGET)-syms: prelink.o xen.lds $(BASEDIR)/common/symbols-dummy.o
>  	    $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
>  	$(NM) -n $(@D)/.$(@F).0 | $(BASEDIR)/tools/symbols >$(@D)/.$(@F).0.S
>  	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0.o
> -	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
> +	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o --build-id=sha1 \
>  	    $(@D)/.$(@F).0.o -o $(@D)/.$(@F).1
>  	$(NM) -n $(@D)/.$(@F).1 | $(BASEDIR)/tools/symbols >$(@D)/.$(@F).1.S
>  	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1.o
> -	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
> +	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o --build-id=sha1 \
>  	    $(@D)/.$(@F).1.o -o $@
>  	rm -f $(@D)/.$(@F).[0-9]*

Which raises the question: What about xen.efi?

> @@ -44,6 +46,36 @@ struct payload {
>      struct tasklet tasklet;
>  };
>  
> +#ifdef CONFIG_ARM
> +static int build_id(char **p, unsigned int *len)
> +{
> +    return 0;
> +}
> +#else

Any reason not to make the build logic common, in order to avoid such
#ifdef-ery?


> +extern char * __note_gnu_build_id_start;  /* defined in linker script */

const, and I think you mean the type to be Elf_Note[].

> @@ -68,9 +100,31 @@ static const char *status2str(int64_t status)
>      return names[status];
>  }
>  
> +#define LEN 128

Because of?

>  void xsplice_printall(unsigned char key)
>  {
>      struct payload *data;
> +    char *binary_id = NULL;
> +    unsigned int len = 0;
> +    int rc;
> +
> +    rc = build_id(&binary_id, &len);
> +    printk("build-id: ");
> +    if ( !rc )
> +    {
> +        unsigned int i;
> +
> +        if ( len > LEN )
> +            len = LEN;
> +
> +        for ( i = 0; i < len; i++ )
> +        {
> +		    uint8_t c = binary_id[i];
> +		    printk("%02x", c);

Hard tabs.

> +        }
> +	    printk("\n");
> +    } else if ( rc < 0 )

Coding style.

> @@ -415,6 +470,34 @@ static int xsplice_action(xen_sysctl_xsplice_action_t *action)
>      return rc;
>  }
>  
> +static int xsplice_info(xen_sysctl_xsplice_info_t *info)
> +{
> +    int rc;
> +    unsigned int len = 0;
> +    char *p = NULL;
> +
> +    if ( info->cmd != XEN_SYSCTL_XSPLICE_INFO_BUILD_ID )
> +        return -EINVAL;
> +
> +    if ( info->size == 0 )
> +        return -EINVAL;
> +
> +    if ( !guest_handle_okay(info->u.info, info->size) )
> +        return -EFAULT;
> +
> +    rc = build_id(&p, &len);
> +    if ( rc )
> +        return rc;
> +
> +    if ( len > info->size )
> +        return -ENOMEM;
> +
> +    if ( copy_to_guest(info->u.info, p, len) )
> +        return -EFAULT;

So how does the caller know how much data got copied?

Jan