Re: [Xen-devel] [PATCH 15/15] xen/arm: traps: Move the implementation of GUEST_BUG_ON in traps.h

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 16 Jul 2018, Julien Grall wrote:
> GUEST_BUG_ON may be used in other files doing guest emulation.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

Given that GUEST_BUG_ON is not actually used in any other files in this
patch series, I assume you are referring to one of your future series?


> ---
>  xen/arch/arm/traps.c        | 24 ------------------------
>  xen/include/asm-arm/traps.h | 24 ++++++++++++++++++++++++
>  2 files changed, 24 insertions(+), 24 deletions(-)
> 
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index d1bf69b245..6751e4d754 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -68,30 +68,6 @@ static inline void check_stack_alignment_constraints(void) 
> {
>  #endif
>  }
>  
> -/*
> - * GUEST_BUG_ON is intended for checking that the guest state has not been
> - * corrupted in hardware and/or that the hardware behaves as we
> - * believe it should (i.e. that certain traps can only occur when the
> - * guest is in a particular mode).
> - *
> - * The intention is to limit the damage such h/w bugs (or spec
> - * misunderstandings) can do by turning them into Denial of Service
> - * attacks instead of e.g. information leaks or privilege escalations.
> - *
> - * GUEST_BUG_ON *MUST* *NOT* be used to check for guest controllable state!
> - *
> - * Compared with regular BUG_ON it dumps the guest vcpu state instead
> - * of Xen's state.
> - */
> -#define guest_bug_on_failed(p)                          \
> -do {                                                    \
> -    show_execution_state(guest_cpu_user_regs());        \
> -    panic("Guest Bug: %pv: '%s', line %d, file %s\n",   \
> -          current, p, __LINE__, __FILE__);              \
> -} while (0)
> -#define GUEST_BUG_ON(p) \
> -    do { if ( unlikely(p) ) guest_bug_on_failed(#p); } while (0)
> -
>  #ifdef CONFIG_ARM_32
>  static int debug_stack_lines = 20;
>  #define stack_words_per_line 8
> diff --git a/xen/include/asm-arm/traps.h b/xen/include/asm-arm/traps.h
> index 70b52d1d16..0acf7de67d 100644
> --- a/xen/include/asm-arm/traps.h
> +++ b/xen/include/asm-arm/traps.h
> @@ -9,6 +9,30 @@
>  # include <asm/arm64/traps.h>
>  #endif
>  
> +/*
> + * GUEST_BUG_ON is intended for checking that the guest state has not been
> + * corrupted in hardware and/or that the hardware behaves as we
> + * believe it should (i.e. that certain traps can only occur when the
> + * guest is in a particular mode).
> + *
> + * The intention is to limit the damage such h/w bugs (or spec
> + * misunderstandings) can do by turning them into Denial of Service
> + * attacks instead of e.g. information leaks or privilege escalations.
> + *
> + * GUEST_BUG_ON *MUST* *NOT* be used to check for guest controllable state!
> + *
> + * Compared with regular BUG_ON it dumps the guest vcpu state instead
> + * of Xen's state.
> + */
> +#define guest_bug_on_failed(p)                          \
> +do {                                                    \
> +    show_execution_state(guest_cpu_user_regs());        \
> +    panic("Guest Bug: %pv: '%s', line %d, file %s\n",   \
> +          current, p, __LINE__, __FILE__);              \
> +} while (0)
> +#define GUEST_BUG_ON(p) \
> +    do { if ( unlikely(p) ) guest_bug_on_failed(#p); } while (0)
> +
>  int check_conditional_instr(struct cpu_user_regs *regs, const union hsr hsr);
>  
>  void advance_pc(struct cpu_user_regs *regs, const union hsr hsr);
> -- 
> 2.11.0
> 

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