[XEN PATCH v4 1/4] xen: add SAF deviation for debugging and logging effects

[Simone Ballarin <simone.ballarin@xxxxxxxxxxx>]

Rule 13.1: Initializer lists shall not contain persistent side effects

Effects caused by debug/logging macros and functions (like ASSERT, 
__bad_atomic_size,
LOG, etc ...) that crash execution or produce logs are not dangerous in 
initializer
lists. The evaluation order in abnormal conditions is not relevant. Evaluation 
order
of logging effects is always safe.

Function hvm_get_guest_tsc_fixed (indirectly) performs different side effects.
For example it calls hvm_get_guest_time_fixed that contains an ASSERT and calls
to spin_lock and spin_unlock.

These side effects are not dangerous: they can be executed regardless of the
initializer list evaluation order

This patch deviates violations using SAF commits caused by debug/logging macros 
and
functions.

Asm volatile statements in initializer lists that do not perform any persistent 
side
effect are safe: this patch deviates violations caused by uses of the current 
macro
(that contains an asm volatile) in initializer lists.

No functional changes.

Signed-off-by: Simone Ballarin <simone.ballarin@xxxxxxxxxxx>
Signed-off-by: Maria Celeste Cesario  <maria.celeste.cesario@xxxxxxxxxxx>

---
Changes in v3:
- change commit prefix from xen/arm to xen
- specify where saf-3-safe comments are applied in guestcopy.c
- reword SAF text
Changes in v2:
New patch based on the discussion for "xen/arm: address violations of MISRA 
C:2012 Rule 13.1".
---
 docs/misra/safe.json     | 16 ++++++++++++++++
 xen/arch/arm/device.c    |  1 +
 xen/arch/arm/guestcopy.c | 16 ++++++++++++----
 xen/arch/x86/hvm/hvm.c   |  1 +
 xen/common/sched/core.c  |  3 +++
 5 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/docs/misra/safe.json b/docs/misra/safe.json
index 952324f85c..5539e8dfda 100644
--- a/docs/misra/safe.json
+++ b/docs/misra/safe.json
@@ -28,6 +28,22 @@
         },
         {
             "id": "SAF-3-safe",
+            "analyser": {
+                "eclair": "MC3R1.R13.1"
+            },
+            "name": "MC3R1.R13.1: effects for debugging and logging",
+            "text": "Effects for debugging and loggings reasons that crash 
execution or produce logs are allowed in initializer lists. The evaluation 
order in abnormal conditions is not relevant."
+        },
+        {
+            "id": "SAF-4-safe",
+            "analyser": {
+                "eclair": "MC3R1.R13.1"
+            },
+            "name": "MC3R1.R13.1: volatile asm statements that do not perform 
any persistent side effect",
+            "text": "Volatile asm statement in an initializer list that does 
not perform persistent side effects is safe."
+        },
+        {
+            "id": "SAF-5-safe",
             "analyser": {},
             "name": "Sentinel",
             "text": "Next ID to be used"
diff --git a/xen/arch/arm/device.c b/xen/arch/arm/device.c
index 1f631d3274..fa331f164d 100644
--- a/xen/arch/arm/device.c
+++ b/xen/arch/arm/device.c
@@ -331,6 +331,7 @@ int handle_device(struct domain *d, struct dt_device_node 
*dev, p2m_type_t p2mt,
         .p2mt = p2mt,
         .skip_mapping = !own_device ||
                         (is_pci_passthrough_enabled() &&
+                        /* SAF-3-safe effects for debugging/logging reasons 
are safe */
                         (device_get_class(dev) == DEVICE_PCI_HOSTBRIDGE)),
         .iomem_ranges = iomem_ranges,
         .irq_ranges = irq_ranges
diff --git a/xen/arch/arm/guestcopy.c b/xen/arch/arm/guestcopy.c
index 6716b03561..b75538252a 100644
--- a/xen/arch/arm/guestcopy.c
+++ b/xen/arch/arm/guestcopy.c
@@ -110,26 +110,34 @@ static unsigned long copy_guest(void *buf, uint64_t addr, 
unsigned int len,
 unsigned long raw_copy_to_guest(void *to, const void *from, unsigned int len)
 {
     return copy_guest((void *)from, (vaddr_t)to, len,
-                      GVA_INFO(current), COPY_to_guest | COPY_linear);
+                      /* SAF-4-safe No persistent side effects */
+                      GVA_INFO(current),
+                      COPY_to_guest | COPY_linear);
 }
 
 unsigned long raw_copy_to_guest_flush_dcache(void *to, const void *from,
                                              unsigned int len)
 {
-    return copy_guest((void *)from, (vaddr_t)to, len, GVA_INFO(current),
+    return copy_guest((void *)from, (vaddr_t)to, len,
+                      /* SAF-4-safe No persistent side effects */
+                      GVA_INFO(current),
                       COPY_to_guest | COPY_flush_dcache | COPY_linear);
 }
 
 unsigned long raw_clear_guest(void *to, unsigned int len)
 {
-    return copy_guest(NULL, (vaddr_t)to, len, GVA_INFO(current),
+    return copy_guest(NULL, (vaddr_t)to, len,
+                      /* SAF-4-safe No persistent side effects */
+                      GVA_INFO(current),
                       COPY_to_guest | COPY_linear);
 }
 
 unsigned long raw_copy_from_guest(void *to, const void __user *from,
                                   unsigned int len)
 {
-    return copy_guest(to, (vaddr_t)from, len, GVA_INFO(current),
+    return copy_guest(to, (vaddr_t)from, len,
+                      /* SAF-4-safe No persistent side effects */
+                      GVA_INFO(current),
                       COPY_from_guest | COPY_linear);
 }
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index e8deeb0222..19322fbb56 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -800,6 +800,7 @@ static int cf_check hvm_save_cpu_ctxt(struct vcpu *v, 
hvm_domain_context_t *h)
 {
     struct segment_register seg;
     struct hvm_hw_cpu ctxt = {
+        /* SAF-3-safe effects for debugging/logging reasons are safe */
         .tsc = hvm_get_guest_tsc_fixed(v, v->domain->arch.hvm.sync_tsc),
         .msr_tsc_aux = v->arch.msrs->tsc_aux,
         .rax = v->arch.user_regs.rax,
diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index d177c675c8..9e973fcf31 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -1521,6 +1521,7 @@ long vcpu_yield(void)
 
     SCHED_STAT_CRANK(vcpu_yield);
 
+    /* SAF-4-safe No persistent side effects */
     TRACE_2D(TRC_SCHED_YIELD, current->domain->domain_id, current->vcpu_id);
     raise_softirq(SCHEDULE_SOFTIRQ);
     return 0;
@@ -1899,6 +1900,7 @@ ret_t do_sched_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
arg)
         if ( copy_from_guest(&sched_shutdown, arg, 1) )
             break;
 
+        /* SAF-4-safe No persistent side effects */
         TRACE_3D(TRC_SCHED_SHUTDOWN,
                  current->domain->domain_id, current->vcpu_id,
                  sched_shutdown.reason);
@@ -1916,6 +1918,7 @@ ret_t do_sched_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
arg)
         if ( copy_from_guest(&sched_shutdown, arg, 1) )
             break;
 
+        /* SAF-4-safe No persistent side effects */
         TRACE_3D(TRC_SCHED_SHUTDOWN_CODE,
                  d->domain_id, current->vcpu_id, sched_shutdown.reason);
 
-- 
2.34.1