[Qemu-devel] [PATCH] arm: Don't crash if user tries to use a Cortex-M CPU without an NVIC

[Qemu-devel] [PATCH] arm: Don't crash if user tries to use a Cortex-M CPU without an NVIC

[Peter Maydell]

The Cortex-M CPU and its NVIC are two intimately intertwined parts of
the same hardware; it is not possible to use one without the other.
Unfortunately a lot of our board models don't do any sanity checking
on the CPU type the user asks for, so a command line like
    qemu-system-arm -M versatilepb -cpu cortex-m3
will create an M3 without an NVIC, and coredump immediately.
In the other direction, trying a non-M-profile CPU in an M-profile
board won't blow up, but doesn't do anything useful either:
    qemu-system-arm -M lm3s6965evb -cpu arm926

Add some checking in the NVIC and CPU realize functions that the
user isn't trying to use an NVIC without an M-profile CPU or
an M-profile CPU without an NVIC, so we can produce a helpful
error message rather than a core dump.

Fixes: https://bugs.launchpad.net/qemu/+bug/1766896
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/arm/armv7m.c       |  7 ++++++-
 hw/intc/armv7m_nvic.c |  6 +++++-
 target/arm/cpu.c      | 18 ++++++++++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
index a4ab7d2069..9e00d4037c 100644
--- a/hw/arm/armv7m.c
+++ b/hw/arm/armv7m.c
@@ -178,6 +178,12 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
             return;
         }
     }
+
+    /* Tell the CPU where the NVIC is; it will fail realize if it doesn't
+     * have one.
+     */
+    s->cpu->env.nvic = &s->nvic;
+
     object_property_set_bool(OBJECT(s->cpu), true, "realized", &err);
     if (err != NULL) {
         error_propagate(errp, err);
@@ -202,7 +208,6 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
     sbd = SYS_BUS_DEVICE(&s->nvic);
     sysbus_connect_irq(sbd, 0,
                        qdev_get_gpio_in(DEVICE(s->cpu), ARM_CPU_IRQ));
-    s->cpu->env.nvic = &s->nvic;
 
     memory_region_add_subregion(&s->container, 0xe000e000,
                                 sysbus_mmio_get_region(sbd, 0));
diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index c51151fa8a..661be8878a 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -2183,7 +2183,11 @@ static void armv7m_nvic_realize(DeviceState *dev, Error **errp)
     int regionlen;
 
     s->cpu = ARM_CPU(qemu_get_cpu(0));
-    assert(s->cpu);
+
+    if (!s->cpu || !arm_feature(&s->cpu->env, ARM_FEATURE_M)) {
+        error_setg(errp, "The NVIC can only be used with a Cortex-M CPU");
+        return;
+    }
 
     if (s->num_irq > NVIC_MAX_IRQ) {
         error_setg(errp, "num-irq %d exceeds NVIC maximum", s->num_irq);
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 5d60893a07..eda1ce14fc 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -767,6 +767,24 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
         return;
     }
 
+#ifndef CONFIG_USER_ONLY
+    /* The NVIC and M-profile CPU are two halves of a single piece of
+     * hardware; trying to use one without the other is a command line
+     * error and will result in segfaults if not caught here.
+     */
+    if (arm_feature(env, ARM_FEATURE_M)) {
+        if (!env->nvic) {
+            error_setg(errp, "This board cannot be used with Cortex-M CPUs");
+            return;
+        }
+    } else {
+        if (env->nvic) {
+            error_setg(errp, "This board can only be used with Cortex-M CPUs");
+            return;
+        }
+    }
+#endif
+
     cpu_exec_realizefn(cs, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
-- 
2.17.1

Re: [Qemu-devel] [Qemu-arm] [PATCH] arm: Don't crash if user tries to use a Cortex-M CPU without an NVIC

[Peter Maydell]

Ping for code review?

