[Qemu-devel] [PATCH 00/20] ARM v8M: exception entry, exit and security

[Qemu-devel] [PATCH 00/20] ARM v8M: exception entry, exit and security

[Peter Maydell]

Another week, another set of v8M patches.
This lot adds:
 * v8M and security extension changes in exception entry and exit
 * the Security Attribution Unit
 * SG and BLXNS instructions
 * secure function return
 * and a couple of fixes for bugs in already-in-master changes

Most of this is just plodding through fairly obvious implementation,
but the handling of the SG instruction is a bit funky (see commit
messages in those patches for detail).

This is very nearly enough to get the mbed uvisor example
running (on a hacked-up mps2 setup): I think the main missing
piece for that is that it expects the banked systick device,
which we haven't implemented yet. (There are also various
missing things that I don't think the uvisor exercises.)

thanks
-- PMM

Peter Maydell (20):
  nvic: Clear the vector arrays and prigroup on reset
  target/arm: Don't switch to target stack early in v7M exception return
  target/arm: Prepare for CONTROL.SPSEL being nonzero in Handler mode
  target/arm: Restore security state on exception return
  target/arm: Restore SPSEL to correct CONTROL register on exception
    return
  target/arm: Check for xPSR mismatch usage faults earlier for v8M
  target/arm: Warn about restoring to unaligned stack
  target/arm: Don't warn about exception return with PC low bit set for
    v8M
  target/arm: Add new-in-v8M SFSR and SFAR
  target/arm: Update excret sanity checks for v8M
  target/arm: Add support for restoring v8M additional state context
  target/arm: Add v8M support to exception entry code
  nvic: Implement Security Attribution Unit registers
  target/arm: Implement security attribute lookups for memory accesses
  target/arm: Fix calculation of secure mm_idx values
  target/arm: Factor out "get mmuidx for specified security state"
  target/arm: Implement SG instruction
  target/arm: Implement BLXNS
  target/arm: Implement secure function return
  nvic: Add missing code for writing SHCSR.HARDFAULTPENDED bit

 target/arm/cpu.h       |  60 ++-
 target/arm/helper.h    |   1 +
 target/arm/internals.h |  23 ++
 hw/intc/armv7m_nvic.c  | 158 +++++++-
 target/arm/cpu.c       |  27 ++
 target/arm/helper.c    | 970 ++++++++++++++++++++++++++++++++++++++++++++-----
 target/arm/machine.c   |  16 +
 target/arm/translate.c |  31 +-
 8 files changed, 1181 insertions(+), 105 deletions(-)

-- 
2.7.4

[Qemu-devel] [PATCH 01/20] nvic: Clear the vector arrays and prigroup on reset

[Peter Maydell]

Reset for devices does not include an automatic clear of the
device state (unlike CPU state, where most of the state
structure is cleared to zero). Add some missing initialization
of NVIC state that meant that the device was left in the wrong
state if the guest did a warm reset.

(In particular, since we were resetting the computed state like
s->exception_prio but not all the state it was computed
from like s->vectors[x].active, the NVIC wound up in an
inconsistent state that could later trigger assertion failures.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/intc/armv7m_nvic.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index d90d8d0..bc7b66d 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -1782,6 +1782,11 @@ static void armv7m_nvic_reset(DeviceState *dev)
     int resetprio;
     NVICState *s = NVIC(dev);
 
+    memset(s->vectors, 0, sizeof(s->vectors));
+    memset(s->sec_vectors, 0, sizeof(s->sec_vectors));
+    s->prigroup[M_REG_NS] = 0;
+    s->prigroup[M_REG_S] = 0;
+
     s->vectors[ARMV7M_EXCP_NMI].enabled = 1;
     /* MEM, BUS, and USAGE are enabled through
      * the System Handler Control register
-- 
2.7.4

Re: [Qemu-devel] [PATCH 01/20] nvic: Clear the vector arrays and prigroup on reset

[Richard Henderson]

On 09/22/2017 09:59 AM, Peter Maydell wrote:
> Reset for devices does not include an automatic clear of the
> device state (unlike CPU state, where most of the state
> structure is cleared to zero). Add some missing initialization
> of NVIC state that meant that the device was left in the wrong
> state if the guest did a warm reset.
> 
> (In particular, since we were resetting the computed state like
> s->exception_prio but not all the state it was computed
> from like s->vectors[x].active, the NVIC wound up in an
> inconsistent state that could later trigger assertion failures.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/intc/armv7m_nvic.c | 5 +++++
>  1 file changed, 5 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: [Qemu-devel] [Qemu-arm] [PATCH 01/20] nvic: Clear the vector arrays and prigroup on reset

[Philippe Mathieu-Daudé]

On 09/22/2017 11:59 AM, Peter Maydell wrote:
> Reset for devices does not include an automatic clear of the
> device state (unlike CPU state, where most of the state
> structure is cleared to zero). Add some missing initialization
> of NVIC state that meant that the device was left in the wrong
> state if the guest did a warm reset.
> 
> (In particular, since we were resetting the computed state like
> s->exception_prio but not all the state it was computed
> from like s->vectors[x].active, the NVIC wound up in an
> inconsistent state that could later trigger assertion failures.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>   hw/intc/armv7m_nvic.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> index d90d8d0..bc7b66d 100644
> --- a/hw/intc/armv7m_nvic.c
> +++ b/hw/intc/armv7m_nvic.c
> @@ -1782,6 +1782,11 @@ static void armv7m_nvic_reset(DeviceState *dev)
>       int resetprio;
>       NVICState *s = NVIC(dev);
>   
> +    memset(s->vectors, 0, sizeof(s->vectors));
> +    memset(s->sec_vectors, 0, sizeof(s->sec_vectors));
> +    s->prigroup[M_REG_NS] = 0;
> +    s->prigroup[M_REG_S] = 0;
> +
>       s->vectors[ARMV7M_EXCP_NMI].enabled = 1;
>       /* MEM, BUS, and USAGE are enabled through
>        * the System Handler Control register
> 

[Qemu-devel] [PATCH 02/20] target/arm: Don't switch to target stack early in v7M exception return

[Peter Maydell]

Currently our M profile exception return code switches to the
target stack pointer relatively early in the process, before
it tries to pop the exception frame off the stack. This is
awkward for v8M for two reasons:
 * in v8M the process vs main stack pointer is not selected
   purely by the value of CONTROL.SPSEL, so updating SPSEL
   and relying on that to switch to the right stack pointer
   won't work
 * the stack we should be reading the stack frame from and
   the stack we will eventually switch to might not be the
   same if the guest is doing strange things

Change our exception return code to use a 'frame pointer'
to read the exception frame rather than assuming that we
can switch the live stack pointer this early.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 127 +++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 95 insertions(+), 32 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 8be78ea..f13b99d 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6040,16 +6040,6 @@ static void v7m_push(CPUARMState *env, uint32_t val)
     stl_phys(cs->as, env->regs[13], val);
 }
 
-static uint32_t v7m_pop(CPUARMState *env)
-{
-    CPUState *cs = CPU(arm_env_get_cpu(env));
-    uint32_t val;
-
-    val = ldl_phys(cs->as, env->regs[13]);
-    env->regs[13] += 4;
-    return val;
-}
-
 /* Return true if we're using the process stack pointer (not the MSP) */
 static bool v7m_using_psp(CPUARMState *env)
 {
@@ -6141,6 +6131,40 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
     env->regs[15] = dest & ~1;
 }
 
+static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
+                                bool spsel)
+{
+    /* Return a pointer to the location where we currently store the
+     * stack pointer for the requested security state and thread mode.
+     * This pointer will become invalid if the CPU state is updated
+     * such that the stack pointers are switched around (eg changing
+     * the SPSEL control bit).
+     * Compare the v8M ARM ARM pseudocode LookUpSP_with_security_mode().
+     * Unlike that pseudocode, we require the caller to pass us in the
+     * SPSEL control bit value; this is because we also use this
+     * function in handling of pushing of the callee-saves registers
+     * part of the v8M stack frame, and in that case the SPSEL bit
+     * comes from the exception return magic LR value.
+     */
+    bool want_psp = threadmode && spsel;
+
+    if (secure == env->v7m.secure) {
+        /* Currently switch_v7m_sp switches SP as it updates SPSEL,
+         * so the SP we want is always in regs[13].
+         * When we decouple SPSEL from the actually selected SP
+         * we need to check want_psp against v7m_using_psp()
+         * to see whether we need regs[13] or v7m.other_sp.
+         */
+        return &env->regs[13];
+    } else {
+        if (want_psp) {
+            return &env->v7m.other_ss_psp;
+        } else {
+            return &env->v7m.other_ss_msp;
+        }
+    }
+}
+
 static uint32_t arm_v7m_load_vector(ARMCPU *cpu)
 {
     CPUState *cs = CPU(cpu);
@@ -6212,6 +6236,7 @@ static void v7m_push_stack(ARMCPU *cpu)
 static void do_v7m_exception_exit(ARMCPU *cpu)
 {
     CPUARMState *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
     uint32_t excret;
     uint32_t xpsr;
     bool ufault = false;
@@ -6219,6 +6244,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
     bool return_to_handler = false;
     bool rettobase = false;
     bool exc_secure = false;
+    bool return_to_secure;
 
     /* We can only get here from an EXCP_EXCEPTION_EXIT, and
      * gen_bx_excret() enforces the architectural rule
@@ -6286,6 +6312,9 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
         g_assert_not_reached();
     }
 
+    return_to_secure = arm_feature(env, ARM_FEATURE_M_SECURITY) &&
+        (excret & R_V7M_EXCRET_S_MASK);
+
     switch (excret & 0xf) {
     case 1: /* Return to Handler */
         return_to_handler = true;
@@ -6315,32 +6344,66 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
         return;
     }
 
-    /* Switch to the target stack.  */
+    /* Set CONTROL.SPSEL from excret.SPSEL. For QEMU this currently
+     * causes us to switch the active SP, but we will change this
+     * later to not do that so we can support v8M.
+     */
     switch_v7m_sp(env, return_to_sp_process);
-    /* Pop registers.  */
-    env->regs[0] = v7m_pop(env);
-    env->regs[1] = v7m_pop(env);
-    env->regs[2] = v7m_pop(env);
-    env->regs[3] = v7m_pop(env);
-    env->regs[12] = v7m_pop(env);
-    env->regs[14] = v7m_pop(env);
-    env->regs[15] = v7m_pop(env);
-    if (env->regs[15] & 1) {
-        qemu_log_mask(LOG_GUEST_ERROR,
-                      "M profile return from interrupt with misaligned "
-                      "PC is UNPREDICTABLE\n");
-        /* Actual hardware seems to ignore the lsbit, and there are several
-         * RTOSes out there which incorrectly assume the r15 in the stack
-         * frame should be a Thumb-style "lsbit indicates ARM/Thumb" value.
+
+    {
+        /* The stack pointer we should be reading the exception frame from
+         * depends on bits in the magic exception return type value (and
+         * for v8M isn't necessarily the stack pointer we will eventually
+         * end up resuming execution with). Get a pointer to the location
+         * in the CPU state struct where the SP we need is currently being
+         * stored; we will use and modify it in place.
+         * We use this limited C variable scope so we don't accidentally
+         * use 'frame_sp_p' after we do something that makes it invalid.
+         */
+        uint32_t *frame_sp_p = get_v7m_sp_ptr(env,
+                                              return_to_secure,
+                                              !return_to_handler,
+                                              return_to_sp_process);
+        uint32_t frameptr = *frame_sp_p;
+
+        /* Pop registers. TODO: make these accesses use the correct
+         * attributes and address space (S/NS, priv/unpriv) and handle
+         * memory transaction failures.
          */
-        env->regs[15] &= ~1U;
+        env->regs[0] = ldl_phys(cs->as, frameptr);
+        env->regs[1] = ldl_phys(cs->as, frameptr + 0x4);
+        env->regs[2] = ldl_phys(cs->as, frameptr + 0x8);
+        env->regs[3] = ldl_phys(cs->as, frameptr + 0xc);
+        env->regs[12] = ldl_phys(cs->as, frameptr + 0x10);
+        env->regs[14] = ldl_phys(cs->as, frameptr + 0x14);
+        env->regs[15] = ldl_phys(cs->as, frameptr + 0x18);
+        if (env->regs[15] & 1) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "M profile return from interrupt with misaligned "
+                          "PC is UNPREDICTABLE\n");
+            /* Actual hardware seems to ignore the lsbit, and there are several
+             * RTOSes out there which incorrectly assume the r15 in the stack
+             * frame should be a Thumb-style "lsbit indicates ARM/Thumb" value.
+             */
+            env->regs[15] &= ~1U;
+        }
+        xpsr = ldl_phys(cs->as, frameptr + 0x1c);
+
+        /* Commit to consuming the stack frame */
+        frameptr += 0x20;
+        /* Undo stack alignment (the SPREALIGN bit indicates that the original
+         * pre-exception SP was not 8-aligned and we added a padding word to
+         * align it, so we undo this by ORing in the bit that increases it
+         * from the current 8-aligned value to the 8-unaligned value. (Adding 4
+         * would work too but a logical OR is how the pseudocode specifies it.)
+         */
+        if (xpsr & XPSR_SPREALIGN) {
+            frameptr |= 4;
+        }
+        *frame_sp_p = frameptr;
     }
-    xpsr = v7m_pop(env);
+    /* This xpsr_write() will invalidate frame_sp_p as it may switch stack */
     xpsr_write(env, xpsr, ~XPSR_SPREALIGN);
-    /* Undo stack alignment.  */
-    if (xpsr & XPSR_SPREALIGN) {
-        env->regs[13] |= 4;
-    }
 
     /* The restored xPSR exception field will be zero if we're
      * resuming in Thread mode. If that doesn't match what the
-- 
2.7.4

Re: [Qemu-devel] [PATCH 02/20] target/arm: Don't switch to target stack early in v7M exception return

[Philippe Mathieu-Daudé]

On 09/22/2017 11:59 AM, Peter Maydell wrote:
> Currently our M profile exception return code switches to the
> target stack pointer relatively early in the process, before
> it tries to pop the exception frame off the stack. This is
> awkward for v8M for two reasons:
>  * in v8M the process vs main stack pointer is not selected
>    purely by the value of CONTROL.SPSEL, so updating SPSEL
>    and relying on that to switch to the right stack pointer
>    won't work
>  * the stack we should be reading the stack frame from and
>    the stack we will eventually switch to might not be the
>    same if the guest is doing strange things
> 
> Change our exception return code to use a 'frame pointer'
> to read the exception frame rather than assuming that we
> can switch the live stack pointer this early.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>  target/arm/helper.c | 127 +++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 95 insertions(+), 32 deletions(-)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 8be78ea..f13b99d 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6040,16 +6040,6 @@ static void v7m_push(CPUARMState *env, uint32_t val)
>      stl_phys(cs->as, env->regs[13], val);
>  }
>  
> -static uint32_t v7m_pop(CPUARMState *env)
> -{
> -    CPUState *cs = CPU(arm_env_get_cpu(env));
> -    uint32_t val;
> -
> -    val = ldl_phys(cs->as, env->regs[13]);
> -    env->regs[13] += 4;
> -    return val;
> -}
> -
>  /* Return true if we're using the process stack pointer (not the MSP) */
>  static bool v7m_using_psp(CPUARMState *env)
>  {
> @@ -6141,6 +6131,40 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
>      env->regs[15] = dest & ~1;
>  }
>  
> +static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
> +                                bool spsel)
> +{
> +    /* Return a pointer to the location where we currently store the
> +     * stack pointer for the requested security state and thread mode.
> +     * This pointer will become invalid if the CPU state is updated
> +     * such that the stack pointers are switched around (eg changing
> +     * the SPSEL control bit).
> +     * Compare the v8M ARM ARM pseudocode LookUpSP_with_security_mode().
> +     * Unlike that pseudocode, we require the caller to pass us in the
> +     * SPSEL control bit value; this is because we also use this
> +     * function in handling of pushing of the callee-saves registers
> +     * part of the v8M stack frame, and in that case the SPSEL bit
> +     * comes from the exception return magic LR value.
> +     */
> +    bool want_psp = threadmode && spsel;
> +
> +    if (secure == env->v7m.secure) {
> +        /* Currently switch_v7m_sp switches SP as it updates SPSEL,
> +         * so the SP we want is always in regs[13].
> +         * When we decouple SPSEL from the actually selected SP
> +         * we need to check want_psp against v7m_using_psp()
> +         * to see whether we need regs[13] or v7m.other_sp.
> +         */
> +        return &env->regs[13];
> +    } else {
> +        if (want_psp) {
> +            return &env->v7m.other_ss_psp;
> +        } else {
> +            return &env->v7m.other_ss_msp;
> +        }
> +    }
> +}
> +
>  static uint32_t arm_v7m_load_vector(ARMCPU *cpu)
>  {
>      CPUState *cs = CPU(cpu);
> @@ -6212,6 +6236,7 @@ static void v7m_push_stack(ARMCPU *cpu)
>  static void do_v7m_exception_exit(ARMCPU *cpu)
>  {
>      CPUARMState *env = &cpu->env;
> +    CPUState *cs = CPU(cpu);
>      uint32_t excret;
>      uint32_t xpsr;
>      bool ufault = false;
> @@ -6219,6 +6244,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>      bool return_to_handler = false;
>      bool rettobase = false;
>      bool exc_secure = false;
> +    bool return_to_secure;
>  
>      /* We can only get here from an EXCP_EXCEPTION_EXIT, and
>       * gen_bx_excret() enforces the architectural rule
> @@ -6286,6 +6312,9 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>          g_assert_not_reached();
>      }
>  
> +    return_to_secure = arm_feature(env, ARM_FEATURE_M_SECURITY) &&
> +        (excret & R_V7M_EXCRET_S_MASK);
> +
>      switch (excret & 0xf) {
>      case 1: /* Return to Handler */
>          return_to_handler = true;
> @@ -6315,32 +6344,66 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>          return;
>      }
>  
> -    /* Switch to the target stack.  */
> +    /* Set CONTROL.SPSEL from excret.SPSEL. For QEMU this currently
> +     * causes us to switch the active SP, but we will change this
> +     * later to not do that so we can support v8M.
> +     */
>      switch_v7m_sp(env, return_to_sp_process);
> -    /* Pop registers.  */
> -    env->regs[0] = v7m_pop(env);
> -    env->regs[1] = v7m_pop(env);
> -    env->regs[2] = v7m_pop(env);
> -    env->regs[3] = v7m_pop(env);
> -    env->regs[12] = v7m_pop(env);
> -    env->regs[14] = v7m_pop(env);
> -    env->regs[15] = v7m_pop(env);
> -    if (env->regs[15] & 1) {
> -        qemu_log_mask(LOG_GUEST_ERROR,
> -                      "M profile return from interrupt with misaligned "
> -                      "PC is UNPREDICTABLE\n");
> -        /* Actual hardware seems to ignore the lsbit, and there are several
> -         * RTOSes out there which incorrectly assume the r15 in the stack
> -         * frame should be a Thumb-style "lsbit indicates ARM/Thumb" value.
> +
> +    {
> +        /* The stack pointer we should be reading the exception frame from
> +         * depends on bits in the magic exception return type value (and
> +         * for v8M isn't necessarily the stack pointer we will eventually
> +         * end up resuming execution with). Get a pointer to the location
> +         * in the CPU state struct where the SP we need is currently being
> +         * stored; we will use and modify it in place.
> +         * We use this limited C variable scope so we don't accidentally
> +         * use 'frame_sp_p' after we do something that makes it invalid.
> +         */
> +        uint32_t *frame_sp_p = get_v7m_sp_ptr(env,
> +                                              return_to_secure,
> +                                              !return_to_handler,
> +                                              return_to_sp_process);
> +        uint32_t frameptr = *frame_sp_p;
> +
> +        /* Pop registers. TODO: make these accesses use the correct
> +         * attributes and address space (S/NS, priv/unpriv) and handle
> +         * memory transaction failures.
>           */
> -        env->regs[15] &= ~1U;
> +        env->regs[0] = ldl_phys(cs->as, frameptr);
> +        env->regs[1] = ldl_phys(cs->as, frameptr + 0x4);
> +        env->regs[2] = ldl_phys(cs->as, frameptr + 0x8);
> +        env->regs[3] = ldl_phys(cs->as, frameptr + 0xc);
> +        env->regs[12] = ldl_phys(cs->as, frameptr + 0x10);
> +        env->regs[14] = ldl_phys(cs->as, frameptr + 0x14);
> +        env->regs[15] = ldl_phys(cs->as, frameptr + 0x18);
> +        if (env->regs[15] & 1) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "M profile return from interrupt with misaligned "
> +                          "PC is UNPREDICTABLE\n");
> +            /* Actual hardware seems to ignore the lsbit, and there are several
> +             * RTOSes out there which incorrectly assume the r15 in the stack
> +             * frame should be a Thumb-style "lsbit indicates ARM/Thumb" value.
> +             */
> +            env->regs[15] &= ~1U;
> +        }
> +        xpsr = ldl_phys(cs->as, frameptr + 0x1c);
> +
> +        /* Commit to consuming the stack frame */
> +        frameptr += 0x20;
> +        /* Undo stack alignment (the SPREALIGN bit indicates that the original
> +         * pre-exception SP was not 8-aligned and we added a padding word to
> +         * align it, so we undo this by ORing in the bit that increases it
> +         * from the current 8-aligned value to the 8-unaligned value. (Adding 4
> +         * would work too but a logical OR is how the pseudocode specifies it.)
> +         */
> +        if (xpsr & XPSR_SPREALIGN) {
> +            frameptr |= 4;
> +        }
> +        *frame_sp_p = frameptr;
>      }
> -    xpsr = v7m_pop(env);
> +    /* This xpsr_write() will invalidate frame_sp_p as it may switch stack */
>      xpsr_write(env, xpsr, ~XPSR_SPREALIGN);
> -    /* Undo stack alignment.  */
> -    if (xpsr & XPSR_SPREALIGN) {
> -        env->regs[13] |= 4;
> -    }
>  
>      /* The restored xPSR exception field will be zero if we're
>       * resuming in Thread mode. If that doesn't match what the
> 

