Re: [Xen-devel] [PATCH, v2] x86/xenoprof: fix kernel/user mode detection for HVM

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 15/10/2012 12:51, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> While trying oprofile under Xen, I noticed that HVM passive domain's
> kernel addresses were showing up as user application. It turns out
> under HVM get_cpu_user_regs()->cs contains 0x0000beef.
> 
> Signed-off-by: Jacob Shin <jacob.shin@xxxxxxx>
> 
> Don't cast away const-ness. Use SS instead of CS to determine ring.
> Special-case real and protected mode.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Keir Fraser <keir@xxxxxxx>

> --- a/xen/arch/x86/oprofile/xenoprof.c
> +++ b/xen/arch/x86/oprofile/xenoprof.c
> @@ -74,16 +74,26 @@ int compat_oprof_arch_counter(XEN_GUEST_
>      return 0;
>  }
>  
> -int xenoprofile_get_mode(const struct vcpu *v,
> -                         const struct cpu_user_regs *regs)
> +int xenoprofile_get_mode(struct vcpu *curr, const struct cpu_user_regs *regs)
>  {
>      if ( !guest_mode(regs) )
>          return 2;
>  
> -    if ( is_hvm_vcpu(v) )
> -        return ((regs->cs & 3) != 3);
> +    if ( !is_hvm_vcpu(curr) )
> +        return guest_kernel_mode(curr, regs);
>  
> -    return guest_kernel_mode(v, regs);
> +    switch ( hvm_guest_x86_mode(curr) )
> +    {
> +        struct segment_register ss;
> +
> +    case 0: /* real mode */
> +        return 1;
> +    case 1: /* vm86 mode */
> +        return 0;
> +    default:
> +        hvm_get_segment_register(curr, x86_seg_ss, &ss);
> +        return (ss.sel & 3) != 3;
> +    }
>  }
>  
>  /*
> --- a/xen/include/asm-x86/xenoprof.h
> +++ b/xen/include/asm-x86/xenoprof.h
> @@ -51,7 +51,7 @@ struct cpu_user_regs;
>  void ibs_init(void);
>  extern u32 ibs_caps;
>  
> -int xenoprofile_get_mode(const struct vcpu *, const struct cpu_user_regs *);
> +int xenoprofile_get_mode(struct vcpu *, const struct cpu_user_regs *);
>  
>  static inline int xenoprof_backtrace_supported(void)
>  {
> 
> 
> 
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> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel



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