thanks
-- PMM

On 1 June 2018 at 17:03, Peter Maydell <peter.maydell@linaro.org> wrote:
> The Cortex-M CPU and its NVIC are two intimately intertwined parts of
> the same hardware; it is not possible to use one without the other.
> Unfortunately a lot of our board models don't do any sanity checking
> on the CPU type the user asks for, so a command line like
>     qemu-system-arm -M versatilepb -cpu cortex-m3
> will create an M3 without an NVIC, and coredump immediately.
> In the other direction, trying a non-M-profile CPU in an M-profile
> board won't blow up, but doesn't do anything useful either:
>     qemu-system-arm -M lm3s6965evb -cpu arm926
>
> Add some checking in the NVIC and CPU realize functions that the
> user isn't trying to use an NVIC without an M-profile CPU or
> an M-profile CPU without an NVIC, so we can produce a helpful
> error message rather than a core dump.
>
> Fixes: https://bugs.launchpad.net/qemu/+bug/1766896
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/arm/armv7m.c       |  7 ++++++-
>  hw/intc/armv7m_nvic.c |  6 +++++-
>  target/arm/cpu.c      | 18 ++++++++++++++++++
>  3 files changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
> index a4ab7d2069..9e00d4037c 100644
> --- a/hw/arm/armv7m.c
> +++ b/hw/arm/armv7m.c
> @@ -178,6 +178,12 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
>              return;
>          }
>      }
> +
> +    /* Tell the CPU where the NVIC is; it will fail realize if it doesn't
> +     * have one.
> +     */
> +    s->cpu->env.nvic = &s->nvic;
> +
>      object_property_set_bool(OBJECT(s->cpu), true, "realized", &err);
>      if (err != NULL) {
>          error_propagate(errp, err);
> @@ -202,7 +208,6 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
>      sbd = SYS_BUS_DEVICE(&s->nvic);
>      sysbus_connect_irq(sbd, 0,
>                         qdev_get_gpio_in(DEVICE(s->cpu), ARM_CPU_IRQ));
> -    s->cpu->env.nvic = &s->nvic;
>
>      memory_region_add_subregion(&s->container, 0xe000e000,
>                                  sysbus_mmio_get_region(sbd, 0));
> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> index c51151fa8a..661be8878a 100644
> --- a/hw/intc/armv7m_nvic.c
> +++ b/hw/intc/armv7m_nvic.c
> @@ -2183,7 +2183,11 @@ static void armv7m_nvic_realize(DeviceState *dev, Error **errp)
>      int regionlen;
>
>      s->cpu = ARM_CPU(qemu_get_cpu(0));
> -    assert(s->cpu);
> +
> +    if (!s->cpu || !arm_feature(&s->cpu->env, ARM_FEATURE_M)) {
> +        error_setg(errp, "The NVIC can only be used with a Cortex-M CPU");
> +        return;
> +    }
>
>      if (s->num_irq > NVIC_MAX_IRQ) {
>          error_setg(errp, "num-irq %d exceeds NVIC maximum", s->num_irq);
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 5d60893a07..eda1ce14fc 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -767,6 +767,24 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
>          return;
>      }
>
> +#ifndef CONFIG_USER_ONLY
> +    /* The NVIC and M-profile CPU are two halves of a single piece of
> +     * hardware; trying to use one without the other is a command line
> +     * error and will result in segfaults if not caught here.
> +     */
> +    if (arm_feature(env, ARM_FEATURE_M)) {
> +        if (!env->nvic) {
> +            error_setg(errp, "This board cannot be used with Cortex-M CPUs");
> +            return;
> +        }
> +    } else {
> +        if (env->nvic) {
> +            error_setg(errp, "This board can only be used with Cortex-M CPUs");
> +            return;
> +        }
> +    }
> +#endif
> +
>      cpu_exec_realizefn(cs, &local_err);
>      if (local_err != NULL) {
>          error_propagate(errp, local_err);
> --
> 2.17.1
>
>

Re: [Qemu-devel] [Qemu-arm] [PATCH] arm: Don't crash if user tries to use a Cortex-M CPU without an NVIC

[Philippe Mathieu-Daudé]

