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

Message ID 20180131165334.23175-4-julien.grall@arm.com
State Superseded
Headers show
Series
  • xen/arm32: Branch predictor hardening (XSA-254 variant 2)
Related show

Commit Message

Julien Grall Jan. 31, 2018, 4:53 p.m.
From: Julien Grall <julien.grall@linaro.org>

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@linaro.org>

---
    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(-)

Comments

Stefano Stabellini Jan. 31, 2018, 5:29 p.m. | #1
On Wed, 31 Jan 2018, Julien Grall wrote:
> From: Julien Grall <julien.grall@linaro.org>
> 
> 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@linaro.org>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>     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
>

Patch

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;