Re: [Qemu-devel] [PATCH 02/20] target/arm: Don't switch to target stack early in v7M exception return

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> Currently our M profile exception return code switches to the
> target stack pointer relatively early in the process, before
> it tries to pop the exception frame off the stack. This is
> awkward for v8M for two reasons:
>  * in v8M the process vs main stack pointer is not selected
>    purely by the value of CONTROL.SPSEL, so updating SPSEL
>    and relying on that to switch to the right stack pointer
>    won't work
>  * the stack we should be reading the stack frame from and
>    the stack we will eventually switch to might not be the
>    same if the guest is doing strange things
> 
> Change our exception return code to use a 'frame pointer'
> to read the exception frame rather than assuming that we
> can switch the live stack pointer this early.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 127 +++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 95 insertions(+), 32 deletions(-)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 8be78ea..f13b99d 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6040,16 +6040,6 @@ static void v7m_push(CPUARMState *env, uint32_t val)
>      stl_phys(cs->as, env->regs[13], val);
>  }
>  
> -static uint32_t v7m_pop(CPUARMState *env)
> -{
> -    CPUState *cs = CPU(arm_env_get_cpu(env));
> -    uint32_t val;
> -
> -    val = ldl_phys(cs->as, env->regs[13]);
> -    env->regs[13] += 4;
> -    return val;
> -}
> -
>  /* Return true if we're using the process stack pointer (not the MSP) */
>  static bool v7m_using_psp(CPUARMState *env)
>  {
> @@ -6141,6 +6131,40 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
>      env->regs[15] = dest & ~1;
>  }
>  
> +static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
> +                                bool spsel)
> +{
> +    /* Return a pointer to the location where we currently store the
> +     * stack pointer for the requested security state and thread mode.
> +     * This pointer will become invalid if the CPU state is updated
> +     * such that the stack pointers are switched around (eg changing
> +     * the SPSEL control bit).
> +     * Compare the v8M ARM ARM pseudocode LookUpSP_with_security_mode().
> +     * Unlike that pseudocode, we require the caller to pass us in the
> +     * SPSEL control bit value; this is because we also use this
> +     * function in handling of pushing of the callee-saves registers
> +     * part of the v8M stack frame, and in that case the SPSEL bit
> +     * comes from the exception return magic LR value.

Exception return magic lr value does not appear to match "pushing".  Did you
mean "poping" here?

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: [Qemu-devel] [PATCH 02/20] target/arm: Don't switch to target stack early in v7M exception return

[Peter Maydell]

On 5 October 2017 at 17:04, Richard Henderson
<richard.henderson@linaro.org> wrote:
> On 09/22/2017 10:59 AM, Peter Maydell wrote:
>> Currently our M profile exception return code switches to the
>> target stack pointer relatively early in the process, before
>> it tries to pop the exception frame off the stack. This is
>> awkward for v8M for two reasons:
>>  * in v8M the process vs main stack pointer is not selected
>>    purely by the value of CONTROL.SPSEL, so updating SPSEL
>>    and relying on that to switch to the right stack pointer
>>    won't work
>>  * the stack we should be reading the stack frame from and
>>    the stack we will eventually switch to might not be the
>>    same if the guest is doing strange things
>>
>> Change our exception return code to use a 'frame pointer'
>> to read the exception frame rather than assuming that we
>> can switch the live stack pointer this early.
>>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>>  target/arm/helper.c | 127 +++++++++++++++++++++++++++++++++++++++-------------
>>  1 file changed, 95 insertions(+), 32 deletions(-)
>>
>> diff --git a/target/arm/helper.c b/target/arm/helper.c
>> index 8be78ea..f13b99d 100644
>> --- a/target/arm/helper.c
>> +++ b/target/arm/helper.c
>> @@ -6040,16 +6040,6 @@ static void v7m_push(CPUARMState *env, uint32_t val)
>>      stl_phys(cs->as, env->regs[13], val);
>>  }
>>
>> -static uint32_t v7m_pop(CPUARMState *env)
>> -{
>> -    CPUState *cs = CPU(arm_env_get_cpu(env));
>> -    uint32_t val;
>> -
>> -    val = ldl_phys(cs->as, env->regs[13]);
>> -    env->regs[13] += 4;
>> -    return val;
>> -}
>> -
>>  /* Return true if we're using the process stack pointer (not the MSP) */
>>  static bool v7m_using_psp(CPUARMState *env)
>>  {
>> @@ -6141,6 +6131,40 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
>>      env->regs[15] = dest & ~1;
>>  }
>>
>> +static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
>> +                                bool spsel)
>> +{
>> +    /* Return a pointer to the location where we currently store the
>> +     * stack pointer for the requested security state and thread mode.
>> +     * This pointer will become invalid if the CPU state is updated
>> +     * such that the stack pointers are switched around (eg changing
>> +     * the SPSEL control bit).
>> +     * Compare the v8M ARM ARM pseudocode LookUpSP_with_security_mode().
>> +     * Unlike that pseudocode, we require the caller to pass us in the
>> +     * SPSEL control bit value; this is because we also use this
>> +     * function in handling of pushing of the callee-saves registers
>> +     * part of the v8M stack frame, and in that case the SPSEL bit
>> +     * comes from the exception return magic LR value.
>
> Exception return magic lr value does not appear to match "pushing".  Did you
> mean "poping" here?

No, because the code creates the exception magic LR value for an
exception entry, and then uses it to determine which SPSEL to use.
In the tailchained-exception case we use the magic LR that
the attempted exception-exit got when figuring out where we need
to push more registers as part of the tailchaining. The pseudocode
chooses to open-code the "find the right stack pointer" for that
codepath (in pseudocode function PushCalleeStack), whereas for this
QEMU code I opted to make the utility function more specific. That's
what this comment is trying to gesture at.

[The push-on-exception-entry code is in "target/arm: Add v8M support
to exception entry code"]

> Otherwise,
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

thanks
-- PMM

Re: [Qemu-devel] [PATCH 02/20] target/arm: Don't switch to target stack early in v7M exception return

[Peter Maydell]

On 5 October 2017 at 17:20, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 5 October 2017 at 17:04, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>> On 09/22/2017 10:59 AM, Peter Maydell wrote:
>>> +static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
>>> +                                bool spsel)
>>> +{
>>> +    /* Return a pointer to the location where we currently store the
>>> +     * stack pointer for the requested security state and thread mode.
>>> +     * This pointer will become invalid if the CPU state is updated
>>> +     * such that the stack pointers are switched around (eg changing
>>> +     * the SPSEL control bit).
>>> +     * Compare the v8M ARM ARM pseudocode LookUpSP_with_security_mode().
>>> +     * Unlike that pseudocode, we require the caller to pass us in the
>>> +     * SPSEL control bit value; this is because we also use this
>>> +     * function in handling of pushing of the callee-saves registers
>>> +     * part of the v8M stack frame, and in that case the SPSEL bit
>>> +     * comes from the exception return magic LR value.
>>
>> Exception return magic lr value does not appear to match "pushing".  Did you
>> mean "poping" here?
>
> No, because the code creates the exception magic LR value for an
> exception entry, and then uses it to determine which SPSEL to use.
> In the tailchained-exception case we use the magic LR that
> the attempted exception-exit got when figuring out where we need
> to push more registers as part of the tailchaining. The pseudocode
> chooses to open-code the "find the right stack pointer" for that
> codepath (in pseudocode function PushCalleeStack), whereas for this
> QEMU code I opted to make the utility function more specific. That's
> what this comment is trying to gesture at.
>
> [The push-on-exception-entry code is in "target/arm: Add v8M support
> to exception entry code"]

I'm going to change this part of the comment to read
     * Compare the v8M ARM ARM pseudocode LookUpSP_with_security_mode().
     * Unlike that pseudocode, we require the caller to pass us in the
     * SPSEL control bit value; this is because we also use this
     * function in handling of pushing of the callee-saves registers
     * part of the v8M stack frame (pseudocode PushCalleeStack()),
     * and in the tailchain codepath the SPSEL bit comes from the exception
     * return magic LR value from the previous exception. The pseudocode
     * opencodes the stack-selection in PushCalleeStack(), but we prefer
     * to make this utility function generic enough to do the job.

which hopefully is a little clearer.

thanks
-- PMM

Re: [Qemu-devel] [PATCH 02/20] target/arm: Don't switch to target stack early in v7M exception return

[Richard Henderson]

On 10/06/2017 09:22 AM, Peter Maydell wrote:
> I'm going to change this part of the comment to read
>      * Compare the v8M ARM ARM pseudocode LookUpSP_with_security_mode().
>      * Unlike that pseudocode, we require the caller to pass us in the
>      * SPSEL control bit value; this is because we also use this
>      * function in handling of pushing of the callee-saves registers
>      * part of the v8M stack frame (pseudocode PushCalleeStack()),
>      * and in the tailchain codepath the SPSEL bit comes from the exception
>      * return magic LR value from the previous exception. The pseudocode
>      * opencodes the stack-selection in PushCalleeStack(), but we prefer
>      * to make this utility function generic enough to do the job.
> 
> which hopefully is a little clearer.

Much, thanks.


r~

[Qemu-devel] [PATCH 03/20] target/arm: Prepare for CONTROL.SPSEL being nonzero in Handler mode

[Peter Maydell]

In the v7M architecture, there is an invariant that if the CPU is
in Handler mode then the CONTROL.SPSEL bit cannot be nonzero.
This in turn means that the current stack pointer is always
indicated by CONTROL.SPSEL, even though Handler mode always uses
the Main stack pointer.

In v8M, this invariant is removed, and CONTROL.SPSEL may now
be nonzero in Handler mode (though Handler mode still always
uses the Main stack pointer). In preparation for this change,
change how we handle this bit: rename switch_v7m_sp() to
the now more accurate write_v7m_control_spsel(), and make it
check both the handler mode state and the SPSEL bit.

Note that this implicitly changes the point at which we switch
active SP on exception exit from before we pop the exception
frame to after it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h      |  8 ++++++-
 hw/intc/armv7m_nvic.c |  2 +-
 target/arm/helper.c   | 65 ++++++++++++++++++++++++++++++++++-----------------
 3 files changed, 51 insertions(+), 24 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 8afceca..ad6eff4 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -991,6 +991,11 @@ void pmccntr_sync(CPUARMState *env);
 #define PSTATE_MODE_EL1t 4
 #define PSTATE_MODE_EL0t 0
 
+/* Write a new value to v7m.exception, thus transitioning into or out
+ * of Handler mode; this may result in a change of active stack pointer.
+ */
+void write_v7m_exception(CPUARMState *env, uint32_t new_exc);
+
 /* Map EL and handler into a PSTATE_MODE.  */
 static inline unsigned int aarch64_pstate_mode(unsigned int el, bool handler)
 {
@@ -1071,7 +1076,8 @@ static inline void xpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)
         env->condexec_bits |= (val >> 8) & 0xfc;
     }
     if (mask & XPSR_EXCP) {
-        env->v7m.exception = val & XPSR_EXCP;
+        /* Note that this only happens on exception exit */
+        write_v7m_exception(env, val & XPSR_EXCP);
     }
 }
 
diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index bc7b66d..a1041c2 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -616,7 +616,7 @@ bool armv7m_nvic_acknowledge_irq(void *opaque)
     vec->active = 1;
     vec->pending = 0;
 
-    env->v7m.exception = s->vectpending;
+    write_v7m_exception(env, s->vectpending);
 
     nvic_irq_update(s);
 
diff --git a/target/arm/helper.c b/target/arm/helper.c
index f13b99d..509a1aa 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6052,21 +6052,44 @@ static bool v7m_using_psp(CPUARMState *env)
         env->v7m.control[env->v7m.secure] & R_V7M_CONTROL_SPSEL_MASK;
 }
 
-/* Switch to V7M main or process stack pointer.  */
-static void switch_v7m_sp(CPUARMState *env, bool new_spsel)
+/* Write to v7M CONTROL.SPSEL bit. This may change the current
+ * stack pointer between Main and Process stack pointers.
+ */
+static void write_v7m_control_spsel(CPUARMState *env, bool new_spsel)
 {
     uint32_t tmp;
-    uint32_t old_control = env->v7m.control[env->v7m.secure];
-    bool old_spsel = old_control & R_V7M_CONTROL_SPSEL_MASK;
+    bool new_is_psp, old_is_psp = v7m_using_psp(env);
+
+    env->v7m.control[env->v7m.secure] =
+        deposit32(env->v7m.control[env->v7m.secure],
+                  R_V7M_CONTROL_SPSEL_SHIFT,
+                  R_V7M_CONTROL_SPSEL_LENGTH, new_spsel);
+
+    new_is_psp = v7m_using_psp(env);
 
-    if (old_spsel != new_spsel) {
+    if (old_is_psp != new_is_psp) {
         tmp = env->v7m.other_sp;
         env->v7m.other_sp = env->regs[13];
         env->regs[13] = tmp;
+    }
+}
+
+void write_v7m_exception(CPUARMState *env, uint32_t new_exc)
+{
+    /* Write a new value to v7m.exception, thus transitioning into or out
+     * of Handler mode; this may result in a change of active stack pointer.
+     */
+    bool new_is_psp, old_is_psp = v7m_using_psp(env);
+    uint32_t tmp;
 
-        env->v7m.control[env->v7m.secure] = deposit32(old_control,
-                                     R_V7M_CONTROL_SPSEL_SHIFT,
-                                     R_V7M_CONTROL_SPSEL_LENGTH, new_spsel);
+    env->v7m.exception = new_exc;
+
+    new_is_psp = v7m_using_psp(env);
+
+    if (old_is_psp != new_is_psp) {
+        tmp = env->v7m.other_sp;
+        env->v7m.other_sp = env->regs[13];
+        env->regs[13] = tmp;
     }
 }
 
@@ -6149,13 +6172,11 @@ static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
     bool want_psp = threadmode && spsel;
 
     if (secure == env->v7m.secure) {
-        /* Currently switch_v7m_sp switches SP as it updates SPSEL,
-         * so the SP we want is always in regs[13].
-         * When we decouple SPSEL from the actually selected SP
-         * we need to check want_psp against v7m_using_psp()
-         * to see whether we need regs[13] or v7m.other_sp.
-         */
-        return &env->regs[13];
+        if (want_psp == v7m_using_psp(env)) {
+            return &env->regs[13];
+        } else {
+            return &env->v7m.other_sp;
+        }
     } else {
         if (want_psp) {
             return &env->v7m.other_ss_psp;
@@ -6198,7 +6219,7 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr)
     uint32_t addr;
 
     armv7m_nvic_acknowledge_irq(env->nvic);
-    switch_v7m_sp(env, 0);
+    write_v7m_control_spsel(env, 0);
     arm_clear_exclusive(env);
     /* Clear IT bits */
     env->condexec_bits = 0;
@@ -6344,11 +6365,11 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
         return;
     }
 
-    /* Set CONTROL.SPSEL from excret.SPSEL. For QEMU this currently
-     * causes us to switch the active SP, but we will change this
-     * later to not do that so we can support v8M.
+    /* Set CONTROL.SPSEL from excret.SPSEL. Since we're still in
+     * Handler mode (and will be until we write the new XPSR.Interrupt
+     * field) this does not switch around the current stack pointer.
      */
-    switch_v7m_sp(env, return_to_sp_process);
+    write_v7m_control_spsel(env, return_to_sp_process);
 
     {
         /* The stack pointer we should be reading the exception frame from
@@ -9163,11 +9184,11 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t maskreg, uint32_t val)
     case 20: /* CONTROL */
         /* Writing to the SPSEL bit only has an effect if we are in
          * thread mode; other bits can be updated by any privileged code.
-         * switch_v7m_sp() deals with updating the SPSEL bit in
+         * write_v7m_control_spsel() deals with updating the SPSEL bit in
          * env->v7m.control, so we only need update the others.
          */
         if (!arm_v7m_is_handler_mode(env)) {
-            switch_v7m_sp(env, (val & R_V7M_CONTROL_SPSEL_MASK) != 0);
+            write_v7m_control_spsel(env, (val & R_V7M_CONTROL_SPSEL_MASK) != 0);
         }
         env->v7m.control[env->v7m.secure] &= ~R_V7M_CONTROL_NPRIV_MASK;
         env->v7m.control[env->v7m.secure] |= val & R_V7M_CONTROL_NPRIV_MASK;
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 03/20] target/arm: Prepare for CONTROL.SPSEL being nonzero in Handler mode

[Philippe Mathieu-Daudé]