On 06/11/2018 11:05 AM, Peter Maydell wrote:
> Ping for code review?
> 
> thanks
> -- PMM
> 
> On 1 June 2018 at 17:03, Peter Maydell <peter.maydell@linaro.org> wrote:
>> The Cortex-M CPU and its NVIC are two intimately intertwined parts of
>> the same hardware; it is not possible to use one without the other.
>> Unfortunately a lot of our board models don't do any sanity checking
>> on the CPU type the user asks for, so a command line like
>>     qemu-system-arm -M versatilepb -cpu cortex-m3
>> will create an M3 without an NVIC, and coredump immediately.
>> In the other direction, trying a non-M-profile CPU in an M-profile
>> board won't blow up, but doesn't do anything useful either:
>>     qemu-system-arm -M lm3s6965evb -cpu arm926
>>
>> Add some checking in the NVIC and CPU realize functions that the
>> user isn't trying to use an NVIC without an M-profile CPU or
>> an M-profile CPU without an NVIC, so we can produce a helpful
>> error message rather than a core dump.
>>
>> Fixes: https://bugs.launchpad.net/qemu/+bug/1766896
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>>  hw/arm/armv7m.c       |  7 ++++++-
>>  hw/intc/armv7m_nvic.c |  6 +++++-
>>  target/arm/cpu.c      | 18 ++++++++++++++++++
>>  3 files changed, 29 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
>> index a4ab7d2069..9e00d4037c 100644
>> --- a/hw/arm/armv7m.c
>> +++ b/hw/arm/armv7m.c
>> @@ -178,6 +178,12 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
>>              return;
>>          }
>>      }
>> +
>> +    /* Tell the CPU where the NVIC is; it will fail realize if it doesn't
>> +     * have one.
>> +     */
>> +    s->cpu->env.nvic = &s->nvic;
>> +
>>      object_property_set_bool(OBJECT(s->cpu), true, "realized", &err);
>>      if (err != NULL) {
>>          error_propagate(errp, err);
>> @@ -202,7 +208,6 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
>>      sbd = SYS_BUS_DEVICE(&s->nvic);
>>      sysbus_connect_irq(sbd, 0,
>>                         qdev_get_gpio_in(DEVICE(s->cpu), ARM_CPU_IRQ));
>> -    s->cpu->env.nvic = &s->nvic;
>>
>>      memory_region_add_subregion(&s->container, 0xe000e000,
>>                                  sysbus_mmio_get_region(sbd, 0));
>> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
>> index c51151fa8a..661be8878a 100644
>> --- a/hw/intc/armv7m_nvic.c
>> +++ b/hw/intc/armv7m_nvic.c
>> @@ -2183,7 +2183,11 @@ static void armv7m_nvic_realize(DeviceState *dev, Error **errp)
>>      int regionlen;
>>
>>      s->cpu = ARM_CPU(qemu_get_cpu(0));
>> -    assert(s->cpu);
>> +
>> +    if (!s->cpu || !arm_feature(&s->cpu->env, ARM_FEATURE_M)) {
>> +        error_setg(errp, "The NVIC can only be used with a Cortex-M CPU");
>> +        return;
>> +    }
>>
>>      if (s->num_irq > NVIC_MAX_IRQ) {
>>          error_setg(errp, "num-irq %d exceeds NVIC maximum", s->num_irq);
>> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
>> index 5d60893a07..eda1ce14fc 100644
>> --- a/target/arm/cpu.c
>> +++ b/target/arm/cpu.c
>> @@ -767,6 +767,24 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
>>          return;
>>      }
>>
>> +#ifndef CONFIG_USER_ONLY
>> +    /* The NVIC and M-profile CPU are two halves of a single piece of
>> +     * hardware; trying to use one without the other is a command line
>> +     * error and will result in segfaults if not caught here.
>> +     */
>> +    if (arm_feature(env, ARM_FEATURE_M)) {
>> +        if (!env->nvic) {
>> +            error_setg(errp, "This board cannot be used with Cortex-M CPUs");
>> +            return;
>> +        }
>> +    } else {
>> +        if (env->nvic) {
>> +            error_setg(errp, "This board can only be used with Cortex-M CPUs");
>> +            return;
>> +        }
>> +    }
>> +#endif
>> +
>>      cpu_exec_realizefn(cs, &local_err);
>>      if (local_err != NULL) {
>>          error_propagate(errp, local_err);
>> --
>> 2.17.1
>>
>>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Re: [Qemu-devel] [PATCH] arm: Don't crash if user tries to use a Cortex-M CPU without an NVIC

[Igor Mammedov]

On Fri,  1 Jun 2018 17:03:55 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:

