Re: [Xen-devel] [PATCH v3.1 13/15] xen/x86: parse Dom0 kernel for PVHv2

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

On Sat, Oct 29, 2016 at 10:59:59AM +0200, Roger Pau Monne wrote:
> Introduce a helper to parse the Dom0 kernel.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> Changes since v2:
>  - Remove debug messages.
>  - Don't hardcode the number of modules to 1.
> ---
>  xen/arch/x86/domain_build.c | 138 
> ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 138 insertions(+)
> 
> diff --git a/xen/arch/x86/domain_build.c b/xen/arch/x86/domain_build.c
> index ec1ac89..168be62 100644
> --- a/xen/arch/x86/domain_build.c
> +++ b/xen/arch/x86/domain_build.c
> @@ -39,6 +39,7 @@
>  #include <asm/hpet.h>
>  
>  #include <public/version.h>
> +#include <public/arch-x86/hvm/start_info.h>
>  
>  static long __initdata dom0_nrpages;
>  static long __initdata dom0_min_nrpages;
> @@ -1895,12 +1896,141 @@ static int __init hvm_setup_p2m(struct domain *d)
>      return 0;
>  }
>  
> +static int __init hvm_load_kernel(struct domain *d, const module_t *image,
> +                                  unsigned long image_headroom,
> +                                  module_t *initrd, char *image_base,
> +                                  char *cmdline, paddr_t *entry,
> +                                  paddr_t *start_info_addr)
> +{
> +    char *image_start = image_base + image_headroom;
> +    unsigned long image_len = image->mod_end;
> +    struct elf_binary elf;
> +    struct elf_dom_parms parms;
> +    paddr_t last_addr;
> +    struct hvm_start_info start_info;
> +    struct hvm_modlist_entry mod;
> +    struct vcpu *saved_current, *v = d->vcpu[0];
> +    int rc;
> +
> +    if ( (rc = bzimage_parse(image_base, &image_start, &image_len)) != 0 )
> +    {
> +        printk("Error trying to detect bz compressed kernel\n");
> +        return rc;
> +    }
> +
> +    if ( (rc = elf_init(&elf, image_start, image_len)) != 0 )
> +    {
> +        printk("Unable to init ELF\n");
> +        return rc;
> +    }
> +#ifdef VERBOSE
> +    elf_set_verbose(&elf);
> +#endif
> +    elf_parse_binary(&elf);
> +    if ( (rc = elf_xen_parse(&elf, &parms)) != 0 )
> +    {
> +        printk("Unable to parse kernel for ELFNOTES\n");

Perhaps s/ELFNOTES/PT_NOTEs/?
> +        return rc;
> +    }
> +
> +    if ( parms.phys_entry == UNSET_ADDR32 ) {
> +        printk("Unable to find kernel entry point, aborting\n");

Perhaps: Unable to find XEN_ELFNOTE_PHYS32_ENTRY point.

> +        return -EINVAL;
> +    }
> +
> +    printk("OS: %s version: %s loader: %s bitness: %s\n", parms.guest_os,
> +           parms.guest_ver, parms.loader,

Hm, I don't know if XEN_ELFNOTE_GUEST_VERSION or XEN_ELFNOTE_GUEST_OS
are mandated.

Perhaps you should do memset(&params) before you pass it to elf_xen_parse?

> +           elf_64bit(&elf) ? "64-bit" : "32-bit");
> +
> +    /* Copy the OS image and free temporary buffer. */
> +    elf.dest_base = (void *)(parms.virt_kstart - parms.virt_base);
> +    elf.dest_size = parms.virt_kend - parms.virt_kstart;
> +
> +    saved_current = current;
> +    set_current(v);
> +
> +    rc = elf_load_binary(&elf);
> +    if ( rc < 0 )
> +    {
> +        printk("Failed to load kernel: %d\n", rc);
> +        printk("Xen dom0 kernel broken ELF: %s\n", elf_check_broken(&elf));
> +        goto out;
> +    }
> +
> +    last_addr = ROUNDUP(parms.virt_kend - parms.virt_base, PAGE_SIZE);
> +
> +    if ( initrd != NULL )
> +    {
> +        rc = hvm_copy_to_guest_phys(last_addr, 
> mfn_to_virt(initrd->mod_start),
> +                                    initrd->mod_end);
> +        if ( rc != HVMCOPY_okay )
> +        {
> +            printk("Unable to copy initrd to guest\n");
> +            rc = -EFAULT;
> +            goto out;
> +        }
> +
> +        mod.paddr = last_addr;
> +        mod.size = initrd->mod_end;
> +        last_addr += ROUNDUP(initrd->mod_end, PAGE_SIZE);
> +    }
> +
> +    /* Free temporary buffers. */
> +    discard_initial_images();
> +
> +    memset(&start_info, 0, sizeof(start_info));
> +    if ( cmdline != NULL )
> +    {
> +        rc = hvm_copy_to_guest_phys(last_addr, cmdline, strlen(cmdline) + 1);
> +        if ( rc != HVMCOPY_okay )
> +        {
> +            printk("Unable to copy guest command line\n");
> +            rc = -EFAULT;
> +            goto out;
> +        }
> +        start_info.cmdline_paddr = last_addr;
> +        last_addr += ROUNDUP(strlen(cmdline) + 1, 8);
> +    }
> +    if ( initrd != NULL )

It may be better if this is an array. You can have multiple initrd's.

> +    {
> +        rc = hvm_copy_to_guest_phys(last_addr, &mod, sizeof(mod));
> +        if ( rc != HVMCOPY_okay )
> +        {
> +            printk("Unable to copy guest modules\n");
> +            rc = -EFAULT;
> +            goto out;
> +        }
> +        start_info.modlist_paddr = last_addr;
> +        start_info.nr_modules = 1;
> +        last_addr += sizeof(mod);
> +    }
> +
> +    start_info.magic = XEN_HVM_START_MAGIC_VALUE;
> +    start_info.flags = SIF_PRIVILEGED | SIF_INITDOMAIN;
> +    rc = hvm_copy_to_guest_phys(last_addr, &start_info, sizeof(start_info));
> +    if ( rc != HVMCOPY_okay )
> +    {
> +        printk("Unable to copy start info to guest\n");
> +        rc = -EFAULT;
> +        goto out;
> +    }
> +
> +    *entry = parms.phys_entry;
> +    *start_info_addr = last_addr;
> +    rc = 0;
> +
> +out:

Extra space in front of the label.
> +    set_current(saved_current);
> +    return rc;
> +}
> +

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