On 09/22/2017 11:59 AM, Peter Maydell wrote:
> In the v7M architecture, there is an invariant that if the CPU is
> in Handler mode then the CONTROL.SPSEL bit cannot be nonzero.
> This in turn means that the current stack pointer is always
> indicated by CONTROL.SPSEL, even though Handler mode always uses
> the Main stack pointer.
> 
> In v8M, this invariant is removed, and CONTROL.SPSEL may now
> be nonzero in Handler mode (though Handler mode still always
> uses the Main stack pointer). In preparation for this change,
> change how we handle this bit: rename switch_v7m_sp() to
> the now more accurate write_v7m_control_spsel(), and make it
> check both the handler mode state and the SPSEL bit.
> 
> Note that this implicitly changes the point at which we switch
> active SP on exception exit from before we pop the exception
> frame to after it.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>  target/arm/cpu.h      |  8 ++++++-
>  hw/intc/armv7m_nvic.c |  2 +-
>  target/arm/helper.c   | 65 ++++++++++++++++++++++++++++++++++-----------------
>  3 files changed, 51 insertions(+), 24 deletions(-)
> 
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index 8afceca..ad6eff4 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -991,6 +991,11 @@ void pmccntr_sync(CPUARMState *env);
>  #define PSTATE_MODE_EL1t 4
>  #define PSTATE_MODE_EL0t 0
>  
> +/* Write a new value to v7m.exception, thus transitioning into or out
> + * of Handler mode; this may result in a change of active stack pointer.
> + */
> +void write_v7m_exception(CPUARMState *env, uint32_t new_exc);
> +
>  /* Map EL and handler into a PSTATE_MODE.  */
>  static inline unsigned int aarch64_pstate_mode(unsigned int el, bool handler)
>  {
> @@ -1071,7 +1076,8 @@ static inline void xpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)
>          env->condexec_bits |= (val >> 8) & 0xfc;
>      }
>      if (mask & XPSR_EXCP) {
> -        env->v7m.exception = val & XPSR_EXCP;
> +        /* Note that this only happens on exception exit */
> +        write_v7m_exception(env, val & XPSR_EXCP);
>      }
>  }
>  
> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> index bc7b66d..a1041c2 100644
> --- a/hw/intc/armv7m_nvic.c
> +++ b/hw/intc/armv7m_nvic.c
> @@ -616,7 +616,7 @@ bool armv7m_nvic_acknowledge_irq(void *opaque)
>      vec->active = 1;
>      vec->pending = 0;
>  
> -    env->v7m.exception = s->vectpending;
> +    write_v7m_exception(env, s->vectpending);
>  
>      nvic_irq_update(s);
>  
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index f13b99d..509a1aa 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6052,21 +6052,44 @@ static bool v7m_using_psp(CPUARMState *env)
>          env->v7m.control[env->v7m.secure] & R_V7M_CONTROL_SPSEL_MASK;
>  }
>  
> -/* Switch to V7M main or process stack pointer.  */
> -static void switch_v7m_sp(CPUARMState *env, bool new_spsel)
> +/* Write to v7M CONTROL.SPSEL bit. This may change the current
> + * stack pointer between Main and Process stack pointers.
> + */
> +static void write_v7m_control_spsel(CPUARMState *env, bool new_spsel)
>  {
>      uint32_t tmp;
> -    uint32_t old_control = env->v7m.control[env->v7m.secure];
> -    bool old_spsel = old_control & R_V7M_CONTROL_SPSEL_MASK;
> +    bool new_is_psp, old_is_psp = v7m_using_psp(env);
> +
> +    env->v7m.control[env->v7m.secure] =
> +        deposit32(env->v7m.control[env->v7m.secure],
> +                  R_V7M_CONTROL_SPSEL_SHIFT,
> +                  R_V7M_CONTROL_SPSEL_LENGTH, new_spsel);
> +
> +    new_is_psp = v7m_using_psp(env);
>  
> -    if (old_spsel != new_spsel) {
> +    if (old_is_psp != new_is_psp) {
>          tmp = env->v7m.other_sp;
>          env->v7m.other_sp = env->regs[13];
>          env->regs[13] = tmp;
> +    }
> +}
> +
> +void write_v7m_exception(CPUARMState *env, uint32_t new_exc)
> +{
> +    /* Write a new value to v7m.exception, thus transitioning into or out
> +     * of Handler mode; this may result in a change of active stack pointer.
> +     */
> +    bool new_is_psp, old_is_psp = v7m_using_psp(env);
> +    uint32_t tmp;
>  
> -        env->v7m.control[env->v7m.secure] = deposit32(old_control,
> -                                     R_V7M_CONTROL_SPSEL_SHIFT,
> -                                     R_V7M_CONTROL_SPSEL_LENGTH, new_spsel);
> +    env->v7m.exception = new_exc;
> +
> +    new_is_psp = v7m_using_psp(env);
> +
> +    if (old_is_psp != new_is_psp) {
> +        tmp = env->v7m.other_sp;
> +        env->v7m.other_sp = env->regs[13];
> +        env->regs[13] = tmp;
>      }
>  }
>  
> @@ -6149,13 +6172,11 @@ static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
>      bool want_psp = threadmode && spsel;
>  
>      if (secure == env->v7m.secure) {
> -        /* Currently switch_v7m_sp switches SP as it updates SPSEL,
> -         * so the SP we want is always in regs[13].
> -         * When we decouple SPSEL from the actually selected SP
> -         * we need to check want_psp against v7m_using_psp()
> -         * to see whether we need regs[13] or v7m.other_sp.
> -         */
> -        return &env->regs[13];
> +        if (want_psp == v7m_using_psp(env)) {
> +            return &env->regs[13];
> +        } else {
> +            return &env->v7m.other_sp;
> +        }
>      } else {
>          if (want_psp) {
>              return &env->v7m.other_ss_psp;
> @@ -6198,7 +6219,7 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr)
>      uint32_t addr;
>  
>      armv7m_nvic_acknowledge_irq(env->nvic);
> -    switch_v7m_sp(env, 0);
> +    write_v7m_control_spsel(env, 0);
>      arm_clear_exclusive(env);
>      /* Clear IT bits */
>      env->condexec_bits = 0;
> @@ -6344,11 +6365,11 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>          return;
>      }
>  
> -    /* Set CONTROL.SPSEL from excret.SPSEL. For QEMU this currently
> -     * causes us to switch the active SP, but we will change this
> -     * later to not do that so we can support v8M.
> +    /* Set CONTROL.SPSEL from excret.SPSEL. Since we're still in
> +     * Handler mode (and will be until we write the new XPSR.Interrupt
> +     * field) this does not switch around the current stack pointer.
>       */
> -    switch_v7m_sp(env, return_to_sp_process);
> +    write_v7m_control_spsel(env, return_to_sp_process);
>  
>      {
>          /* The stack pointer we should be reading the exception frame from
> @@ -9163,11 +9184,11 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t maskreg, uint32_t val)
>      case 20: /* CONTROL */
>          /* Writing to the SPSEL bit only has an effect if we are in
>           * thread mode; other bits can be updated by any privileged code.
> -         * switch_v7m_sp() deals with updating the SPSEL bit in
> +         * write_v7m_control_spsel() deals with updating the SPSEL bit in
>           * env->v7m.control, so we only need update the others.
>           */
>          if (!arm_v7m_is_handler_mode(env)) {
> -            switch_v7m_sp(env, (val & R_V7M_CONTROL_SPSEL_MASK) != 0);
> +            write_v7m_control_spsel(env, (val & R_V7M_CONTROL_SPSEL_MASK) != 0);
>          }
>          env->v7m.control[env->v7m.secure] &= ~R_V7M_CONTROL_NPRIV_MASK;
>          env->v7m.control[env->v7m.secure] |= val & R_V7M_CONTROL_NPRIV_MASK;
> 

Re: [Qemu-devel] [PATCH 03/20] target/arm: Prepare for CONTROL.SPSEL being nonzero in Handler mode

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> In the v7M architecture, there is an invariant that if the CPU is
> in Handler mode then the CONTROL.SPSEL bit cannot be nonzero.
> This in turn means that the current stack pointer is always
> indicated by CONTROL.SPSEL, even though Handler mode always uses
> the Main stack pointer.
> 
> In v8M, this invariant is removed, and CONTROL.SPSEL may now
> be nonzero in Handler mode (though Handler mode still always
> uses the Main stack pointer). In preparation for this change,
> change how we handle this bit: rename switch_v7m_sp() to
> the now more accurate write_v7m_control_spsel(), and make it
> check both the handler mode state and the SPSEL bit.
> 
> Note that this implicitly changes the point at which we switch
> active SP on exception exit from before we pop the exception
> frame to after it.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/cpu.h      |  8 ++++++-
>  hw/intc/armv7m_nvic.c |  2 +-
>  target/arm/helper.c   | 65 ++++++++++++++++++++++++++++++++++-----------------
>  3 files changed, 51 insertions(+), 24 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 04/20] target/arm: Restore security state on exception return

[Peter Maydell]

Now that we can handle the CONTROL.SPSEL bit not necessarily being
in sync with the current stack pointer, we can restore the correct
security state on exception return. This happens before we start
to read registers off the stack frame, but after we have taken
possible usage faults for bad exception return magic values and
updated CONTROL.SPSEL.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 509a1aa..a3c63c3 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6371,6 +6371,8 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
      */
     write_v7m_control_spsel(env, return_to_sp_process);
 
+    switch_v7m_security_state(env, return_to_secure);
+
     {
         /* The stack pointer we should be reading the exception frame from
          * depends on bits in the magic exception return type value (and
-- 
2.7.4

Re: [Qemu-devel] [PATCH 04/20] target/arm: Restore security state on exception return

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> Now that we can handle the CONTROL.SPSEL bit not necessarily being
> in sync with the current stack pointer, we can restore the correct
> security state on exception return. This happens before we start
> to read registers off the stack frame, but after we have taken
> possible usage faults for bad exception return magic values and
> updated CONTROL.SPSEL.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 2 ++
>  1 file changed, 2 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 05/20] target/arm: Restore SPSEL to correct CONTROL register on exception return

[Peter Maydell]

On exception return for v8M, the SPSEL bit in the EXC_RETURN magic
value should be restored to the SPSEL bit in the CONTROL register
banked specified by the EXC_RETURN.ES bit.

Add write_v7m_control_spsel_for_secstate() which behaves like
write_v7m_control_spsel() but allows the caller to specify which
CONTROL bank to use, reimplement write_v7m_control_spsel() in
terms of it, and use it in exception return.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 40 +++++++++++++++++++++++++++-------------
 1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index a3c63c3..4444d04 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6052,28 +6052,42 @@ static bool v7m_using_psp(CPUARMState *env)
         env->v7m.control[env->v7m.secure] & R_V7M_CONTROL_SPSEL_MASK;
 }
 
-/* Write to v7M CONTROL.SPSEL bit. This may change the current
- * stack pointer between Main and Process stack pointers.
+/* Write to v7M CONTROL.SPSEL bit for the specified security bank.
+ * This may change the current stack pointer between Main and Process
+ * stack pointers if it is done for the CONTROL register for the current
+ * security state.
  */
-static void write_v7m_control_spsel(CPUARMState *env, bool new_spsel)
+static void write_v7m_control_spsel_for_secstate(CPUARMState *env,
+                                                 bool new_spsel,
+                                                 bool secstate)
 {
-    uint32_t tmp;
-    bool new_is_psp, old_is_psp = v7m_using_psp(env);
+    bool old_is_psp = v7m_using_psp(env);
 
-    env->v7m.control[env->v7m.secure] =
-        deposit32(env->v7m.control[env->v7m.secure],
+    env->v7m.control[secstate] =
+        deposit32(env->v7m.control[secstate],
                   R_V7M_CONTROL_SPSEL_SHIFT,
                   R_V7M_CONTROL_SPSEL_LENGTH, new_spsel);
 
-    new_is_psp = v7m_using_psp(env);
+    if (secstate == env->v7m.secure) {
+        bool new_is_psp = v7m_using_psp(env);
+        uint32_t tmp;
 
-    if (old_is_psp != new_is_psp) {
-        tmp = env->v7m.other_sp;
-        env->v7m.other_sp = env->regs[13];
-        env->regs[13] = tmp;
+        if (old_is_psp != new_is_psp) {
+            tmp = env->v7m.other_sp;
+            env->v7m.other_sp = env->regs[13];
+            env->regs[13] = tmp;
+        }
     }
 }
 
+/* Write to v7M CONTROL.SPSEL bit. This may change the current
+ * stack pointer between Main and Process stack pointers.
+ */
+static void write_v7m_control_spsel(CPUARMState *env, bool new_spsel)
+{
+    write_v7m_control_spsel_for_secstate(env, new_spsel, env->v7m.secure);
+}
+
 void write_v7m_exception(CPUARMState *env, uint32_t new_exc)
 {
     /* Write a new value to v7m.exception, thus transitioning into or out
@@ -6369,7 +6383,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
      * Handler mode (and will be until we write the new XPSR.Interrupt
      * field) this does not switch around the current stack pointer.
      */
-    write_v7m_control_spsel(env, return_to_sp_process);
+    write_v7m_control_spsel_for_secstate(env, return_to_sp_process, exc_secure);
 
     switch_v7m_security_state(env, return_to_secure);
 
-- 
2.7.4

Re: [Qemu-devel] [PATCH 05/20] target/arm: Restore SPSEL to correct CONTROL register on exception return

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> On exception return for v8M, the SPSEL bit in the EXC_RETURN magic
> value should be restored to the SPSEL bit in the CONTROL register
> banked specified by the EXC_RETURN.ES bit.
> 
> Add write_v7m_control_spsel_for_secstate() which behaves like
> write_v7m_control_spsel() but allows the caller to specify which
> CONTROL bank to use, reimplement write_v7m_control_spsel() in
> terms of it, and use it in exception return.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 40 +++++++++++++++++++++++++++-------------
>  1 file changed, 27 insertions(+), 13 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 06/20] target/arm: Check for xPSR mismatch usage faults earlier for v8M

[Peter Maydell]

ARM v8M specifies that the INVPC usage fault for mismatched
xPSR exception field and handler mode bit should be checked
before updating the PSR and SP, so that the fault is taken
with the existing stack frame rather than by pushing a new one.
Perform this check in the right place for v8M.

Since v7M specifies in its pseudocode that this usage fault
check should happen later, we have to retain the original
code for that check rather than being able to merge the two.
(The distinction is architecturally visible but only in
very obscure corner cases like attempting an invalid exception
return with an exception frame in read only memory.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 4444d04..a2e46fb 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6426,6 +6426,29 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
         }
         xpsr = ldl_phys(cs->as, frameptr + 0x1c);
 
+        if (arm_feature(env, ARM_FEATURE_V8)) {
+            /* For v8M we have to check whether the xPSR exception field
+             * matches the EXCRET value for return to handler/thread
+             * before we commit to changing the SP and xPSR.
+             */
+            bool will_be_handler = (xpsr & XPSR_EXCP) != 0;
+            if (return_to_handler != will_be_handler) {
+                /* Take an INVPC UsageFault on the current stack.
+                 * By this point we will have switched to the security state
+                 * for the background state, so this UsageFault will target
+                 * that state.
+                 */
+                armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE,
+                                        env->v7m.secure);
+                env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK;
+                v7m_exception_taken(cpu, excret);
+                qemu_log_mask(CPU_LOG_INT, "...taking UsageFault on existing "
+                              "stackframe: failed exception return integrity "
+                              "check\n");
+                return;
+            }
+        }
+
         /* Commit to consuming the stack frame */
         frameptr += 0x20;
         /* Undo stack alignment (the SPREALIGN bit indicates that the original
@@ -6445,12 +6468,13 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
     /* The restored xPSR exception field will be zero if we're
      * resuming in Thread mode. If that doesn't match what the
      * exception return excret specified then this is a UsageFault.
+     * v7M requires we make this check here; v8M did it earlier.
      */
     if (return_to_handler != arm_v7m_is_handler_mode(env)) {
-        /* Take an INVPC UsageFault by pushing the stack again.
-         * TODO: the v8M version of this code should target the
-         * background state for this exception.
+        /* Take an INVPC UsageFault by pushing the stack again;
+         * we know we're v7M so this is never a Secure UsageFault.
          */
+        assert(!arm_feature(env, ARM_FEATURE_V8));
         armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, false);
         env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK;
         v7m_push_stack(cpu);
-- 
2.7.4

Re: [Qemu-devel] [PATCH 06/20] target/arm: Check for xPSR mismatch usage faults earlier for v8M

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> ARM v8M specifies that the INVPC usage fault for mismatched
> xPSR exception field and handler mode bit should be checked
> before updating the PSR and SP, so that the fault is taken
> with the existing stack frame rather than by pushing a new one.
> Perform this check in the right place for v8M.
> 
> Since v7M specifies in its pseudocode that this usage fault
> check should happen later, we have to retain the original
> code for that check rather than being able to merge the two.
> (The distinction is architecturally visible but only in
> very obscure corner cases like attempting an invalid exception
> return with an exception frame in read only memory.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 30 +++++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 07/20] target/arm: Warn about restoring to unaligned stack

[Peter Maydell]

Attempting to do an exception return with an exception frame that
is not 8-aligned is UNPREDICTABLE in v8M; warn about this.
(It is not UNPREDICTABLE in v7M, and our implementation can
handle the merely-4-aligned case fine, so we don't need to
do anything except warn.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index a2e46fb..979129e 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6403,6 +6403,13 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                                               return_to_sp_process);
         uint32_t frameptr = *frame_sp_p;
 
+        if (!QEMU_IS_ALIGNED(frameptr, 8) &&
+            arm_feature(env, ARM_FEATURE_V8)) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "M profile exception return with non-8-aligned SP "
+                          "for destination state is UNPREDICTABLE\n");
+        }
+
         /* Pop registers. TODO: make these accesses use the correct
          * attributes and address space (S/NS, priv/unpriv) and handle
          * memory transaction failures.
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 07/20] target/arm: Warn about restoring to unaligned stack

[Philippe Mathieu-Daudé]

On 09/22/2017 11:59 AM, Peter Maydell wrote:
> Attempting to do an exception return with an exception frame that
> is not 8-aligned is UNPREDICTABLE in v8M; warn about this.
> (It is not UNPREDICTABLE in v7M, and our implementation can
> handle the merely-4-aligned case fine, so we don't need to
> do anything except warn.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>   target/arm/helper.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index a2e46fb..979129e 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6403,6 +6403,13 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>                                                 return_to_sp_process);
>           uint32_t frameptr = *frame_sp_p;
>   
> +        if (!QEMU_IS_ALIGNED(frameptr, 8) &&
> +            arm_feature(env, ARM_FEATURE_V8)) {
> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "M profile exception return with non-8-aligned SP "
> +                          "for destination state is UNPREDICTABLE\n");
> +        }
> +
>           /* Pop registers. TODO: make these accesses use the correct
>            * attributes and address space (S/NS, priv/unpriv) and handle
>            * memory transaction failures.
> 

Re: [Qemu-devel] [PATCH 07/20] target/arm: Warn about restoring to unaligned stack

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> Attempting to do an exception return with an exception frame that
> is not 8-aligned is UNPREDICTABLE in v8M; warn about this.
> (It is not UNPREDICTABLE in v7M, and our implementation can
> handle the merely-4-aligned case fine, so we don't need to
> do anything except warn.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 7 +++++++
>  1 file changed, 7 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 08/20] target/arm: Don't warn about exception return with PC low bit set for v8M

[Peter Maydell]

In the v8M architecture, return from an exception to a PC which
has bit 0 set is not UNPREDICTABLE; it is defined that bit 0
is discarded [R_HRJH]. Restrict our complaint about this to v7M.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 979129e..59a07d2 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6421,16 +6421,22 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
         env->regs[12] = ldl_phys(cs->as, frameptr + 0x10);
         env->regs[14] = ldl_phys(cs->as, frameptr + 0x14);
         env->regs[15] = ldl_phys(cs->as, frameptr + 0x18);
-        if (env->regs[15] & 1) {
+
+        /* Returning from an exception with a PC with bit 0 set is defined
+         * behaviour on v8M (bit 0 is ignored), but for v7M it was specified
+         * to be UNPREDICTABLE. In practice actual v7M hardware seems to ignore
+         * the lsbit, and there are several RTOSes out there which incorrectly
+         * assume the r15 in the stack frame should be a Thumb-style "lsbit
+         * indicates ARM/Thumb" value, so ignore the bit on v7M as well, but
+         * complain about the badly behaved guest.
+         */
+        if ((env->regs[15] & 1) && !arm_feature(env, ARM_FEATURE_V8)) {
             qemu_log_mask(LOG_GUEST_ERROR,
                           "M profile return from interrupt with misaligned "
-                          "PC is UNPREDICTABLE\n");
-            /* Actual hardware seems to ignore the lsbit, and there are several
-             * RTOSes out there which incorrectly assume the r15 in the stack
-             * frame should be a Thumb-style "lsbit indicates ARM/Thumb" value.
-             */
-            env->regs[15] &= ~1U;
+                          "PC is UNPREDICTABLE on v7M\n");
         }
+        env->regs[15] &= ~1U;
+
         xpsr = ldl_phys(cs->as, frameptr + 0x1c);
 
         if (arm_feature(env, ARM_FEATURE_V8)) {
-- 
2.7.4

Re: [Qemu-devel] [PATCH 08/20] target/arm: Don't warn about exception return with PC low bit set for v8M

[Philippe Mathieu-Daudé]

On 09/22/2017 11:59 AM, Peter Maydell wrote:
> In the v8M architecture, return from an exception to a PC which
> has bit 0 set is not UNPREDICTABLE; it is defined that bit 0
> is discarded [R_HRJH]. Restrict our complaint about this to v7M.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>   target/arm/helper.c | 20 +++++++++++++-------
>   1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 979129e..59a07d2 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6421,16 +6421,22 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>           env->regs[12] = ldl_phys(cs->as, frameptr + 0x10);
>           env->regs[14] = ldl_phys(cs->as, frameptr + 0x14);
>           env->regs[15] = ldl_phys(cs->as, frameptr + 0x18);
> -        if (env->regs[15] & 1) {
> +
> +        /* Returning from an exception with a PC with bit 0 set is defined
> +         * behaviour on v8M (bit 0 is ignored), but for v7M it was specified
> +         * to be UNPREDICTABLE. In practice actual v7M hardware seems to ignore
> +         * the lsbit, and there are several RTOSes out there which incorrectly
> +         * assume the r15 in the stack frame should be a Thumb-style "lsbit
> +         * indicates ARM/Thumb" value, so ignore the bit on v7M as well, but
> +         * complain about the badly behaved guest.
> +         */
> +        if ((env->regs[15] & 1) && !arm_feature(env, ARM_FEATURE_V8)) {
>               qemu_log_mask(LOG_GUEST_ERROR,
>                             "M profile return from interrupt with misaligned "
> -                          "PC is UNPREDICTABLE\n");
> -            /* Actual hardware seems to ignore the lsbit, and there are several
> -             * RTOSes out there which incorrectly assume the r15 in the stack
> -             * frame should be a Thumb-style "lsbit indicates ARM/Thumb" value.
> -             */
> -            env->regs[15] &= ~1U;
> +                          "PC is UNPREDICTABLE on v7M\n");
>           }
> +        env->regs[15] &= ~1U;
> +
>           xpsr = ldl_phys(cs->as, frameptr + 0x1c);
>   
>           if (arm_feature(env, ARM_FEATURE_V8)) {
> 

Re: [Qemu-devel] [PATCH 08/20] target/arm: Don't warn about exception return with PC low bit set for v8M

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> +        if ((env->regs[15] & 1) && !arm_feature(env, ARM_FEATURE_V8)) {
>              qemu_log_mask(LOG_GUEST_ERROR,
>                            "M profile return from interrupt with misaligned "
> -                          "PC is UNPREDICTABLE\n");
> -            /* Actual hardware seems to ignore the lsbit, and there are several
> -             * RTOSes out there which incorrectly assume the r15 in the stack
> -             * frame should be a Thumb-style "lsbit indicates ARM/Thumb" value.
> -             */
> -            env->regs[15] &= ~1U;
> +                          "PC is UNPREDICTABLE on v7M\n");
>          }
> +        env->regs[15] &= ~1U;

If you're going to always test regs[15] & 1, you might as well use that and
avoid an unlikely(?) writeback.

    if (env->regs[15] & 1) {
        if (!arm_feature(env, ARM_FEATURE_V8)) {
            qemu_log_mask(...);
        }
        env->regs[15] &= ~1U;
    }

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: [Qemu-devel] [PATCH 08/20] target/arm: Don't warn about exception return with PC low bit set for v8M

[Richard Henderson]