> The Cortex-M CPU and its NVIC are two intimately intertwined parts of
> the same hardware; it is not possible to use one without the other.
> Unfortunately a lot of our board models don't do any sanity checking
> on the CPU type the user asks for, so a command line like
>     qemu-system-arm -M versatilepb -cpu cortex-m3
> will create an M3 without an NVIC, and coredump immediately.
> In the other direction, trying a non-M-profile CPU in an M-profile
> board won't blow up, but doesn't do anything useful either:
>     qemu-system-arm -M lm3s6965evb -cpu arm926
> 
> Add some checking in the NVIC and CPU realize functions that the
> user isn't trying to use an NVIC without an M-profile CPU or
> an M-profile CPU without an NVIC, so we can produce a helpful
> error message rather than a core dump.
> 
> Fixes: https://bugs.launchpad.net/qemu/+bug/1766896
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/arm/armv7m.c       |  7 ++++++-
>  hw/intc/armv7m_nvic.c |  6 +++++-
>  target/arm/cpu.c      | 18 ++++++++++++++++++
>  3 files changed, 29 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
> index a4ab7d2069..9e00d4037c 100644
> --- a/hw/arm/armv7m.c
> +++ b/hw/arm/armv7m.c
> @@ -178,6 +178,12 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
>              return;
>          }
>      }
> +
> +    /* Tell the CPU where the NVIC is; it will fail realize if it doesn't
> +     * have one.
> +     */
> +    s->cpu->env.nvic = &s->nvic;
> +
>      object_property_set_bool(OBJECT(s->cpu), true, "realized", &err);
>      if (err != NULL) {
>          error_propagate(errp, err);
> @@ -202,7 +208,6 @@ static void armv7m_realize(DeviceState *dev, Error **errp)
>      sbd = SYS_BUS_DEVICE(&s->nvic);
>      sysbus_connect_irq(sbd, 0,
>                         qdev_get_gpio_in(DEVICE(s->cpu), ARM_CPU_IRQ));
> -    s->cpu->env.nvic = &s->nvic;
>  
>      memory_region_add_subregion(&s->container, 0xe000e000,
>                                  sysbus_mmio_get_region(sbd, 0));
> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> index c51151fa8a..661be8878a 100644
> --- a/hw/intc/armv7m_nvic.c
> +++ b/hw/intc/armv7m_nvic.c
> @@ -2183,7 +2183,11 @@ static void armv7m_nvic_realize(DeviceState *dev, Error **errp)
>      int regionlen;
>  
>      s->cpu = ARM_CPU(qemu_get_cpu(0));
> -    assert(s->cpu);
> +
> +    if (!s->cpu || !arm_feature(&s->cpu->env, ARM_FEATURE_M)) {
> +        error_setg(errp, "The NVIC can only be used with a Cortex-M CPU");
> +        return;
> +    }
>  
>      if (s->num_irq > NVIC_MAX_IRQ) {
>          error_setg(errp, "num-irq %d exceeds NVIC maximum", s->num_irq);
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 5d60893a07..eda1ce14fc 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -767,6 +767,24 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
>          return;
>      }
>  
> +#ifndef CONFIG_USER_ONLY
> +    /* The NVIC and M-profile CPU are two halves of a single piece of
> +     * hardware; trying to use one without the other is a command line
> +     * error and will result in segfaults if not caught here.
> +     */
> +    if (arm_feature(env, ARM_FEATURE_M)) {
> +        if (!env->nvic) {
> +            error_setg(errp, "This board cannot be used with Cortex-M CPUs");
mentioning board in CPU's realize seems a little bit strange,
maybe something similar to following would be better:

  "Cortex-M CPUs require device_foo for working"

> +            return;
> +        }
> +    } else {
> +        if (env->nvic) {
> +            error_setg(errp, "This board can only be used with Cortex-M CPUs");
> +            return;
> +        }
> +    }
> +#endif
> +
>      cpu_exec_realizefn(cs, &local_err);
>      if (local_err != NULL) {
>          error_propagate(errp, local_err);

Re: [Qemu-devel] [PATCH] arm: Don't crash if user tries to use a Cortex-M CPU without an NVIC

[Peter Maydell]

On 11 June 2018 at 16:26, Igor Mammedov <imammedo@redhat.com> wrote:
> On Fri,  1 Jun 2018 17:03:55 +0100
> Peter Maydell <peter.maydell@linaro.org> wrote:
>
>> The Cortex-M CPU and its NVIC are two intimately intertwined parts of
>> the same hardware; it is not possible to use one without the other.
>> Unfortunately a lot of our board models don't do any sanity checking
>> on the CPU type the user asks for, so a command line like
>>     qemu-system-arm -M versatilepb -cpu cortex-m3
>> will create an M3 without an NVIC, and coredump immediately.
>> In the other direction, trying a non-M-profile CPU in an M-profile
>> board won't blow up, but doesn't do anything useful either:
>>     qemu-system-arm -M lm3s6965evb -cpu arm926

>> +#ifndef CONFIG_USER_ONLY
>> +    /* The NVIC and M-profile CPU are two halves of a single piece of
>> +     * hardware; trying to use one without the other is a command line
>> +     * error and will result in segfaults if not caught here.
>> +     */
>> +    if (arm_feature(env, ARM_FEATURE_M)) {
>> +        if (!env->nvic) {
>> +            error_setg(errp, "This board cannot be used with Cortex-M CPUs");
> mentioning board in CPU's realize seems a little bit strange,
> maybe something similar to following would be better:
>
>   "Cortex-M CPUs require device_foo for working"

I think the text as I have it is of more practical use to the
user, who is clearly not going to be very familiar with how
M-profile systems work if they've run into this error message.
"requires an NVIC" doesn't tell them what's actually wrong;
"this board doesn't work with this CPU" gives them a fighting
chance of understanding that they've given two incompatible
command line options.

thanks
-- PMM