Re: [Xen-devel] [PATCH v2 3/7] xen/arm32: entry: Add missing trap_reset entry

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 31 Jan 2018, Julien Grall wrote:
> From: Julien Grall <julien.grall@xxxxxxxxxx>
> 
> At the moment, the reset vector is defined as .word 0 (e.g andeq r0, r0,
> r0).
> 
> This is rather unintuitive and will result to execute the trap
> undefined. Instead introduce trap helpers for reset and will generate an
> error message in the unlikely case that reset will be called.
> 
> This is part of XSA-254.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>     Changes in v2:
>         - Replace .word 0 by trap_reset
> ---
>  xen/arch/arm/arm32/entry.S | 3 ++-
>  xen/arch/arm/arm32/traps.c | 5 +++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/arm32/entry.S b/xen/arch/arm/arm32/entry.S
> index c6490d2847..64876c1184 100644
> --- a/xen/arch/arm/arm32/entry.S
> +++ b/xen/arch/arm/arm32/entry.S
> @@ -137,7 +137,7 @@ trap_##trap:                                              
>               \
>  
>          .align 5
>  GLOBAL(hyp_traps_vector)
> -        .word 0                         /* 0x00 - Reset */
> +        b trap_reset                    /* 0x00 - Reset */
>          b trap_undefined_instruction    /* 0x04 - Undefined Instruction */
>          b trap_hypervisor_call          /* 0x08 - Hypervisor Call */
>          b trap_prefetch_abort           /* 0x0c - Prefetch Abort */
> @@ -146,6 +146,7 @@ GLOBAL(hyp_traps_vector)
>          b trap_irq                      /* 0x18 - IRQ */
>          b trap_fiq                      /* 0x1c - FIQ */
>  
> +DEFINE_TRAP_ENTRY(reset)
>  DEFINE_TRAP_ENTRY(undefined_instruction)
>  DEFINE_TRAP_ENTRY(hypervisor_call)
>  DEFINE_TRAP_ENTRY(prefetch_abort)
> diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
> index 705255883e..4f27543dec 100644
> --- a/xen/arch/arm/arm32/traps.c
> +++ b/xen/arch/arm/arm32/traps.c
> @@ -23,6 +23,11 @@
>  
>  #include <asm/processor.h>
>  
> +void do_trap_reset(struct cpu_user_regs *regs)
> +{
> +    do_unexpected_trap("Reset", regs);
> +}
> +
>  void do_trap_undefined_instruction(struct cpu_user_regs *regs)
>  {
>      uint32_t pc = regs->pc;
> -- 
> 2.11.0
> 

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