On 10/05/2017 12:32 PM, Richard Henderson wrote:
>     if (env->regs[15] & 1) {
>         if (!arm_feature(env, ARM_FEATURE_V8)) {
>             qemu_log_mask(...);
>         }
>         env->regs[15] &= ~1U;
>     }

Bah.  Even better to move the bit clear statement before the feature check.
The two loads from env->regs[15] will no longer be separated by a function call
and therefore CSEd by the compiler.


r~

[Qemu-devel] [PATCH 09/20] target/arm: Add new-in-v8M SFSR and SFAR

[Peter Maydell]

Add the new M profile Secure Fault Status Register
and Secure Fault Address Register.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h      | 12 ++++++++++++
 hw/intc/armv7m_nvic.c | 34 ++++++++++++++++++++++++++++++++++
 target/arm/machine.c  |  2 ++
 3 files changed, 48 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index ad6eff4..9e3a16d 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -443,8 +443,10 @@ typedef struct CPUARMState {
         uint32_t cfsr[M_REG_NUM_BANKS]; /* Configurable Fault Status */
         uint32_t hfsr; /* HardFault Status */
         uint32_t dfsr; /* Debug Fault Status Register */
+        uint32_t sfsr; /* Secure Fault Status Register */
         uint32_t mmfar[M_REG_NUM_BANKS]; /* MemManage Fault Address */
         uint32_t bfar; /* BusFault Address */
+        uint32_t sfar; /* Secure Fault Address Register */
         unsigned mpu_ctrl[M_REG_NUM_BANKS]; /* MPU_CTRL */
         int exception;
         uint32_t primask[M_REG_NUM_BANKS];
@@ -1260,6 +1262,16 @@ FIELD(V7M_DFSR, DWTTRAP, 2, 1)
 FIELD(V7M_DFSR, VCATCH, 3, 1)
 FIELD(V7M_DFSR, EXTERNAL, 4, 1)
 
+/* V7M SFSR bits */
+FIELD(V7M_SFSR, INVEP, 0, 1)
+FIELD(V7M_SFSR, INVIS, 1, 1)
+FIELD(V7M_SFSR, INVER, 2, 1)
+FIELD(V7M_SFSR, AUVIOL, 3, 1)
+FIELD(V7M_SFSR, INVTRAN, 4, 1)
+FIELD(V7M_SFSR, LSPERR, 5, 1)
+FIELD(V7M_SFSR, SFARVALID, 6, 1)
+FIELD(V7M_SFSR, LSERR, 7, 1)
+
 /* v7M MPU_CTRL bits */
 FIELD(V7M_MPU_CTRL, ENABLE, 0, 1)
 FIELD(V7M_MPU_CTRL, HFNMIENA, 1, 1)
diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index a1041c2..deea637 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -1017,6 +1017,22 @@ static uint32_t nvic_readl(NVICState *s, uint32_t offset, MemTxAttrs attrs)
             goto bad_offset;
         }
         return cpu->env.pmsav8.mair1[attrs.secure];
+    case 0xde4: /* SFSR */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return 0;
+        }
+        return cpu->env.v7m.sfsr;
+    case 0xde8: /* SFAR */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return 0;
+        }
+        return cpu->env.v7m.sfar;
     default:
     bad_offset:
         qemu_log_mask(LOG_GUEST_ERROR, "NVIC: Bad read offset 0x%x\n", offset);
@@ -1368,6 +1384,24 @@ static void nvic_writel(NVICState *s, uint32_t offset, uint32_t value,
          * only affect cacheability, and we don't implement caching.
          */
         break;
+    case 0xde4: /* SFSR */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return;
+        }
+        cpu->env.v7m.sfsr &= ~value; /* W1C */
+        break;
+    case 0xde8: /* SFAR */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return;
+        }
+        cpu->env.v7m.sfsr = value;
+        break;
     case 0xf00: /* Software Triggered Interrupt Register */
     {
         int excnum = (value & 0x1ff) + NVIC_FIRST_IRQ;
diff --git a/target/arm/machine.c b/target/arm/machine.c
index e5fe083..d4b3baf 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -276,6 +276,8 @@ static const VMStateDescription vmstate_m_security = {
         VMSTATE_UINT32(env.v7m.ccr[M_REG_S], ARMCPU),
         VMSTATE_UINT32(env.v7m.mmfar[M_REG_S], ARMCPU),
         VMSTATE_UINT32(env.v7m.cfsr[M_REG_S], ARMCPU),
+        VMSTATE_UINT32(env.v7m.sfsr, ARMCPU),
+        VMSTATE_UINT32(env.v7m.sfar, ARMCPU),
         VMSTATE_END_OF_LIST()
     }
 };
-- 
2.7.4

Re: [Qemu-devel] [PATCH 09/20] target/arm: Add new-in-v8M SFSR and SFAR

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> Add the new M profile Secure Fault Status Register
> and Secure Fault Address Register.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/cpu.h      | 12 ++++++++++++
>  hw/intc/armv7m_nvic.c | 34 ++++++++++++++++++++++++++++++++++
>  target/arm/machine.c  |  2 ++
>  3 files changed, 48 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 10/20] target/arm: Update excret sanity checks for v8M

[Peter Maydell]

In v8M, more bits are defined in the exception-return magic
values; update the code that checks these so we accept
the v8M values when the CPU permits them.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 73 ++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 58 insertions(+), 15 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 59a07d2..da3a36e 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6275,8 +6275,9 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
     uint32_t excret;
     uint32_t xpsr;
     bool ufault = false;
-    bool return_to_sp_process = false;
-    bool return_to_handler = false;
+    bool sfault = false;
+    bool return_to_sp_process;
+    bool return_to_handler;
     bool rettobase = false;
     bool exc_secure = false;
     bool return_to_secure;
@@ -6310,6 +6311,19 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                       excret);
     }
 
+    if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+        /* EXC_RETURN.ES validation check (R_SMFL). We must do this before
+         * we pick which FAULTMASK to clear.
+         */
+        if (!env->v7m.secure &&
+            ((excret & R_V7M_EXCRET_ES_MASK) ||
+             !(excret & R_V7M_EXCRET_DCRS_MASK))) {
+            sfault = 1;
+            /* For all other purposes, treat ES as 0 (R_HXSR) */
+            excret &= ~R_V7M_EXCRET_ES_MASK;
+        }
+    }
+
     if (env->v7m.exception != ARMV7M_EXCP_NMI) {
         /* Auto-clear FAULTMASK on return from other than NMI.
          * If the security extension is implemented then this only
@@ -6347,24 +6361,53 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
         g_assert_not_reached();
     }
 
+    return_to_handler = !(excret & R_V7M_EXCRET_MODE_MASK);
+    return_to_sp_process = excret & R_V7M_EXCRET_SPSEL_MASK;
     return_to_secure = arm_feature(env, ARM_FEATURE_M_SECURITY) &&
         (excret & R_V7M_EXCRET_S_MASK);
 
-    switch (excret & 0xf) {
-    case 1: /* Return to Handler */
-        return_to_handler = true;
-        break;
-    case 13: /* Return to Thread using Process stack */
-        return_to_sp_process = true;
-        /* fall through */
-    case 9: /* Return to Thread using Main stack */
-        if (!rettobase &&
-            !(env->v7m.ccr[env->v7m.secure] & R_V7M_CCR_NONBASETHRDENA_MASK)) {
+    if (arm_feature(env, ARM_FEATURE_V8)) {
+        if (!arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+            /* UNPREDICTABLE if S == 1 or DCRS == 0 or ES == 1 (R_XLCP);
+             * we choose to take the UsageFault.
+             */
+            if ((excret & R_V7M_EXCRET_S_MASK) ||
+                (excret & R_V7M_EXCRET_ES_MASK) ||
+                !(excret & R_V7M_EXCRET_DCRS_MASK)) {
+                ufault = true;
+            }
+        }
+        if (excret & R_V7M_EXCRET_RES0_MASK) {
             ufault = true;
         }
-        break;
-    default:
-        ufault = true;
+    } else {
+        /* For v7M we only recognize certain combinations of the low bits */
+        switch (excret & 0xf) {
+        case 1: /* Return to Handler */
+            break;
+        case 13: /* Return to Thread using Process stack */
+        case 9: /* Return to Thread using Main stack */
+            /* We only need to check NONBASETHRDENA for v7M, because in
+             * v8M this bit does not exist (it is RES1).
+             */
+            if (!rettobase &&
+                !(env->v7m.ccr[env->v7m.secure] &
+                  R_V7M_CCR_NONBASETHRDENA_MASK)) {
+                ufault = true;
+            }
+            break;
+        default:
+            ufault = true;
+        }
+    }
+
+    if (sfault) {
+        env->v7m.sfsr |= R_V7M_SFSR_INVER_MASK;
+        armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
+        v7m_exception_taken(cpu, excret);
+        qemu_log_mask(CPU_LOG_INT, "...taking SecureFault on existing "
+                      "stackframe: failed EXC_RETURN.ES validity check\n");
+        return;
     }
 
     if (ufault) {
-- 
2.7.4

Re: [Qemu-devel] [PATCH 10/20] target/arm: Update excret sanity checks for v8M

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> In v8M, more bits are defined in the exception-return magic
> values; update the code that checks these so we accept
> the v8M values when the CPU permits them.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 73 ++++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 58 insertions(+), 15 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 11/20] target/arm: Add support for restoring v8M additional state context

[Peter Maydell]

For v8M, exceptions from Secure to Non-Secure state will save
callee-saved registers to the exception frame as well as the
caller-saved registers. Add support for unstacking these
registers in exception exit when necessary.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index da3a36e..25f5675 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6453,6 +6453,36 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                           "for destination state is UNPREDICTABLE\n");
         }
 
+        /* Do we need to pop callee-saved registers? */
+        if (return_to_secure &&
+            ((excret & R_V7M_EXCRET_ES_MASK) == 0 ||
+             (excret & R_V7M_EXCRET_DCRS_MASK) == 0)) {
+            uint32_t expected_sig = 0xfefa125b;
+            uint32_t actual_sig = ldl_phys(cs->as, frameptr);
+
+            if (expected_sig != actual_sig) {
+                /* Take a SecureFault on the current stack */
+                env->v7m.sfsr |= R_V7M_SFSR_INVIS_MASK;
+                armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
+                v7m_exception_taken(cpu, excret);
+                qemu_log_mask(CPU_LOG_INT, "...taking SecureFault on existing "
+                              "stackframe: failed exception return integrity "
+                              "signature check\n");
+                return;
+            }
+
+            env->regs[4] = ldl_phys(cs->as, frameptr + 0x8);
+            env->regs[5] = ldl_phys(cs->as, frameptr + 0xc);
+            env->regs[6] = ldl_phys(cs->as, frameptr + 0x10);
+            env->regs[7] = ldl_phys(cs->as, frameptr + 0x14);
+            env->regs[8] = ldl_phys(cs->as, frameptr + 0x18);
+            env->regs[9] = ldl_phys(cs->as, frameptr + 0x1c);
+            env->regs[10] = ldl_phys(cs->as, frameptr + 0x20);
+            env->regs[11] = ldl_phys(cs->as, frameptr + 0x24);
+
+            frameptr += 0x28;
+        }
+
         /* Pop registers. TODO: make these accesses use the correct
          * attributes and address space (S/NS, priv/unpriv) and handle
          * memory transaction failures.
-- 
2.7.4

Re: [Qemu-devel] [PATCH 11/20] target/arm: Add support for restoring v8M additional state context

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> For v8M, exceptions from Secure to Non-Secure state will save
> callee-saved registers to the exception frame as well as the
> caller-saved registers. Add support for unstacking these
> registers in exception exit when necessary.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 12/20] target/arm: Add v8M support to exception entry code

[Peter Maydell]

Add support for v8M and in particular the security extension
to the exception entry code. This requires changes to:
 * calculation of the exception-return magic LR value
 * push the callee-saves registers in certain cases
 * clear registers when taking non-secure exceptions to avoid
   leaking information from the interrupted secure code
 * switch to the correct security state on entry
 * use the vector table for the security state we're targeting

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 165 +++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 145 insertions(+), 20 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 25f5675..7511566 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6200,12 +6200,12 @@ static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
     }
 }
 
-static uint32_t arm_v7m_load_vector(ARMCPU *cpu)
+static uint32_t arm_v7m_load_vector(ARMCPU *cpu, bool targets_secure)
 {
     CPUState *cs = CPU(cpu);
     CPUARMState *env = &cpu->env;
     MemTxResult result;
-    hwaddr vec = env->v7m.vecbase[env->v7m.secure] + env->v7m.exception * 4;
+    hwaddr vec = env->v7m.vecbase[targets_secure] + env->v7m.exception * 4;
     uint32_t addr;
 
     addr = address_space_ldl(cs->as, vec,
@@ -6217,13 +6217,48 @@ static uint32_t arm_v7m_load_vector(ARMCPU *cpu)
          * Since we don't model Lockup, we just report this guest error
          * via cpu_abort().
          */
-        cpu_abort(cs, "Failed to read from exception vector table "
-                  "entry %08x\n", (unsigned)vec);
+        cpu_abort(cs, "Failed to read from %s exception vector table "
+                  "entry %08x\n", targets_secure ? "secure" : "nonsecure",
+                  (unsigned)vec);
     }
     return addr;
 }
 
-static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr)
+static void v7m_push_callee_stack(ARMCPU *cpu, uint32_t lr, bool dotailchain)
+{
+    /* For v8M, push the callee-saves register part of the stack frame.
+     * Compare the v8M pseudocode PushCalleeStack().
+     * In the tailchaining case this may not be the current stack.
+     */
+    CPUARMState *env = &cpu->env;
+    CPUState *cs = CPU(cpu);
+    uint32_t *frame_sp_p;
+    uint32_t frameptr;
+
+    if (dotailchain) {
+        frame_sp_p = get_v7m_sp_ptr(env, true,
+                                    lr & R_V7M_EXCRET_MODE_MASK,
+                                    lr & R_V7M_EXCRET_SPSEL_MASK);
+    } else {
+        frame_sp_p = &env->regs[13];
+    }
+
+    frameptr = *frame_sp_p - 0x28;
+
+    stl_phys(cs->as, frameptr, 0xfefa125b);
+    stl_phys(cs->as, frameptr + 0x8, env->regs[4]);
+    stl_phys(cs->as, frameptr + 0xc, env->regs[5]);
+    stl_phys(cs->as, frameptr + 0x10, env->regs[6]);
+    stl_phys(cs->as, frameptr + 0x14, env->regs[7]);
+    stl_phys(cs->as, frameptr + 0x18, env->regs[8]);
+    stl_phys(cs->as, frameptr + 0x1c, env->regs[9]);
+    stl_phys(cs->as, frameptr + 0x20, env->regs[10]);
+    stl_phys(cs->as, frameptr + 0x24, env->regs[11]);
+
+    *frame_sp_p = frameptr;
+}
+
+static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr, bool dotailchain)
 {
     /* Do the "take the exception" parts of exception entry,
      * but not the pushing of state to the stack. This is
@@ -6231,14 +6266,84 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr)
      */
     CPUARMState *env = &cpu->env;
     uint32_t addr;
+    bool targets_secure;
+
+    targets_secure = armv7m_nvic_acknowledge_irq(env->nvic);
 
-    armv7m_nvic_acknowledge_irq(env->nvic);
+    if (arm_feature(env, ARM_FEATURE_V8)) {
+        if (arm_feature(env, ARM_FEATURE_M_SECURITY) &&
+            (lr & R_V7M_EXCRET_S_MASK)) {
+            /* The background code (the owner of the registers in the
+             * exception frame) is Secure. This means it may either already
+             * have or now needs to push callee-saves registers.
+             */
+            if (targets_secure) {
+                if (dotailchain && !(lr & R_V7M_EXCRET_ES_MASK)) {
+                    /* We took an exception from Secure to NonSecure
+                     * (which means the callee-saved registers got stacked)
+                     * and are now tailchaining to a Secure exception.
+                     * Clear DCRS so eventual return from this Secure
+                     * exception unstacks the callee-saved registers.
+                     */
+                    lr &= ~R_V7M_EXCRET_DCRS_MASK;
+                }
+            } else {
+                /* We're going to a non-secure exception; push the
+                 * callee-saves registers to the stack now, if they're
+                 * not already saved.
+                 */
+                if (lr & R_V7M_EXCRET_DCRS_MASK &&
+                    !(dotailchain && (lr & R_V7M_EXCRET_ES_MASK))) {
+                    v7m_push_callee_stack(cpu, lr, dotailchain);
+                }
+                lr |= R_V7M_EXCRET_DCRS_MASK;
+            }
+        }
+
+        lr &= ~R_V7M_EXCRET_ES_MASK;
+        if (targets_secure || !arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+            lr |= R_V7M_EXCRET_ES_MASK;
+        }
+        lr &= ~R_V7M_EXCRET_SPSEL_MASK;
+        if (env->v7m.control[targets_secure] & R_V7M_CONTROL_SPSEL_MASK) {
+            lr |= R_V7M_EXCRET_SPSEL_MASK;
+        }
+
+        /* Clear registers if necessary to prevent non-secure exception
+         * code being able to see register values from secure code.
+         * Where register values become architecturally UNKNOWN we leave
+         * them with their previous values.
+         */
+        if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+            if (!targets_secure) {
+                /* Always clear the caller-saved registers (they have been
+                 * pushed to the stack earlier in v7m_push_stack()).
+                 * Clear callee-saved registers if the background code is
+                 * Secure (in which case these regs were saved in
+                 * v7m_push_callee_stack()).
+                 */
+                int i;
+
+                for (i = 0; i < 13; i++) {
+                    /* r4..r11 are callee-saves, zero only if EXCRET.S == 1 */
+                    if (i < 4 || i > 11 || (lr & R_V7M_EXCRET_S_MASK)) {
+                        env->regs[i] = 0;
+                    }
+                }
+                /* Clear EAPSR */
+                xpsr_write(env, 0, XPSR_NZCV | XPSR_Q | XPSR_GE | XPSR_IT);
+            }
+        }
+    }
+
+    /* Switch to target security state -- must do this before writing SPSEL */
+    switch_v7m_security_state(env, targets_secure);
     write_v7m_control_spsel(env, 0);
     arm_clear_exclusive(env);
     /* Clear IT bits */
     env->condexec_bits = 0;
     env->regs[14] = lr;
-    addr = arm_v7m_load_vector(cpu);
+    addr = arm_v7m_load_vector(cpu, targets_secure);
     env->regs[15] = addr & 0xfffffffe;
     env->thumb = addr & 1;
 }
@@ -6404,7 +6509,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
     if (sfault) {
         env->v7m.sfsr |= R_V7M_SFSR_INVER_MASK;
         armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
-        v7m_exception_taken(cpu, excret);
+        v7m_exception_taken(cpu, excret, true);
         qemu_log_mask(CPU_LOG_INT, "...taking SecureFault on existing "
                       "stackframe: failed EXC_RETURN.ES validity check\n");
         return;
@@ -6416,7 +6521,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
          */
         env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK;
         armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, env->v7m.secure);
-        v7m_exception_taken(cpu, excret);
+        v7m_exception_taken(cpu, excret, true);
         qemu_log_mask(CPU_LOG_INT, "...taking UsageFault on existing "
                       "stackframe: failed exception return integrity check\n");
         return;
@@ -6464,7 +6569,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                 /* Take a SecureFault on the current stack */
                 env->v7m.sfsr |= R_V7M_SFSR_INVIS_MASK;
                 armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
-                v7m_exception_taken(cpu, excret);
+                v7m_exception_taken(cpu, excret, true);
                 qemu_log_mask(CPU_LOG_INT, "...taking SecureFault on existing "
                               "stackframe: failed exception return integrity "
                               "signature check\n");
@@ -6527,7 +6632,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
                 armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE,
                                         env->v7m.secure);
                 env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK;
-                v7m_exception_taken(cpu, excret);
+                v7m_exception_taken(cpu, excret, true);
                 qemu_log_mask(CPU_LOG_INT, "...taking UsageFault on existing "
                               "stackframe: failed exception return integrity "
                               "check\n");
@@ -6564,7 +6669,7 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
         armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE, false);
         env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK;
         v7m_push_stack(cpu);
-        v7m_exception_taken(cpu, excret);
+        v7m_exception_taken(cpu, excret, false);
         qemu_log_mask(CPU_LOG_INT, "...taking UsageFault on new stackframe: "
                       "failed exception return integrity check\n");
         return;
@@ -6708,20 +6813,40 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
         return; /* Never happens.  Keep compiler happy.  */
     }
 
-    lr = R_V7M_EXCRET_RES1_MASK |
-        R_V7M_EXCRET_S_MASK |
-        R_V7M_EXCRET_DCRS_MASK |
-        R_V7M_EXCRET_FTYPE_MASK |
-        R_V7M_EXCRET_ES_MASK;
-    if (env->v7m.control[env->v7m.secure] & R_V7M_CONTROL_SPSEL_MASK) {
-        lr |= R_V7M_EXCRET_SPSEL_MASK;
+    if (arm_feature(env, ARM_FEATURE_V8)) {
+        lr = R_V7M_EXCRET_RES1_MASK |
+            R_V7M_EXCRET_DCRS_MASK |
+            R_V7M_EXCRET_FTYPE_MASK;
+        /* The S bit indicates whether we should return to Secure
+         * or NonSecure (ie our current state).
+         * The ES bit indicates whether we're taking this exception
+         * to Secure or NonSecure (ie our target state). We set it
+         * later, in v7m_exception_taken().
+         * The SPSEL bit is also set in v7m_exception_taken() for v8M.
+         * This corresponds to the ARM ARM pseudocode for v8M setting
+         * some LR bits in PushStack() and some in ExceptionTaken();
+         * the distinction matters for the tailchain cases where we
+         * can take an exception without pushing the stack.
+         */
+        if (env->v7m.secure) {
+            lr |= R_V7M_EXCRET_S_MASK;
+        }
+    } else {
+        lr = R_V7M_EXCRET_RES1_MASK |
+            R_V7M_EXCRET_S_MASK |
+            R_V7M_EXCRET_DCRS_MASK |
+            R_V7M_EXCRET_FTYPE_MASK |
+            R_V7M_EXCRET_ES_MASK;
+        if (env->v7m.control[M_REG_NS] & R_V7M_CONTROL_SPSEL_MASK) {
+            lr |= R_V7M_EXCRET_SPSEL_MASK;
+        }
     }
     if (!arm_v7m_is_handler_mode(env)) {
         lr |= R_V7M_EXCRET_MODE_MASK;
     }
 
     v7m_push_stack(cpu);
-    v7m_exception_taken(cpu, lr);
+    v7m_exception_taken(cpu, lr, false);
     qemu_log_mask(CPU_LOG_INT, "... as %d\n", env->v7m.exception);
 }
 
-- 
2.7.4

Re: [Qemu-devel] [PATCH 12/20] target/arm: Add v8M support to exception entry code

[Richard Henderson]

On 09/22/2017 10:59 AM, Peter Maydell wrote:
> Add support for v8M and in particular the security extension
> to the exception entry code. This requires changes to:
>  * calculation of the exception-return magic LR value
>  * push the callee-saves registers in certain cases
>  * clear registers when taking non-secure exceptions to avoid
>    leaking information from the interrupted secure code
>  * switch to the correct security state on entry
>  * use the vector table for the security state we're targeting
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 165 +++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 145 insertions(+), 20 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 13/20] nvic: Implement Security Attribution Unit registers

[Peter Maydell]

Implement the register interface for the SAU: SAU_CTRL,
SAU_TYPE, SAU_RNR, SAU_RBAR and SAU_RLAR. None of the
actual behaviour is implemented here; registers just
read back as written.

