Re: [Xen-devel] [PATCH v12 for-xen-4.5 01/20] common/symbols: Export hypervisor symbols to privileged guest

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 09/25/2014 03:28 PM, Boris Ostrovsky wrote:
> Export Xen's symbols as {<address><type><name>} triplet via new XENPF_get_symbol
> hypercall
>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Reviewed-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
> Tested-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
For the XSM parts:
Acked-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>

One comment on the patch in general (outside the XSM parts):
[...]
> diff --git a/xen/arch/x86/platform_hypercall.c 
> b/xen/arch/x86/platform_hypercall.c
> index 2162811..68bc6d9 100644
> --- a/xen/arch/x86/platform_hypercall.c
> +++ b/xen/arch/x86/platform_hypercall.c
> @@ -23,6 +23,7 @@
>   #include <xen/cpu.h>
>   #include <xen/pmstat.h>
>   #include <xen/irq.h>
> +#include <xen/symbols.h>
>   #include <asm/current.h>
>   #include <public/platform.h>
>   #include <acpi/cpufreq/processor_perf.h>
> @@ -601,6 +602,38 @@ ret_t 
> do_platform_op(XEN_GUEST_HANDLE_PARAM(xen_platform_op_t) u_xenpf_op)
>       }
>       break;
>
> +    case XENPF_get_symbol:
> +    {
> +        static char name[KSYM_NAME_LEN + 1]; /* protected by xenpf_lock */
> +        XEN_GUEST_HANDLE(char) nameh;
> +        uint32_t namelen, copylen;
> +
> +        guest_from_compat_handle(nameh, op->u.symdata.name);
> +
> +        ret = xensyms_read(&op->u.symdata.symnum, &op->u.symdata.type,
> +                           &op->u.symdata.address, name);
> +
> +        namelen = strlen(name) + 1;
> +
> +        if ( namelen > op->u.symdata.namelen )
> +        {
> +            /* Caller's buffer is too small for the whole string */
> +            if ( op->u.symdata.namelen )
> +                name[op->u.symdata.namelen] = '\0';
I don't think this assignment is needed at all: name[copylen] is never
copied to the guest and the buffer is not reused internally.

> +            copylen = op->u.symdata.namelen;
> +        }
> +        else
> +            copylen = namelen;
> +
> +        op->u.symdata.namelen = namelen;
> +
> +        if ( !ret && copy_to_guest(nameh, name, copylen) )
> +            ret = -EFAULT;
> +        if ( !ret && __copy_field_to_guest(u_xenpf_op, op, u.symdata) )
> +            ret = -EFAULT;
> +    }
> +    break;
> +
>       default:
>           ret = -ENOSYS;
>           break;
[...]

--
Daniel De Graaf
National Security Agency

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