Re: [Xen-devel] [PATCH 04/18] PVH xen: add params to read_segment_register

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.05.13 at 03:25, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> wrote:
> @@ -240,10 +240,10 @@ void do_double_fault(struct cpu_user_regs *regs)
>      crs[2] = read_cr2();
>      crs[3] = read_cr3();
>      crs[4] = read_cr4();
> -    regs->ds = read_segment_register(ds);
> -    regs->es = read_segment_register(es);
> -    regs->fs = read_segment_register(fs);
> -    regs->gs = read_segment_register(gs);
> +    regs->ds = read_segment_register(current, regs, ds);
> +    regs->es = read_segment_register(current, regs, es);
> +    regs->fs = read_segment_register(current, regs, fs);
> +    regs->gs = read_segment_register(current, regs, gs);

In patch 9 you start using the first parameter of
read_segment_register() in ways not compatible with the use of
current here - the double fault handler (and in general all host side
exception handling code, i.e. the change to show_registers() is
questionable too) wants to use the real register value, not what's
in regs->. Even more, with the VMEXIT code storing at best
a known bad value into these fields, is it really valid to use them
at all (i.e. things ought to work much like the if() portion of
show_registers() which you _do not_ modify).

Jan


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