When the CPU definition for Cortex-M33 is eventually
added, its initfn will set cpu->sau_sregion, in the same
way that we currently set cpu->pmsav7_dregion for the
M3 and M4.

Number of SAU regions is typically a configurable
CPU parameter, but this patch doesn't provide a
QEMU CPU property for it. We can easily add one when
we have a board that requires it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h      |  10 +++++
 hw/intc/armv7m_nvic.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++
 target/arm/cpu.c      |  27 ++++++++++++
 target/arm/machine.c  |  14 ++++++
 4 files changed, 167 insertions(+)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 9e3a16d..441e584 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -568,6 +568,14 @@ typedef struct CPUARMState {
         uint32_t mair1[M_REG_NUM_BANKS];
     } pmsav8;
 
+    /* v8M SAU */
+    struct {
+        uint32_t *rbar;
+        uint32_t *rlar;
+        uint32_t rnr;
+        uint32_t ctrl;
+    } sau;
+
     void *nvic;
     const struct arm_boot_info *boot_info;
     /* Store GICv3CPUState to access from this struct */
@@ -663,6 +671,8 @@ struct ARMCPU {
     bool has_mpu;
     /* PMSAv7 MPU number of supported regions */
     uint32_t pmsav7_dregion;
+    /* v8M SAU number of supported regions */
+    uint32_t sau_sregion;
 
     /* PSCI conduit used to invoke PSCI methods
      * 0 - disabled, 1 - smc, 2 - hvc
diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index deea637..bd1d5d3 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -1017,6 +1017,60 @@ static uint32_t nvic_readl(NVICState *s, uint32_t offset, MemTxAttrs attrs)
             goto bad_offset;
         }
         return cpu->env.pmsav8.mair1[attrs.secure];
+    case 0xdd0: /* SAU_CTRL */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return 0;
+        }
+        return cpu->env.sau.ctrl;
+    case 0xdd4: /* SAU_TYPE */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return 0;
+        }
+        return cpu->sau_sregion;
+    case 0xdd8: /* SAU_RNR */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return 0;
+        }
+        return cpu->env.sau.rnr;
+    case 0xddc: /* SAU_RBAR */
+    {
+        int region = cpu->env.sau.rnr;
+
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return 0;
+        }
+        if (region >= cpu->sau_sregion) {
+            return 0;
+        }
+        return cpu->env.sau.rbar[region];
+    }
+    case 0xde0: /* SAU_RLAR */
+    {
+        int region = cpu->env.sau.rnr;
+
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return 0;
+        }
+        if (region >= cpu->sau_sregion) {
+            return 0;
+        }
+        return cpu->env.sau.rlar[region];
+    }
     case 0xde4: /* SFSR */
         if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
             goto bad_offset;
@@ -1384,6 +1438,68 @@ static void nvic_writel(NVICState *s, uint32_t offset, uint32_t value,
          * only affect cacheability, and we don't implement caching.
          */
         break;
+    case 0xdd0: /* SAU_CTRL */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return;
+        }
+        cpu->env.sau.ctrl = value & 3;
+    case 0xdd4: /* SAU_TYPE */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        break;
+    case 0xdd8: /* SAU_RNR */
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return;
+        }
+        if (value >= cpu->sau_sregion) {
+            qemu_log_mask(LOG_GUEST_ERROR, "SAU region out of range %"
+                          PRIu32 "/%" PRIu32 "\n",
+                          value, cpu->sau_sregion);
+        } else {
+            cpu->env.sau.rnr = value;
+        }
+        break;
+    case 0xddc: /* SAU_RBAR */
+    {
+        int region = cpu->env.sau.rnr;
+
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return;
+        }
+        if (region >= cpu->sau_sregion) {
+            return;
+        }
+        cpu->env.sau.rbar[region] = value & ~0x1f;
+        tlb_flush(CPU(cpu));
+        break;
+    }
+    case 0xde0: /* SAU_RLAR */
+    {
+        int region = cpu->env.sau.rnr;
+
+        if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
+            goto bad_offset;
+        }
+        if (!attrs.secure) {
+            return;
+        }
+        if (region >= cpu->sau_sregion) {
+            return;
+        }
+        cpu->env.sau.rlar[region] = value & ~0x1c;
+        tlb_flush(CPU(cpu));
+        break;
+    }
     case 0xde4: /* SFSR */
         if (!arm_feature(&cpu->env, ARM_FEATURE_V8)) {
             goto bad_offset;
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 3344979..1627836 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -285,6 +285,18 @@ static void arm_cpu_reset(CPUState *s)
         env->pmsav8.mair1[M_REG_S] = 0;
     }
 
+    if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+        if (cpu->sau_sregion > 0) {
+            memset(env->sau.rbar, 0, sizeof(*env->sau.rbar) * cpu->sau_sregion);
+            memset(env->sau.rlar, 0, sizeof(*env->sau.rlar) * cpu->sau_sregion);
+        }
+        env->sau.rnr = 0;
+        /* SAU_CTRL reset value is IMPDEF; we choose 0, which is what
+         * the Cortex-M33 does.
+         */
+        env->sau.ctrl = 0;
+    }
+
     set_flush_to_zero(1, &env->vfp.standard_fp_status);
     set_flush_inputs_to_zero(1, &env->vfp.standard_fp_status);
     set_default_nan_mode(1, &env->vfp.standard_fp_status);
@@ -870,6 +882,20 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
         }
     }
 
+    if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+        uint32_t nr = cpu->sau_sregion;
+
+        if (nr > 0xff) {
+            error_setg(errp, "v8M SAU #regions invalid %" PRIu32, nr);
+            return;
+        }
+
+        if (nr) {
+            env->sau.rbar = g_new0(uint32_t, nr);
+            env->sau.rlar = g_new0(uint32_t, nr);
+        }
+    }
+
     if (arm_feature(env, ARM_FEATURE_EL3)) {
         set_feature(env, ARM_FEATURE_VBAR);
     }
@@ -1141,6 +1167,7 @@ static void cortex_m4_initfn(Object *obj)
     cpu->midr = 0x410fc240; /* r0p0 */
     cpu->pmsav7_dregion = 8;
 }
+
 static void arm_v7m_class_init(ObjectClass *oc, void *data)
 {
     CPUClass *cc = CPU_CLASS(oc);
diff --git a/target/arm/machine.c b/target/arm/machine.c
index d4b3baf..a52d0f9 100644
--- a/target/arm/machine.c
+++ b/target/arm/machine.c
@@ -242,6 +242,13 @@ static bool s_rnr_vmstate_validate(void *opaque, int version_id)
     return cpu->env.pmsav7.rnr[M_REG_S] < cpu->pmsav7_dregion;
 }
 
+static bool sau_rnr_vmstate_validate(void *opaque, int version_id)
+{
+    ARMCPU *cpu = opaque;
+
+    return cpu->env.sau.rnr < cpu->sau_sregion;
+}
+
 static bool m_security_needed(void *opaque)
 {
     ARMCPU *cpu = opaque;
@@ -278,6 +285,13 @@ static const VMStateDescription vmstate_m_security = {
         VMSTATE_UINT32(env.v7m.cfsr[M_REG_S], ARMCPU),
         VMSTATE_UINT32(env.v7m.sfsr, ARMCPU),
         VMSTATE_UINT32(env.v7m.sfar, ARMCPU),
+        VMSTATE_VARRAY_UINT32(env.sau.rbar, ARMCPU, sau_sregion, 0,
+                              vmstate_info_uint32, uint32_t),
+        VMSTATE_VARRAY_UINT32(env.sau.rlar, ARMCPU, sau_sregion, 0,
+                              vmstate_info_uint32, uint32_t),
+        VMSTATE_UINT32(env.sau.rnr, ARMCPU),
+        VMSTATE_VALIDATE("SAU_RNR is valid", sau_rnr_vmstate_validate),
+        VMSTATE_UINT32(env.sau.ctrl, ARMCPU),
         VMSTATE_END_OF_LIST()
     }
 };
-- 
2.7.4

Re: [Qemu-devel] [PATCH 13/20] nvic: Implement Security Attribution Unit registers

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> Implement the register interface for the SAU: SAU_CTRL,
> SAU_TYPE, SAU_RNR, SAU_RBAR and SAU_RLAR. None of the
> actual behaviour is implemented here; registers just
> read back as written.
> 
> When the CPU definition for Cortex-M33 is eventually
> added, its initfn will set cpu->sau_sregion, in the same
> way that we currently set cpu->pmsav7_dregion for the
> M3 and M4.
> 
> Number of SAU regions is typically a configurable
> CPU parameter, but this patch doesn't provide a
> QEMU CPU property for it. We can easily add one when
> we have a board that requires it.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/cpu.h      |  10 +++++
>  hw/intc/armv7m_nvic.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  target/arm/cpu.c      |  27 ++++++++++++
>  target/arm/machine.c  |  14 ++++++
>  4 files changed, 167 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 14/20] target/arm: Implement security attribute lookups for memory accesses

[Peter Maydell]

Implement the security attribute lookups for memory accesses
in the get_phys_addr() functions, causing these to generate
various kinds of SecureFault for bad accesses.

The major subtlety in this code relates to handling of the
case when the security attributes the SAU assigns to the
address don't match the current security state of the CPU.

In the ARM ARM pseudocode for validating instruction
accesses, the security attributes of the address determine
whether the Secure or NonSecure MPU state is used. At face
value, handling this would require us to encode the relevant
bits of state into mmu_idx for both S and NS at once, which
would result in our needing 16 mmu indexes. Fortunately we
don't actually need to do this because a mismatch between
address attributes and CPU state means either:
 * some kind of fault (usually a SecureFault, but in theory
   perhaps a UserFault for unaligned access to Device memory)
 * execution of the SG instruction in NS state from a
   Secure & NonSecure code region

The purpose of SG is simply to flip the CPU into Secure
state, so we can handle it by emulating execution of that
instruction directly in arm_v7m_cpu_do_interrupt(), which
means we can treat all the mismatch cases as "throw an
exception" and we don't need to encode the state of the
other MPU bank into our mmu_idx values.

This commit doesn't include the actual emulation of SG;
it also doesn't include implementation of the IDAU, which
is a per-board way to specify hard-coded memory attributes
for addresses, which override the CPU-internal SAU if they
specify a more secure setting than the SAU is programmed to.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/internals.h |  15 ++++
 target/arm/helper.c    | 182 ++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 195 insertions(+), 2 deletions(-)

diff --git a/target/arm/internals.h b/target/arm/internals.h
index 18be370..fd9a7e8 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -71,6 +71,21 @@ FIELD(V7M_EXCRET, DCRS, 5, 1)
 FIELD(V7M_EXCRET, S, 6, 1)
 FIELD(V7M_EXCRET, RES1, 7, 25) /* including the must-be-1 prefix */
 
+/* We use a few fake FSR values for internal purposes in M profile.
+ * M profile cores don't have A/R format FSRs, but currently our
+ * get_phys_addr() code assumes A/R profile and reports failures via
+ * an A/R format FSR value. We then translate that into the proper
+ * M profile exception and FSR status bit in arm_v7m_cpu_do_interrupt().
+ * Mostly the FSR values we use for this are those defined for v7PMSA,
+ * since we share some of that codepath. A few kinds of fault are
+ * only for M profile and have no A/R equivalent, though, so we have
+ * to pick a value from the reserved range (which we never otherwise
+ * generate) to use for these.
+ * These values will never be visible to the guest.
+ */
+#define M_FAKE_FSR_NSC_EXEC 0xf /* NS executing in S&NSC memory */
+#define M_FAKE_FSR_SFAULT 0xe /* SecureFault INVTRAN, INVEP or AUVIOL */
+
 /*
  * For AArch64, map a given EL to an index in the banked_spsr array.
  * Note that this mapping and the AArch32 mapping defined in bank_number()
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 7511566..b1ecb66 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -31,6 +31,16 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
                                target_ulong *page_size_ptr, uint32_t *fsr,
                                ARMMMUFaultInfo *fi);
 
+/* Security attributes for an address, as returned by v8m_security_lookup. */
+typedef struct V8M_SAttributes {
+    bool ns;
+    bool nsc;
+    uint8_t sregion;
+    bool srvalid;
+    uint8_t iregion;
+    bool irvalid;
+} V8M_SAttributes;
+
 /* Definitions for the PMCCNTR and PMCR registers */
 #define PMCRD   0x8
 #define PMCRC   0x4
@@ -6748,6 +6758,46 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
          * raises the fault, in the A profile short-descriptor format.
          */
         switch (env->exception.fsr & 0xf) {
+        case M_FAKE_FSR_NSC_EXEC:
+            /* Exception generated when we try to execute code at an address
+             * which is marked as Secure & Non-Secure Callable and the CPU
+             * is in the Non-Secure state. The only instruction which can
+             * be executed like this is SG (and that only if both halves of
+             * the SG instruction have the same security attributes.)
+             * Everything else must generate an INVEP SecureFault, so we
+             * emulate the SG instruction here.
+             * TODO: actually emulate SG.
+             */
+            env->v7m.sfsr |= R_V7M_SFSR_INVEP_MASK;
+            armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
+            qemu_log_mask(CPU_LOG_INT,
+                          "...really SecureFault with SFSR.INVEP\n");
+            break;
+        case M_FAKE_FSR_SFAULT:
+            /* Various flavours of SecureFault for attempts to execute or
+             * access data in the wrong security state.
+             */
+            switch (cs->exception_index) {
+            case EXCP_PREFETCH_ABORT:
+                if (env->v7m.secure) {
+                    env->v7m.sfsr |= R_V7M_SFSR_INVTRAN_MASK;
+                    qemu_log_mask(CPU_LOG_INT,
+                                  "...really SecureFault with SFSR.INVTRAN\n");
+                } else {
+                    env->v7m.sfsr |= R_V7M_SFSR_INVEP_MASK;
+                    qemu_log_mask(CPU_LOG_INT,
+                                  "...really SecureFault with SFSR.INVEP\n");
+                }
+                break;
+            case EXCP_DATA_ABORT:
+                /* This must be an NS access to S memory */
+                env->v7m.sfsr |= R_V7M_SFSR_AUVIOL_MASK;
+                qemu_log_mask(CPU_LOG_INT,
+                              "...really SecureFault with SFSR.AUVIOL\n");
+                break;
+            }
+            armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
+            break;
         case 0x8: /* External Abort */
             switch (cs->exception_index) {
             case EXCP_PREFETCH_ABORT:
@@ -8834,9 +8884,89 @@ static bool get_phys_addr_pmsav7(CPUARMState *env, uint32_t address,
     return !(*prot & (1 << access_type));
 }
 
+static bool v8m_is_sau_exempt(CPUARMState *env,
+                              uint32_t address, MMUAccessType access_type)
+{
+    /* The architecture specifies that certain address ranges are
+     * exempt from v8M SAU/IDAU checks.
+     */
+    return
+        (access_type == MMU_INST_FETCH && m_is_system_region(env, address)) ||
+        (address >= 0xe0000000 && address <= 0xe0002fff) ||
+        (address >= 0xe000e000 && address <= 0xe000efff) ||
+        (address >= 0xe002e000 && address <= 0xe002efff) ||
+        (address >= 0xe0040000 && address <= 0xe0041fff) ||
+        (address >= 0xe00ff000 && address <= 0xe00fffff);
+}
+
+static void v8m_security_lookup(CPUARMState *env, uint32_t address,
+                                MMUAccessType access_type, ARMMMUIdx mmu_idx,
+                                V8M_SAttributes *sattrs)
+{
+    /* Look up the security attributes for this address. Compare the
+     * pseudocode SecurityCheck() function.
+     * We assume the caller has zero-initialized *sattrs.
+     */
+    ARMCPU *cpu = arm_env_get_cpu(env);
+    int r;
+
+    /* TODO: implement IDAU */
+
+    if (access_type == MMU_INST_FETCH && extract32(address, 28, 4) == 0xf) {
+        /* 0xf0000000..0xffffffff is always S for insn fetches */
+        return;
+    }
+
+    if (v8m_is_sau_exempt(env, address, access_type)) {
+        sattrs->ns = !regime_is_secure(env, mmu_idx);
+        return;
+    }
+
+    switch (env->sau.ctrl & 3) {
+    case 0: /* SAU.ENABLE == 0, SAU.ALLNS == 0 */
+        break;
+    case 2: /* SAU.ENABLE == 0, SAU.ALLNS == 1 */
+        sattrs->ns = true;
+        break;
+    default: /* SAU.ENABLE == 1 */
+        for (r = 0; r < cpu->sau_sregion; r++) {
+            if (env->sau.rlar[r] & 1) {
+                uint32_t base = env->sau.rbar[r] & ~0x1f;
+                uint32_t limit = env->sau.rlar[r] | 0x1f;
+
+                if (base <= address && limit >= address) {
+                    if (sattrs->srvalid) {
+                        /* If we hit in more than one region then we must report
+                         * as Secure, not NS-Callable, with no valid region
+                         * number info.
+                         */
+                        sattrs->ns = false;
+                        sattrs->nsc = false;
+                        sattrs->sregion = 0;
+                        sattrs->srvalid = false;
+                        break;
+                    } else {
+                        if (env->sau.rlar[r] & 2) {
+                            sattrs->nsc = true;
+                        } else {
+                            sattrs->ns = true;
+                        }
+                        sattrs->srvalid = true;
+                        sattrs->sregion = r;
+                    }
+                }
+            }
+        }
+
+        /* TODO when we support the IDAU then it may override the result here */
+        break;
+    }
+}
+
 static bool get_phys_addr_pmsav8(CPUARMState *env, uint32_t address,
                                  MMUAccessType access_type, ARMMMUIdx mmu_idx,
-                                 hwaddr *phys_ptr, int *prot, uint32_t *fsr)
+                                 hwaddr *phys_ptr, MemTxAttrs *txattrs,
+                                 int *prot, uint32_t *fsr)
 {
     ARMCPU *cpu = arm_env_get_cpu(env);
     bool is_user = regime_is_user(env, mmu_idx);
@@ -8844,10 +8974,58 @@ static bool get_phys_addr_pmsav8(CPUARMState *env, uint32_t address,
     int n;
     int matchregion = -1;
     bool hit = false;
+    V8M_SAttributes sattrs = {};
 
     *phys_ptr = address;
     *prot = 0;
 
+    if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+        v8m_security_lookup(env, address, access_type, mmu_idx, &sattrs);
+        if (access_type == MMU_INST_FETCH) {
+            /* Instruction fetches always use the MMU bank and the
+             * transaction attribute determined by the fetch address,
+             * regardless of CPU state. This is painful for QEMU
+             * to handle, because it would mean we need to encode
+             * into the mmu_idx not just the (user, negpri) information
+             * for the current security state but also that for the
+             * other security state, which would balloon the number
+             * of mmu_idx values needed alarmingly.
+             * Fortunately we can avoid this because it's not actually
+             * possible to arbitrarily execute code from memory with
+             * the wrong security attribute: it will always generate
+             * an exception of some kind or another, apart from the
+             * special case of an NS CPU executing an SG instruction
+             * in S&NSC memory. So we always just fail the translation
+             * here and sort things out in the exception handler
+             * (including possibly emulating an SG instruction).
+             */
+            if (sattrs.ns != !secure) {
+                *fsr = sattrs.nsc ? M_FAKE_FSR_NSC_EXEC : M_FAKE_FSR_SFAULT;
+                return true;
+            }
+        } else {
+            /* For data accesses we always use the MMU bank indicated
+             * by the current CPU state, but the security attributes
+             * might downgrade a secure access to nonsecure.
+             */
+            if (sattrs.ns) {
+                txattrs->secure = false;
+            } else if (!secure) {
+                /* NS access to S memory must fault.
+                 * Architecturally we should first check whether the
+                 * MPU information for this address indicates that we
+                 * are doing an unaligned access to Device memory, which
+                 * should generate a UsageFault instead. QEMU does not
+                 * currently check for that kind of unaligned access though.
+                 * If we added it we would need to do so as a special case
+                 * for M_FAKE_FSR_SFAULT in arm_v7m_cpu_do_interrupt().
+                 */
+                *fsr = M_FAKE_FSR_SFAULT;
+                return true;
+            }
+        }
+    }
+
     /* Unlike the ARM ARM pseudocode, we don't need to check whether this
      * was an exception vector read from the vector table (which is always
      * done using the default system address map), because those accesses
@@ -9112,7 +9290,7 @@ static bool get_phys_addr(CPUARMState *env, target_ulong address,
         if (arm_feature(env, ARM_FEATURE_V8)) {
             /* PMSAv8 */
             ret = get_phys_addr_pmsav8(env, address, access_type, mmu_idx,
-                                       phys_ptr, prot, fsr);
+                                       phys_ptr, attrs, prot, fsr);
         } else if (arm_feature(env, ARM_FEATURE_V7)) {
             /* PMSAv7 */
             ret = get_phys_addr_pmsav7(env, address, access_type, mmu_idx,
-- 
2.7.4

Re: [Qemu-devel] [PATCH 14/20] target/arm: Implement security attribute lookups for memory accesses

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> Implement the security attribute lookups for memory accesses
> in the get_phys_addr() functions, causing these to generate
> various kinds of SecureFault for bad accesses.
> 
> The major subtlety in this code relates to handling of the
> case when the security attributes the SAU assigns to the
> address don't match the current security state of the CPU.
> 
> In the ARM ARM pseudocode for validating instruction
> accesses, the security attributes of the address determine
> whether the Secure or NonSecure MPU state is used. At face
> value, handling this would require us to encode the relevant
> bits of state into mmu_idx for both S and NS at once, which
> would result in our needing 16 mmu indexes. Fortunately we
> don't actually need to do this because a mismatch between
> address attributes and CPU state means either:
>  * some kind of fault (usually a SecureFault, but in theory
>    perhaps a UserFault for unaligned access to Device memory)
>  * execution of the SG instruction in NS state from a
>    Secure & NonSecure code region
> 
> The purpose of SG is simply to flip the CPU into Secure
> state, so we can handle it by emulating execution of that
> instruction directly in arm_v7m_cpu_do_interrupt(), which
> means we can treat all the mismatch cases as "throw an
> exception" and we don't need to encode the state of the
> other MPU bank into our mmu_idx values.
> 
> This commit doesn't include the actual emulation of SG;
> it also doesn't include implementation of the IDAU, which
> is a per-board way to specify hard-coded memory attributes
> for addresses, which override the CPU-internal SAU if they
> specify a more secure setting than the SAU is programmed to.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/internals.h |  15 ++++
>  target/arm/helper.c    | 182 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 195 insertions(+), 2 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 15/20] target/arm: Fix calculation of secure mm_idx values

[Peter Maydell]

In cpu_mmu_index() we try to do this:
        if (env->v7m.secure) {
            mmu_idx += ARMMMUIdx_MSUser;
        }
but it will give the wrong answer, because ARMMMUIdx_MSUser
includes the 0x40 ARM_MMU_IDX_M field, and so does the
mmu_idx we're adding to, and we'll end up with 0x8n rather
than 0x4n. This error is then nullified by the call to
arm_to_core_mmu_idx() which masks out the high part, but
we're about to factor out the code that calculates the
ARMMMUIdx values so it can be used without passing it through
arm_to_core_mmu_idx(), so fix this bug first.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 441e584..70c1f85 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -2335,14 +2335,16 @@ static inline int cpu_mmu_index(CPUARMState *env, bool ifetch)
     int el = arm_current_el(env);
 
     if (arm_feature(env, ARM_FEATURE_M)) {
-        ARMMMUIdx mmu_idx = el == 0 ? ARMMMUIdx_MUser : ARMMMUIdx_MPriv;
+        ARMMMUIdx mmu_idx;
 
-        if (armv7m_nvic_neg_prio_requested(env->nvic, env->v7m.secure)) {
-            mmu_idx = ARMMMUIdx_MNegPri;
+        if (el == 0) {
+            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSUser : ARMMMUIdx_MUser;
+        } else {
+            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSPriv : ARMMMUIdx_MPriv;
         }
 
-        if (env->v7m.secure) {
-            mmu_idx += ARMMMUIdx_MSUser;
+        if (armv7m_nvic_neg_prio_requested(env->nvic, env->v7m.secure)) {
+            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSNegPri : ARMMMUIdx_MNegPri;
         }
 
         return arm_to_core_mmu_idx(mmu_idx);
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 15/20] target/arm: Fix calculation of secure mm_idx values

[Philippe Mathieu-Daudé]

On 09/22/2017 12:00 PM, Peter Maydell wrote:
> In cpu_mmu_index() we try to do this:
>         if (env->v7m.secure) {
>             mmu_idx += ARMMMUIdx_MSUser;
>         }
> but it will give the wrong answer, because ARMMMUIdx_MSUser
> includes the 0x40 ARM_MMU_IDX_M field, and so does the
> mmu_idx we're adding to, and we'll end up with 0x8n rather
> than 0x4n. This error is then nullified by the call to
> arm_to_core_mmu_idx() which masks out the high part, but
> we're about to factor out the code that calculates the
> ARMMMUIdx values so it can be used without passing it through
> arm_to_core_mmu_idx(), so fix this bug first.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>  target/arm/cpu.h | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index 441e584..70c1f85 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -2335,14 +2335,16 @@ static inline int cpu_mmu_index(CPUARMState *env, bool ifetch)
>      int el = arm_current_el(env);
>  
>      if (arm_feature(env, ARM_FEATURE_M)) {
> -        ARMMMUIdx mmu_idx = el == 0 ? ARMMMUIdx_MUser : ARMMMUIdx_MPriv;
> +        ARMMMUIdx mmu_idx;
>  
> -        if (armv7m_nvic_neg_prio_requested(env->nvic, env->v7m.secure)) {
> -            mmu_idx = ARMMMUIdx_MNegPri;
> +        if (el == 0) {
> +            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSUser : ARMMMUIdx_MUser;
> +        } else {
> +            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSPriv : ARMMMUIdx_MPriv;
>          }
>  
> -        if (env->v7m.secure) {
> -            mmu_idx += ARMMMUIdx_MSUser;
> +        if (armv7m_nvic_neg_prio_requested(env->nvic, env->v7m.secure)) {
> +            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSNegPri : ARMMMUIdx_MNegPri;
>          }
>  
>          return arm_to_core_mmu_idx(mmu_idx);
> 

Re: [Qemu-devel] [PATCH 15/20] target/arm: Fix calculation of secure mm_idx values

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> In cpu_mmu_index() we try to do this:
>         if (env->v7m.secure) {
>             mmu_idx += ARMMMUIdx_MSUser;
>         }
> but it will give the wrong answer, because ARMMMUIdx_MSUser
> includes the 0x40 ARM_MMU_IDX_M field, and so does the
> mmu_idx we're adding to, and we'll end up with 0x8n rather
> than 0x4n. This error is then nullified by the call to
> arm_to_core_mmu_idx() which masks out the high part, but
> we're about to factor out the code that calculates the
> ARMMMUIdx values so it can be used without passing it through
> arm_to_core_mmu_idx(), so fix this bug first.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/cpu.h | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 16/20] target/arm: Factor out "get mmuidx for specified security state"

[Peter Maydell]

For the SG instruction and secure function return we are going
to want to do memory accesses using the MMU index of the CPU
in secure state, even though the CPU is currently in non-secure
state. Write arm_v7m_mmu_idx_for_secstate() to do this job,
and use it in cpu_mmu_index().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/cpu.h | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 70c1f85..89d49cd 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -2329,23 +2329,33 @@ static inline int arm_mmu_idx_to_el(ARMMMUIdx mmu_idx)
     }
 }
 
+/* Return the MMU index for a v7M CPU in the specified security state */
+static inline ARMMMUIdx arm_v7m_mmu_idx_for_secstate(CPUARMState *env,
+                                                     bool secstate)
+{
+    int el = arm_current_el(env);
+    ARMMMUIdx mmu_idx;
+
+    if (el == 0) {
+        mmu_idx = secstate ? ARMMMUIdx_MSUser : ARMMMUIdx_MUser;
+    } else {
+        mmu_idx = secstate ? ARMMMUIdx_MSPriv : ARMMMUIdx_MPriv;
+    }
+
+    if (armv7m_nvic_neg_prio_requested(env->nvic, secstate)) {
+        mmu_idx = secstate ? ARMMMUIdx_MSNegPri : ARMMMUIdx_MNegPri;
+    }
+
+    return mmu_idx;
+}
+
 /* Determine the current mmu_idx to use for normal loads/stores */
 static inline int cpu_mmu_index(CPUARMState *env, bool ifetch)
 {
     int el = arm_current_el(env);
 
     if (arm_feature(env, ARM_FEATURE_M)) {
-        ARMMMUIdx mmu_idx;
-
-        if (el == 0) {
-            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSUser : ARMMMUIdx_MUser;
-        } else {
-            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSPriv : ARMMMUIdx_MPriv;
-        }
-
-        if (armv7m_nvic_neg_prio_requested(env->nvic, env->v7m.secure)) {
-            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSNegPri : ARMMMUIdx_MNegPri;
-        }
+        ARMMMUIdx mmu_idx = arm_v7m_mmu_idx_for_secstate(env, env->v7m.secure);
 
         return arm_to_core_mmu_idx(mmu_idx);
     }
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 16/20] target/arm: Factor out "get mmuidx for specified security state"

[Philippe Mathieu-Daudé]

On 09/22/2017 12:00 PM, Peter Maydell wrote:
> For the SG instruction and secure function return we are going
> to want to do memory accesses using the MMU index of the CPU
> in secure state, even though the CPU is currently in non-secure
> state. Write arm_v7m_mmu_idx_for_secstate() to do this job,
> and use it in cpu_mmu_index().
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>  target/arm/cpu.h | 32 +++++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 11 deletions(-)
> 
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index 70c1f85..89d49cd 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -2329,23 +2329,33 @@ static inline int arm_mmu_idx_to_el(ARMMMUIdx mmu_idx)
>      }
>  }
>  
> +/* Return the MMU index for a v7M CPU in the specified security state */
> +static inline ARMMMUIdx arm_v7m_mmu_idx_for_secstate(CPUARMState *env,
> +                                                     bool secstate)
> +{
> +    int el = arm_current_el(env);
> +    ARMMMUIdx mmu_idx;
> +
> +    if (el == 0) {
> +        mmu_idx = secstate ? ARMMMUIdx_MSUser : ARMMMUIdx_MUser;
> +    } else {
> +        mmu_idx = secstate ? ARMMMUIdx_MSPriv : ARMMMUIdx_MPriv;
> +    }
> +
> +    if (armv7m_nvic_neg_prio_requested(env->nvic, secstate)) {
> +        mmu_idx = secstate ? ARMMMUIdx_MSNegPri : ARMMMUIdx_MNegPri;
> +    }
> +
> +    return mmu_idx;
> +}
> +
>  /* Determine the current mmu_idx to use for normal loads/stores */
>  static inline int cpu_mmu_index(CPUARMState *env, bool ifetch)
>  {
>      int el = arm_current_el(env);
>  
>      if (arm_feature(env, ARM_FEATURE_M)) {
> -        ARMMMUIdx mmu_idx;
> -
> -        if (el == 0) {
> -            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSUser : ARMMMUIdx_MUser;
> -        } else {
> -            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSPriv : ARMMMUIdx_MPriv;
> -        }
> -
> -        if (armv7m_nvic_neg_prio_requested(env->nvic, env->v7m.secure)) {
> -            mmu_idx = env->v7m.secure ? ARMMMUIdx_MSNegPri : ARMMMUIdx_MNegPri;
> -        }
> +        ARMMMUIdx mmu_idx = arm_v7m_mmu_idx_for_secstate(env, env->v7m.secure);
>  
>          return arm_to_core_mmu_idx(mmu_idx);
>      }
> 

Re: [Qemu-devel] [PATCH 16/20] target/arm: Factor out "get mmuidx for specified security state"

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> For the SG instruction and secure function return we are going
> to want to do memory accesses using the MMU index of the CPU
> in secure state, even though the CPU is currently in non-secure
> state. Write arm_v7m_mmu_idx_for_secstate() to do this job,
> and use it in cpu_mmu_index().
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/cpu.h | 32 +++++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 11 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 17/20] target/arm: Implement SG instruction

[Peter Maydell]

Implement the SG instruction, which we emulate 'by hand' in the
exception handling code path.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 124 insertions(+), 5 deletions(-)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index b1ecb66..8df819d 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -41,6 +41,10 @@ typedef struct V8M_SAttributes {
     bool irvalid;
 } V8M_SAttributes;
 
+static void v8m_security_lookup(CPUARMState *env, uint32_t address,
+                                MMUAccessType access_type, ARMMMUIdx mmu_idx,
+                                V8M_SAttributes *sattrs);
+
 /* Definitions for the PMCCNTR and PMCR registers */
 #define PMCRD   0x8
 #define PMCRC   0x4
@@ -6724,6 +6728,123 @@ static void arm_log_exception(int idx)
     }
 }
 
+static bool v7m_read_half_insn(ARMCPU *cpu, ARMMMUIdx mmu_idx, uint16_t *insn)
+{
+    /* Load a 16-bit portion of a v7M instruction, returning true on success,
+     * or false on failure (in which case we will have pended the appropriate
+     * exception).
+     * We need to do the instruction fetch's MPU and SAU checks
+     * like this because there is no MMU index that would allow
+     * doing the load with a single function call. Instead we must
+     * first check that the security attributes permit the load
+     * and that they don't mismatch on the two halves of the instruction,
+     * and then we do the load as a secure load (ie using the security
+     * attributes of the address, not the CPU, as architecturally required).
+     */
+    CPUState *cs = CPU(cpu);
+    CPUARMState *env = &cpu->env;
+    V8M_SAttributes sattrs = {};
+    MemTxAttrs attrs = {};
+    ARMMMUFaultInfo fi = {};
+    MemTxResult txres;
+    target_ulong page_size;
+    hwaddr physaddr;
+    int prot;
+    uint32_t fsr;
+
+    v8m_security_lookup(env, env->regs[15], MMU_INST_FETCH, mmu_idx, &sattrs);
+    if (!sattrs.nsc || sattrs.ns) {
+        /* This must be the second half of the insn, and it straddles a
+         * region boundary with the second half not being S&NSC.
+         */
+        env->v7m.sfsr |= R_V7M_SFSR_INVEP_MASK;
+        armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
+        qemu_log_mask(CPU_LOG_INT,
+                      "...really SecureFault with SFSR.INVEP\n");
+        return false;
+    }
+    if (get_phys_addr(env, env->regs[15], MMU_INST_FETCH, mmu_idx,
+                      &physaddr, &attrs, &prot, &page_size, &fsr, &fi)) {
+        /* the MPU lookup failed */
+        env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_IACCVIOL_MASK;
+        armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_MEM, env->v7m.secure);
+        qemu_log_mask(CPU_LOG_INT, "...really MemManage with CFSR.IACCVIOL\n");
+        return false;
+    }
+    *insn = address_space_lduw_le(arm_addressspace(cs, attrs), physaddr,
+                                 attrs, &txres);
+    if (txres != MEMTX_OK) {
+        env->v7m.cfsr[M_REG_NS] |= R_V7M_CFSR_IBUSERR_MASK;
+        armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_BUS, false);
+        qemu_log_mask(CPU_LOG_INT, "...really BusFault with CFSR.IBUSERR\n");
+        return false;
+    }
+    return true;
+}
+
+static bool v7m_handle_execute_nsc(ARMCPU *cpu)
+{
+    /* Check whether this attempt to execute code in a Secure & NS-Callable
+     * memory region is for an SG instruction; if so, then emulate the
+     * effect of the SG instruction and return true. Otherwise pend
+     * the correct kind of exception and return false.
+     */
+    CPUARMState *env = &cpu->env;
+    ARMMMUIdx mmu_idx;
+    uint16_t insn;
+
+    /* We should never get here unless get_phys_addr_pmsav8() caused
+     * an exception for NS executing in S&NSC memory.
+     */
+    assert(!env->v7m.secure);
+    assert(arm_feature(env, ARM_FEATURE_M_SECURITY));
+
+    /* We want to do the MPU lookup as secure; work out what mmu_idx that is */
+    mmu_idx = arm_v7m_mmu_idx_for_secstate(env, true);
+
+    if (!v7m_read_half_insn(cpu, mmu_idx, &insn)) {
+        return false;
+    }
+
+    if (!env->thumb) {
+        goto gen_invep;
+    }
+
+    if (insn != 0xe97f) {
+        /* Not an SG instruction first half (we choose the IMPDEF
+         * early-SG-check option).
+         */
+        goto gen_invep;
+    }
+
+    if (!v7m_read_half_insn(cpu, mmu_idx, &insn)) {
+        return false;
+    }
+
+    if (insn != 0xe97f) {
+        /* Not an SG instruction second half */
+        goto gen_invep;
+    }
+
+    /* OK, we have confirmed that we really have an SG instruction.
+     * We know we're NS in S memory so don't need to repeat those checks.
+     */
+    qemu_log_mask(CPU_LOG_INT, "...really an SG instruction at 0x%08" PRIx32
+                  ", executing it\n", env->regs[15]);
+    env->regs[14] &= ~1;
+    switch_v7m_security_state(env, true);
+    xpsr_write(env, 0, XPSR_IT);
+    env->regs[15] += 4;
+    return true;
+
+gen_invep:
+    env->v7m.sfsr |= R_V7M_SFSR_INVEP_MASK;
+    armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
+    qemu_log_mask(CPU_LOG_INT,
+                  "...really SecureFault with SFSR.INVEP\n");
+    return false;
+}
+
 void arm_v7m_cpu_do_interrupt(CPUState *cs)
 {
     ARMCPU *cpu = ARM_CPU(cs);
@@ -6766,12 +6887,10 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
              * the SG instruction have the same security attributes.)
              * Everything else must generate an INVEP SecureFault, so we
              * emulate the SG instruction here.
-             * TODO: actually emulate SG.
              */
-            env->v7m.sfsr |= R_V7M_SFSR_INVEP_MASK;
-            armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_SECURE, false);
-            qemu_log_mask(CPU_LOG_INT,
-                          "...really SecureFault with SFSR.INVEP\n");
+            if (v7m_handle_execute_nsc(cpu)) {
+                return;
+            }
             break;
         case M_FAKE_FSR_SFAULT:
             /* Various flavours of SecureFault for attempts to execute or
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 17/20] target/arm: Implement SG instruction

[Peter Maydell]

On 22 September 2017 at 16:00, Peter Maydell <peter.maydell@linaro.org> wrote:
> Implement the SG instruction, which we emulate 'by hand' in the
> exception handling code path.

I've just realised that this patch is correct as far as it goes
but it only implements the common path case for SG (where it is
in S&NSC memory and executed by a CPU in NS state). There is
also defined behaviour for:
 * SG in NS memory (behaves as a NOP)
 * SG in S memory and CPU already secure (clears IT bits and
   does nothing else)

Those can be implemented in translate.c in the usual way;
I'll put a patch for that in the next set (or in a respin
of this set).

thanks
-- PMM

Re: [Qemu-devel] [PATCH 17/20] target/arm: Implement SG instruction

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> Implement the SG instruction, which we emulate 'by hand' in the
> exception handling code path.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 124 insertions(+), 5 deletions(-)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index b1ecb66..8df819d 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -41,6 +41,10 @@ typedef struct V8M_SAttributes {
>      bool irvalid;
>  } V8M_SAttributes;
>  
> +static void v8m_security_lookup(CPUARMState *env, uint32_t address,
> +                                MMUAccessType access_type, ARMMMUIdx mmu_idx,
> +                                V8M_SAttributes *sattrs);
> +
>  /* Definitions for the PMCCNTR and PMCR registers */
>  #define PMCRD   0x8
>  #define PMCRC   0x4
> @@ -6724,6 +6728,123 @@ static void arm_log_exception(int idx)
>      }
>  }
>  
> +static bool v7m_read_half_insn(ARMCPU *cpu, ARMMMUIdx mmu_idx, uint16_t *insn)
> +{

This function doesn't take an address ...

> +    if (get_phys_addr(env, env->regs[15], MMU_INST_FETCH, mmu_idx,
> +                      &physaddr, &attrs, &prot, &page_size, &fsr, &fi)) {

... reading it directly from r15 ...

> +    if (insn != 0xe97f) {
> +        /* Not an SG instruction first half (we choose the IMPDEF
> +         * early-SG-check option).
> +         */
> +        goto gen_invep;
> +    }
> +
> +    if (!v7m_read_half_insn(cpu, mmu_idx, &insn)) {
> +        return false;
> +    }
> +
> +    if (insn != 0xe97f) {
> +        /* Not an SG instruction second half */
> +        goto gen_invep;
> +    }

... but somehow expects to get two different values read from the same address?

Certainly you'd get the wrong exception frame if you incremented r15 in between.

> +    env->regs[15] += 4;

... that make this right and the implicit address to the readers wrong.

I don't see anything else amiss in the patch.


r~

Re: [Qemu-devel] [PATCH 17/20] target/arm: Implement SG instruction

[Peter Maydell]

On 5 October 2017 at 19:50, Richard Henderson
<richard.henderson@linaro.org> wrote:
> On 09/22/2017 11:00 AM, Peter Maydell wrote:
>> Implement the SG instruction, which we emulate 'by hand' in the
>> exception handling code path.
>>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>>  target/arm/helper.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 124 insertions(+), 5 deletions(-)
>>
>> diff --git a/target/arm/helper.c b/target/arm/helper.c
>> index b1ecb66..8df819d 100644
>> --- a/target/arm/helper.c
>> +++ b/target/arm/helper.c
>> @@ -41,6 +41,10 @@ typedef struct V8M_SAttributes {
>>      bool irvalid;
>>  } V8M_SAttributes;
>>
>> +static void v8m_security_lookup(CPUARMState *env, uint32_t address,
>> +                                MMUAccessType access_type, ARMMMUIdx mmu_idx,
>> +                                V8M_SAttributes *sattrs);
>> +
>>  /* Definitions for the PMCCNTR and PMCR registers */
>>  #define PMCRD   0x8
>>  #define PMCRC   0x4
>> @@ -6724,6 +6728,123 @@ static void arm_log_exception(int idx)
>>      }
>>  }
>>
>> +static bool v7m_read_half_insn(ARMCPU *cpu, ARMMMUIdx mmu_idx, uint16_t *insn)
>> +{
>
> This function doesn't take an address ...
>
>> +    if (get_phys_addr(env, env->regs[15], MMU_INST_FETCH, mmu_idx,
>> +                      &physaddr, &attrs, &prot, &page_size, &fsr, &fi)) {
>
> ... reading it directly from r15 ...
>
>> +    if (insn != 0xe97f) {
>> +        /* Not an SG instruction first half (we choose the IMPDEF
>> +         * early-SG-check option).
>> +         */
>> +        goto gen_invep;
>> +    }
>> +
>> +    if (!v7m_read_half_insn(cpu, mmu_idx, &insn)) {
>> +        return false;
>> +    }
>> +
>> +    if (insn != 0xe97f) {
>> +        /* Not an SG instruction second half */
>> +        goto gen_invep;
>> +    }
>
> ... but somehow expects to get two different values read from the same address?
>
> Certainly you'd get the wrong exception frame if you incremented r15 in between.

Oops. I missed this in my testing because it happens that the
two halves of an SG instruction are the same value :-)

thanks
-- PMM

Re: [Qemu-devel] [PATCH 17/20] target/arm: Implement SG instruction

[Richard Henderson]

On 10/05/2017 02:55 PM, Peter Maydell wrote:
> Oops. I missed this in my testing because it happens that the
> two halves of an SG instruction are the same value :-)

Hah.  I didn't notice that either.


r~

[Qemu-devel] [PATCH 18/20] target/arm: Implement BLXNS

[Peter Maydell]

Implement the BLXNS instruction, which allows secure code to
call non-secure code.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.h    |  1 +
 target/arm/internals.h |  1 +
 target/arm/helper.c    | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
 target/arm/translate.c | 17 +++++++++++++--
 4 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/target/arm/helper.h b/target/arm/helper.h
index 64afbac..2cf6f74 100644
--- a/target/arm/helper.h
+++ b/target/arm/helper.h
@@ -64,6 +64,7 @@ DEF_HELPER_3(v7m_msr, void, env, i32, i32)
 DEF_HELPER_2(v7m_mrs, i32, env, i32)
 
 DEF_HELPER_2(v7m_bxns, void, env, i32)
+DEF_HELPER_2(v7m_blxns, void, env, i32)
 
 DEF_HELPER_4(access_check_cp_reg, void, env, ptr, i32, i32)
 DEF_HELPER_3(set_cp_reg, void, env, ptr, i32)
diff --git a/target/arm/internals.h b/target/arm/internals.h
index fd9a7e8..1746737 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -60,6 +60,7 @@ static inline bool excp_is_internal(int excp)
 FIELD(V7M_CONTROL, NPRIV, 0, 1)
 FIELD(V7M_CONTROL, SPSEL, 1, 1)
 FIELD(V7M_CONTROL, FPCA, 2, 1)
+FIELD(V7M_CONTROL, SFPA, 3, 1)
 
 /* Bit definitions for v7M exception return payload */
 FIELD(V7M_EXCRET, ES, 0, 1)
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 8df819d..30dc2a9 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -5890,6 +5890,12 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
     g_assert_not_reached();
 }
 
+void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
+{
+    /* translate.c should never generate calls here in user-only mode */
+    g_assert_not_reached();
+}
+
 void switch_mode(CPUARMState *env, int mode)
 {
     ARMCPU *cpu = arm_env_get_cpu(env);
@@ -6182,6 +6188,59 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
     env->regs[15] = dest & ~1;
 }
 
+void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
+{
+    /* Handle v7M BLXNS:
+     *  - bit 0 of the destination address is the target security state
+     */
+
+    /* At this point regs[15] is the address just after the BLXNS */
+    uint32_t nextinst = env->regs[15] | 1;
+    uint32_t sp = env->regs[13] - 8;
+    uint32_t saved_psr;
+
+    /* translate.c will have made BLXNS UNDEF unless we're secure */
+    assert(env->v7m.secure);
+
+    if (dest & 1) {
+        /* target is Secure, so this is just a normal BLX,
+         * except that the low bit doesn't indicate Thumb/not.
+         */
+        env->regs[14] = nextinst;
+        env->thumb = 1;
+        env->regs[15] = dest & ~1;
+        return;
+    }
+
+    /* Target is non-secure: first push a stack frame */
+    if (!QEMU_IS_ALIGNED(sp, 8)) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "BLXNS with misaligned SP is UNPREDICTABLE\n");
+    }
+
+    saved_psr = env->v7m.exception;
+    if (env->v7m.control[M_REG_S] & R_V7M_CONTROL_SFPA_MASK) {
+        saved_psr |= XPSR_SFPA;
+    }
+
+    /* Note that these stores can throw exceptions on MPU faults */
+    cpu_stl_data(env, sp, nextinst);
+    cpu_stl_data(env, sp + 4, saved_psr);
+
+    env->regs[13] = sp;
+    env->regs[14] = 0xfeffffff;
+    if (arm_v7m_is_handler_mode(env)) {
+        /* Write a dummy value to IPSR, to avoid leaking the current secure
+         * exception number to non-secure code. This is guaranteed not
+         * to cause write_v7m_exception() to actually change stacks.
+         */
+        write_v7m_exception(env, 1);
+    }
+    switch_v7m_security_state(env, dest & 1);
+    env->thumb = 1;
+    env->regs[15] = dest & ~1;
+}
+
 static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
                                 bool spsel)
 {
diff --git a/target/arm/translate.c b/target/arm/translate.c
index ab1a12a..53694bb 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -1013,6 +1013,20 @@ static inline void gen_bxns(DisasContext *s, int rm)
     s->base.is_jmp = DISAS_EXIT;
 }
 
+static inline void gen_blxns(DisasContext *s, int rm)
+{
+    TCGv_i32 var = load_reg(s, rm);
+
+    /* We don't need to sync condexec state, for the same reason as blxns.
+     * We do however need to set the PC, because the blxns helper reads it.
+     * The blxns helper may throw an exception.
+     */
+    gen_set_pc_im(s, s->pc);
+    gen_helper_v7m_blxns(cpu_env, var);
+    tcg_temp_free_i32(var);
+    s->base.is_jmp = DISAS_EXIT;
+}
+
 /* Variant of store_reg which uses branch&exchange logic when storing
    to r15 in ARM architecture v7 and above. The source must be a temporary
    and will be marked as dead. */
@@ -11221,8 +11235,7 @@ static void disas_thumb_insn(CPUARMState *env, DisasContext *s)
                         goto undef;
                     }
                     if (link) {
-                        /* BLXNS: not yet implemented */
-                        goto undef;
+                        gen_blxns(s, rm);
                     } else {
                         gen_bxns(s, rm);
                     }
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 18/20] target/arm: Implement BLXNS

[Philippe Mathieu-Daudé]

On 09/22/2017 12:00 PM, Peter Maydell wrote:
> Implement the BLXNS instruction, which allows secure code to
> call non-secure code.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>  target/arm/helper.h    |  1 +
>  target/arm/internals.h |  1 +
>  target/arm/helper.c    | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  target/arm/translate.c | 17 +++++++++++++--
>  4 files changed, 76 insertions(+), 2 deletions(-)
> 
> diff --git a/target/arm/helper.h b/target/arm/helper.h
> index 64afbac..2cf6f74 100644
> --- a/target/arm/helper.h
> +++ b/target/arm/helper.h
> @@ -64,6 +64,7 @@ DEF_HELPER_3(v7m_msr, void, env, i32, i32)
>  DEF_HELPER_2(v7m_mrs, i32, env, i32)
>  
>  DEF_HELPER_2(v7m_bxns, void, env, i32)
> +DEF_HELPER_2(v7m_blxns, void, env, i32)
>  
>  DEF_HELPER_4(access_check_cp_reg, void, env, ptr, i32, i32)
>  DEF_HELPER_3(set_cp_reg, void, env, ptr, i32)
> diff --git a/target/arm/internals.h b/target/arm/internals.h
> index fd9a7e8..1746737 100644
> --- a/target/arm/internals.h
> +++ b/target/arm/internals.h
> @@ -60,6 +60,7 @@ static inline bool excp_is_internal(int excp)
>  FIELD(V7M_CONTROL, NPRIV, 0, 1)
>  FIELD(V7M_CONTROL, SPSEL, 1, 1)
>  FIELD(V7M_CONTROL, FPCA, 2, 1)
> +FIELD(V7M_CONTROL, SFPA, 3, 1)
>  
>  /* Bit definitions for v7M exception return payload */
>  FIELD(V7M_EXCRET, ES, 0, 1)
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 8df819d..30dc2a9 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -5890,6 +5890,12 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
>      g_assert_not_reached();
>  }
>  
> +void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
> +{
> +    /* translate.c should never generate calls here in user-only mode */
> +    g_assert_not_reached();
> +}
> +
>  void switch_mode(CPUARMState *env, int mode)
>  {
>      ARMCPU *cpu = arm_env_get_cpu(env);
> @@ -6182,6 +6188,59 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
>      env->regs[15] = dest & ~1;
>  }
>  
> +void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
> +{
> +    /* Handle v7M BLXNS:
> +     *  - bit 0 of the destination address is the target security state
> +     */
> +
> +    /* At this point regs[15] is the address just after the BLXNS */
> +    uint32_t nextinst = env->regs[15] | 1;
> +    uint32_t sp = env->regs[13] - 8;
> +    uint32_t saved_psr;
> +
> +    /* translate.c will have made BLXNS UNDEF unless we're secure */
> +    assert(env->v7m.secure);
> +
> +    if (dest & 1) {
> +        /* target is Secure, so this is just a normal BLX,
> +         * except that the low bit doesn't indicate Thumb/not.
> +         */
> +        env->regs[14] = nextinst;
> +        env->thumb = 1;
> +        env->regs[15] = dest & ~1;
> +        return;
> +    }
> +
> +    /* Target is non-secure: first push a stack frame */
> +    if (!QEMU_IS_ALIGNED(sp, 8)) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "BLXNS with misaligned SP is UNPREDICTABLE\n");
> +    }
> +
> +    saved_psr = env->v7m.exception;
> +    if (env->v7m.control[M_REG_S] & R_V7M_CONTROL_SFPA_MASK) {
> +        saved_psr |= XPSR_SFPA;
> +    }
> +
> +    /* Note that these stores can throw exceptions on MPU faults */
> +    cpu_stl_data(env, sp, nextinst);
> +    cpu_stl_data(env, sp + 4, saved_psr);
> +
> +    env->regs[13] = sp;
> +    env->regs[14] = 0xfeffffff;
> +    if (arm_v7m_is_handler_mode(env)) {
> +        /* Write a dummy value to IPSR, to avoid leaking the current secure
> +         * exception number to non-secure code. This is guaranteed not
> +         * to cause write_v7m_exception() to actually change stacks.
> +         */
> +        write_v7m_exception(env, 1);
> +    }
> +    switch_v7m_security_state(env, dest & 1);
> +    env->thumb = 1;
> +    env->regs[15] = dest & ~1;
> +}
> +
>  static uint32_t *get_v7m_sp_ptr(CPUARMState *env, bool secure, bool threadmode,
>                                  bool spsel)
>  {
> diff --git a/target/arm/translate.c b/target/arm/translate.c
> index ab1a12a..53694bb 100644
> --- a/target/arm/translate.c
> +++ b/target/arm/translate.c
> @@ -1013,6 +1013,20 @@ static inline void gen_bxns(DisasContext *s, int rm)
>      s->base.is_jmp = DISAS_EXIT;
>  }
>  
> +static inline void gen_blxns(DisasContext *s, int rm)
> +{
> +    TCGv_i32 var = load_reg(s, rm);
> +
> +    /* We don't need to sync condexec state, for the same reason as blxns.
> +     * We do however need to set the PC, because the blxns helper reads it.
> +     * The blxns helper may throw an exception.
> +     */
> +    gen_set_pc_im(s, s->pc);
> +    gen_helper_v7m_blxns(cpu_env, var);
> +    tcg_temp_free_i32(var);
> +    s->base.is_jmp = DISAS_EXIT;
> +}
> +
>  /* Variant of store_reg which uses branch&exchange logic when storing
>     to r15 in ARM architecture v7 and above. The source must be a temporary
>     and will be marked as dead. */
> @@ -11221,8 +11235,7 @@ static void disas_thumb_insn(CPUARMState *env, DisasContext *s)
>                          goto undef;
>                      }
>                      if (link) {
> -                        /* BLXNS: not yet implemented */
> -                        goto undef;
> +                        gen_blxns(s, rm);
>                      } else {
>                          gen_bxns(s, rm);
>                      }
> 

Re: [Qemu-devel] [PATCH 18/20] target/arm: Implement BLXNS

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> +void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
> +{
...
> +    if (dest & 1) {
> +        /* target is Secure, so this is just a normal BLX,
> +         * except that the low bit doesn't indicate Thumb/not.
> +         */
> +        env->regs[14] = nextinst;
> +        env->thumb = 1;
> +        env->regs[15] = dest & ~1;
> +        return;
> +    }
...
> +    switch_v7m_security_state(env, dest & 1);
> +    env->thumb = 1;
> +    env->regs[15] = dest & ~1;

dest & 1 is known to be 0.

> +static inline void gen_blxns(DisasContext *s, int rm)
> +{
> +    TCGv_i32 var = load_reg(s, rm);
> +
> +    /* We don't need to sync condexec state, for the same reason as blxns.

s/blxns/bxns/ ?

Otherwise,

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: [Qemu-devel] [PATCH 18/20] target/arm: Implement BLXNS

[Peter Maydell]

On 5 October 2017 at 19:56, Richard Henderson
<richard.henderson@linaro.org> wrote:
> On 09/22/2017 11:00 AM, Peter Maydell wrote:
>> +void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
>> +{
> ...
>> +    if (dest & 1) {
>> +        /* target is Secure, so this is just a normal BLX,
>> +         * except that the low bit doesn't indicate Thumb/not.
>> +         */
>> +        env->regs[14] = nextinst;
>> +        env->thumb = 1;
>> +        env->regs[15] = dest & ~1;
>> +        return;
>> +    }
> ...
>> +    switch_v7m_security_state(env, dest & 1);
>> +    env->thumb = 1;
>> +    env->regs[15] = dest & ~1;
>
> dest & 1 is known to be 0.

Yes. I liked the symmetry with the tail end of the v7m_bxns helper,
which is conceptually doing the same thing, and assumed the
compiler would be smart enough not to generate unnecessary code.

>> +static inline void gen_blxns(DisasContext *s, int rm)
>> +{
>> +    TCGv_i32 var = load_reg(s, rm);
>> +
>> +    /* We don't need to sync condexec state, for the same reason as blxns.
>
> s/blxns/bxns/ ?

Yes.

thanks
-- PMM

[Qemu-devel] [PATCH 19/20] target/arm: Implement secure function return

[Peter Maydell]

Secure function return happens when a non-secure function has been
called using BLXNS and so has a particular magic LR value (either
0xfefffffe or 0xfeffffff). The function return via BX behaves
specially when the new PC value is this magic value, in the same
way that exception returns are handled.

Adjust our BX excret guards so that they recognize the function
return magic number as well, and perform the function-return
unstacking in do_v7m_exception_exit().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/internals.h |   7 +++
 target/arm/helper.c    | 115 +++++++++++++++++++++++++++++++++++++++++++++----
 target/arm/translate.c |  14 +++++-
 3 files changed, 126 insertions(+), 10 deletions(-)

diff --git a/target/arm/internals.h b/target/arm/internals.h
index 1746737..43106a2 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -72,6 +72,13 @@ FIELD(V7M_EXCRET, DCRS, 5, 1)
 FIELD(V7M_EXCRET, S, 6, 1)
 FIELD(V7M_EXCRET, RES1, 7, 25) /* including the must-be-1 prefix */
 
+/* Minimum value which is a magic number for exception return */
+#define EXC_RETURN_MIN_MAGIC 0xff000000
+/* Minimum number which is a magic number for function or exception return
+ * when using v8M security extension
+ */
+#define FNC_RETURN_MIN_MAGIC 0xfefffffe
+
 /* We use a few fake FSR values for internal purposes in M profile.
  * M profile cores don't have A/R format FSRs, but currently our
  * get_phys_addr() code assumes A/R profile and reports failures via
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 30dc2a9..888fe0a 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6167,7 +6167,17 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
      *  - if the return value is a magic value, do exception return (like BX)
      *  - otherwise bit 0 of the return value is the target security state
      */
-    if (dest >= 0xff000000) {
+    uint32_t min_magic;
+
+    if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+        /* Covers FNC_RETURN and EXC_RETURN magic */
+        min_magic = FNC_RETURN_MIN_MAGIC;
+    } else {
+        /* EXC_RETURN magic only */
+        min_magic = EXC_RETURN_MIN_MAGIC;
+    }
+
+    if (dest >= min_magic) {
         /* This is an exception return magic value; put it where
          * do_v7m_exception_exit() expects and raise EXCEPTION_EXIT.
          * Note that if we ever add gen_ss_advance() singlestep support to
@@ -6460,12 +6470,19 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
     bool exc_secure = false;
     bool return_to_secure;
 
-    /* We can only get here from an EXCP_EXCEPTION_EXIT, and
-     * gen_bx_excret() enforces the architectural rule
-     * that jumps to magic addresses don't have magic behaviour unless
-     * we're in Handler mode (compare pseudocode BXWritePC()).
+    /* If we're not in Handler mode then jumps to magic exception-exit
+     * addresses don't have magic behaviour. However for the v8M
+     * security extensions the magic secure-function-return has to
+     * work in thread mode too, so to avoid doing an extra check in
+     * the generated code we allow exception-exit magic to also cause the
+     * internal exception and bring us here in thread mode. Correct code
+     * will never try to do this (the following insn fetch will always
+     * fault) so we the overhead of having taken an unnecessary exception
+     * doesn't matter.
      */
-    assert(arm_v7m_is_handler_mode(env));
+    if (!arm_v7m_is_handler_mode(env)) {
+        return;
+    }
 
     /* In the spec pseudocode ExceptionReturn() is called directly
      * from BXWritePC() and gets the full target PC value including
@@ -6753,6 +6770,78 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
     qemu_log_mask(CPU_LOG_INT, "...successful exception return\n");
 }
 
+static bool do_v7m_function_return(ARMCPU *cpu)
+{
+    /* v8M security extensions magic function return.
+     * We may either:
+     *  (1) throw an exception (longjump)
+     *  (2) return true if we successfully handled the function return
+     *  (3) return false if we failed a consistency check and have
+     *      pended a UsageFault that needs to be taken now
+     *
+     * At this point the magic return value is split between env->regs[15]
+     * and env->thumb. We don't bother to reconstitute it because we don't
+     * need it (all values are handled the same way).
+     */
+    CPUARMState *env = &cpu->env;
+    uint32_t newpc, newpsr, newpsr_exc;
+
+    qemu_log_mask(CPU_LOG_INT, "...really v7M secure function return\n");
+
+    {
+        bool threadmode, spsel;
+        TCGMemOpIdx oi;
+        ARMMMUIdx mmu_idx;
+        uint32_t *frame_sp_p;
+        uint32_t frameptr;
+
+        /* Pull the return address and IPSR from the Secure stack */
+        threadmode = !arm_v7m_is_handler_mode(env);
+        spsel = env->v7m.control[M_REG_S] & R_V7M_CONTROL_SPSEL_MASK;
+
+        frame_sp_p = get_v7m_sp_ptr(env, true, threadmode, spsel);
+        frameptr = *frame_sp_p;
+
+        /* These loads may throw an exception (for MPU faults). We want to
+         * do them as secure, so work out what MMU index that is.
+         */
+        mmu_idx = arm_v7m_mmu_idx_for_secstate(env, true);
+        oi = make_memop_idx(MO_LE, arm_to_core_mmu_idx(mmu_idx));
+        newpc = helper_le_ldul_mmu(env, frameptr, oi, 0);
+        newpsr = helper_le_ldul_mmu(env, frameptr + 4, oi, 0);
+
+        /* Consistency checks on new IPSR */
+        newpsr_exc = newpsr & XPSR_EXCP;
+        if (!((env->v7m.exception == 0 && newpsr_exc == 0) ||
+              (env->v7m.exception == 1 && newpsr_exc != 0))) {
+            /* Pend the fault and tell our caller to take it */
+            env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK;
+            armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE,
+                                    env->v7m.secure);
+            qemu_log_mask(CPU_LOG_INT,
+                          "...taking INVPC UsageFault: "
+                          "IPSR consistency check failed\n");
+            return false;
+        }
+
+        *frame_sp_p = frameptr + 8;
+    }
+
+    /* This invalidates frame_sp_p */
+    switch_v7m_security_state(env, true);
+    env->v7m.exception = newpsr_exc;
+    env->v7m.control[M_REG_S] &= ~R_V7M_CONTROL_SFPA_MASK;
+    if (newpsr & XPSR_SFPA) {
+        env->v7m.control[M_REG_S] |= R_V7M_CONTROL_SFPA_MASK;
+    }
+    xpsr_write(env, 0, XPSR_IT);
+    env->thumb = newpc & 1;
+    env->regs[15] = newpc & ~1;
+
+    qemu_log_mask(CPU_LOG_INT, "...function return successful\n");
+    return true;
+}
+
 static void arm_log_exception(int idx)
 {
     if (qemu_loglevel_mask(CPU_LOG_INT)) {
@@ -7034,8 +7123,18 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
     case EXCP_IRQ:
         break;
     case EXCP_EXCEPTION_EXIT:
-        do_v7m_exception_exit(cpu);
-        return;
+        if (env->regs[15] < EXC_RETURN_MIN_MAGIC) {
+            /* Must be v8M security extension function return */
+            assert(env->regs[15] >= FNC_RETURN_MIN_MAGIC);
+            assert(arm_feature(env, ARM_FEATURE_M_SECURITY));
+            if (do_v7m_function_return(cpu)) {
+                return;
+            }
+        } else {
+            do_v7m_exception_exit(cpu);
+            return;
+        }
+        break;
     default:
         cpu_abort(cs, "Unhandled exception 0x%x\n", cs->exception_index);
         return; /* Never happens.  Keep compiler happy.  */
diff --git a/target/arm/translate.c b/target/arm/translate.c
index 53694bb..f5cca07 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -960,7 +960,8 @@ static inline void gen_bx_excret(DisasContext *s, TCGv_i32 var)
      * s->base.is_jmp that we need to do the rest of the work later.
      */
     gen_bx(s, var);
-    if (s->v7m_handler_mode && arm_dc_feature(s, ARM_FEATURE_M)) {
+    if (arm_dc_feature(s, ARM_FEATURE_M_SECURITY) ||
+        (s->v7m_handler_mode && arm_dc_feature(s, ARM_FEATURE_M))) {
         s->base.is_jmp = DISAS_BX_EXCRET;
     }
 }
@@ -969,9 +970,18 @@ static inline void gen_bx_excret_final_code(DisasContext *s)
 {
     /* Generate the code to finish possible exception return and end the TB */
     TCGLabel *excret_label = gen_new_label();
+    uint32_t min_magic;
+
+    if (arm_dc_feature(s, ARM_FEATURE_M_SECURITY)) {
+        /* Covers FNC_RETURN and EXC_RETURN magic */
+        min_magic = FNC_RETURN_MIN_MAGIC;
+    } else {
+        /* EXC_RETURN magic only */
+        min_magic = EXC_RETURN_MIN_MAGIC;
+    }
 
     /* Is the new PC value in the magic range indicating exception return? */
-    tcg_gen_brcondi_i32(TCG_COND_GEU, cpu_R[15], 0xff000000, excret_label);
+    tcg_gen_brcondi_i32(TCG_COND_GEU, cpu_R[15], min_magic, excret_label);
     /* No: end the TB as we would for a DISAS_JMP */
     if (is_singlestepping(s)) {
         gen_singlestep_exception(s);
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 19/20] target/arm: Implement secure function return

[Philippe Mathieu-Daudé]

On 09/22/2017 12:00 PM, Peter Maydell wrote:
> Secure function return happens when a non-secure function has been
> called using BLXNS and so has a particular magic LR value (either
> 0xfefffffe or 0xfeffffff). The function return via BX behaves
> specially when the new PC value is this magic value, in the same
> way that exception returns are handled.
> 
> Adjust our BX excret guards so that they recognize the function
> return magic number as well, and perform the function-return
> unstacking in do_v7m_exception_exit().
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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

> ---
>  target/arm/internals.h |   7 +++
>  target/arm/helper.c    | 115 +++++++++++++++++++++++++++++++++++++++++++++----
>  target/arm/translate.c |  14 +++++-
>  3 files changed, 126 insertions(+), 10 deletions(-)
> 
> diff --git a/target/arm/internals.h b/target/arm/internals.h
> index 1746737..43106a2 100644
> --- a/target/arm/internals.h
> +++ b/target/arm/internals.h
> @@ -72,6 +72,13 @@ FIELD(V7M_EXCRET, DCRS, 5, 1)
>  FIELD(V7M_EXCRET, S, 6, 1)
>  FIELD(V7M_EXCRET, RES1, 7, 25) /* including the must-be-1 prefix */
>  
> +/* Minimum value which is a magic number for exception return */
> +#define EXC_RETURN_MIN_MAGIC 0xff000000
> +/* Minimum number which is a magic number for function or exception return
> + * when using v8M security extension
> + */
> +#define FNC_RETURN_MIN_MAGIC 0xfefffffe
> +
>  /* We use a few fake FSR values for internal purposes in M profile.
>   * M profile cores don't have A/R format FSRs, but currently our
>   * get_phys_addr() code assumes A/R profile and reports failures via
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 30dc2a9..888fe0a 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6167,7 +6167,17 @@ void HELPER(v7m_bxns)(CPUARMState *env, uint32_t dest)
>       *  - if the return value is a magic value, do exception return (like BX)
>       *  - otherwise bit 0 of the return value is the target security state
>       */
> -    if (dest >= 0xff000000) {
> +    uint32_t min_magic;
> +
> +    if (arm_feature(env, ARM_FEATURE_M_SECURITY)) {
> +        /* Covers FNC_RETURN and EXC_RETURN magic */
> +        min_magic = FNC_RETURN_MIN_MAGIC;
> +    } else {
> +        /* EXC_RETURN magic only */
> +        min_magic = EXC_RETURN_MIN_MAGIC;
> +    }
> +
> +    if (dest >= min_magic) {
>          /* This is an exception return magic value; put it where
>           * do_v7m_exception_exit() expects and raise EXCEPTION_EXIT.
>           * Note that if we ever add gen_ss_advance() singlestep support to
> @@ -6460,12 +6470,19 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>      bool exc_secure = false;
>      bool return_to_secure;
>  
> -    /* We can only get here from an EXCP_EXCEPTION_EXIT, and
> -     * gen_bx_excret() enforces the architectural rule
> -     * that jumps to magic addresses don't have magic behaviour unless
> -     * we're in Handler mode (compare pseudocode BXWritePC()).
> +    /* If we're not in Handler mode then jumps to magic exception-exit
> +     * addresses don't have magic behaviour. However for the v8M
> +     * security extensions the magic secure-function-return has to
> +     * work in thread mode too, so to avoid doing an extra check in
> +     * the generated code we allow exception-exit magic to also cause the
> +     * internal exception and bring us here in thread mode. Correct code
> +     * will never try to do this (the following insn fetch will always
> +     * fault) so we the overhead of having taken an unnecessary exception
> +     * doesn't matter.
>       */
> -    assert(arm_v7m_is_handler_mode(env));
> +    if (!arm_v7m_is_handler_mode(env)) {
> +        return;
> +    }
>  
>      /* In the spec pseudocode ExceptionReturn() is called directly
>       * from BXWritePC() and gets the full target PC value including
> @@ -6753,6 +6770,78 @@ static void do_v7m_exception_exit(ARMCPU *cpu)
>      qemu_log_mask(CPU_LOG_INT, "...successful exception return\n");
>  }
>  
> +static bool do_v7m_function_return(ARMCPU *cpu)
> +{
> +    /* v8M security extensions magic function return.
> +     * We may either:
> +     *  (1) throw an exception (longjump)
> +     *  (2) return true if we successfully handled the function return
> +     *  (3) return false if we failed a consistency check and have
> +     *      pended a UsageFault that needs to be taken now
> +     *
> +     * At this point the magic return value is split between env->regs[15]
> +     * and env->thumb. We don't bother to reconstitute it because we don't
> +     * need it (all values are handled the same way).
> +     */
> +    CPUARMState *env = &cpu->env;
> +    uint32_t newpc, newpsr, newpsr_exc;
> +
> +    qemu_log_mask(CPU_LOG_INT, "...really v7M secure function return\n");
> +
> +    {
> +        bool threadmode, spsel;
> +        TCGMemOpIdx oi;
> +        ARMMMUIdx mmu_idx;
> +        uint32_t *frame_sp_p;
> +        uint32_t frameptr;
> +
> +        /* Pull the return address and IPSR from the Secure stack */
> +        threadmode = !arm_v7m_is_handler_mode(env);
> +        spsel = env->v7m.control[M_REG_S] & R_V7M_CONTROL_SPSEL_MASK;
> +
> +        frame_sp_p = get_v7m_sp_ptr(env, true, threadmode, spsel);
> +        frameptr = *frame_sp_p;
> +
> +        /* These loads may throw an exception (for MPU faults). We want to
> +         * do them as secure, so work out what MMU index that is.
> +         */
> +        mmu_idx = arm_v7m_mmu_idx_for_secstate(env, true);
> +        oi = make_memop_idx(MO_LE, arm_to_core_mmu_idx(mmu_idx));
> +        newpc = helper_le_ldul_mmu(env, frameptr, oi, 0);
> +        newpsr = helper_le_ldul_mmu(env, frameptr + 4, oi, 0);
> +
> +        /* Consistency checks on new IPSR */
> +        newpsr_exc = newpsr & XPSR_EXCP;
> +        if (!((env->v7m.exception == 0 && newpsr_exc == 0) ||
> +              (env->v7m.exception == 1 && newpsr_exc != 0))) {
> +            /* Pend the fault and tell our caller to take it */
> +            env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_INVPC_MASK;
> +            armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE,
> +                                    env->v7m.secure);
> +            qemu_log_mask(CPU_LOG_INT,
> +                          "...taking INVPC UsageFault: "
> +                          "IPSR consistency check failed\n");
> +            return false;
> +        }
> +
> +        *frame_sp_p = frameptr + 8;
> +    }
> +
> +    /* This invalidates frame_sp_p */
> +    switch_v7m_security_state(env, true);
> +    env->v7m.exception = newpsr_exc;
> +    env->v7m.control[M_REG_S] &= ~R_V7M_CONTROL_SFPA_MASK;
> +    if (newpsr & XPSR_SFPA) {
> +        env->v7m.control[M_REG_S] |= R_V7M_CONTROL_SFPA_MASK;
> +    }
> +    xpsr_write(env, 0, XPSR_IT);
> +    env->thumb = newpc & 1;
> +    env->regs[15] = newpc & ~1;
> +
> +    qemu_log_mask(CPU_LOG_INT, "...function return successful\n");
> +    return true;
> +}
> +
>  static void arm_log_exception(int idx)
>  {
>      if (qemu_loglevel_mask(CPU_LOG_INT)) {
> @@ -7034,8 +7123,18 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
>      case EXCP_IRQ:
>          break;
>      case EXCP_EXCEPTION_EXIT:
> -        do_v7m_exception_exit(cpu);
> -        return;
> +        if (env->regs[15] < EXC_RETURN_MIN_MAGIC) {
> +            /* Must be v8M security extension function return */
> +            assert(env->regs[15] >= FNC_RETURN_MIN_MAGIC);
> +            assert(arm_feature(env, ARM_FEATURE_M_SECURITY));
> +            if (do_v7m_function_return(cpu)) {
> +                return;
> +            }
> +        } else {
> +            do_v7m_exception_exit(cpu);
> +            return;
> +        }
> +        break;
>      default:
>          cpu_abort(cs, "Unhandled exception 0x%x\n", cs->exception_index);
>          return; /* Never happens.  Keep compiler happy.  */
> diff --git a/target/arm/translate.c b/target/arm/translate.c
> index 53694bb..f5cca07 100644
> --- a/target/arm/translate.c
> +++ b/target/arm/translate.c
> @@ -960,7 +960,8 @@ static inline void gen_bx_excret(DisasContext *s, TCGv_i32 var)
>       * s->base.is_jmp that we need to do the rest of the work later.
>       */
>      gen_bx(s, var);
> -    if (s->v7m_handler_mode && arm_dc_feature(s, ARM_FEATURE_M)) {
> +    if (arm_dc_feature(s, ARM_FEATURE_M_SECURITY) ||
> +        (s->v7m_handler_mode && arm_dc_feature(s, ARM_FEATURE_M))) {
>          s->base.is_jmp = DISAS_BX_EXCRET;
>      }
>  }
> @@ -969,9 +970,18 @@ static inline void gen_bx_excret_final_code(DisasContext *s)
>  {
>      /* Generate the code to finish possible exception return and end the TB */
>      TCGLabel *excret_label = gen_new_label();
> +    uint32_t min_magic;
> +
> +    if (arm_dc_feature(s, ARM_FEATURE_M_SECURITY)) {
> +        /* Covers FNC_RETURN and EXC_RETURN magic */
> +        min_magic = FNC_RETURN_MIN_MAGIC;
> +    } else {
> +        /* EXC_RETURN magic only */
> +        min_magic = EXC_RETURN_MIN_MAGIC;
> +    }
>  
>      /* Is the new PC value in the magic range indicating exception return? */
> -    tcg_gen_brcondi_i32(TCG_COND_GEU, cpu_R[15], 0xff000000, excret_label);
> +    tcg_gen_brcondi_i32(TCG_COND_GEU, cpu_R[15], min_magic, excret_label);
>      /* No: end the TB as we would for a DISAS_JMP */
>      if (is_singlestepping(s)) {
>          gen_singlestep_exception(s);
> 

Re: [Qemu-devel] [PATCH 19/20] target/arm: Implement secure function return

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> Secure function return happens when a non-secure function has been
> called using BLXNS and so has a particular magic LR value (either
> 0xfefffffe or 0xfeffffff). The function return via BX behaves
> specially when the new PC value is this magic value, in the same
> way that exception returns are handled.
> 
> Adjust our BX excret guards so that they recognize the function
> return magic number as well, and perform the function-return
> unstacking in do_v7m_exception_exit().
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/internals.h |   7 +++
>  target/arm/helper.c    | 115 +++++++++++++++++++++++++++++++++++++++++++++----
>  target/arm/translate.c |  14 +++++-
>  3 files changed, 126 insertions(+), 10 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

[Qemu-devel] [PATCH 20/20] nvic: Add missing code for writing SHCSR.HARDFAULTPENDED bit

[Peter Maydell]

When we added support for the new SHCSR bits in v8M in commit
437d59c17e9 the code to support writing to the new HARDFAULTPENDED
bit was accidentally only added for non-secure writes; the
secure banked version of the bit should also be writable.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/intc/armv7m_nvic.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
index bd1d5d3..22d5e6e 100644
--- a/hw/intc/armv7m_nvic.c
+++ b/hw/intc/armv7m_nvic.c
@@ -1230,6 +1230,7 @@ static void nvic_writel(NVICState *s, uint32_t offset, uint32_t value,
             s->sec_vectors[ARMV7M_EXCP_BUS].enabled = (value & (1 << 17)) != 0;
             s->sec_vectors[ARMV7M_EXCP_USAGE].enabled =
                 (value & (1 << 18)) != 0;
+            s->sec_vectors[ARMV7M_EXCP_HARD].pending = (value & (1 << 21)) != 0;
             /* SecureFault not banked, but RAZ/WI to NS */
             s->vectors[ARMV7M_EXCP_SECURE].active = (value & (1 << 4)) != 0;
             s->vectors[ARMV7M_EXCP_SECURE].enabled = (value & (1 << 19)) != 0;
-- 
2.7.4

Re: [Qemu-devel] [Qemu-arm] [PATCH 20/20] nvic: Add missing code for writing SHCSR.HARDFAULTPENDED bit

[Philippe Mathieu-Daudé]

On 09/22/2017 12:00 PM, Peter Maydell wrote:
> When we added support for the new SHCSR bits in v8M in commit
> 437d59c17e9 the code to support writing to the new HARDFAULTPENDED
> bit was accidentally only added for non-secure writes; the
> secure banked version of the bit should also be writable.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/intc/armv7m_nvic.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> index bd1d5d3..22d5e6e 100644
> --- a/hw/intc/armv7m_nvic.c
> +++ b/hw/intc/armv7m_nvic.c
> @@ -1230,6 +1230,7 @@ static void nvic_writel(NVICState *s, uint32_t offset, uint32_t value,

        if (attrs.secure) {

if banked then arch is v8M,

>              s->sec_vectors[ARMV7M_EXCP_BUS].enabled = (value & (1 << 17)) != 0;
>              s->sec_vectors[ARMV7M_EXCP_USAGE].enabled =
>                  (value & (1 << 18)) != 0;
> +            s->sec_vectors[ARMV7M_EXCP_HARD].pending = (value & (1 << 21)) != 0;

therefore this bit is present.

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

>              /* SecureFault not banked, but RAZ/WI to NS */
>              s->vectors[ARMV7M_EXCP_SECURE].active = (value & (1 << 4)) != 0;
>              s->vectors[ARMV7M_EXCP_SECURE].enabled = (value & (1 << 19)) != 0;
> 

Re: [Qemu-devel] [PATCH 20/20] nvic: Add missing code for writing SHCSR.HARDFAULTPENDED bit

[Richard Henderson]

On 09/22/2017 11:00 AM, Peter Maydell wrote:
> When we added support for the new SHCSR bits in v8M in commit
> 437d59c17e9 the code to support writing to the new HARDFAULTPENDED
> bit was accidentally only added for non-secure writes; the
> secure banked version of the bit should also be writable.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/intc/armv7m_nvic.c | 1 +
>  1 file changed, 1 insertion(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: [Qemu-devel] [Qemu-arm] [PATCH 00/20] ARM v8M: exception entry, exit and security

[Philippe Mathieu-Daudé]

On 09/22/2017 11:59 AM, Peter Maydell wrote:
> Another week, another set of v8M patches.
> This lot adds:
>  * v8M and security extension changes in exception entry and exit
>  * the Security Attribution Unit
>  * SG and BLXNS instructions
>  * secure function return
>  * and a couple of fixes for bugs in already-in-master changes
> 
> Most of this is just plodding through fairly obvious implementation,

Heavy stuff still...

> but the handling of the SG instruction is a bit funky (see commit
> messages in those patches for detail).
[...]

Re: [Qemu-devel] [Qemu-arm] [PATCH 00/20] ARM v8M: exception entry, exit and security

[Peter Maydell]

On 22 September 2017 at 15:59, Peter Maydell <peter.maydell@linaro.org> wrote:
> Another week, another set of v8M patches.
> This lot adds:
>  * v8M and security extension changes in exception entry and exit
>  * the Security Attribution Unit
>  * SG and BLXNS instructions
>  * secure function return
>  * and a couple of fixes for bugs in already-in-master changes

Thanks to Richard and Philippe for review. I'm going to queue
patches 1-16 and 20 in target-arm.next, with the minor tweaks
suggested for patches 2 and 8.

17 needs more significant rework so I'll resend 17-19 in
the next patchset (there are a few more patches cooking
which make a coherent set with those anyway).

thanks
-- PMM